NOBLE DRILLING CORP
8-K, 1996-07-16
DRILLING OIL & GAS WELLS
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<PAGE>   1



                     SECURITIES AND EXCHANGE COMMISSION
                           Washington, D.C.  20549


                                  FORM 8-K

                               CURRENT REPORT


                   Pursuant to Section 13 or 15(d) of the
                       Securities Exchange Act of 1934

              Date of Report (Date of earliest event reported):

                                JULY 1, 1996


                         NOBLE DRILLING CORPORATION
           (Exact name of registrant as specified in its charter)



    Delaware                     0-13857                   73-0374541
    (State or other              (Commission               (IRS Employer
    jurisdiction of              File Number)              Identification No.)
    incorporation)



            10370 Richmond Avenue, Suite 400, Houston, Texas  77042
            (Address of principal executive offices)     (Zip Code)



              Registrant's telephone number, including area code:

                                 (713) 974-3131

<PAGE>   2
Item 2.  Acquisition or Disposition of Assets.

       On July 1, 1996, Noble Drilling Corporation (unless otherwise required
by the context, together with its consolidated subsidiaries, the "Company")
completed its previously announced agreement with Royal Nedlloyd N.V.
("Nedlloyd") and its wholly owned subsidiary, Neddrill Holding B.V., to acquire
the assets of Nedlloyd's offshore drilling division Neddrill ("Neddrill"). The
Company acquired the assets of Neddrill utilized in its offshore contract
drilling, accommodation and other oil and gas exploration and production
related service businesses, $25,000,000 in net working capital, and the
personnel employed by Neddrill for $300,000,000 in cash plus 5,000,000 shares
of common stock of the Company. For additional information regarding the
acquisition, see the sections captioned "Use of Proceeds" and "The
Acquisition," which appear on pages 14 and 23-25, respectively, of the
Prospectus of the Company dated June 26, 1996, which constitutes Part I of the
Registration Statement of the Company on Form S-3 (Registration No. 333-02927)
(the "Equity Registration Statement"), which sections are incorporated herein
by reference.

       In connection with the closing of the acquisition, the Company closed
its offering of 21,850,000 shares of common stock of the Company (including
2,850,000 shares issued in connection with the exercise by the underwriters of
the over-allotment options) and its offering of $125,000,000 principal amount
of 9-1/8% Senior Notes due 2006 of the Company.

Item 7.  Financial Statements and Exhibits.

       (a)   Financial Statements of Businesses Acquired.

             The financial statements required by this item of Form 8-K have
been previously reported (within the meaning thereof as defined in Rule 12b-2)
by the Company in the Equity Registration Statement and are accordingly not
included herein in reliance on General Instruction B.3 to Form 8-K.

       (b)   Pro Forma Financial Information.

             The pro forma financial information required by this item of Form
8-K has been previously reported (within the meaning thereof as defined in Rule
12b-2) by the Company in the Equity Registration Statement and is accordingly
not included herein in reliance on General Instruction B.3 to Form 8-K.

       (c)   Exhibits.

          Exhibit 2.1 -  Agreement of Sale and Purchase dated as of April 25,
                         1996 between the Registrant and Royal Nedlloyd N.V. and
                         Neddrill Holding B.V. (filed as Exhibit 2.1 to the
                         Equity Registration Statement and incorporated herein
                         by reference).





                                     -2-
<PAGE>   3
          Exhibit 4.1 -  Indenture dated as of July 1, 1996 governing the
                         9-1/8% Senior Notes due 2006.

          Exhibit 99.1 - Sections captioned "Use of Proceeds" and "The
                         Acquisition," which appear on pages 14 and 23-25,
                         respectively, of the Prospectus of the Company dated
                         June 26, 1996, which constitutes Part I of the
                         Equity Registration Statement.





                                      -3-
<PAGE>   4
                                   SIGNATURES

       Pursuant to the requirement of the Securities Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


Date:  July 16, 1996                NOBLE DRILLING CORPORATION


                                    By: /s/ BYRON L. WELLIVER               
                                        ----------------------------------------
                                        Byron L. Welliver,
                                        Senior Vice President-Finance, Treasurer
                                        and Controller





                                      -4-
<PAGE>   5
                               INDEX TO EXHIBITS



<TABLE>   
<CAPTION>                                                       
 Exhibit                                                         
 Number                            Exhibit                      
 -------       ----------------------------------------------    
 <S>           <C>
 2.1 -         Agreement of Sale and Purchase dated as of
               April 25, 1996 between the Registrant and
               Royal Nedlloyd N.V. and Neddrill Holding B.V.
               (filed as Exhibit 2.1 to the Equity
               Registration Statement and incorporated herein
               by reference).
          
 4.1 -         Indenture dated as of July 1, 1996 governing
               the 9-1/8% Senior Notes due 2006.

 99.1 -        Sections captioned "Use of Proceeds" and "The
               Acquisition," which appear on pages 14 and 23-
               25, respectively, of the Prospectus of the
               Company dated June 26, 1996, which constitutes
               Part I of the Equity Registration Statement.
</TABLE>  





                                      

<PAGE>   1

                                                                     EXHIBIT 4.1


================================================================================







                          NOBLE DRILLING CORPORATION

                                      to

                  TEXAS COMMERCE BANK NATIONAL ASSOCIATION,
                                   Trustee





                                  INDENTURE





                           Dated as of July 1, 1996

                                 $125,000,000

                         9-1/8% Senior Notes due 2006







================================================================================

<PAGE>   2

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                       Page
                                                                                                       ----
                                                            ARTICLE I

                                                 Definitions and Other Provisions
                                                      of General Application

<S>              <C>                                                                                    <C>
SECTION 1.01.    Definitions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
SECTION 1.02.    Incorporation by Reference to Trust Indenture Act  . . . . . . . . . . . . . . . . . . 25
SECTION 1.03.    Compliance Certificate and Opinions  . . . . . . . . . . . . . . . . . . . . . . . . . 26
SECTION 1.04.    Form of Documents Delivered to Trustee . . . . . . . . . . . . . . . . . . . . . . . . 26
SECTION 1.05.    Acts of Holders  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
SECTION 1.06.    Notices, etc., to Trustee and Company  . . . . . . . . . . . . . . . . . . . . . . . . 28
SECTION 1.07.    Notice to Holders; Waiver  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
SECTION 1.08.    Conflict with Trust Indenture Act  . . . . . . . . . . . . . . . . . . . . . . . . . . 28
SECTION 1.09.    Effect of Headings and Table of Contents   . . . . . . . . . . . . . . . . . . . . . . 29
SECTION 1.10.    Successors and Assigns   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
SECTION 1.11.    Severability Clause  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
SECTION 1.12.    Benefits of Indenture  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
SECTION 1.13.    Governing Law; Submission to Jurisdiction  . . . . . . . . . . . . . . . . . . . . . . 29
SECTION 1.14.    Legal Holidays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29


                                                            ARTICLE II

                                                          Form of Notes

SECTION 2.01.    Forms Generally  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
SECTION 2.02.    Form of Note . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
SECTION 2.03.    Form of Trustee's Certificate of Authentication  . . . . . . . . . . . . . . . . . . . 36


                                                           ARTICLE III

                                                            The Notes

SECTION 3.01.    Title and Terms  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
SECTION 3.02.    Authorized Denominations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
SECTION 3.03.    Execution, Authentication, Delivery and Dating . . . . . . . . . . . . . . . . . . . . 37
</TABLE>




                                     -i-
<PAGE>   3

<TABLE>
<CAPTION>
                                                                                                       Page
                                                                                                       ----
<S>              <C>                                                                                    <C>
SECTION 3.04.    Temporary Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
SECTION 3.05.    Paying Agent To Hold Money in Trust  . . . . . . . . . . . . . . . . . . . . . . . . . 38
SECTION 3.06.    Registrar; Registration, Registration of Transfer
                      and Exchange  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
SECTION 3.07.    Mutilated, Destroyed, Lost and Stolen Notes  . . . . . . . . . . . . . . . . . . . . . 40
SECTION 3.08.    Payment of Interest; Interest Rights Preserved . . . . . . . . . . . . . . . . . . . . 41
SECTION 3.09.    Persons Deemed Owners  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SECTION 3.10.    Cancellation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SECTION 3.11.    Computation of Interest  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SECTION 3.12.    CUSIP Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SECTION 3.13.    Book-Entry Provisions for Global Note  . . . . . . . . . . . . . . . . . . . . . . . . 42


                                                            ARTICLE IV

                                                    Satisfaction and Discharge

SECTION 4.01.    Satisfaction and Discharge of Indenture  . . . . . . . . . . . . . . . . . . . . . . . 43
SECTION 4.02.    Deposited Moneys and U.S. Government Obligations
                      To Be Held in Trust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
SECTION 4.03.    Repayment to Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
SECTION 4.04.    Reinstatement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46


                                                            ARTICLE V

                                                             Remedies

SECTION 5.01.    Events of Default  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
SECTION 5.02.    Acceleration of Maturity; Rescission and Annulment . . . . . . . . . . . . . . . . . . 48
SECTION 5.03.    Collection of Indebtedness and Suits for Enforcement
                      by Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
SECTION 5.04.    Trustee May File Proofs of Claim . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
SECTION 5.05.    Trustee May Enforce Claims without Possession of the
                      Notes   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
SECTION 5.06.    Application of Money Collected . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
SECTION 5.07.    Limitation on Suits  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
</TABLE>




                                      -ii-
<PAGE>   4

<TABLE>
<CAPTION>
                                                                                                       Page
                                                                                                       ----
<S>              <C>                                                                                    <C>
SECTION 5.08.    Unconditional Right of Holders to Receive Principal,
                      Premium and Interest  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
SECTION 5.09.    Restoration of Rights and Remedies . . . . . . . . . . . . . . . . . . . . . . . . . . 51
SECTION 5.10.    Rights and Remedies Cumulative . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
SECTION 5.11.    Delay or Omission Not Waiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
SECTION 5.12.    Control By Holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
SECTION 5.13.    Waiver of Past Defaults  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
SECTION 5.14.    Undertaking for Costs  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
SECTION 5.15.    Waiver of Stay or Extension Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . 53


                                                        ARTICLE VI

                                                       The Trustee

SECTION 6.01.    Certain Duties and Responsibilities  . . . . . . . . . . . . . . . . . . . . . . . . . 53
SECTION 6.02.    Notice of Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
SECTION 6.03.    Certain Rights of Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
SECTION 6.04.    Not Responsible for Recitals or Issuance of Notes  . . . . . . . . . . . . . . . . . . 56
SECTION 6.05.    May Hold Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SECTION 6.06.    Money Held in Trust  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SECTION 6.07.    Compensation and Reimbursement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
SECTION 6.08.    Disqualification; Conflicting Interests  . . . . . . . . . . . . . . . . . . . . . . . 57
SECTION 6.09.    Corporate Trustee Required; Eligibility  . . . . . . . . . . . . . . . . . . . . . . . 57
SECTION 6.10.    Resignation and Removal; Appointment of Successor  . . . . . . . . . . . . . . . . . . 57
SECTION 6.11.    Acceptance of Appointment by Successor . . . . . . . . . . . . . . . . . . . . . . . . 59
SECTION 6.12.    Merger, Conversion, Consolidation or Succession
                       to Business  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
SECTION 6.13.    Preferential Collection of Claims Against Company  . . . . . . . . . . . . . . . . . . 60


                                                           ARTICLE VII

                                                  Holders' Lists and Reports by
                                                       Trustee and Company

SECTION 7.01.    Company To Furnish Trustee Names and Addresses
                       of Holders   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
</TABLE>




                                     -iii-
<PAGE>   5

<TABLE>
<CAPTION>
                                                                                                       Page
                                                                                                       ----
<S>              <C>                                                                                    <C>
SECTION 7.02.    Preservation of Information; Communications to Holders . . . . . . . . . . . . . . . . 60
SECTION 7.03.    Reports by the Trustee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
SECTION 7.04.    Reports by the Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61


                                                           ARTICLE VIII

                                                Consolidation, Merger, Conveyance,
                                                        Lease or Transfer

SECTION 8.01.    Company May Consolidate, etc., Only on Certain Terms . . . . . . . . . . . . . . . . . 61
SECTION 8.02.    Successor Corporation Substituted  . . . . . . . . . . . . . . . . . . . . . . . . . . 63


                                                            ARTICLE IX

                                                     Supplemental Indentures

SECTION 9.01.    Supplemental Indentures without Consent of Holders . . . . . . . . . . . . . . . . . . 63
SECTION 9.02.    Supplemental Indentures with Consent of Holders  . . . . . . . . . . . . . . . . . . . 64
SECTION 9.03.    Execution of Supplemental Indentures . . . . . . . . . . . . . . . . . . . . . . . . . 65
SECTION 9.04.    Effect of Supplemental Indentures  . . . . . . . . . . . . . . . . . . . . . . . . . . 65
SECTION 9.05.    Conformity with Trust Indenture Act  . . . . . . . . . . . . . . . . . . . . . . . . . 65
SECTION 9.06.    Reference in Notes to Supplemental Indentures  . . . . . . . . . . . . . . . . . . . . 65


                                                            ARTICLE X

                                                            Covenants

SECTION 10.01.   Payment of Principal, Premium and Interest . . . . . . . . . . . . . . . . . . . . . . 65
SECTION 10.02.   Maintenance of Office or Agency  . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
SECTION 10.03.   Money for the Note Payments to Be Held in Trust  . . . . . . . . . . . . . . . . . . . 66
SECTION 10.04.   Corporate Existence  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
SECTION 10.05.   Maintenance of Property  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
SECTION 10.06.   Payment of Taxes and Other Claims  . . . . . . . . . . . . . . . . . . . . . . . . . . 67
SECTION 10.07.   Transactions with Affiliates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
SECTION 10.08.   Limitation on Restricted Payments  . . . . . . . . . . . . . . . . . . . . . . . . . . 67
</TABLE>




                                      -iv-
<PAGE>   6

<TABLE>
<CAPTION>
                                                                                                       Page
                                                                                                       ----
<S>              <C>                                                                                    <C>
SECTION 10.09.   Limitation on Indebtedness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
SECTION 10.10.   Limitation on Subsidiary Indebtedness and Preferred Stock  . . . . . . . . . . . . . . 69
SECTION 10.11.   Limitation on Dividends and Other Payment Restrictions
                      Affecting Subsidiaries  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
SECTION 10.12.   Change of Control  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
SECTION 10.13.   Limitation on Asset Sales  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
SECTION 10.14.   Limitation on Sale and Lease-Back Transactions . . . . . . . . . . . . . . . . . . . . 75
SECTION 10.15.   Limitation on Liens  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
SECTION 10.16.   Certificate as to Default  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
SECTION 10.17.   Insurance  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
SECTION 10.18.   Changes to NN-1 Agreement of Limited Partnership . . . . . . . . . . . . . . . . . . . 76
SECTION 10.19.   Certain Covenants Suspended  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76


                                                            ARTICLE XI

                                                           Redemptions

SECTION 11.01.   Notice to Trustee  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
SECTION 11.02.   Selection of the Notes To Be Redeemed  . . . . . . . . . . . . . . . . . . . . . . . . 77
SECTION 11.03.   Notice of Redemption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
SECTION 11.04.   Effect of Notice of Redemption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
SECTION 11.05.   Deposit of Redemption Price on Redemption  . . . . . . . . . . . . . . . . . . . . . . 78
SECTION 11.06.   Notes Redeemed in Part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Schedule 1.01A   Existing Indebtedness  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Schedule 1.01B   Existing Liens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Schedule 10.11   Existing Encumbrances or Restrictions  . . . . . . . . . . . . . . . . . . . . . . . . 82
</TABLE>




                                      -v-
<PAGE>   7

            INDENTURE dated as of July 1, 1996, between NOBLE
      DRILLING CORPORATION, a Delaware corporation (the "Company")
      having its principal office at 10370 Richmond Avenue, Suite 400,
      Houston, Texas 77042 and TEXAS COMMERCE BANK NATIONAL ASSOCIATION,
      as trustee hereunder (the "Trustee"), having its Corporate Trust
      Office at 600 Travis, 8th Floor, Houston, Texas 77002.


                            RECITALS OF THE COMPANY

            The Company has duly authorized the creation and issue of its 
9-1/8% Senior Notes due 2006 (the "Notes") of substantially the tenor and amount
hereinafter set forth, and to provide therefor the Company has duly authorized
the execution and delivery of this Indenture.

            All things necessary to make the Notes, when executed by the
Company and authenticated and delivered by the Trustee hereunder and duly
issued by the Company, the valid obligations of the Company, and to make this
Indenture a valid agreement of the Company, in accordance with their respective
terms, have been done.


            NOW, THEREFORE, THIS INDENTURE WITNESSETH, that, each party agrees
as follows for the benefit of the other party and for the equal and ratable
benefit of the Notes of the Holders (as defined herein):


                                   ARTICLE I

                        Definitions and Other Provisions
                             of General Application

            SECTION 1.01.  Definitions.  For all purposes of this Indenture,
except as otherwise expressly provided or unless the context otherwise
requires:

            (1)   the terms defined in this Article have the meanings assigned
      to them in this Article, and include the plural as well as the singular;

            (2)   all accounting terms not otherwise defined herein have the
      meanings assigned to them in accordance with GAAP; and
<PAGE>   8
            (3)   the words "herein," "hereof" and "hereunder" and other words
      of similar import refer to this Indenture as a whole and not to any
      particular Article, Section or other subdivision.

            "Act" when used with respect to any Holder has the meaning
specified in Section 1.05.

            "Affiliate" of any specified Person means any other Person (i)
which directly or indirectly through one or more intermediaries controls, or is
controlled by, or is under common control with, such specified Person, (ii)
which beneficially owns or holds 10% or more of the Voting Stock of such
specified Person or a subsidiary of such specified Person or (iii) of which 10%
or more of the Voting Stock is beneficially owned or held by such specified
Person or a subsidiary of such specified Person.  For the purposes of this
definition, "control" when used with respect to any specified Person means the
power to direct the management and policies of such Person directly or
indirectly, whether through the ownership of Voting Stock, by contract or
otherwise; and the terms "controlling" and "controlled" have meanings
correlative to the foregoing.

            "Agent Members" has the meaning specified in Section 3.13.

            "Appraised Value" means (i) with respect to property, equipment, or
other Consolidated Tangible Assets consisting of investments or other tangible
financial assets (excluding cash, cash equivalents and investments in
marketable securities) without a readily determinable market value, the Fair
Value of such Properties as determined within 60 days of the date of the
transaction giving rise to the need to calculate Appraised Value by means of a
written appraisal or valuation report by a nationally recognized investment
banking firm, independent appraisal firm or marine surveyor, in each case, (a)
specializing in, or having a specialty in, valuing or appraising Property of
the Company and the Subsidiaries of the type to be appraised or valued and (b)
that is not an Affiliate of the Company, (ii) with respect to marketable
securities of the Company and the Subsidiaries with a readily determinable
market value, the market value of such assets, as determined within five
trading days of the date of the transaction giving rise to the need to
calculate Appraised Value, and as determined by reference to a published or
otherwise readily accessible market data source selected in good faith by the
Company, (iii) with respect to cash and cash equivalents of the Company and the
Subsidiaries, the carrying value thereof reflected in the accounting records of
the Company and (iv) with respect to all other Consolidated Tangible Assets of
the Company and the Subsidiaries, the Fair Value of such assets, as determined
in good faith by the Board of Directors; provided, however, that written
appraisals or valuation reports shall not be required in respect of any
Consolidated Tangible Assets of the Company and the Subsidiaries described in
clause (i) of this definition to the extent that the Company determines in good
faith the Fair Value of such unappraised or unvalued assets and the aggregate
Fair Value of such assets does not exceed $25,000,000.

            "Asset Sale" means any direct or indirect sale, conveyance,
transfer, lease or other disposition (including, without limitation, by means
of a Sale and Lease-back Transaction (other





                                     -2-
<PAGE>   9
than a Sale and Lease-back Transaction that results in the creation or
incurrence of a Capital Lease Obligation of the Company or any Subsidiary) or
by way of merger or consolidation) (collectively, for purposes of this
definition, a "transfer") by the Company or any Subsidiary to any Person other
than the Company or a Subsidiary, in one transaction, or a series of related
transactions, of (i) any Capital Stock of any Subsidiary or (ii) any other
Property or assets of the Company or any Subsidiary, other than (a) sales of
inventory in the ordinary course of business of the Company and the
Subsidiaries and consistent with past practices, (b) sales of obsolete or worn
out equipment in the ordinary course of business, (c) sales of directors'
qualifying shares in a Subsidiary, (d) any charter (bareboat or otherwise) or
other lease of Property entered into by the Company or any Subsidiary in the
ordinary course of business, other than any charter or lease that provides for
acquisition of such Property by the charterer or lessee during or at the end of
the term thereof, (e) the issuance by the Company of its Capital Stock, (f)
sales in the ordinary course of business of drill pipe and associated equipment
utilized in connection with a drilling contract for the employment of a
drilling rig, (g) a Restricted Payment permitted by Section 10.08 hereof, (h) a
Change of Control, (i) any transfer in a transaction or series of related
transactions of Properties (other than a transfer specifically permitted under
clause (a) through (h), (j) or (k) of this definition) having an aggregate Fair
Value of less than $500,000, (j) any sale or sales of land drilling rigs or
barge drilling rigs of the Company or any Subsidiary owned as of the Issue Date
(or any subsequent disposition of any non-cash consideration received by the
Company or any Subsidiary in any such sale or sales), (k) any trade or exchange
by the Company or any Subsidiary of one or more drilling rigs and related
equipment for one or more other drilling rigs and related equipment owned or
held by another Person that is not an Affiliate of the Company but only to the
extent that the Fair Value of the Property traded or exchanged by the Company
or a Subsidiary (other than cash or cash equivalents) is reasonably equivalent
to the Fair Value of the Properties (together with cash or cash equivalents not
to exceed 15 percent of such Fair Value) to be received by the Company or such
Subsidiary as determined by the Board of Directors, provided that if cash and
cash equivalents to be received by the Company or such Subsidiary is greater
than 15 percent of the Fair Value of the Properties to be received, the trade
or exchange shall be treated as an Asset Sale only to the extent that such cash
and cash equivalents exceed the 15 percent amount and (l) the disposition of
shares of Capital Stock of Offshore Logistics, Inc. and of Century Drilling
Limited owned by the Company or any Subsidiary on the Issue Date. An Asset
Sale shall include the requisition of title to, seizure of or forfeiture of any
Property or assets, or any actual or constructive total loss or an agreed or
compromised total loss of any Property or assets, other than as provided for in
clause (ii) (f) of the preceding sentence of this definition.

            "Asset Sale Offer" has the meaning specified in Section 10.13(b).

            "Average Life" means, as of any date, with respect to any debt
security, the quotient obtained by dividing (i) the sum of the products of (x)
the number of years from such date to the date of each scheduled principal
payment (including any sinking fund or mandatory redemption payment
requirements) of such debt security multiplied in each case by (y) the amount
of such principal payment by (ii) the sum of all such principal payments.





                                     -3-
<PAGE>   10
            "Bankruptcy Code" means the United States Bankruptcy Code, Title 11
of the United States Code.

            "Board of Directors" means either the board of directors of the
Company, or (except for purposes of the definitions of "Change of Control" and
"Continuing Director") any duly authorized committee of such board.

            "Board Resolution" means a copy of a resolution certified by the
Secretary or an Assistant Secretary of the Company to have been duly adopted by
the Board of Directors and to be in full force and effect on the date of such
certification, and delivered to the Trustee.

            "Business Day" means each day other than a Saturday or Sunday that
is not a day on which banking institutions in the Borough of Manhattan, The
City of New York, or the location of the Corporate Trust Office are authorized
or obligated by law, executive order or regulation to remain closed.

            "Capital Lease Obligation" means, at any time as to any Person with
respect to any Property leased by such Person as lessee, the amount of the
liability with respect to such lease that would be required at such time to be
capitalized and accounted for as a capital lease on the balance sheet of such
Person prepared in accordance with GAAP.

            "Capital Stock" in any Person means any and all shares, interests,
participations or other equivalents in the equity interest (however designated)
in such Person and any rights (other than debt securities convertible into an
equity interest), warrants or options to acquire an equity interest in such
Person.

            "Cash Proceeds" means, with respect to any Asset Sale by any
Person, the aggregate consideration received for such Asset Sale by such Person
in the form of cash or cash equivalents (including any amounts of insurance or
other proceeds received in connection with an Asset Sale of the type described
in the last sentence of the definition thereof), including payments in respect
of deferred payment obligations when received in the form of cash or cash
equivalents (except to the extent that such obligations are financed or sold
with recourse to such Person or any subsidiary thereof). For purposes of this
definition, "cash or cash equivalents" shall be deemed to include, for a period
not to exceed 12 months from the related Asset Sale, noncash consideration
received with respect to an Asset Sale to the extent that such noncash
consideration consists of (i) publicly traded debt securities of a Person,
which securities are rated at least "BBB-" by S&P and at least "Baa3" by
Moody's or having a comparable rating from the successors of each of such
Rating Agencies or (ii) other Indebtedness or publicly traded Capital Stock of
a Person if (x) the lowest rated long-term, unsecured debt obligation issued by
such Person is rated at least "BBB-" by S&P and at least "Baa3" by Moody's or
having a comparable rating from the successors of each of such Rating Agencies
or (y) in the case of other Indebtedness, the payment of such other
Indebtedness is secured by an irrevocable letter of credit issued by a
commercial bank having capital and surplus in excess of





                                      -4-
<PAGE>   11
$100,000,000 and long-term unsecured debt obligations rated at least "A-" by
S&P and at least "A3" by Moody's or having a comparable rating from the
successors of each of such Rating Agencies.

            "Change of Control" means (i) a determination by the Company that
any person or group (as defined in Section 13(d)(3) or 14(d)(2) of the Exchange
Act) has become the direct or indirect beneficial owner (as defined in Rule
13d-3 under the Exchange Act) of more than 50 percent of the Voting Stock of
the Company, (ii) the Company is merged with or into or consolidated with
another corporation and, immediately after giving effect to the merger or
consolidation, less than 50 percent of the outstanding voting securities
entitled to vote generally in the election of directors or persons who serve
similar functions of the surviving or resulting entity are then beneficially
owned (within the meaning of Rule 13d-3 under the Exchange Act) in the
aggregate by (x) the stockholders of the Company immediately prior to such
merger or consolidation or (y) if a record date has been set to determine the
stockholders of the Company entitled to vote on such merger or consolidation,
the stockholders of the Company as of such record date, (iii) the Company,
either individually or in conjunction with one or more Subsidiaries, sells,
conveys, transfers or leases, or the Subsidiaries sell, convey, transfer or
lease, all or substantially all of the property of the Company and the
Subsidiaries, taken as a whole (either in one transaction or a series of
related transactions), including Capital Stock of the Subsidiaries, to any
Person (other than a Wholly Owned Subsidiary), (iv) the liquidation or
dissolution of the Company or (v) the first day on which a majority of the
individuals who constitute the Board of Directors are not Continuing Directors.

            "Change of Control Offer" has the meaning given such term in
Section 10.12.

            "Change of Control Payment Date" has the meaning given such term in
Section 10.12.

            "Commission" means the Securities and Exchange Commission, as from
time to time constituted, created under the Exchange Act, or, if at any time
after the execution of this Indenture such commission is not existing and
performing the duties now assigned to it under the Trust Indenture Act, the
body performing such duties at such time.

            "Company" means the Person named as the "Company" in the first
paragraph of this instrument until a successor Person shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Company" shall mean such successor Person.

            "Company Request" or "Company Order" means a written request or
order signed in the name of the Company by its Chairman of the Board, its
President, a Vice Chairman or a Vice President, and by its Treasurer, an
Assistant Treasurer, its Secretary or an Assistant Secretary, and delivered to
the Trustee.

            "Consolidated Asset Coverage Ratio" means as of the date of the
transaction giving rise to the need to calculate the Consolidated Asset
Coverage Ratio (the "Measurement Date") and after giving pro forma effect to
the incurrence of any Project Finance Indebtedness on the





                                      -5-
<PAGE>   12
Measurement Date, the ratio of (i) the aggregate Appraised Value of the
Consolidated Tangible Assets of the Company (other than accounts receivable,
inventory, and the Properties of the Company and its Subsidiaries described in
this Section 1.01 under clause (xix) of the definition of "Permitted Liens" as
of the Measurement Date) that are not, and will not be, subject to any Lien
(other than Permitted Liens of the type described in this Section 1.01 under
clauses (vii), (viii) and (ix) of the definition of "Permitted Liens") to (ii)
the aggregate principal amount of the Notes plus the aggregate principal amount
of  unsecured Indebtedness of the Company and its Subsidiaries for borrowed
money that is pari passu in right of payment to the Notes, in each case
outstanding as of the Measurement Date.

            "Consolidated Current Liabilities" of any Person means, as of any
date, the total liabilities (including tax and other proper accruals) of such
Person and its subsidiaries on a consolidated basis at such date which may
properly be classified as current liabilities in accordance with GAAP.

            "Consolidated Interest Coverage Ratio" means as of the date of the
transaction giving rise to the need to calculate the Consolidated Interest
Coverage Ratio (the "Transaction Date"), the ratio of (i) the sum of (a) the
aggregate amount of EBITDA of the Company and its consolidated Subsidiaries for
the four fiscal quarters for which financial information in respect thereof is
available immediately prior to the applicable Transaction Date (the
"Determination Period") and (b) with respect to any fiscal quarter ending prior
to April 1, 1996, and the period from April 1, 1996 to the Issue Date included
in the calculation set forth in clause (a) above, the EBITDA for any such
quarter or period attributable to the Neddrill Assets to (ii) the aggregate
Consolidated Interest Expense of the Company and its consolidated Subsidiaries
that is anticipated to accrue during a period consisting of the fiscal quarter
in which the Transaction Date occurs and the three fiscal quarters immediately
subsequent thereto (based upon the pro forma amount and maturity of, and
interest payments in respect of, Indebtedness of the Company and its
consolidated Subsidiaries reasonably expected by the Company to be outstanding
on the Transaction Date and reasonably expected by the Company to be
outstanding from time to time during such period), assuming for the purposes of
this measurement the continuation of market interest rates prevailing on the
Transaction Date and base interest rates in respect of floating interest rate
obligations equal to the base interest rates on such obligations in effect as
of the Transaction Date; provided that if the Company or any of its
consolidated Subsidiaries is a party to any Interest-Swap Obligation which
would have the effect of changing the interest rate on any Indebtedness of the
Company or any of its consolidated Subsidiaries for such four quarter period
(or a portion thereof), the resulting rate shall be used for such four quarter
period or portion thereof; provided, further, that any Consolidated Interest
Expense with respect to Indebtedness incurred or retired by the Company or any
of its Subsidiaries during the fiscal quarter in which the Transaction Date
occurs shall be calculated as if such debt was so incurred or retired on the
first day of the fiscal quarter in which the Transaction Date occurs; provided,
further, that if the transaction giving rise to the need to calculate the
Consolidated Interest Coverage Ratio would have the effect of increasing or
decreasing EBITDA in the future and if such increase or decrease is readily
quantifiable and is directly attributable to such transaction, EBITDA shall be
calculated on a pro forma basis as if such transaction had occurred on the
first day of the four fiscal





                                      -6-
<PAGE>   13
quarters referred to in clause (i) of this definition, and if, during the same
four fiscal quarters, (x) the Company or any of its consolidated Subsidiaries
shall have engaged in any Asset Sale, EBITDA for such period shall be reduced
by an amount equal to the EBITDA (if positive), or increased by an amount equal
to the EBITDA (if negative), directly attributable to the assets which are the
subject of such Asset Sale for such period calculated on a pro forma basis as
if such Asset Sale and any related retirement of Indebtedness had occurred on
the first day of such period or (y) after the Issue Date, the Company or any of
its consolidated Subsidiaries shall have acquired any material assets out of
the ordinary course of business, EBITDA and Consolidated Interest Expense (if
Indebtedness is incurred or assumed in connection with such acquisition) shall
be calculated on a pro forma basis as if such asset acquisition and related
financing had occurred on the first day of such period.

            "Consolidated Interest Expense" means, with respect to any Person
for any period, without duplication (A) the sum of (i) the aggregate amount of
cash and non-cash interest expense (including capitalized interest) of such
Person and its subsidiaries for such period as determined on a consolidated
basis in accordance with GAAP in respect of Indebtedness (including, without
limitation, (v) any amortization of debt discount, (w) net costs associated
with Interest-Swap Obligations (including any amortization of discounts), (x)
the interest portion of any deferred payment obligation, (y) all accrued
interest and (z) all commissions, discounts and other fees and charges owed
with respect to letters of credit, bankers' acceptances or similar facilities)
paid or accrued, or scheduled to be paid or accrued, during such period, (ii)
dividends on preferred stock (other than dividends on the Preferred Stock) of
such Person (and of its subsidiaries if paid to a Person other than such Person
or its subsidiaries) declared and payable in cash, (iii) the portion of any
rental obligation of such Person or its subsidiaries in respect of any Capital
Lease Obligation allocable to interest expense in accordance with GAAP, (iv)
the portion of any rental obligation of such Person or its subsidiaries in
respect of any Sale and Lease-Back Transaction allocable to interest expense
(determined as if such were treated as a Capital Lease Obligation), (v) to the
extent any debt of any other Person is Guaranteed by such Person or any of its
subsidiaries, the aggregate amount of interest paid, accrued or scheduled to be
paid or accrued, by such other Person during such period attributable to any
such debt, less (B) to the extent included in (A) above, amortization or
write-off of deferred financing costs of such Person and its subsidiaries
during such period and any charge related to any premium or penalty paid in
connection with redeeming or retiring any Indebtedness of such Person and its
subsidiaries prior to its stated maturity; in the case of both (A) and (B)
above, after elimination of intercompany accounts among such Person and its
subsidiaries and as determined in accordance with GAAP and (vi) with respect to
any fiscal quarter ending prior to April 1, 1996, an amount equal to quarterly
interest expense accrued in respect of the Notes  had such Notes been
outstanding in the amount issued on the Issue Date during the entirety of such
fiscal quarter.

            "Consolidated Net Income" of any Person means, for any period, the
aggregate net income (or net loss, as the case may be) of such Person and its
subsidiaries for such period on a consolidated basis, determined in accordance
with GAAP; provided that there shall be excluded therefrom, without
duplication, (i) gains and losses from Asset Sales or reserves relating
thereto, (ii) items classified as extraordinary (other than the tax benefit of
the utilization of net operating loss





                                      -7-
<PAGE>   14
carryforwards and alternative minimum tax credits), (iii) except to the extent
of the amount of cash dividends or other cash distributions in respect of
Capital Stock actually paid to such specified Person or a subsidiary thereof by
any other Person during such period, the net income (or loss) of such other
Person other than a subsidiary of such specified Person, (iv) the net income of
any Person acquired by such specified Person or any of its subsidiaries in a
pooling-of-interests transaction for any period prior to the date of such
acquisition, (v) any gain or loss, net of taxes, realized on the termination of
any employee pension benefit plan, (vi) the effect of the adoption of Statement
of Financial Accounting Standards No. 106 to the extent expenses recognized
pursuant to such adoption exceed the amount with respect to such expenses which
would have been recognized during such period using the "pay as you go"
accounting method, (vii) any charge against income for impairment or write-down
of long-lived assets of the Company or any Subsidiary made in accordance with
Statement of Financial Accounting Standards No. 121 and (viii) the net income
of any subsidiary of such specified Person to the extent that the transfer to
that Person of that income is not at the time permitted, directly or
indirectly, by any means (including by dividend, distribution, advance or loan
or otherwise), by operation of the terms of its charter or any agreement with a
Person other than with such specified Person or any Affiliate thereof,
instrument held by a Person other than by such specified Person or any
Affiliate thereof, judgment, decree, order, statute, law, rule or governmental
regulations applicable to such subsidiary or its stockholders, except for any
dividends or distributions actually paid by such subsidiary to such Person.

            "Consolidated Net Tangible Assets" of any Person means, as of any
date, Consolidated Tangible Assets of such Person at such date, after deducting
therefrom (without duplication of deductions) all Consolidated Current
Liabilities of such Person at such date.

            "Consolidated Net Worth" of any Person means, as of any date, the
sum of the Capital Stock and additional paid-in capital plus retained earnings
(or minus accumulated deficit) of such Person and its subsidiaries on a
consolidated basis at such date, each item determined in accordance with GAAP,
less amounts attributable to Redeemable Stock of such Person and any of its
subsidiaries.

            "Consolidated Tangible Assets" of any Person means, as of any date,
the sum of the Property of such Person and its subsidiaries on a consolidated
basis at such date, after eliminating intercompany items, and after deducting
from such total, without duplication, (i) all Property that would be classified
as intangibles under GAAP (including, without limitation, goodwill,
organizational expenses, trademarks, trade names, copyrights, patents, licenses
and any rights in any thereof), and (ii) any prepaid expenses, deferred charges
and unamortized debt discount and expense, each such item determined in
accordance with GAAP.

            "Continuing Director" means an individual who (i) is a member of
the Board of Directors and (ii) either (a) was a member of the Board of
Directors on the Issue Date or (b) whose nomination for election or election to
the Board of Directors was approved by a vote of at least 66-2/3% of the
Continuing Directors who were members of the Board of Directors at the time of
such nomination or election.





                                      -8-
<PAGE>   15
            "Corporate Trust Office" means the principal office of the Trustee
at which at any particular time its corporate trust business shall be
principally administered, which office is, at the date of execution of this
instrument, located at 600 Travis, 8th Floor, Houston, Texas 77002.  For
purposes of Section 10.02 hereof, the Corporate Trust Office shall include the
office of the Trustee's agent located on the date of execution of this
Indenture at 55 Water Street, North Bldg., Room 234, Windows 20 & 21, New York,
New York 10041.

            "corporation" includes corporations, limited liability companies,
associations, companies and business trusts.

            "Currency Hedge Obligations" means, at any time as to any Person,
the obligations of such Person at such time which were incurred in the ordinary
course of business pursuant to any foreign currency exchange agreement, option
or future contract or other similar agreement or arrangement designed to
protect against or manage such Person's or any of its subsidiaries' exposure to
fluctuations in foreign currency exchange rates.

            "Default" means any event, act or condition the occurrence of which
is, or after notice or the passage of time or both would be, an Event of
Default.

            "Defaulted Interest" has the meaning specified in Section 3.08.

            "Depository" means The Depository Trust Company, its nominees and
their respective successors, or such other clearing agency registered under the
Exchange Act that is designated by the Company to act as Depository for the
Global Notes.

            "Determination Period" has the meaning specified in this Section
1.01 under the definition of "Consolidated Interest Coverage Ratio."

            "Discharged" means that the Company shall be deemed to have paid
and discharged the entire indebtedness represented by, and obligations under,
the Notes and to have satisfied all the obligations under this Indenture
relating to the Notes (and the Trustee, at the expense of the Company, shall
execute proper instruments acknowledging the same), except (i) the rights of
Holders to receive, from the trust funds described in clause (b)(A) of Section
4.01, payment of the principal of, premium, if any, and the interest on Notes
when such payments are due, (ii) the Company's obligations with respect to the
Notes under Sections 3.06, 3.07, 4.02, 6.07, 6.10, 10.01 and 10.02, (iii) the
Company's obligations with respect to the Notes under Sections 10.12 and 10.13,
in each case with respect to the obligation to make offers to purchase Notes
which obligation has accrued prior to the deposit of such trust funds and (iv)
the rights, powers, trusts, duties and immunities of the Trustee hereunder,
including without limitation, the provisions of Section 6.07.

            "drilling rig" means any drillship, drilling ship, semisubmersible
drilling unit, jackup or self-elevating drilling unit, submersible drilling
unit, drilling barge or posted barge, platform





                                      -9-
<PAGE>   16
drilling unit or land drilling rig or any other similar equipment used in oil,
gas or other mineral or thermal well drilling or workover operations.

            "EBITDA" means, with respect to any Person for any period, the
Consolidated Net Income of such Person and its subsidiaries for such period,
plus to the extent reflected in the income statement of such Person for such
period from which Consolidated Net Income is determined, without duplication,
(i) the Consolidated Interest Expense of such Person for such period, (ii)
income tax expense, (iii) depreciation expense, (iv) amortization expense and
(v) any charge related to any premium or penalty paid in connection with
redeeming or retiring any Indebtedness prior to its stated maturity.

            "Equity Offerings" has the meaning specified on the cover page of
those certain final prospectuses of the Company constituting Part I of the
Company's Registration Statement on Form S-3 (No. 333-02929) registering the
Notes under the Securities Act of 1933, as amended.

            "Event of Default" has the meaning specified in Section 5.01.

            "Excess Proceeds" has the meaning specified in Section 10.13.

            "Exchange Act" means the Securities Exchange Act of 1934, as
amended from time to time, and the rules and regulations promulgated
thereunder.

            "Fair Market Value" means, with respect to the total consideration
received pursuant to any Asset Sale or by any Person as contemplated by Section
10.07 or any noncash consideration received by any Person, the fair market
value of such consideration as determined in good faith by the Board of
Directors.

            "Fair Value" means, with respect to any asset or Property, the
price which could be negotiated in an arm's- length free market transaction,
for cash, between a willing seller and a willing buyer, neither of whom is
under undue pressure or compulsion to complete the transaction.

            "GAAP" means, at any date, United States generally accepted
accounting principles, consistently applied, as set forth in the opinions of
the Accounting Principles Board of the American Institute of Certified Public
Accountants ("AICPA") and statements of the Financial Accounting Standards
Board, or in such other statements by such other entity as may be designated by
the AICPA, that are applicable to the circumstances as of the date of
determination; provided, however, that all calculations made for purposes of
determining compliance with Section 8.01 or Article X of this Indenture shall
utilize GAAP in effect at the Issue Date.

            "Global Note" means a security that evidences all or a part of the
Notes and is registered in the name of, and delivered to or on behalf of, the
Depository or a nominee thereof.





                                     -10-
<PAGE>   17
            "Guarantee" means any direct or indirect obligation, contingent or
otherwise, of a Person guaranteeing or having the economic effect of
guaranteeing any Indebtedness of any other Person in any manner.

            "Holder" means a Person in whose name a Note is registered in the
Security Register.

            "Indebtedness" as applied to any Person means, at any time, without
duplication, (i) any obligation of such Person, contingent or otherwise, for
borrowed money, (ii) any obligation of such Person evidenced by bonds,
debentures, notes or other similar instruments, (iii) any obligation of such
Person for all or any part of the purchase price of Property or for the cost of
Property constructed or of improvements thereto (including any obligation under
or in connection with any letter of credit related thereto), other than
accounts payable included in current liabilities incurred in respect of
Property and services purchased in the ordinary course of business, (iv) any
obligation of such Person upon which interest charges are customarily paid
(other than accounts payable incurred in the ordinary course of business), (v)
any obligation of such Person under conditional sale or other title retention
agreements relating to purchased Property, (vi) any obligation of such Person
issued or assumed as the deferred purchase price of Property (other than
accounts payable incurred in the ordinary course of business), (vii) any
Capital Lease Obligation or any obligation pursuant to any Sale and Lease-Back
Transaction of such Person, (viii) any obligation of any other Person secured
by (or for which the obligee thereof has an existing right, contingent or
otherwise, to be secured by) any Lien on Property owned or acquired, whether or
not any obligation secured thereby has been assumed, by such Person, (ix) any
obligation of such Person in respect of any letter of credit supporting any
obligation of any other Person, (x) the maximum fixed repurchase price of any
Redeemable Stock of such Person (or if such Person is a subsidiary, any
preferred stock of such Person), (xi) any Interest-Swap obligation or Currency
Hedge Obligation of such Person and (xii) any obligation which is in economic
effect a Guarantee, regardless of its characterization, with respect to any
Indebtedness of another Person, to the extent guaranteed. For purposes of the
preceding sentence, the maximum fixed repurchase price of any Redeemable Stock
or subsidiary preferred stock that does not have a fixed repurchase price shall
be calculated in accordance with the terms of such Redeemable Stock or
subsidiary preferred stock as if such Redeemable Stock or subsidiary preferred
stock were repurchased on any date on which Indebtedness shall be required to
be determined pursuant to this Indenture; provided, however, that if such
Redeemable Stock or subsidiary preferred stock is not then permitted to be
repurchased, the repurchase price shall be the book value of such Redeemable
Stock or subsidiary preferred stock. The amount of Indebtedness of any Person
at any date shall be (x) the outstanding book value at such date of all
unconditional obligations as described above and (y) the maximum liability of
any such contingent obligation at such date.

            "Indenture" means this instrument as originally executed or as it
may from time to time be supplemented or amended by one or more indentures
supplemental hereto entered into pursuant to the applicable provisions hereof.





                                     -11-
<PAGE>   18
            "Interest-Payment Date" means the Stated Maturity of an installment
of interest on the Notes.

            "Interest-Swap Obligations" means, with respect to any Person, the
obligations of such Person pursuant to any interest rate swap agreement,
interest rate cap, collar or floor agreement or other similar agreement or
arrangement designed to protect against or manage such Person's or any of its
subsidiaries' exposure to fluctuations in interest rates.

            "Investment" means any direct or indirect loan, advance, guarantee
or other extension of credit or capital contribution to (by means of transfers
of cash or other Property to others or payments for Property or services for
the account or use of others, or otherwise), or purchase or acquisition of
Capital Stock, bonds, notes, debentures or other securities or evidences of
Indebtedness issued by, any other Person. The amount of any Investment shall
be the original cost of such Investment, plus the cost of all additions
thereto, and minus the amount of any portion of such Investment repaid to such
Person in cash as a repayment of principal or a return of capital, as the case
may be, but without any other adjustments for increases or decreases in value,
or write-ups, write-downs or write-offs with respect to such Investment. In
determining the amount of any Investment involving a transfer of any Property
other than cash, such Property shall be valued at its Fair Value at the time of
such transfer, as determined in good faith by the board of directors (or
comparable body) of the Person making such transfer.

            "Investment Grade Ratings" has the meaning set forth in Section
10.19.

            "Issue Date" means the date on which the Notes are first
authenticated and delivered under this instrument.

            "Lien" means any mortgage, pledge, hypothecation, charge,
assignment, deposit arrangement, encumbrance, security interest, lien
(statutory or other), or preference, priority or other security or similar
agreement or preferential arrangement of any kind or nature whatsoever
(including, without limitation, any agreement to give or grant a Lien or any
lease, conditional sale or other title retention agreement having substantially
the same economic effect as any of the foregoing).

            "Material Subsidiary" means a Subsidiary that (i) has assets with
an aggregate book value in an amount greater than 5% of the Consolidated Net
Tangible Assets of the Company as of any date of determination as shown on a
separate balance sheet of such Subsidiary or (ii) had operating revenues in
excess of 5% of the operating revenues of the Company and the Subsidiaries as
determined on a consolidated basis in accordance with GAAP for the four
calendar quarters immediately preceding the calendar quarter that includes the
determination date.

            "Maturity" means the date on which the principal of a Note becomes
due and payable as provided therein or herein, whether at the Stated Maturity
or by declaration of acceleration or otherwise.





                                      -12-
<PAGE>   19
            "Measurement Date" has the meaning specified in this Section 1.01
under the definition of "Consolidated Asset Coverage Ratio."

            "Moody's" means Moody's Investors Service, Inc. and its successors.

            "Neddrill Agreement" means the Agreement of Sale and Purchase dated
as of April 25, 1996, between the Company and Royal Nedlloyd N.V. and Neddrill
Holding B.V.

            "Neddrill Assets" means the Assets (as defined in the Neddrill
Agreement) being acquired by the Company and the Subsidiaries pursuant to the
Neddrill Agreement.

            "Neddrill Joint Ventures" means (i) the drillship joint venture
described in the Acquisition Agreement relating to the Neddrill Muravlenko and
(ii) a joint venture relating to the drillship Valentin Shashin pursuant to
which Neddrill or an Affiliate of Neddrill may in the future acquire an
indirect ownership interest in such drillship.

            "Net Available Proceeds" means, as to any Asset Sale, the Cash
Proceeds therefrom, (i) minus, without duplication, the sum of (a) reasonable
legal and title expenses, commissions and other reasonable fees and expenses
incurred, and all Federal, state, provincial, foreign, recording and local
taxes payable as a consequence of such Asset Sale and (b) all payments made to
any Person other than the Company or a Subsidiary on any Indebtedness of the
Company or its Subsidiaries which is secured by such assets, in accordance with
the terms of any Lien upon or with respect to such assets, or which must by its
terms, or in order to obtain a necessary consent to such Asset Sale, or by
applicable law, be repaid out of the proceeds from such Asset Sale, and (ii) in
the case of an Asset Sale by a Subsidiary, multiplied by the percentage of the
Voting Stock of such Subsidiary directly or indirectly owned by the Company.

            "Net Proceeds Deficiency" has the meaning given such term in
Section 10.13(b).

            "Net Proceeds Offer" has the meaning given such term in Section
10.13(b).

            "Net Proceeds Offer Date" has the meaning specified in Section
10.13(b).

            "Non-Recourse Indebtedness" means any Indebtedness of a
Non-Recourse Subsidiary (i) in respect of which neither the Company nor any of
its Subsidiaries (other than a Non-Recourse Subsidiary) is liable or obligated
in any manner including, without limitation, liabilities or obligations
constituting Indebtedness of the Company or any of its Subsidiaries (other than
a Non-Recourse Subsidiary) and (ii) the occurrence of any event or the
existence of any condition under any agreement or instrument relating to which
shall not at any time have the effect of accelerating, or permitting the
acceleration of, the maturity of any Indebtedness of the Company or of its
Subsidiaries (other than a Non-Recourse Subsidiary) or otherwise permitting any
such Indebtedness to be declared to be due and payable, or to be required to be
prepaid, purchased or redeemed, prior to the stated maturity thereof.





                                      -13-
<PAGE>   20
            "Non-Recourse Subsidiary" means a Subsidiary that (i) owns only
Property acquired by such Subsidiary after the Issue Date and (ii) has no
Indebtedness other than Non-Recourse Indebtedness.

            "Notes" has the meaning specified in the first recital of this
instrument and more particularly means any of the Notes authenticated and
delivered under this Indenture.

            "Offered Price" has the meaning specified in Section 10.13(b).

            "Officers' Certificate" means a certificate signed by the Chairman
of the Board, the President, a Vice Chairman or a Vice President, and by the
Treasurer, an Assistant Treasurer, the Secretary or an Assistant Secretary, of
the Company, and delivered to the Trustee, which shall comply with Section
1.03.

            "Opinion of Counsel" means a written opinion of legal counsel, who
may be either (i) an employee of the Company or (ii) counsel to the Company
reasonably satisfactory to the Trustee, which opinion is delivered to the
Trustee and which shall comply with Section 1.03; provided, however, that any
Opinion of Counsel delivered pursuant to Section 4.01 shall not be rendered by
an employee of the Company.

            "Outstanding" when used with respect to the Notes, means, as of the
date of determination, all Notes theretofore authenticated and delivered under
this Indenture, except:

            (i)   Notes theretofore cancelled by the Trustee or delivered to
      the Trustee for cancellation;

            (ii)  Notes, or portions thereof, for whose payment or redemption
      money or U.S. Government Obligations in the necessary amount has been
      theretofore deposited with the Trustee or any Paying Agent (other than
      the Company) in trust or set aside and segregated in trust by the Company
      (if the Company shall act as its own Paying Agent) for the Holders of
      such Notes; provided that, if such Notes are to be redeemed, notice of
      such redemption has been duly given pursuant to this Indenture or
      provision therefor satisfactory to the Trustee has been made; and

            (iii) Notes in exchange for or in lieu of which other Notes have
      been authenticated and delivered pursuant to this Indenture;

provided, however, that in determining whether the Holders of the requisite
principal amount of Outstanding Notes have given any request, demand,
authorization, direction, notice, consent or waiver hereunder, Notes owned by
the Company or any other obligor upon the Notes or any Affiliate of the Company
or of such other obligor shall be disregarded and deemed not to be Outstanding,
except that, in determining whether the Trustee shall be protected in relying
upon such request, demand, authorization, direction, notice, consent or waiver,
only Notes which the Trustee knows to





                                      -14-
<PAGE>   21
be so owned shall be so disregarded. Notes so owned which have been pledged in
good faith may be regarded as Outstanding if the pledgee establishes to the
satisfaction of the Trustee the pledgee's right so to act with respect to such
Notes and that the pledgee is not the Company or any other obligor upon the
Notes or any Affiliate of the Company or of such other obligor.

            "Pari Passu Indebtedness" means any then outstanding Indebtedness
of the Company that is pari passu in right of payment to the Notes.

            "Pari Passu Indebtedness Amount" has the meaning given such term in
Section 10.13(b).

            "Pari Passu Offer" has the meaning given such term in Section
10.13(b).

            "Paying Agent" means any Person authorized by the Company to pay
the principal of or interest on any Notes on behalf of the Company.

            "Payment Amount" has the meaning given such term in Section
10.13(b).

            "Permitted Indebtedness" means:

            (i)   Indebtedness of the Company under the Notes;

            (ii)  Indebtedness of the Company and the Subsidiaries under one or
      more bank credit facilities; provided that at the date such Indebtedness
      is incurred and after giving effect to the incurrence of such
      Indebtedness and any substantially concurrent repayment of Indebtedness
      permitted under this clause (ii) or under any bank credit facility
      permitted pursuant to clause (v) hereof, the aggregate amount of all
      Indebtedness outstanding at such time under this clause (ii) and under
      any bank credit facility permitted pursuant to clause (v) hereof shall
      not exceed $100,000,000 (except as such amount may be permanently reduced
      by the application of Net Available Proceeds in accordance with clause
      (ii) of Section 10.13(b));

            (iii) Indebtedness of the Company or any Subsidiary under
      Interest-Swap obligations; provided that (a) such Interest-Swap
      Obligations are related to payment obligations on Indebtedness otherwise
      permitted by Section 10.09 and (b) the notional principal amount of such
      Interest-Swap Obligations does not exceed the principal amount of the
      Indebtedness to which such Interest-Swap Obligations relate;

            (iv)  Indebtedness of the Company or any Subsidiary under Currency
      Hedge Obligations; provided that (a) such Currency Hedge Obligations are
      related to payment obligations on Indebtedness otherwise permitted by
      Section 10.09 or to the foreign currency cash flows reasonably expected
      to be generated by the Company and the Subsidiaries and (b) the notional
      principal amount of such Currency Hedge Obligations does not exceed the





                                      -15-
<PAGE>   22
      principal amount of the Indebtedness or the amount of the foreign
      currency cash flows to which such Currency Hedge Obligations relate;

            (v)   Indebtedness of the Company or any Subsidiary outstanding on
      the Issue Date and listed on Schedule 1.01A;

            (vi)  Indebtedness of the Company or any Subsidiary in respect of
      performance bonds, surety bonds, appeal bonds and letters of credit
      issued for the account of the Company or any Subsidiary, in each case
      incurred in the ordinary course of business and not in connection with
      the borrowing of money;

            (vii) Indebtedness of the Company to any Wholly Owned Subsidiary
      (but only so long as it remains a Wholly Owned Subsidiary);

            (viii) Indebtedness of any Subsidiary to the Company or any
      Wholly Owned Subsidiary (but only so long as it remains a Wholly Owned
      Subsidiary);

            (ix)  Non-Recourse Indebtedness of any Non-Recourse Subsidiary;

            (x)   Indebtedness of the Company in connection with a purchase of
      the Notes pursuant to a Change of Control Offer; provided that the
      aggregate principal amount of such Indebtedness does not exceed 101% of
      the aggregate principal amount of the Notes purchased pursuant to such
      Change of Control Offer plus the amount of expenses incurred in
      connection therewith; provided, further, that such Indebtedness (a) has
      an Average Life equal to or greater than the remaining Average Life of
      the Notes and (b) does not mature prior to one year following the Stated
      Maturity of the Notes;

            (xi)  other Indebtedness of the Company or any Subsidiary; provided
      that at the date such Indebtedness is incurred and after giving effect to
      the incurrence of such Indebtedness, the aggregate amount of all
      Indebtedness outstanding at such time under this clause (xi) shall not
      exceed $30,000,000;

            (xii) Permitted Refinancing Indebtedness;

            (xiii) Indebtedness of any Subsidiary, if any, in respect of the
      Safe Harbor Leases, the Letter of Credit Agreement and the Mortgage, as
      such terms are defined in, and as contemplated by, the Assets Purchase
      Agreement dated August 20, 1993, between the Company and Portal Rig
      Corporation; and

            (xiv) Project Finance Indebtedness, provided that at the date such
      Indebtedness is incurred and after giving effect to the incurrence of
      such Indebtedness, the aggregate principal amount of all Indebtedness
      incurred and outstanding at such time under this clause





                                      -16-
<PAGE>   23
      (xiv) (or under clause (i) of Section 10.10 by reason of this clause
      (xiv) being referenced therein) shall not exceed $75,000,000.

So as to avoid duplication in determining the amount of Permitted Indebtedness
under any clause of this definition, Guarantees of, or obligations in respect
of letters of credit supporting, Indebtedness otherwise included in the
determination of such amount shall not also be included.

            "Permitted Investments" means:

            (i)   certificates of deposit, bankers' acceptances, time deposits,
      Eurocurrency deposits and similar types of investments routinely offered
      by commercial banks with final maturities of one year or less issued by
      commercial banks having capital and surplus in excess of $100,000,000;

            (ii)  commercial paper issued by any corporation, if such
      commercial paper has credit ratings of at least A-1 by S&P and at least
      P-1 by Moody's;

            (iii) U.S. Government Obligations with a maturity of four years or
      less;

            (iv)  repurchase obligations for instruments of the type described
      in clause (iii) hereof;

            (v)   shares of money market mutual or similar funds having assets
      in excess of $100,000,000;

            (vi)  payroll advances in the ordinary course of business;

            (vii) other advances and loans to officers and employees of the
      Company or any Subsidiary, so long as the aggregate principal amount of
      such advances and loans does not exceed $500,000 at any one time
      outstanding;

            (viii) Investments represented by that portion of the proceeds
      from Asset Sales (a) that is not Cash Proceeds or (b) that is deemed to
      be Cash Proceeds pursuant to the second sentence of the definition of
      "Cash Proceeds" set forth in this Section 1.01;

            (ix)  Investments in the NN-1 Limited Partnership, a Texas limited
      partnership, pursuant to the Agreement of Limited Partnership of the NN-1
      Limited Partnership in an aggregate amount not to exceed the amount of
      U.S. Government Guaranteed Ship Financing Sinking Fund Bonds outstanding
      on the Issue Date; and

            (x)   Investments in respect of the interest being acquired by the
      Company or any Subsidiary in the Neddrill Joint Ventures.





                                      -17-
<PAGE>   24
            "Permitted Liens" means:

            (i)    Liens in existence on the Issue Date and set forth on
      Schedule 1.01B;

            (ii)   Liens created for the benefit of the Notes;

            (iii)  Liens covering (a) accounts receivable and inventory of the
      Company and the Subsidiaries and (b) other assets of the Company and the
      Subsidiaries with a Fair Value (as determined in good faith by the Board
      of Directors) not to exceed $100,000,000, in each case securing
      Indebtedness that may be incurred under clause (ii) of the definition of
      "Permitted Indebtedness" set forth in this Section 1.01, provided that
      if, at the time Liens are proposed to be granted or created in reliance
      on this clause (b), Liens have been granted to secure Project Finance
      Indebtedness as permitted by the proviso of clause (xii) of this
      definition and the aggregate principal amount of such secured Project
      Finance Indebtedness exceeds $75,000,000, then the Fair Value of assets
      on which Liens may be granted or created under this clause (b) shall be
      limited to the greater of (x) $100,000,000 less the amount by which the
      outstanding aggregate principal of Project Finance Indebtedness exceeds
      $75,000,000, (y) an amount that would permit the Company, after the grant
      or creation of proposed Liens pursuant to this clause (b), to incur at
      least $1.00 of additional secured Project Finance Indebtedness under the
      proviso of clause (xii) of this definition and (z) an amount such that
      the Consolidated Assets Coverage Ratio would have been at least 2.50 to 1
      at the time of the incurrence of Liens in reliance on the proviso of
      clause (xii) of this definition had the Liens proposed to be granted or
      created under this clause (b) been granted or created immediately prior
      to the Measurement Date of such Consolidated Asset Coverage Ratio;

            (iv)   Liens on Property of a Person existing at the time such
      Person is merged or consolidated with or into the Company or a Subsidiary
      (and not incurred as a result of, or in anticipation of, such
      transaction); provided, that such Lien relates solely to the Property
      subject thereto;

            (v)    Liens on Property existing at the time of the acquisition
      thereof (and not incurred as a result of, or in anticipation of, such
      transaction); provided that such Lien relates solely to the Property
      subject thereto;

            (vi)   Liens incurred or pledges and deposits in connection with
      worker's compensation, unemployment insurance and other social security
      benefits, statutory obligations, surety or appeal bonds, performance
      bonds or other obligations of a like nature (and obligations with respect
      to any letters of credit issued in favor of the Company or a Subsidiary
      and in order to secure or obtain any of the foregoing), in each case
      incurred in the ordinary course of business and not in connection with
      the borrowing of money;

            (vii)  Liens imposed by law or arising by operation of law,
      including, without limitation, landlords', mechanics', carriers',
      warehousemen's, materialmen's, suppliers' and





                                      -18-
<PAGE>   25
      vendors' Liens and Liens for master's and crew's wages and other similar
      maritime Liens, and incurred in the ordinary course of business;

            (viii) zoning restrictions, easements, licenses, covenants,
      reservations, restrictions on the use of real property and defects,
      irregularities and deficiencies in title to real property that do not,
      individually or in the aggregate, materially affect the ability of the
      Company or any Subsidiary to conduct its business as presently conducted;

            (ix)   Liens for taxes or assessments or other governmental charges
      or levies not yet due and payable, or the validity of which is being
      contested by the Company or a Subsidiary in good faith by appropriate
      proceedings upon stay of execution or the enforcement thereof and for
      which adequate reserves in accordance with GAAP or other appropriate
      provision has been made;

            (x)    Liens to secure the payment of all or a part of the purchase
      price or construction cost of Property acquired or constructed after the
      Issue Date; provided that (a) the principal amount of Indebtedness
      secured by such Liens shall not exceed the lesser of cost or Fair Market
      Value of the Assets or Property so acquired or constructed; and (b) such
      Liens shall not encumber any other assets or Property of the Company or
      any Subsidiary and shall attach to such Property within 120 days of the
      construction or acquisition of such Property;

            (xi)   Liens securing Capital Lease Obligations; provided, that
      such Liens secure Capital Lease Obligations which, when combined with (a)
      the outstanding secured Indebtedness of the Company (other than
      Indebtedness secured by Liens described in clauses (ii), (iii), (x) and
      (xix) hereof), (b) all Indebtedness and the aggregate liquidation value
      of all preferred stock of any Subsidiary (other than a Non-Recourse
      Subsidiary) incurred and outstanding in accordance with Section 10.10
      (other than of the type described in clauses (iii), (x), (xv) and (xix)
      hereof) and (c) the aggregate amount of all other Capital Lease
      Obligations of the Company and the Subsidiaries, does not exceed 10% of
      the Consolidated Net Tangible Assets of the Company;

            (xii)  Liens securing Project Finance Indebtedness incurred under
      clause (xiv) of the definition of "Permitted Indebtedness" as set forth
      in this Section 1.01; provided, that if, at the date such Project Finance
      Indebtedness is incurred and after giving effect to the incurrence of
      such Indebtedness, the Consolidated Asset Coverage Ratio shall equal or
      exceed 2.50 to 1.0 and such additional Indebtedness can be incurred under
      paragraph (a) of Section 10.09 then, notwithstanding the $75,000,000
      limitation set forth in clause (xiv) of the definition of "Permitted
      Indebtedness" set forth in this Section 1.01, the aggregate principal
      amount of Project Finance Indebtedness that may be secured under this
      clause (xii) shall not exceed (i) $250,000,000, if the Consolidated
      Interest Coverage Ratio (after giving pro forma effect to the incurrence
      of such Project Finance Indebtedness) shall be equal to or greater than
      3.00 to 1.0 but less than 4.00 to 1.0 or (ii) $400,000,000, if the
      Consolidated





                                      -19-
<PAGE>   26
      Interest Coverage Ratio (after giving pro forma effect to the incurrence
      of such Project Finance Indebtedness) shall be equal to or greater than
      4.00 to 1.0;

            (xiii) Liens securing Indebtedness of the Company or any
      Subsidiary; provided, that such Liens secure Indebtedness which, when
      combined with (a) the outstanding secured Indebtedness of the Company
      (other than Indebtedness secured by Liens described under clauses (ii),
      (iii), (x) and (xix) hereof), (b) all Indebtedness and the aggregate
      liquidation value of all preferred stock of any Subsidiary (other than a
      Non-Recourse Subsidiary) incurred and outstanding in accordance with
      Section 10.10 (other than of the type described in clauses (iii), (x),
      (xv) and (xix) hereof) and (c) the aggregate amount of all Capital Lease
      Obligations of the Company and the Subsidiaries, does not exceed 10% of
      the Consolidated Net Tangible Assets of the Company;

            (xiv)  Liens to secure any extension, renewal, refinancing or
      refunding (or successive extensions, renewals, refinancings or
      refundings), in whole or in part, of any Indebtedness secured by Liens
      referred to in the foregoing clauses (i), (ii), (iv) and (v); provided
      that such Lien does not extend to any other Property of the Company or
      any Subsidiary and the principal amount of the Indebtedness secured by
      such Lien is not increased;

            (xv)   Liens granted by a Non-Recourse Subsidiary securing
      Non-Recourse Indebtedness of such Non-Recourse Subsidiary and Liens on
      the Capital Stock of a NonRecourse Subsidiary securing Non-Recourse
      Indebtedness of such Non-Recourse Subsidiary;

            (xvi)  any charter or lease that would not constitute an Asset Sale
      pursuant to clause (ii)(d) of the definition of "Asset Sale" set forth in
      this Section 1.01;

            (xvii) leases or subleases of real property to other Persons;

            (xviii) Liens under the Safe Harbor Leases, the Letter of Credit
      Agreement and the Mortgage, as such terms are defined in, and as
      contemplated by, the Assets Purchase Agreement dated August 20, 1993,
      between the Company and Portal Rig Corporation, with respect to the
      Property being acquired pursuant to such Assets Purchase Agreement;

            (xix)  Liens on (a) up to eight submersible drilling rigs, owned by
      the Company or any Subsidiaries as of the Issue Date including any
      improvements on such rigs, provided, that the Company may from time to
      time designate one or more of such rigs as Property that is not, and will
      not be, subject to this clause (xix) by delivery of written notice of
      such designation to the Trustee under this Indenture, whereupon such
      designated rig or rigs shall cease to be covered by this clause (xix)
      and, if unencumbered by any Lien (other than Permitted Liens described in
      clauses (vii), (viii) and (ix) of this definition), the Appraised Value
      of such designated rig or rigs as of any Measurement Date shall be
      included in any





                                      -20-
<PAGE>   27
      determination of Consolidated Asset Coverage Ratio under this Indenture
      or (ii) the Property described in clause (ii)(l) of the definition of
      "Asset Sale" set forth in this Section 1.01; and

             (xx)  Liens resulting from the deposit of funds or evidences of
      Indebtedness in trust for the purpose of defeasing Indebtedness of the
      Company or any of the Subsidiaries.

            "Permitted Refinancing Indebtedness" means Indebtedness of the
Company or a Subsidiary, incurred in exchange for, or the proceeds of which are
used to renew, extend, refinance, refund or repurchase, outstanding
Indebtedness of the Company or any Subsidiary which outstanding Indebtedness
was incurred in accordance with, or is otherwise permitted by, the terms of
this Indenture, other than any such Indebtedness permitted pursuant to clause
(xi) of the definition of "Permitted Indebtedness" set forth in this Section
1.01; provided that (i) if the Indebtedness being renewed, extended,
refinanced, refunded or repurchased is pari passu with or subordinated in right
of payment to the Notes, then such new Indebtedness is pari passu with or
subordinated in right of payment to, as the case may be, the Notes at least to
the same extent as the Indebtedness being renewed, extended, refinanced,
refunded or repurchased, (ii) such new Indebtedness is scheduled to mature
later than the Indebtedness being renewed, extended, refinanced, refunded or
repurchased, (iii) such new Indebtedness has an Average Life at the time such
Indebtedness is incurred that is greater than the Average Life of the
Indebtedness being renewed, extended, refinanced, refunded or repurchased and
(iv) such new Indebtedness is in an aggregate principal amount (or, if such
Indebtedness provides for an amount less than the principal amount thereof to
be due and payable upon a declaration of acceleration of the maturity thereof,
the original issue price of such Indebtedness is) not in excess of the
aggregate principal amount then outstanding of the Indebtedness being renewed,
extended, refinanced, refunded or repurchased (or if the Indebtedness being
renewed, extended, refinanced, refunded or repurchased provides for an amount
less than the principal amount thereof to be due and payable upon a declaration
of acceleration of the maturity thereof, the original issue price of such
Indebtedness plus any accreted value attributable thereto since the original
issuance of such Indebtedness) plus the amount of any premium required to be
paid in connection therewith pursuant to the terms of such Indebtedness or the
amount of any premium reasonably determined by the Company or the Subsidiary,
as applicable, as necessary to accomplish the foregoing by means of a tender or
exchange offer or privately negotiated purchase, plus the amount of fees and
expenses in connection therewith; provided, further that Permitted Refinancing
Indebtedness shall not include (a) Indebtedness of a Subsidiary that is
incurred to renew, extend, refinance, refund or repurchase Indebtedness of the
Company and (b) Indebtedness (other than Non-Recourse Indebtedness of the
related Non-Recourse Subsidiary) that is incurred to renew, extend, refinance,
refund or repurchase Non-Recourse Indebtedness of such Non-Recourse Subsidiary.

            "Person" means any individual, corporation, partnership, joint
venture, limited liability company, joint- stock company, unincorporated
organization or government or any agency or political subdivision thereof.

            "Physical Notes" has the meaning specified in Section 2.01.





                                      -21-
<PAGE>   28
            "Predecessor Security" of any particular Note means every previous
Note evidencing all or a portion of the same debt as that evidenced by such
particular Note; and, for the purposes of this definition, any Note
authenticated and delivered under Section 3.07 in exchange for or in lieu of a
mutilated, lost, destroyed or stolen Note shall be deemed to evidence the same
debt as the mutilated, lost, destroyed or stolen Note.

            "Preferred Stock" means the $1.50 Convertible Preferred Stock of
the Company outstanding as of the Issue Date.

            "Project Finance Indebtedness" of a Person means any Indebtedness
the proceeds of which will be used solely to make capital expenditures to
repair, refurbish, upgrade or improve one or more drilling rigs owned or
acquired  (or to be owned or acquired) by such Person or an Affiliate thereof.

            "Property" means, with respect to any Person, any interest of such
Person in any kind of property or asset, whether real, personal or mixed, or
tangible or intangible, excluding Capital Stock in any other Person.

            "Purchase Notice" has the meaning given such term in Section
10.13(b).

            "Rating Agencies" has the meaning given such term in Section 10.19.

            "Record Date" for the interest payable on any Interest Payment Date
means the date specified in Section 3.08.

            "Redeemable Dividend" means, for any dividend payable by a Person
with regard to Redeemable Stock issued by it, the quotient of the dividend
divided by the difference between one and the maximum statutory Federal income
tax rate (expressed as a decimal number between 1 and 0) then applicable to
such Person.

            "Redeemable Stock" means, with respect to any Person, any equity
security that by its terms or otherwise is required to be redeemed, or is
redeemable at the option of the holder thereof, at any time prior to one year
following the Stated Maturity of the Notes or is exchangeable into Indebtedness
of such Person or any of its subsidiaries.

            "Redemption Date" when used with respect to any Note to be redeemed
shall mean the date fixed for such redemption pursuant to this Indenture.

            "Registrar" has the meaning given such term in Section 3.06.

            "Replacement Asset" means, with respect to any Asset Sale, a
Property or asset that, as determined by the Board of Directors as evidenced by
a Board Resolution, is used or useful in a line of business of the Company or
any Subsidiary existing on the Issue Date.





                                      -22-
<PAGE>   29
            "Repurchase Price" has the meaning given such term in Section
10.12.

            "Responsible Officer," when used with respect to the Trustee, means
the chairman or any vice-chairman of the board of directors, the chairman or
any vice-chairman of the executive committee of the board of directors, the
chairman of the trust committee, the president, any vice president, any
assistant vice president, the secretary, any assistant secretary, the
treasurer, any assistant treasurer, the cashier, any assistant cashier, any
trust officer or assistant trust officer, the controller or any assistant
controller or any other officer of the Trustee customarily performing functions
similar to those performed by any of the above designated officers and also
means, with respect to a particular corporate trust matter, any other officer
to whom such matter is referred because of such officer's knowledge of and
familiarity with the particular subject.

            "Restricted Payment" means to (i) declare or pay any dividend on,
or make any distribution in respect of, or purchase, redeem, retire or
otherwise acquire for value any Capital Stock of the Company or any Affiliate
of the Company, or warrants, rights or options to acquire such Capital Stock,
other than (a) dividends payable solely in the Capital Stock (other than
Redeemable Stock) of the Company or such Affiliate, as the case may be, or in
warrants, rights or options to acquire such Capital Stock and (b) dividends or
distributions by a Subsidiary to the Company or to a Wholly Owned Subsidiary
(except a Non-Recourse Subsidiary), (ii) make any principal payment on, or
redeem, repurchase, defease or otherwise acquire or retire for value, prior to
any scheduled principal payment, scheduled sinking fund payment or other stated
maturity, Indebtedness of the Company or any Subsidiary which is subordinated
in right of payment to the Notes or (iii) make any Investment (other than
Permitted Investments and Investments made by the Company in Wholly Owned
Subsidiaries (or any Person that will be a Wholly Owned Subsidiary as a result
of such Investment) except Non-Recourse Subsidiaries, or by a Subsidiary in the
Company or one or more Wholly owned Subsidiaries (or any Person that will be a
Wholly Owned Subsidiary as a result of such Investment) except Non-Recourse
Subsidiaries) in any Person.

            "Retired Indebtedness" has the meaning given such term in Section
10.08(e).

            "Retired Indebtedness or Stock" has the meaning given such term in
Section 10.10(v).

            "S&P" means Standard & Poor's Corporation and its successors.

            "Sale and Lease-Back Transaction" means, with respect to any
Person, any direct or indirect arrangement pursuant to which Property is sold
or transferred by such Person or a subsidiary of such Person and is thereafter
leased back from the purchaser or transferee thereof by such Person or one of
its subsidiaries.

            "Security Register" has the meaning specified in Section 3.06.

            "Special Payment Date" has the meaning specified in Section 3.08.





                                      -23-
<PAGE>   30
            "Special Record Date" for the payment of Defaulted Interest means a
date fixed by the Trustee pursuant to Section 3.08.

            "Stated Maturity," when used with respect to any Note or any
installment of interest thereon, means the date specified in such Note as the
fixed date on which the principal of such Note or such installment of interest
is due and payable.

            "Subordinated Indebtedness" means any Indebtedness of the Company
that is subordinated in right of payment to the Notes and does not mature prior
to one year following the Stated Maturity of the Notes.

            "subsidiary" means, with respect to any Person, (i) any corporation
more than 50% of the outstanding Voting Stock of which is owned, directly or
indirectly, by such Person, or by one or more other subsidiaries of such
Person, or by such Person and one or more other subsidiaries of such Person,
(ii) any general partnership, joint venture or similar entity, more than 50% of
the outstanding partnership or similar interests of which is owned, directly or
indirectly, by such Person, or by one or more other subsidiaries of such
Person, or by such Person and one or more other subsidiaries of such Person and
(iii) any limited partnership of which such Person or any subsidiary of such
Person is a general partner.

            "Subsidiary" means a subsidiary of the Company.

            "Surviving Entity" has the meaning specified in Section 8.01.

            "Suspended Covenants" has the meaning set forth in Section 10.19.

            "Transaction Date" has the meaning specified in this Section 1.01
under the definition of "Consolidated Interest Coverage Ratio."

            "Trigger Date" has the meaning specified in Section 10.13(b).

            "Trustee" means the Person named as the "Trustee" in the first
paragraph of this instrument until a successor Trustee shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Trustee" shall mean or include each Person who is such a successor Trustee.

            "Trust Indenture Act" means the Trust Indenture Act of 1939, as
amended by the Trust Indenture Reform Act of 1990, as in force at the date as
of which this instrument was executed, except as provided in Section 9.05.

            "U.S. Government Obligations" means securities that are (i) direct
obligations of the United States of America for the payment of which its full
faith and credit is pledged, (ii) obligations of a Person controlled or
supervised by and acting as an agency or instrumentality of the United





                                      -24-
<PAGE>   31
States of America the payment of which is unconditionally guaranteed as a full
faith and credit obligation by the United States of America, which, in either
case under clauses (i) or (ii) are not callable or redeemable at the option of
the issuer thereof or (iii) depository receipts issued by a bank or trust
company as custodian with respect to any such U.S. Government Obligations or a
specific payment of interest on or principal of any such U.S. Government
Obligation held by such custodian for the account of the holder of a depository
receipt; provided that (except as required by law) such custodian is not
authorized to make any deduction from the amount payable to the holder of such
depository receipt from any amount received by the custodian in respect of the
U.S. Government Obligation or the specific payment of interest on or principal
of the U.S. Government Obligation evidenced by such depository receipt.

            "Voting Stock" means, with respect to any Person, securities of any
class or classes of Capital Stock in such Person entitling the holders thereof
(whether at all times or at the times that such class of Capital Stock has
voting power by reason of the happening of any contingency) to vote in the
election of members of the board of directors (or comparable body) of such
Person.

            "Wholly Owned Subsidiary" means any Subsidiary of which 100% of the
total Voting Stock (other than directors' qualifying shares) is at the time
owned by the Company, either directly or indirectly through ownership of one or
more Subsidiaries.

            SECTION 1.02.   Incorporation by Reference to Trust Indenture Act.
Whenever this Indenture refers to a provision of the Trust Indenture Act, the
provision is incorporated by reference in and made a part of this Indenture.
The following Trust Indenture Act terms incorporated by reference in this
Indenture have the following meanings:

            "Bankruptcy Act" means the Bankruptcy Code.

            "indenture securities" means the Notes.

            "indenture security holder" means a Holder.

            "indenture to be qualified" means this Indenture.

            "indenture trustee" or "institutional trustee" means the Trustee.

            "obligor" on the indenture securities means the Company or any
other obligor on the Notes, if any.

            All other Trust Indenture Act terms used or incorporated by
reference in this Indenture that are defined by the Trust Indenture Act,
defined by Trust Indenture Act reference to another statute or defined by
Commission rule have the meanings assigned to them therein.





                                      -25-
<PAGE>   32
            SECTION 1.03.   Compliance Certificate and Opinions. Upon any
application or request by the Company to the Trustee to take any action under
any provision of this Indenture, the Company shall furnish to the Trustee an
Officers' Certificate stating that all conditions precedent, if any, provided
for in this Indenture relating to the proposed action have been complied with
and an Opinion of Counsel stating that in the opinion of such counsel all such
conditions precedent, if any, have been complied with, except that in the case
of any such application or request as to which the furnishing of such documents
is specifically required by any provision of this Indenture relating to such
particular application or request, no additional certificate or opinion need be
furnished.

            Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Indenture (other than the annual
certificate provided pursuant to Section 10.16) shall include:

            (1)    a statement that each individual signing such certificate or
      opinion has read such covenant, condition or provision and the
      definitions herein relating thereto;

            (2)    a brief statement as to the nature and scope of the
      examination or investigation upon which the statements or opinions
      contained in such certificate or opinion are based;

            (3)    a statement that, in the opinion of each such individual, he
      has made such examination or investigation as is necessary to enable him
      to express an informed opinion as to whether or not such covenant,
      condition or provision has been complied with; and

            (4)    a statement as to whether, in the opinion of each such
      individual, such covenant, condition or provision has been complied with.

            SECTION 1.04.   Form of Documents Delivered to Trustee.  In any
case where several matters are required to be certified by, or covered by an
opinion of, any specified Person, it is not necessary that all such matters be
certified by, or covered by the opinion of, only one such Person, or that they
be so certified or covered by only one document, but one such Person may
certify or give an opinion with respect to some matters and one or more other
such Persons as to other matters, and any such Person may certify or give an
opinion as to such matters in one or several documents.

            Any certificate or opinion of an officer of the Company may be
based, insofar as it relates to legal matters, upon a certificate or opinion
of, or representations by, counsel, unless such officer knows, or in the
exercise of reasonable care should know, that the certificate or opinion or
representations with respect to the matters upon which his or her certificate
or opinion is based are erroneous.  Any such certificate or Opinion of Counsel
may be based, insofar as it relates to factual matters, upon a certificate or
opinion of, or representations by, an officer or officers of the Company
stating that the information with respect to such factual matters is in the
possession of the Company,





                                      -26-
<PAGE>   33
unless such counsel knows, or in the exercise of reasonable care should know,
that the certificate or opinion or representations with respect to such matters
are erroneous.

            Where any Person is required to make, give or execute two or more
applications, requests, consents, certificates, statements, opinions or other
instruments under this Indenture, they may, but need not, be consolidated and
form one instrument.

            SECTION 1.05.   Acts of Holders.  (a) Any request, demand,
authorization, direction, notice, consent, waiver or other action provided by
this Indenture to be given or taken by Holders may be embodied in and evidenced
by one or more instruments of substantially similar tenor signed by such
Holders in person or by agent duly appointed in writing; and, except as herein
otherwise expressly provided, such action shall become effective when such
instrument or instruments are delivered to the Trustee and, where it is hereby
expressly required, to the Company.  Such instrument or instruments (and the
action embodied therein and evidenced thereby) are herein sometimes referred to
as the "Act" of the Holders signing such instrument or instruments.  Proof of
execution of any such instrument or of a writing appointing any such agent
shall be sufficient for any purpose of this Indenture and (subject to Section
6.01) conclusive in favor of the Trustee and the Company, if made in the manner
provided in this Section.

            (b)    The fact and date of the execution by any Person of any such
instrument or writing may be proved by the affidavit of a witness of such
execution or by an acknowledgment of a notary public or other officer
authorized by law to take acknowledgments of deeds, certifying that the
individual signing such instrument or writing acknowledged to him the execution
thereof. Where such execution is by a signer acting in a capacity other than
such signer's individual capacity, such certificate or affidavit shall also
constitute sufficient proof of the signer's authority. The fact and date of the
execution of any such instrument or writing, or the authority of the person
executing the same, may also be proved in any other manner which the Trustee
deems sufficient.

            (c)    The ownership of Notes shall be proved by the Security
Register.

            (d)    Any request, demand, authorization, direction, notice,
consent, waiver or other Act of the Holder of any Note shall bind every future
Holder of the same Note and the Holder of any Note issued upon the registration
of transfer thereof or in exchange therefor or in lieu thereof in respect of
anything done, suffered or omitted to be done by the Trustee or the Company in
reliance thereon, whether or not notation of such action is made upon such
Note.

            (e)    The Company may, but shall not be obligated to, fix a record
date for the purpose of determining the Holders entitled to take any action
under this Indenture by vote or consent. Such record date shall be the later of
30 days prior to the first solicitation of such consent or vote or the date of
the most recent list of Holders furnished to the Trustee pursuant to Section
7.01 prior to such solicitation. If a record date is fixed, those persons who
were Holders of Notes at such record date (or their duly designated proxies),
and only those persons, shall be entitled to take such action by vote or
consent or to revoke any vote or consent previously given, whether or not such





                                      -27-
<PAGE>   34
persons continue to be Holders after such record date; provided, however, that
unless such vote or consent is obtained from the Holders (or their duly
designated proxies) of the requisite principal amount of Notes that are
Outstanding prior to the date which is the 120th day after such record date,
any such vote or consent previously given shall automatically and without
further action by any Holder be cancelled and of no further effect.

            SECTION 1.06.   Notices, etc., to Trustee and Company.  Except as
otherwise provided in Article V, any request, demand, authorization, direction,
notice, consent, waiver or other Act of Holders or other document provided or
permitted by this Indenture to be made upon, given or furnished to, or filed
with,

            (1)    the Trustee by any Holder or by the Company shall be
      sufficient for every purpose hereunder if made, given, furnished or filed
      in writing to or with the Trustee at its Corporate Trust office,
      Attention of Vice President, Corporate Trust Department, or

            (2)    the Company by the Trustee or by any Holder shall be
      sufficient for every purpose hereunder (unless otherwise herein expressly
      provided) if in writing and by certified mail, to the Company addressed
      to it at the address of its principal office specified in the first
      paragraph of this instrument or at any other address previously furnished
      in writing to the Trustee by the Company, Attention of President.

            SECTION 1.07.   Notice to Holders; Waiver.  Where this Indenture
provides for the giving of notice to Holders of any event, such notice shall be
sufficiently given (unless otherwise herein expressly provided) if in writing
and mailed, first-class postage prepaid, to each Holder affected by such event,
at such Holder's address as appears in the Security Register, not later than
the latest date, and not earlier than the earliest date, prescribed for the
giving of such notice.  In any case where notice to Holders is given by mail,
neither the failure to mail such notice, nor any defect in any notice so
mailed, to any particular Holder shall affect the sufficiency of such notice
with respect to other Holders.  Where this Indenture provides for notice in any
manner, such notice may be waived in writing by the Person entitled to receive
such notice, either before or after the event, and such waiver shall be the
equivalent of such notice.  Waivers of notice by Holders shall be filed with
the Trustee, but such filing shall not be a condition precedent to the validity
of any action taken in reliance upon such waiver.

            In the event of suspension of regular mail service or for any other
reason it shall be impracticable to give such notice by mail, then such a
notification as shall be made with the approval of the Trustee shall constitute
a sufficient notification for every purpose hereunder.

            SECTION 1.08.   Conflict with Trust Indenture Act.  If and to the
extent that any provision hereof limits, qualifies or conflicts with the duties
imposed by, or with another provision (an "incorporated provision") included
in, this Indenture by operation of, Sections 310 through 318, inclusive, of the
Trust Indenture Act, such imposed duties or incorporated provision shall
control.





                                      -28-
<PAGE>   35
            SECTION 1.09.   Effect of Headings and Table of Contents. The
Article and Section headings herein and the Table of Contents are for
convenience of reference only and shall not affect the construction hereof.

            SECTION 1.10.   Successors and Assigns.  All covenants and
agreements in this Indenture by the Company shall bind its successors and
assigns, whether so expressed or not.

            SECTION 1.11.   Severability Clause.  In case any provision in this
Indenture or in the Notes shall be invalid, illegal or unenforceable to the
extent permitted by law, the validity, legality and enforceability of the
remaining provisions shall not in any way be affected or impaired thereby.

            SECTION 1.12. Benefits of Indenture.  Nothing in this Indenture or
in the Notes, express or implied, shall give to any Person, other than the
parties hereto and their successors hereunder, any Paying Agent and the
Holders, any benefit or any legal or equitable right, remedy or claim under
this Indenture.

            SECTION 1.13.   Governing Law; Submission to Jurisdiction.  THIS
INDENTURE AND THE NOTES SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH
THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO APPLICABLE
PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS
OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY. THE COMPANY HEREBY
IRREVOCABLY SUBMITS TO THE NONEXCLUSIVE JURISDICTION OF THE UNITED STATES
DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW YORK AND OF ANY NEW YORK STATE
COURT SITTING IN NEW YORK CITY FOR PURPOSES OF ALL LEGAL PROCEEDINGS ARISING
OUT OF OR RELATING TO THIS INDENTURE OR THE TRANSACTIONS CONTEMPLATED HEREBY.
THE COMPANY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ANY
OBJECTION WHICH IT MAY NOW OR HEREAFTER HAVE TO THE LAYING OF THE VENUE OF ANY
SUCH PROCEEDING BROUGHT IN SUCH A COURT AND ANY CLAIM THAT ANY SUCH PROCEEDING
BROUGHT IN SUCH A COURT HAS BEEN BROUGHT IN AN INCONVENIENT FORUM.

            SECTION 1.14.   Legal Holidays.  In any case where any Interest
Payment Date, Change of Control Payment Date, Asset Sale Offer Date, Stated
Maturity or other payment date of any of the Notes shall not be a Business Day,
then (notwithstanding any other provision of this Indenture or of the Notes)
payment of interest on or principal of (and premium, if any, on) such Note need
not be made on such payment date, but may be made on the next succeeding
Business Day with the same force and effect as if made on such payment date,
and no interest shall accrue for the period from and after such payment date.





                                      -29-
<PAGE>   36
                                   ARTICLE II

                                 Form of Notes

            SECTION 2.01.   Forms Generally.  The Notes (including the
Trustee's certificate of authentication) shall be issued initially in the form
of one or more Global Notes duly executed by the Company and authenticated by
the Trustee as hereinafter provided in substantially the forms set forth in
Sections 2.02 and 2.03 and deposited with the Trustee, as custodian for the
Depository.  Subject to the limitations set forth in Section 3.13, the
principal amount of the Global Notes may be decreased by adjustments made in
accordance with the standing instructions and procedures existing between the
Depository and the Trustee.  Global Notes shall bear a legend in substantially
the following form:

      "This Note is a Global Note within the meaning of the Indenture
      hereinafter referred to and is registered in the name of a
      Depository or a nominee thereof. This Note may not be transferred
      to, or registered or exchanged for Notes registered in the name of,
      any Person other than the Depository or a nominee thereof and no
      such transfer may be registered, except in the limited circumstances
      described in the Indenture. Every Note authenticated and delivered
      upon registration of transfer of, or in exchange for or in lieu of,
      this Note shall be a Global Note subject to the foregoing, except in
      such limited circumstances."

            Notes (including the Trustees' certificate of authentication)
authenticated and delivered pursuant to Section 3.13(d) hereof shall be issued
in the form of permanent certificated securities in registered form in
substantially the form set forth in Sections 2.02 and 2.03 (the "Physical
Notes").

            All Notes (including the Trustee's certificate of authentication)
shall be in substantially the forms set forth in this Article, with such
appropriate insertions, omissions, substitutions and other variations as are
required or permitted by this Indenture and may have such letters, CUSIP or
other numbers or other marks of identification and such legends or endorsements
placed thereon as may be required to comply with the rules of any securities
exchange or market, or as may, consistent herewith, be determined by the
officers executing such Notes, as evidenced by their execution of the Notes.

            The definitive Notes shall be printed, lithographed or engraved or
produced by any combination of these methods on steel engraved borders or may
be produced in any other manner permitted by the rules of any securities
exchange on which the Notes may be listed, all as determined by the officers
executing such Notes, as evidenced by their execution of the Notes.





                                      -30-
<PAGE>   37
            SECTION 2.02.   Form of Note.  Each Note shall be in substantially
the following form.

                                 (Face of Note)

                           NOBLE DRILLING CORPORATION

                          9-1/8% Senior Notes due 2006

No. _______________                                          $__________________

            NOBLE DRILLING CORPORATION, a corporation duly organized and
existing under the laws of the State of Delaware (the "Company," which term
includes any successor corporation under the Indenture hereinafter referred
to), for value received, hereby promises to pay to ____________________________
or registered assigns, the principal amount of ___________________ DOLLARS on
              2006 and to pay interest on such principal amount at the rate
of 9-1/8% per annum from July 1, 1996, or from the most recent Interest
Payment Date to which interest has been paid or duly provided for, semiannually
on January 1 and July 1 of each year until the principal hereof is paid or made
available for payment.  The interest so payable, and punctually paid or duly
provided for, on any Interest Payment Date will, subject to certain exceptions
provided in the Indenture referred to on the reverse hereof, be paid to the
person in whose name this Note (or the Note in exchange or substitution for
which this Note was issued) is registered at the close of business on the
Record Date for interest payable on such Interest Payment Date.  The Record
Date for any interest payment is the close of business on the December 15 or
June 15, as the case may be, whether or not a Business Day, immediately
preceding the Interest Payment Date on which such interest is payable.  Any
such interest not so punctually paid or duly provided for shall forthwith cease
to be payable to the Holder on such Record Date and shall be paid as provided
in the Indenture.  The principal of (and premium, if any) and interest on this
Note are payable at the office or agency of the Company in the Borough of
Manhattan, The City of New York, in such coin or currency of the United States
of America as at the time of payment is legal tender for the payment of public
and private debts; provided that interest may be payable, at the option of the
Company, by check mailed to the address of the person entitled thereto as such
address shall appear on the registry books of the Company.

            Reference is hereby made to the further provisions of this Note set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

            Unless the certificate of authentication hereon has been duly
executed by the Trustee referred to on the reverse hereof by manual signature,
this Note shall not be entitled to any benefit under the Indenture or be valid
or obligatory for any purposes.

            IN WITNESS WHEREOF, the Company has caused this Note to be duly
executed under its corporate seal.





                                      -31-
<PAGE>   38

Dated:                               NOBLE DRILLING CORPORATION,

                          
                                     by _______________________________________
                                        Title:
[Corporate Seal]          
                          
Attest:                   

__________________________________
Treasurer
 
                               (Reverse of Note)

            1.    This Note is one of a duly authorized issue of debt
securities of the Company designated as its "9-1/8% Senior Notes due 2006"
(herein called the "Notes") limited in aggregate principal amount to
$125,000,000, issued and to be issued in a single series under an indenture
dated as of July 1, 1996 (as amended or supplemented from time to time, the
"Indenture"), between the Company and Texas Commerce Bank National Association,
as trustee (the "Trustee," which term includes any successor Trustee under the
Indenture), to which Indenture reference is hereby made for a statement of the
respective rights, limitations of rights, duties and immunities thereunder of
the Company, the Trustee and each of the Holders of the Notes and of the terms
upon which the Notes are, and are to be, authenticated and delivered.  All
terms used in this Note which are not defined herein shall have the meanings
assigned to them in the Indenture.

            2.    Interest on this Note will be computed on the basis of a
360-day year of twelve 30-day months.  Each payment of interest in respect of
an Interest Payment Date will include interest accrued through the day before
such Interest Payment Date.  If an Interest Payment Date falls on a day that is
not a Business Day, the interest payment to be made on such Interest Payment
Date will be made on the next succeeding Business Day with the same force and
effect as if made on such Interest Payment Date, and no additional interest
will accrue as a result of such delayed payment.  Defaulted Interest shall bear
interest, to the extent lawful, at the rate set forth on the face of the Notes.

            3.    Upon the occurrence of a Change of Control, and subject to
certain limitations, the Holder of this Note may require the Company to
repurchase this Note at a price equal to 101% of the principal amount hereof
plus accrued and unpaid interest hereon, if any, to the Change of Control
Payment Date.  The Company is required to give Holders notice of such right of
repurchase within 30 calendar days subsequent to the date of any Change of
Control.  Holders are required to tender their Notes for repurchase on or prior
to the close of business on the Change of Control Payment Date.  In addition,
under certain circumstances, the Company will be required to make an offer to
repurchase Notes, at par plus accrued interest, from certain proceeds of Asset
Sales,





                                      -32-
<PAGE>   39
to the extent described in the Indenture.  The Holder's right of repurchase
referred to in this paragraph is as provided in and subject to the terms of the
Indenture.

            4.    The Notes may not be redeemed prior to July 1, 2001.  On or
after such date, the Notes may be redeemed at the election of the Company as a
whole at any time or in part from time to time at the Redemption Prices
(expressed in percentages of principal amount) set forth below plus accrued
interest to the Redemption Date, if redeemed during the 12-month period
beginning                , of the years indicated below:

<TABLE>
<CAPTION>
                  Year                           Redemption Price
                  ----                           ----------------
                  <S>                                <C>
                  2001                               104.563%
                  2002                               103.042%
                  2003                               101.521%
                  2004 and thereafter                100.00%
</TABLE>

            5.    Notice of redemption will be mailed at least 30 days but
not more than 60 days before the Redemption Date to each Holder of Notes to be
redeemed, at such Holder's registered address.  Notes in denominations larger
than $1,000 may be redeemed in part but only in whole multiples of $1,000. On
and after the Redemption Date interest ceases to accrue on Notes or portions
of them called for redemption.

            6.    The Notes are not entitled to the benefit of any mandatory
sinking fund payments.

            7.    If an Event of Default shall have occurred and be continuing,
the principal of all the Notes may be declared due and payable in the manner
and with the effect provided in the Indenture.

            8.    The Indenture permits, with certain exceptions as therein
provided, the amendment thereof and the modification of the rights and
obligations of the Company and the rights of the Holders to be affected under
the Indenture at any time by the Company and the Trustee with the consent of
the Holders of not less than a majority in aggregate principal amount of the
Notes at the time Outstanding.  The Indenture also contains provisions
permitting the Holders of specific percentages in aggregate principal amount of
the Notes Outstanding, on behalf of the Holders of all the Notes, to waive
compliance by the Company with certain provisions of the Indenture and certain
past defaults under the Indenture and their consequences.  Any such consent or
waiver by the Holder of this Note shall be conclusive and binding upon such
Holder and upon all future Holders of this Note and of any Note issued upon the
registration of transfer hereof or in exchange herefor or in lieu hereof,
whether or not notation of such consent or waiver is made upon this Note.

            9.    Holders may not enforce their rights pursuant to the
Indenture or the Notes except as provided in the Indenture.  No reference
herein to the Indenture and no provision of this Note or of the Indenture shall
alter or impair the obligation of the Company, which is absolute and





                                      -33-
<PAGE>   40
unconditional, to pay the principal of (and premium, if any) and interest on
this Note at the times, place and rate, and in the coin or currency, herein
prescribed.

           10.    The Indenture imposes certain limitations on the
ability of the Company and the Subsidiaries to, among other things, make
certain Investments and other Restricted Payments, pay dividends and other
distributions, create or incur Indebtedness, enter into or permit certain
transactions with Affiliates, create or incur Liens, enter into or permit
certain Sale and Lease-Back Transactions or merge or consolidate with or into,
or sell, lease or otherwise transfer their Property to, any other Person.

           11.    As provided in the Indenture and subject to certain
limitations therein set forth, the transfer of this Note shall be registered in
the Security Register, upon surrender of this Note for registration of transfer
at the office or agency of the Company in the Borough of Manhattan, The City of
New York, duly endorsed by, or accompanied by a written instrument of transfer
in form satisfactory to the Company, the Trustee and the Registrar, duly
executed by the Holder hereof or such Holder's attorney duly authorized in
writing, and thereupon one or more new Notes, of authorized denominations and
for the same aggregate principal amount, will be issued to the designated
transferee or transferees.

           12.    The Notes are only issuable without coupons and in
registered form in denominations of $1,000 and any larger amount that is an
integral multiple of $1,000.  As provided in the Indenture and subject to
certain limitations therein set forth, Notes are exchangeable for a like
aggregate principal amount of Notes of different authorized denominations.

           13.    No service charge shall be made for any registration of
transfer or exchange, but the Company may require payment by the Holder of a
sum sufficient to cover any tax or other governmental charge payable in
connection therewith.

           14.    Prior to due presentment of this Note for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Note is registered as the owner hereof
for all purposes, whether or not this Note be overdue, and neither the Company,
the Trustee nor any such agent shall be affected by notice to the contrary.

           15.    Pursuant to a recommendation promulgated by the Committee
on Uniform Security Identification Procedures, the Company has caused CUSIP
numbers to be printed on the Notes as a convenience to the Holders thereof.
No representation is made as to the accuracy of such numbers as printed on the
Notes and reliance may be placed only on the other identifying information
printed hereon.

           16.    This Note shall be governed by and construed in accordance
with the laws of the State of New York without regard to conflicts of law
principles.





                                      -34-
<PAGE>   41
           THE COMPANY WILL FURNISH TO ANY HOLDER WITHOUT CHARGE UPON WRITTEN
REQUEST A COPY OF THE INDENTURE. REQUESTS MAY BE MADE TO NOBLE DRILLING
CORPORATION, 10370 RICHMOND AVENUE, SUITE 400, HOUSTON, TEXAS 77042, ATTENTION:
SENIOR VICE PRESIDENT-FINANCE.

                                   ASSIGNMENT
                    (To be executed by the registered holder
                 if such holder desires to transfer this Note)

FOR VALUE RECEIVED __________________________________ hereby sells, assigns and
transfers unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
TAX IDENTIFYING NUMBER OF TRANSFEREE

________________________________________________________________________________

________________________________________________________________________________
                (Please print name and address of transferee)


________________________________________________________________________________
this Note, together with all right, title and interest herein, and does hereby
irrevocably constitute and appoint ______________________ Attorney to transfer
this Note on the Security Register, with full power of substitution.

Dated: _______________________    ______________________________________________
                                  Signature
                                                  
                                  ______________________________________________
                                  Signature Guarantee
                                  (all signatures must be guaranteed by a
                                  member of a national securities exchange or
                                  of the National Association of Securities
                                  Dealers, Inc. or by a commercial bank or
                                  trust company located in the United States)
                                  
NOTICE:  The signature to the foregoing Assignment must correspond to the name
as written upon the face of this Note in every particular, without alteration
or any change whatsoever.


                    ELECTION OF HOLDER TO REQUIRE REPURCHASE

          1.     Pursuant to Section 10.12 or 10.13 of the Indenture, as
applicable, the undersigned hereby elects to have this Note repurchased by the
Company.

          2.     The undersigned hereby directs the Trustee or Paying Agent to
pay it or _________________________________________________ an amount in cash
equal to (i) 101% of the principal amount hereof plus accrued and unpaid
interest, if any, hereon to the Change of Control Payment Date, if this Note is
repurchased pursuant to Section 10.12 of the Indenture, or (ii) 100% of the
principal amount hereof plus accrued and unpaid interest, if any, hereon to the
Net Proceeds Offer Date, if this Note is repurchased pursuant to Section 10.13
of the Indenture.





                                      -35-
<PAGE>   42

Dated: ______________________     ______________________________________________
                                  Signature
                           
                                  ______________________________________________
                                  Signature Guarantee
                                  (all signatures must be guaranteed by a
                                  member of a national securities exchange or
                                  of the National Association of Securities
                                  Dealers, Inc. or by a commercial bank or
                                  trust company located in the United States)

NOTICE:  The signature to the foregoing Election must correspond to the Name as
written upon the face of this Note in every particular, without alteration or
any change whatsoever.

                 SECTION 2.03.   Form of Trustee's Certificate of
Authentication. The Trustee's certificate of authentication on each Note shall
be in substantially the following form:

                         CERTIFICATE OF AUTHENTICATION

                 This is one of the 9-1/8% Senior Notes due 2006 issued under
the Indenture referred to in this Note.

                                      Texas Commerce Bank
                                      National Association, as
                                      Trustee,
                                    
                                    
                                      by _______________________________________
                                         Authorized Signatory


                                  ARTICLE III

                                   The Notes

                 SECTION 3.01.   Title and Terms.  The aggregate principal
amount of Notes Outstanding at any time may not exceed the amount of
$125,000,000, except for Notes authenticated and delivered upon registration of
transfer of, or in exchange for, or in lieu of, other Notes pursuant to Section
3.04, 3.06, 3.07, 9.06, 10.12, 10.13 or 11.06.

                 The Notes shall be issued in a single series, known and
designated as the "9-1/8% Senior Notes due 2006" of the Company.  The Stated
Maturity for the payment of principal of the Notes shall be July 1, 2006, and
the Notes shall bear interest at 9-1/8% per annum from July 1, 1996





                                      -36-
<PAGE>   43
or from the most recent Interest Payment Date to which interest has been paid
thereon or duly provided for, payable semiannually on January 1 and July 1 of
each year (commencing January 1, 1997) until the principal thereof is paid or
duly provided for.

                 The principal of (and premium, if any) and interest on the
Notes shall be payable at the office or agency of the Company in the Borough of
Manhattan, The City of New York, maintained for such purpose and at any other
office or agency maintained by the Company for such purpose; provided, however,
that interest may be payable at the option of the Company by check mailed to
the address of the person entitled thereto as such address shall appear on the
Security Register.

                 SECTION 3.02.   Authorized Denominations.  The Notes shall be
issuable in denominations of $1,000 and any integral multiple thereof.

                 SECTION 3.03.   Execution, Authentication, Delivery and
Dating.  The Notes shall be executed on behalf of the Company by its Chairman
of the Board, its President, a Vice Chairman or one of its Vice Presidents,
under its corporate seal reproduced or imprinted on the Notes by facsimile or
otherwise, and shall be attested by the Company's Secretary or one of its
Assistant Secretaries or its Treasurer or one of its Assistant Treasurers, in
each case by manual or facsimile signature.

                 In the event that any of the Notes shall have been signed
(either manually or by facsimile) by a Person that shall have ceased to be an
appropriate officer of the Company before any such Notes shall have been
authenticated and delivered by the Trustee, or disposed of by the Company, such
Notes nevertheless may be authenticated and delivered or disposed of as though
the Person who signed such Notes had not ceased to be such appropriate officer
of the Company, and any Note may be signed on behalf of the Company by such
Persons as, at the actual time of execution of such Note, shall be the proper
officers of the Company, although at the date of such Note or of the execution
of this instrument such Person was not such officer.

                 At any time after the execution and delivery of this
Indenture, the Company may deliver Notes executed by the Company to the Trustee
for authentication, together with a Company Order for the authentication and
delivery of such Notes; and the Trustee in accordance with such Company order
shall authenticate and deliver such Notes as in this Indenture provided.

                 The Notes may contain such notations, legends or endorsements
required by law, stock exchange rule or usage.  Each Note shall be dated the
date of its authentication.

                 A Note shall not be valid or entitled to any benefit under
this Indenture or obligatory for any purpose unless executed and issued by the
Company and authenticated by the manual signature of the Trustee as provided
herein.  The signature of the Trustee shall be conclusive evidence, and the
only evidence, that the Note has been authenticated and delivered under this
Indenture.





                                      -37-
<PAGE>   44
                 SECTION 3.04.   Temporary Notes.  Pending the preparation of
definitive Notes, the Company may execute, and upon Company Order the Trustee
shall authenticate and deliver, temporary Notes which are printed,
lithographed, or otherwise produced, in any authorized denomination,
substantially of the tenor of the definitive Notes in lieu of which they are
issued and with such appropriate insertions, omissions, substitutions and other
variations as the officers executing such Notes may determine, as conclusively
evidenced by their execution of such Notes.

                 If temporary Notes are issued, the Company shall cause
definitive Notes to be prepared without unreasonable delay, except that any
Global Notes issued pursuant to Section 3.01 may be held in temporary form
unless and until a transfer of Physical Notes is proposed to be made in
accordance with Section 3.13.  After the preparation of definitive Notes, the
temporary Notes shall be exchangeable for definitive Notes upon surrender of
the temporary Notes at any office or agency of the Company designated pursuant
to Section 10.02, without charge to the Holder.  Upon surrender for
cancellation of any one or more temporary Notes, the Company shall execute and
the Trustee shall authenticate and deliver in exchange therefor a like
principal amount of definitive Notes of authorized denominations.  Until so
exchanged, the temporary Notes shall in all respects be entitled to the same
benefits under this Indenture as definitive Notes.

                 SECTION 3.05.   Paying Agent To Hold Money in Trust.  The
Company shall cause each Paying Agent other than the Trustee to execute and
deliver to the Trustee an instrument in which such Paying Agent shall agree
that such Paying Agent will:

                 (1)      hold in trust for the benefit of the Holders or the
         Trustee all money held by the Paying Agent for the payment of
         principal of (and premium, if any) or interest on the Notes until such
         money shall be paid to the Holders or otherwise disposed of as
         provided herein;

                 (2)      give the Trustee notice of any Default by the Company
         (or any other obligor on the Notes) in the making of any such payment;
         and

                 (3)      at any time during the continuance of any such
         Default, upon the written request of the Trustee, forthwith pay to the
         Trustee all sums so held in trust by such Paying Agent and account for
         any funds disbursed; and, upon such payment and accounting by any
         Paying Agent to the Trustee, such Paying Agent shall be released from
         all further liability with respect to such money.

                 If the Company, any Subsidiary or any of their Affiliates acts
as Paying Agent, it shall segregate all money held by it hereunder in a
separate trust for the benefit of Holders.

                 SECTION 3.06.   Registrar; Registration, Registration of
Transfer and Exchange.  The Company shall maintain an office or agency where
the Notes may be presented for registration of transfer or for exchange.  The
Company shall cause to be kept at such office a register (the register
maintained in such office and in any other office or agency designated pursuant
to Section 10.02





                                      -38-
<PAGE>   45
being herein sometimes referred to as the "Security Register") in which,
subject to such reasonable regulations as it may prescribe, the Company shall
provide for the registration of Notes and of transfers of Notes entitled to be
registered or transferred as provided herein.  The Trustee, at its Corporate
Trust office, is initially appointed "Registrar" for the purpose of registering
Notes and transfers of Notes as herein provided.  The Company may, upon written
notice to the Trustee, change the designation of the Trustee as Registrar and
appoint another Person to act as Registrar for purposes of this Indenture.  If
any Person other than the Trustee acts as Registrar, the Trustee shall have the
right at any time, upon reasonable notice, to inspect or examine the Security
Register and to make such inquiries of the Registrar as the Trustee shall in
its discretion deem necessary or desirable in performing its duties hereunder.

                 The Company shall enter into an appropriate agency agreement
with any Person designated by the Company as Registrar or Paying Agent that is
not a party to this Indenture, which agreement shall incorporate the provisions
of the Trust Indenture Act and shall implement the provisions of this Indenture
that relate to such Registrar or Paying Agent.  Prior to the designation of any
such Person, the Company shall, by written notice (which notice shall include
the name and address of such Person), inform the Trustee of such designation.
If the Company fails to maintain a Registrar or Paying Agent, the Trustee shall
act as such.

                 Upon surrender for registration of transfer of any Note at an
office or agency of the Company designated pursuant to Section 10.02 for such
purpose, the Company shall execute, and the Trustee shall authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Notes of any authorized denomination or denominations, of like tenor and
aggregate principal amount, all as requested by the transferor.

                  Any beneficial owner of an interest in the Global Note shall,
by acceptance of such Global Note, agree that transfers of beneficial interests
in such Global Note may be effected only through a book-entry system maintained
by the Holder of such Global Note (or its agent), and that ownership of a
beneficial interest in the Notes shall be reflected in book-entry form.

                 At the option of the Holder, Notes may be exchanged for other
Notes of any authorized denomination or denominations, of a like aggregate
principal amount, upon surrender of the Notes to be exchanged at such office or
agency, and upon payment, if the Company shall so require, of the charges
hereinafter provided.  Whenever any Notes are so surrendered for exchange, the
Company shall execute, and the Trustee shall authenticate and deliver, the
Notes which the Holder making the exchange is entitled to receive.

                 All Notes issued upon any registration of transfer or exchange
of Notes shall be the valid obligations of the company, evidencing the same
debt, and entitled to the same benefits under this Indenture, as the Notes
surrendered upon such registration of transfer or exchange.

                 Every Note presented or surrendered for registration of
transfer or for exchange shall (if so required by the Company, the Trustee or
the Registrar) be duly endorsed, or be accompanied





                                      -39-
<PAGE>   46
by a duly executed instrument of transfer in form satisfactory to the Company,
the Trustee and the Registrar, by the Holder thereof or such Holder's attorney
duly authorized in writing.

                 No service charge shall be made for any registration of
transfer or exchange of Notes, but the Company may require payment by the
Holder of a sum sufficient to cover any tax or other governmental charge that
may be imposed in connection with any transfer, registration of transfer or
exchange of Notes, other than exchanges pursuant to Section 3.04 or 9.06 not
involving any transfer.

                 SECTION 3.07.   Mutilated, Destroyed, Lost and Stolen Notes.
If any mutilated Note is surrendered to the Trustee, the Company shall execute
and upon its written request the Trustee shall authenticate and deliver, in
exchange for any such mutilated Note, a new Note containing identical
provisions and of like principal amount, bearing a number not contemporaneously
outstanding.

                 If there shall be delivered to the Company and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Note
and (ii) such security or indemnity as may be required by them to save them and
any agent of each of them harmless, then, in the absence of notice to the
Company or the Trustee that such Note has been acquired by a bona fide
purchaser, the Company shall execute and upon its written request the Trustee
shall authenticate and deliver, in lieu of any such destroyed, lost or stolen
Note, a new Note containing identical provisions and of like principal amount,
bearing a number not contemporaneously outstanding.

                 In case any such mutilated, destroyed, lost or stolen Note has
become or is about to become due and payable, the Company in its discretion
may, instead of issuing a new Note, pay such Note.

                 Upon the issuance of any new Note under this Section 3.07, the
Company may require the payment by the Holder of a sum sufficient to cover any
tax or other governmental charge that may be imposed in relation thereto and
any other expenses (including the fees and expenses of the Trustee) connected
therewith.

                 Every new Note issued pursuant to this Section 3.07 in lieu of
any destroyed, lost or stolen Note shall constitute an original additional
contractual obligation of the Company, whether or not the destroyed, lost or
stolen Note shall be at any time enforceable by anyone, and shall be entitled
to all the benefits of this Indenture equally and proportionately with any and
all other Notes duly issued hereunder.

                 The provisions of this Section 3.07 are exclusive and shall
preclude (to the extent lawful) all other rights and remedies with respect to
the replacement or payment of mutilated, destroyed, lost or stolen Notes.





                                      -40-
<PAGE>   47
                 SECTION 3.08.   Payment of Interest; Interest Rights
Preserved.  Interest on any Note which is payable, and is punctually paid or
duly provided for, on any Interest Payment Date shall be paid to the Person in
whose name such Note (or one or more Predecessor Securities) is registered at
the close of business on the Record Date for such interest, which shall be the
December 15 or June 15 (whether or not a Business Day) immediately preceding
such Interest Payment Date.

                 Any interest on any Note which is payable, but is not
punctually paid or duly provided for, on any Interest Payment Date (herein
called "Defaulted Interest") shall forthwith cease to be payable to the
registered Holder on the relevant Record Date; and except as hereinafter
provided, such Defaulted Interest, and any interest payable on such Defaulted
Interest, may be paid by the Company, at its election as provided in clause (1)
or (2) below:

                 (1)      The Company may elect to make payment of any
         Defaulted Interest, and any interest payable on such Defaulted
         Interest, to the Persons in whose names the Notes (or their respective
         Predecessor securities) are registered at the close of business on a
         Special Record Date for the payment of such Defaulted Interest, which
         shall be fixed in the following manner.  The Company shall notify the
         Trustee in writing not less than 30 days prior to a Special Payment
         Date of the amount of Defaulted Interest and any interest payable on
         such Defaulted Interest proposed to be paid on the Notes and the date
         of the proposed payment (the "Special Payment Date"), and at the same
         time the Company shall deposit with the Trustee an amount of money
         equal to the aggregate amount proposed to be paid in respect of such
         Defaulted Interest and any interest payable on such Defaulted Interest
         or shall make arrangements satisfactory to the Trustee for such
         deposit on or prior to the Special Payment Date, such money when
         deposited to be held in trust for the benefit of the Persons entitled
         to such Defaulted Interest and any interest payable on such Defaulted
         Interest as provided in this clause.  Thereupon the Trustee shall fix
         a Special Record Date for the payment of such Defaulted Interest and
         any interest payable thereon which shall be not more than 15 days
         prior to the Special Payment Date and not less than the later of (x)
         10 days prior to the Special Payment Date and (y) 10 days after the
         receipt by the Trustee of the notice of the Special Payment Date.  The
         Trustee shall promptly notify the Company of such Special Record Date
         and, in the name and at the expense of the Company, shall cause notice
         of the Special Payment Date and the Special Record Date therefor to be
         mailed, first-class postage prepaid, to each Holder at such Holder's
         address as it appears in the Security Register, not less than 10 days
         prior to such Special Record Date.  Notice of the Special Payment Date
         and the Special Record Date therefor having been mailed as aforesaid,
         such Defaulted Interest and any interest payable thereon shall be paid
         to the Persons in whose names the Notes (or their respective
         Predecessor Securities) are registered at the close of business on
         such Special Record Date and shall no longer be payable pursuant to
         the following clause (2).

                 (2)      The Company may make payment of any Defaulted
         Interest, and any interest payable on such Defaulted Interest, on the
         Notes in any other lawful manner not inconsistent with the
         requirements of any securities exchange on which the Notes may be
         listed, and upon such notice as may be required by such exchange, if,
         after notice given by the Company to





                                      -41-
<PAGE>   48
         the Trustee of the Special Payment Date pursuant to this clause, such
         manner of payment shall be deemed practicable by the Trustee.

                 Subject to the foregoing provisions of this Section 3.08, each
Note delivered under this Indenture upon registration of transfer of or in
exchange for or in lieu of any other Note shall carry the rights to interest
accrued and unpaid, and to accrue, which were carried by such other Note.

                 SECTION 3.09.   Persons Deemed Owners.  Prior to due
presentment of a Note for registration of transfer, the Company, the Trustee
and any agent of the Company or the Trustee may treat the Person in whose name
such Note is registered as the owner of such Note for the purpose of receiving
payment of principal of (and premium, if any) and (subject to Section 3.08)
interest on such Note and for all other purposes whatsoever, whether or not
such Note be overdue, and neither the Company, the Trustee nor any agent of the
Company or the Trustee shall be affected by notice to the contrary.

                 SECTION 3.10.   Cancellation.  All Notes surrendered for
payment, registration of transfer or exchange shall, if surrendered to any
Person other than the Trustee, be delivered to the Trustee and shall be
promptly cancelled by it.  The Company may at any time deliver to the Trustee
for cancellation any Notes previously authenticated and delivered hereunder
which the Company may have acquired in any manner whatsoever, and all Notes so
delivered shall be promptly cancelled by the Trustee.  No Notes shall be
authenticated in lieu of or in exchange for any Notes cancelled as provided in
this Section 3.10, except as expressly permitted by this Indenture.  All
cancelled Notes held by the Trustee shall be retained by the Trustee unless by
a Company Order the Company shall direct that the cancelled Notes be returned
to it.

                 SECTION 3.11.   Computation of Interest.  Interest on the
Notes shall be computed on the basis of a year of twelve 30-day months.

                 SECTION 3.12.   CUSIP Number. The Company in issuing the Notes
may use a "CUSIP" number and, if so, the Trustee shall use the CUSIP number in
any notices to Holders as a convenience to such Holders; provided that any such
notice may state that no representation is made as to the correctness or
accuracy of the CUSIP number printed in the notice or on the Notes and that
reliance may be placed only on the other identification numbers printed on the
Notes.  The Company shall promptly notify the Trustee of any change in the
CUSIP number.

                 SECTION 3.13.   Book-Entry Provisions for Global Note.  (a)
The Global Note initially shall be registered in the name of the Depository for
such Global Note or the nominee of such Depository and be delivered to the
Trustee as custodian for such Depository.

                 (b)      Members of, or participants in, the Depository
("Agent Members") shall have no rights under this Indenture with respect to any
Global Note held on their behalf by the Depository, or the Trustee as its
custodian, or under the Global Note, and the Depository may be treated by the
Company, the Trustee and any agent of the Company or the Trustee as the
absolute owner of such





                                      -42-
<PAGE>   49
Global Note for all purposes whatsoever.  Notwithstanding the foregoing,
nothing herein shall prevent the Company, the Trustee or any agent of the
Company or the Trustee, from giving effect to any written certification, proxy
or other authorization furnished by the Depository or shall impair, as between
the Depository and its Agent Members, the operation of customary practices
governing the exercise of the rights of a holder of any Note.

                 (c)      Transfers of the Global Note shall be limited to
transfers of such Global Note in whole, but not in part, to the Depository, its
successors or their respective nominees.  Interests of beneficial owners in the
Global Note may be transferred in accordance with the rules and procedures of
the Depository.  As soon as practicable Physical Notes shall be transferred to
all beneficial owners in exchange for their beneficial interests in the Global
Note if, and only if, either (1) the Depository notifies the Company that it is
unwilling or unable to continue as depositary for the Global Note and a
successor depositary is not appointed by the Company within 90 days of such
notice, or (2) an Event of Default has occurred and is continuing and the
Registrar has received a request from the Depository to issue Physical Notes in
lieu of all or a portion of the Global Note (in which case the Company shall
deliver Physical Notes within 30 days of such request).

                 (d)      In connection with the transfer of the entire Global
Note to beneficial owners pursuant to this Section, the Global Note shall be
deemed to be surrendered to the Trustee for cancellation, and the Company shall
execute, and the Trustee shall authenticate and deliver, to each beneficial
owner or Agent Member identified by the Depository, in exchange for its
beneficial interest in the Global Note, an equal aggregate principal amount of
Physical Notes of authorized denominations.

                 (e)      The beneficial owners of the Global Note may grant
proxies and otherwise authorize any person, including Agent Members and persons
that may hold interests through Agent Members, to take any action which a
Holder is entitled to take under this Indenture or the Notes.


                                   ARTICLE IV

                           Satisfaction and Discharge

                 SECTION 4.01.   Satisfaction and Discharge of Indenture.  (a)
This Indenture shall cease to be of further effect (except that the Company's
obligations under Sections 4.03, 4.04 and 6.07 shall survive) when (i) all
Outstanding Notes theretofore authenticated and issued hereunder have been
delivered (other than any Notes which shall have been destroyed, lost or stolen
and which shall have been replaced or paid as provided in Section 3.07) to the
Trustee for cancellation and (ii) the Company shall have deposited with the
Trustee funds or U.S. Government Obligations in trust sufficient (without
consideration of interest income to be earned) to pay all sums payable
hereunder and under the Notes.





                                      -43-
<PAGE>   50
                 (b)      In addition to the provisions of Section 4.01(a), at
the Company's option, either (i) the Company shall be deemed to have been
Discharged from its obligations with respect to the Notes on the 91st day after
the applicable conditions set forth below have been satisfied or (ii) the
Company shall cease to be under any obligation to comply with any term,
provision or condition set forth in Section 8.01, Sections 10.07 to 10.15,
inclusive, Section 10.17, Section 10.18 and Sections 12.01 to 12.03, inclusive,
with respect to the Notes at any time after the applicable conditions set forth
below have been satisfied:

                 (A)      the Company shall have deposited or caused to be
         deposited irrevocably with the Trustee as trust funds in trust,
         specifically pledged as security for, and dedicated solely to, the
         benefit of the Holders (1) money, or (2) U.S. Government Obligations,
         which through the payment of interest and principal in respect thereof
         in accordance with their terms will provide (without any reinvestment
         of such interest or principal), not later than the opening of business
         at the Corporate Trust Office, on the due date of any payment, money
         or (3) a combination of (1) and (2), in an amount sufficient, in the
         opinion (with respect to (2) and (3)) of a nationally recognized firm
         of independent public accountants expressed in a written certification
         thereof delivered to the Trustee at or prior to the time of such
         deposit, to pay and discharge each installment of principal of, and
         interest on, the Outstanding Notes on the dates such installments of
         interest or principal are due;

                 (B)      the Company shall have delivered to the Trustee an
         Officers' Certificate certifying as to whether the Notes are then
         listed on the New York Stock Exchange;

                 (C)      if the Notes are then listed on the New York Stock
         Exchange, the Company shall have delivered to the Trustee an opinion
         of Counsel to the effect that the Company's exercise of its option
         under this Section would not cause such Notes to be delisted;

                 (D)      no Default or Event of Default with respect to this
         Indenture or the Notes shall have occurred and be continuing on the
         date of such deposit or shall occur as a result of such deposit and
         such deposit will not result in a breach or violation of, or
         constitute a default under, any other instrument to which the Company
         is a party or by which it is bound, as evidenced to the Trustee in an
         Officers' Certificate delivered to the Trustee concurrently with such
         deposit;

                 (E)      the Company shall have delivered to the Trustee an
         Opinion of Counsel to the effect that (and containing no qualification
         and no assumption, other than an assumption of fact customarily
         contained in legal opinions) Holders will not recognize income, gain
         or loss for Federal income tax purposes as a result of the Company's
         exercise of its option under this Section and will be subject to
         Federal income tax on the same amount and in the same manner and at
         the same time as would have been the case if such option had not been
         exercised, and, in the case of Notes being Discharged, accompanied by
         a ruling to that effect received from or published by the Internal
         Revenue Service (it being understood that (1) such Opinion shall also
         state that such ruling is consistent with the conclusions reached in
         such





                                      -44-
<PAGE>   51
         opinion and (2) the Trustee shall be under no obligation to
         investigate the basis or correctness of such ruling);

                 (F)      the Company shall have delivered to the Trustee an
         Opinion of Counsel to the effect that the company's exercise of its
         option under this Section will not result in any of the Company, the
         Trustee or the trust created by the Company's deposit hereunder
         becoming or being deemed to be an "investment company" under the
         Investment Company Act of 1940;

                 (G)      the Company shall have paid or duly provided for
         payment of all amounts then due to the Trustee pursuant to Section
         6.07;

                 (H)      the Company shall have delivered to the Trustee an
         officers' Certificate and an opinion of Counsel, each stating that all
         conditions precedent provided for herein relating to the satisfaction
         and discharge of this Indenture have been complied with; and

                 (I)      the Company shall have delivered to the Trustee an
         Opinion of Counsel to the effect that after the passage of 90 days
         after the deposit, the trust funds will not be subject to the effect
         of any applicable Federal or state bankruptcy, insolvency or similar
         law.

                 SECTION 4.02.   Deposited Moneys and U.S. Government
Obligations To Be Held in Trust.  All moneys and U.S. Government Obligations
deposited with the Trustee pursuant to Section 4.01 in respect of Notes shall
be held in trust and applied by it, in accordance with the provisions of the
Notes and this Indenture, to the payment, either directly or through any Paying
Agent (including the Company acting as its own Paying Agent) as the Trustee may
determine, to the Holders of all sums due and to become due thereon for
principal of (and premium if any) and interest on the Notes.

                 SECTION 4.03.   Repayment to Company.  The Trustee and any
Paying Agent shall promptly pay or return to the Company upon Company Request
any money or securities held by them at any time that are not required for the
payment of the principal of (and premium, if any) and interest on the Notes.

                 Any money deposited with the Trustee or any Paying Agent, or
then held by the Company, in trust for the payment of the principal of (or
premium, if any) or interest on any Note and remaining unclaimed for two years
after the date upon which such payment shall have become due, shall be paid to
the Company on Company Request or, if then held by the Company, shall be
discharged from such trust; provided, however, that the Company shall cause to
be published at least once in a newspaper of general circulation in The City of
New York or mailed to each Holder entitled to such unclaimed money, notice that
such money remains unclaimed and that, after a date specified therein, which
shall be a date not less than 30 days from the date of such publication or
mailing, any unclaimed balance of such money remaining as of such date shall be
repaid to the Company.  After repayment to the Company, any Holder entitled to
such money shall thereafter, as





                                      -45-
<PAGE>   52
an unsecured general creditor, look (unless an applicable law designates
another Person) only to the Company for payment, and all liability of the
Trustee or such Paying Agent with respect to such trust money, and all
liability of the Company as trustee thereof, shall thereupon cease.

                 SECTION 4.04.   Reinstatement.  If the Trustee is unable to
apply any money or U.S. Government Obligations in accordance with Section 4.01
by reason of any legal proceeding or by reason of any order or judgment of any
court or governmental authority enjoining, restraining or otherwise prohibiting
such application, the Company's obligations under this Indenture and the Notes
shall be revived and reinstated as though no deposit had occurred pursuant to
Section 4.01 until such time as the Trustee is permitted to apply all such
money or U.S. Government Obligations in accordance with Section 4.01; provided,
however, that if the Company has made any payment of interest on or principal
of any Notes because of the reinstatement of its obligations, the Company shall
be subrogated to the rights of the Holders to receive such payment from the
money or U.S. Government Obligations held by the Trustee.


                                   ARTICLE V

                                    Remedies

                 SECTION 5.01.   Events of Default. "Event of Default,"
wherever used herein with respect to the Notes, means any one of the following
events (whatever the reason for such event and whether it shall be voluntary or
involuntary or be effected by operation of law, pursuant to any judgment,
decree or order of any court or any order, rule or regulation of any
administrative or governmental body):

                 (1)      default in the payment of any installment of interest
         upon any Note when it becomes due and payable, and the continuance of
         such default for a period of 30 days; or

                 (2)      default in the payment of the principal of (or
         premium, if any, on) any Note at its Maturity, upon repurchase, upon
         redemption, upon acceleration or otherwise; or

                 (3)      the Company fails to comply with any of its covenants
         or agreements contained in Section 10.12 or fails to make an Asset
         Sale Offer in accordance with Section 10.13 and such failure continues
         for a period of five days; or

                 (4)      default in the performance, or breach, of any
         covenant or warranty of the Company in this Indenture (other than a
         covenant or warranty a default in whose performance or whose breach is
         elsewhere in this Section specifically dealt with) and continuance of
         such default or breach for a period of 30 days after written notice
         thereof has been mailed, by registered or certified mail, to the
         Company by the Trustee or to the Company and the Trustee by the
         Holders of at least 25% in principal amount of the





                                      -46-
<PAGE>   53
         Outstanding Notes, specifying such default or breach and requiring it
         to be remedied and stating that such notice is a "Notice of Default"
         hereunder; or

                 (5)      a default under any bond, debenture, note or other
         evidence of Indebtedness (other than Non- Recourse Indebtedness) of
         the Company or any Subsidiary, or under any mortgage, indenture or
         instrument under which there may be issued or by which there may be
         secured or evidenced any Indebtedness (other than Non- Recourse
         Indebtedness) of the Company or any Subsidiary, whether such
         Indebtedness now exists or shall hereafter be created, which default
         shall involve the failure to pay principal of such Indebtedness at the
         final maturity thereof or which shall have resulted in such
         Indebtedness becoming or being declared due and payable prior to the
         date on which it would otherwise become due and payable in an amount
         in excess of $10,000,000 for any Indebtedness individually or in the
         aggregate; or

                 (6)      the entry by a court of competent jurisdiction of one
         or more judgments or orders against the Company or any Subsidiary in
         an uninsured or unindemnified aggregate amount in excess of
         $10,000,000 which remain undischarged or unsatisfied for a period of
         60 consecutive days after the right to appeal them has expired; or

                 (7)      the entry of a decree or order for relief in respect
         of the Company or any Material Subsidiary by a court of competent
         jurisdiction in the premises in an involuntary case under the Federal
         bankruptcy laws, as now or hereafter constituted, or any other Federal
         or state bankruptcy, insolvency or other similar law, or appointing a
         receiver, liquidator, assignee, custodian, trustee, sequestrator (or
         other similar official) of the Company or any Material Subsidiary or
         of any substantial part of the Property of the Company or any Material
         Subsidiary, or ordering the winding up or liquidation of the affairs
         of the Company or any Material Subsidiary, and the continuance of any
         such decree or order unstayed and in effect for a period of 60
         consecutive days; or

                 (8)      (a) the commencement by the Company or any Material
         Subsidiary of a voluntary case under the Federal bankruptcy laws, as
         now or hereafter constituted, or any other applicable Federal or state
         bankruptcy, insolvency or other similar law, or (b) the consent by the
         Company or any Material Subsidiary to the entry of an order for relief
         in an involuntary case under any such law or to the appointment of a
         receiver, liquidator, assignee, custodian, trustee, sequestrator (or
         other similar official) of the Company or any Material Subsidiary or
         of any substantial part of the Property of the Company or any Material
         Subsidiary, or the making by the Company or any Material Subsidiary of
         an assignment for the benefit of creditors, or the admission by the
         Company or any Material Subsidiary in writing of its inability to pay
         its debts generally as they become due, or the taking of corporate
         action by the Company or any Material Subsidiary in furtherance of any
         such action.





                                      -47-
<PAGE>   54
                 SECTION 5.02.   Acceleration of Maturity; Rescission and
Annulment.  If an Event of Default (other than an Event of Default specified in
Sections 5.01(7) and 5.01(8)) occurs and is continuing, then and in every such
case the Trustee or the Holders of not less than 25% in principal amount of
Outstanding Notes may declare the unpaid principal of (and premium, if any) and
accrued and unpaid interest on all the Notes then Outstanding to be immediately
due and payable, by a notice in writing to the Company (and to the Trustee if
given by Holders), and, upon any such declaration, such principal amount (and
premium, if any) and accrued interest shall become and shall be immediately due
and payable, notwithstanding anything contained in this Indenture or the Notes
to the contrary.

                 If an Event of Default specified in Section 5.01(7) or 5.01(8)
occurs, all unpaid principal of (and premium, if any) and accrued and unpaid
interest on the Notes then Outstanding shall ipso facto become due and payable
without any declaration or other act on the part of the Trustee or any Holder.
Upon payment of such principal amount (and premium, if any) and interest, any
interest payable on overdue payments of principal (and premium, if any) or
interest (to the extent legally permissible) and all other obligations of the
Company under this Indenture and the Notes (including obligations under Section
6.07), all the Company's obligations under this Indenture and the Notes shall
terminate.

                 At any time after a declaration of acceleration with respect
to Notes has been made and before a judgment or decree for payment of the money
due has been obtained by the Trustee as hereinafter in this Article provided,
the Holders of a majority in principal amount of the Outstanding Notes, by
written notice to the Company and the Trustee, may rescind and annul such
declaration and its consequences if:

                 (1)      the Company has paid or deposited with the Trustee a
         sum sufficient to pay:

                          (A)     all overdue installments of interest on all
                 Notes,

                          (B)     the principal of (and premium, if any, on)
                 any Notes which have become due otherwise than by such
                 declaration of acceleration and interest thereon at the rate
                 or rates prescribed therefor in such Notes,

                          (C)     to the extent that payment of such interest
                 is lawful, interest on the Defaulted Interest at the rate or
                 rates prescribed therefor in the Notes and

                          (D)     all moneys paid or advanced by the Trustee
                 hereunder and the reasonable compensation, expenses,
                 disbursements and advances of the Trustee, its agents and
                 counsel required to be paid by the Company under this
                 Indenture;

                 and





                                      -48-
<PAGE>   55
                 (2)      all Events of Default with respect to the Notes,
         other than the non-payment of the principal of Notes which have become
         due solely by such declaration of acceleration, have been cured or
         waived as provided in Section 5.13.

No such rescission shall affect any subsequent Default or impair any right
consequent thereon.

                 SECTION 5.03.   Collection of Indebtedness and Suits for
Enforcement by Trustee.  The Company covenants that if an Event of Default
specified in Section 5.01(l) or 5.01(2) occurs the Company shall, upon demand
of the Trustee, pay to the Trustee, for the benefit of the Holders of such
Notes, the whole amount then due and payable on such Notes for principal (and
premium, if any) and interest and, to the extent that payment of such interest
shall be legally enforceable, interest upon the overdue principal (and premium,
if any) and upon overdue installments of interest, at the rate or rates
prescribed therefor in such Notes; and, in addition thereto, such further
amount as shall be sufficient to cover the costs and expenses of collection,
including the reasonable compensation, expenses disbursements and advances of
the Trustee, its agents and counsel.

                 If the Company fails to pay such amounts forthwith upon such
demand, the Trustee, in its own name and as trustee of an express trust, may
institute a judicial proceeding for the collection of the sums so due and
unpaid, and may prosecute such proceeding to judgment or final decree, and may
enforce the same against the Company or any other obligor upon such Notes and
collect the moneys adjudged or decreed to be payable in the manner provided by
law out of the Property of the Company or any other obligor upon such Notes,
wherever situated.

                 If an Event of Default with respect to the Notes occurs and is
continuing, the Trustee may in its discretion proceed to protect and enforce
its rights and the rights of the Holders by such appropriate judicial
proceedings as the Trustee shall deem most effectual to protect and enforce any
such rights, whether for the specific enforcement of any covenant or agreement
in this Indenture or in aid of the exercise of any power granted herein, or to
enforce any other proper remedy.

                 SECTION 5.04.   Trustee May File Proofs of Claim. In case of
the pendency of any receivership, insolvency, liquidation, bankruptcy,
reorganization, arrangement, adjustment, composition or other judicial
proceedings, or any voluntary or involuntary case under the Federal bankruptcy
laws as now or hereafter constituted, relative to the Company or any other
obligor upon the Notes or the Property of the Company or of such other obligor
or their creditors, the Trustee (irrespective of whether the principal of such
Notes shall then be due and payable as therein expressed or by declaration or
otherwise and irrespective of whether the Trustee shall have made any demand on
the Company for the payment of overdue principal or interest) shall be entitled
and empowered, by intervention in such proceeding or otherwise,

                 (1)      to file and prove a claim for the whole amount of
         principal (and premium, if any) and interest owing and unpaid in
         respect of the Notes and to file such other papers or documents as may
         be necessary or advisable in order to have the claims of the Trustee
         (including any claim for the reasonable compensation, expenses,
         disbursements and advances





                                      -49-
<PAGE>   56
         of the Trustee, its agents and counsel) and of the Holders allowed in
         such judicial proceeding, and

                 (2)      to collect and receive any moneys or other property
         payable or deliverable on any such claims and to distribute the same;

and any receiver, assignee, trustee, custodian, liquidator, sequestrator (or
other similar official) in any such proceeding is hereby authorized by each
Holder to make such payments to the Trustee, and in the event that the Trustee
shall consent to the making of such payments directly to the Holders, to pay to
the Trustee any amount due it for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, and any
other amounts due the Trustee under Section 6.07.  To the extent that the
payment of any such compensation, expenses, disbursements and advances of the
Trustee, its agents and counsel and any other amounts due under Section 6.07
out of the estate is sought and such proceedings shall deny such payment for
any reason, payment of the same shall be secured by a Lien on, and paid out of,
any and all distributions, dividends, money, securities and other properties
which the Holders may be entitled to receive in such proceeding whether in
liquidation, under a plan of reorganization or otherwise.

                 Nothing contained herein shall be deemed to authorize the
Trustee to authorize or consent to or accept or adopt on behalf of any Holder
any plan of reorganization, arrangement, adjustment or composition affecting
the Notes or the rights of any Holder thereof, or to authorize the Trustee to
vote in respect of the claim of any Holder in any such proceeding.

                 SECTION 5.05.   Trustee May Enforce Claims without Possession
of the Notes.  All rights of action and claims under this Indenture or the
Notes may be prosecuted and enforced by the Trustee without the possession of
any of the Notes or the production thereof in any proceeding relating thereto,
and any such proceeding instituted by the Trustee shall be brought in its own
name, as trustee of an express trust, and any recovery of judgment shall, after
provision for the payment of the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, be for the
ratable benefit of the Holders.

                 SECTION 5.06.   Application of Money Collected.  Any money
collected by the Trustee pursuant to this Article shall be applied in the
following order, at the date or dates fixed by the Trustee and, in case of the
distribution of such money on account of principal (and premium, if any), upon
presentation of the Notes and the notation thereon of the payment if only
partially paid and upon surrender thereof if fully paid:

                 FIRST:  To the payment of all amounts due the Trustee under
         Section 6.07;

                 SECOND:  To the payment of the amounts then due and unpaid for
         interest on the Notes and any Defaulted Interest and any interest
         payable thereon, principal of (and premium, if any, on) the Notes,
         ratably, without preference or priority of any kind, according





                                      -50-
<PAGE>   57
         to the amounts due and payable on such Notes for principal (and
         premium, if any), interest and Defaulted Interest, respectively; and

                 THIRD:  To the payment of the remainder, if any, to the
         Company or to whosoever may be lawfully entitled thereto or as a court
         of competent jurisdiction may direct.

                 SECTION 5.07.   Limitation on Suits.  No Holder of any of the
Notes shall have any right to institute any proceeding, judicial or otherwise,
with respect to this Indenture, or for the appointment of a receiver or
trustee, or for any other remedy hereunder, unless

                 (1)      such Holder has previously given written notice to
         the Trustee of a continuing Event of Default with respect to the
         Notes;

                 (2)      the Holders of not less than 25% in principal amount
         of the Outstanding Notes shall have made written request to the
         Trustee to institute proceedings in respect of such Event of Default
         in its own name as Trustee hereunder;

                 (3)      such Holder or Holders have offered to the Trustee
         security or indemnity satisfactory to the Trustee in its reasonable
         discretion against the costs, expenses and liabilities to be incurred
         in compliance with such request;

                 (4)      the Trustee for 60 days after its receipt of such
         notice, request and offer of indemnity has failed to institute any
         such proceeding; and

                 (5)      no direction inconsistent with such written request
         has been given to the Trustee during such 60-day period by the Holders
         of a majority in principal amount of the Outstanding Notes;

it being understood and intended that no one or more Holders shall have any
right in any manner whatever by virtue of, or by availing of, any provision of
this Indenture to affect, disturb or prejudice the rights of any other such
Holders, or to obtain or to seek to obtain priority or preference over any
other of such Holders or to enforce any right under this Indenture, except in
the manner herein provided and for the equal and ratable benefit of all of the
Holders.

                 SECTION 5.08.   Unconditional Right of Holders to Receive
Principal, Premium and Interest.  Subject to the provisions of Section 5.02,
and notwithstanding any other provision in this Indenture, the Holder of any
Note shall have the right, which is absolute and unconditional, to receive
payment of the principal of (and premium, if any) and (subject to Section 3.08)
interest on such Note at the Stated Maturity and to institute suit for the
enforcement of any such payment, and such right shall not be impaired without
the consent of such Holder.

                 SECTION 5.09.   Restoration of Rights and Remedies.  If the
Trustee or any Holder has instituted any proceeding to enforce any right or
remedy under this Indenture and such





                                      -51-
<PAGE>   58
proceeding has been discontinued or abandoned for any reason, or has been
determined adversely to the Trustee or to such Holder, then and in every such
case the Company, the Trustee and the Holders shall, subject to any
determination in such proceeding, be restored severally and respectively to
their former positions hereunder, and thereafter all rights and remedies of the
Trustee and the Holders shall continue as though no such proceeding had been
instituted.

                 SECTION 5.10.   Rights and Remedies Cumulative.  Except as
otherwise provided in Section 3.07, no right or remedy herein conferred upon or
reserved to the Trustee or to the Holders is intended to be exclusive of any
other right or remedy, and every right and remedy shall, to the extent
permitted by law, be cumulative and in addition to every other right and remedy
given hereunder or now or hereafter existing at law or in equity or otherwise.
The assertion or employment of any right or remedy hereunder, or otherwise,
shall not prevent the concurrent assertion or employment of any other
appropriate right or remedy.

                 SECTION 5.11.   Delay or Omission Not Waiver.  No delay or
omission of the Trustee or of any Holder of any Note to exercise any right or
remedy accruing upon any Event of Default shall impair any such right or remedy
or constitute a waiver of any such Event of Default or an acquiescence therein.
Every right and remedy given by this Article or by law to the Trustee or to the
Holders may be exercised from time to time, and as often as may be deemed
expedient, by the Trustee or by the Holders, as the case may be.

                 SECTION 5.12.   Control by Holders.  The Holders of a majority
in principal amount of the Outstanding Notes shall have the right to direct the
time, method and place of conducting any proceeding for any remedy available to
the Trustee or exercising any trust or power conferred on the Trustee, provided
that:

                 (1)      such direction shall not be in conflict with any rule
         of law or with this Indenture or unduly prejudicial to the rights of
         other Holders or involve the Trustee in personal liability for which
         indemnity is not provided hereunder, and

                 (2)      the Trustee may take any other action deemed proper
         by the Trustee which is not inconsistent with such direction.

                 SECTION 5.13.   Waiver of Past Defaults.  The Holders of not
less than a majority in principal amount of the Outstanding Notes may on behalf
of the Holders of all the Notes waive any past Default or Event of Default
hereunder and its consequences, except a Default

                 (1)      in the payment of the principal of (or premium, if
         any) or interest on any Note or

                 (2)      in respect of a covenant or provision hereof which
         under Article IX cannot be modified or amended without the consent of
         the Holder of each Outstanding Note affected.





                                      -52-
<PAGE>   59
                 Upon any such waiver, such Default shall cease to exist, and
any Event of Default arising therefrom shall be deemed to have been cured, for
every purpose of this Indenture; but no such waiver shall extend to any
subsequent or other Default or impair any right consequent thereon.

                 SECTION 5.14.   Undertaking for Costs.  All parties to this
Indenture agree, and each Holder of any Note by such Holder's acceptance
thereof shall be deemed to have agreed, that any court may in its discretion
require, in any suit for the enforcement of any right or remedy under this
Indenture, or in any suit against the Trustee for any action taken, suffered or
omitted by it as Trustee, the filing by any party litigant in such suit of an
undertaking to pay the costs of such suit and that such court may in its
discretion assess reasonable costs, including reasonable attorneys' fees,
against any party litigant in such suit, having due regard to the merits and
good faith of the claims or defenses made by such party litigant; but the
provisions of this Section shall not apply to any suit instituted by the
Trustee, to any suit instituted by any Holder, or group of Holders, holding in
the aggregate more than 10% in principal amount of the Outstanding Notes, or to
any suit instituted by any Holder for the enforcement of the payment of the
principal of (or premium, if any) or interest on any Note on or after its
Stated Maturity.

                 SECTION 5.15.   Waiver of Stay or Extension Laws.  The Company
covenants (to the extent that it may lawfully do so) that it shall not at any
time insist upon, or plead, or in any manner whatsoever claim or take the
benefit or advantage of, any stay or extension law wherever enacted, now or at
any time hereafter in force, which may affect the covenants or the performance
of this Indenture; and the Company (to the extent that it may lawfully do so)
hereby expressly waives all benefit or advantage of any such law, and covenants
that it will not hinder, delay or impede the execution of any power herein
granted to the Trustee, but will suffer and permit the execution of every such
power as though no such law had been enacted.

                                   ARTICLE VI

                                  The Trustee

                 SECTION 6.01.   Certain Duties and Responsibilities. (a)
Except during the continuance of an Event of Default:

                 (1)      the Trustee undertakes to perform such duties and
         only such duties as are specifically set forth in this Indenture, and
         no implied covenants or obligations shall be read into this Indenture
         against the Trustee; and

                 (2)      in the absence of bad faith on its part, the Trustee
         may conclusively rely, as to the truth of the statements and the
         correctness of the opinions expressed therein, upon certificates or
         opinions furnished to the Trustee and conforming to the requirements
         of this





                                      -53-
<PAGE>   60
         Indenture; but in the case of any such certificates or opinions which
         by any provisions hereof are specifically required to be furnished to
         the Trustee, the Trustee shall be under a duty to examine the same to
         determine whether or not they conform to the requirements of this
         Indenture (but need not confirm or investigate the accuracy of
         mathematical calculations or other facts stated therein).

                 (b)      In case an Event of Default has occurred and is
continuing, the Trustee shall exercise such of the rights and powers vested in
it by this Indenture, and use the same degree of care and skill in their
exercise, as a prudent person would exercise or use under the circumstances in
the conduct of his or her own affairs.

                 (c)      No provision of this Indenture shall be construed to
relieve the Trustee from liability for its own negligent action, its own
negligent failure to act, or its own willful misconduct, except that

                 (1)      this Subsection shall not be construed to limit the
         effect of Subsection (a) of this Section;

                 (2)      the Trustee shall not be liable for any error of
         judgment made in good faith by a Responsible Officer, unless it shall
         be proved that the Trustee was negligent in ascertaining the pertinent
         facts; and

                 (3)      the Trustee shall not be liable with respect to any
         action taken, suffered or omitted to be taken by it with respect to
         the Notes in good faith in accordance with the direction of the
         Holders of a majority in principal amount of the Outstanding Notes
         relating to the time, method and place of conducting any proceeding
         for any remedy available to the Trustee, or exercising any trust or
         power conferred upon the Trustee, under this Indenture.

                 (d)      No provision of this Indenture shall require the
Trustee to expend or risk its own funds or otherwise incur any financial
liability in the performance of any of its duties hereunder, or in the exercise
of any of its rights or powers, if it shall have reasonable grounds for
believing that repayment of such funds or adequate indemnity against such risk
or liability is not reasonably assured to it.

                 (e)      Whether or not therein expressly so provided, every
provision of this Indenture relating to the conduct or affecting the liability
of or affording protection to the Trustee shall be subject to the provisions of
this Section.

                 SECTION 6.02.   Notice of Defaults.  Within 90 days after the
occurrence of any Default hereunder with respect to the Notes, the Trustee
shall transmit by mail to all Holders, as their names and addresses appear in
the Security Register, notice of such Default hereunder known to the Trustee,
unless such Default shall have been cured or waived; provided, however, that,
except in the case of a Default in the payment of the principal of (or premium,
if any) or interest on any Note, the Trustee shall be protected in withholding
such notice if and so long as the board of directors, the executive committee
or a trust committee of directors and/or Responsible Officers of the Trustee in
good faith determine that the withholding of such notice is in the interest of
the Holders; provided





                                      -54-
<PAGE>   61
further, that in the case of any Default of the character specified in section
5.01(4), no notice of such Default to Holders as described therein shall be
given until at least 30 days after the notice in connection with Section
5.01(4) has been mailed.

                 SECTION 6.03.   Certain Rights of Trustee.  Except as
otherwise provided in Section 6.01:

                 (a)      the Trustee may rely and shall be protected in acting
or refraining from acting upon any resolution, certificate, statement,
instrument, opinion, report, notice, request, direction, consent, order, bond,
debenture, note, other evidence of indebtedness, or other paper or document
believed by it to be genuine and to have been signed or presented by the proper
party or parties;

                 (b)      any request or direction of the Company mentioned
herein shall be sufficiently evidenced by a Company Request or Company Order
and any resolution of the Board of Directors shall be sufficiently evidenced by
a Board Resolution;

                 (c)      whenever in the administration of this Indenture the
Trustee shall deem it desirable that a matter be proved or established prior to
taking, suffering or omitting any action hereunder, the Trustee (unless other
evidence be herein specifically prescribed) may, in the absence of bad faith on
its part, rely upon an Officers' Certificate;

                 (d)      the Trustee may consult with counsel of its selection
and the advice of such counsel selected by it with due care or any Opinion of
Counsel shall be full and complete authorization and protection in respect of
any action taken, suffered or omitted by it hereunder in good faith and in
reliance thereon;

                 (e)      the Trustee shall be under no obligation to exercise
any of the rights or powers vested in it by this Indenture at the request or
direction of any of the Holders pursuant to this Indenture, unless such Holders
shall have offered to the Trustee security or indemnity, satisfactory to the
Trustee in its reasonable discretion, against the costs, expenses and
liabilities which might be incurred by it in compliance with such request or
direction;

                 (f)      the Trustee shall not be bound to make any
investigation into the facts or matters stated in any resolution, certificate,
statement, instrument, opinion, report, notice, request, direction, consent,
order, bond, debenture, note, other evidence of indebtedness or other paper or
document, but the Trustee, in its discretion, may make such further inquiry or
investigation into such facts or matters as it may see fit;

                 (g)      the Trustee may execute any of the trusts or powers
hereunder or perform any duties hereunder either directly or by or through
agents or attorneys and the Trustee shall not be responsible for any misconduct
or negligence on the part of any agent or attorney appointed with due care by
it hereunder;





                                      -55-
<PAGE>   62
                 (h)      the Trustee shall not be liable for any action taken,
suffered or omitted by it in good faith and reasonably believed by it to be
authorized or within the discretion or rights or powers conferred upon it by
this Indenture; and

                 (i)      for all purposes under this Indenture, the Trustee
shall not be deemed to have notice or knowledge of any Event of Default (other
than under Section 5.01(l) or 5.02(2)) unless a Responsible Officer assigned to
and working in the Trustee's Corporate Trust Office has actual knowledge
thereof or unless written notice of any Event of Default is received by the
Trustee at the Corporate Trust Office and such notice references the Notes
generally, the Company or this Indenture.

                 SECTION 6.04.   Not Responsible for Recitals or Issuance of
Notes.  The recitals contained herein and in the Notes, except the Trustee's
certificates of authentication, shall be taken as the statements of the
Company, and the Trustee assumes no responsibility for their correctness.  The
Trustee makes no representations as to the validity or sufficiency of this
Indenture or of the Notes.  The Trustee shall not be accountable for the use or
application by the Company of any Notes or the proceeds thereof.

                 SECTION 6.05.   May Hold Notes.  The Trustee, any Paying
Agent, the Registrar or any other agent of the Company, in its individual or
any other capacity, may become the owner or pledgee of Notes, and, subject to
Sections 6.08 and 6.13, may otherwise deal with the Company with the same
rights it would have if it were not Trustee, Paying Agent, Registrar or such
other agent.

                 SECTION 6.06.   Money Held in Trust.  Money held by the
Trustee in trust hereunder need not be segregated from other funds except to
the extent required by law.  The Trustee shall be under no liability for
interest on any money received by it hereunder except as otherwise agreed in
writing with the Company.

                 SECTION 6.07.   Compensation and Reimbursement.  The Company
agrees:

                 (1)      to pay to the Trustee from time to time such
compensation, as the Company and the Trustee shall from time to time agree in
writing, for all services rendered by it hereunder (which compensation shall
not be limited by any provision of law in regard to the compensation of a
trustee of an express trust);

                 (2)      except as otherwise expressly provided herein, to
reimburse the Trustee upon its request for all reasonable expenses,
disbursements and advances incurred or made by the Trustee in accordance with
any provision of this Indenture (including the reasonable compensation and the
reasonable expenses and disbursements of its agents and counsel), except any
such expense, disbursement or advance as may be attributable to its negligence
or bad faith; and

                 (3)      to indemnify each of the Trustee, and its successors
and assigns, legal representatives, agents, servants (including employees),
officers and directors and any predecessor





                                      -56-
<PAGE>   63
Trustee for, and to hold it harmless against, any and all loss, damage, claim,
liability or expense, including taxes (other than taxes based upon, or measured
or determined by, compensation received by the Trustee for rendering its
services hereunder) incurred without negligence or bad faith on its part,
arising out of or in connection with the acceptance or administration of this
trust or performance of its duties hereunder, including the costs and expenses
of defending itself against any claim or liability in connection with the
exercise or performance of any of its powers or duties hereunder.  Such
indemnities shall survive payment of the Notes and the Indebtedness and any
resignation, removal or replacement of the Trustee.

                 As security for the performance of the obligations of the
Company under this Section, the Trustee shall have a claim prior to the Notes
upon all property and funds held or collected by the Trustee as such, except
funds held in trust for the payment of principal of (and premium, if any) or
interest on the Notes.

                 If the Trustee incurs expenses or renders services in
connection with an Event of Default under Section 5.01(7) or 5.01(8), the
Trustee's expenses (including reasonable attorneys' fees and expenses) and its
compensation for such services, are intended to constitute expenses of
administration under applicable Federal or state bankruptcy, insolvency or
other similar law.

                 SECTION 6.08.   Disqualification; Conflicting Interests.  If
the Trustee has or shall acquire any "conflicting interest" within the meaning
of Section 310(b) of the Trust Indenture Act, the Trustee and the Company shall
in all respects comply with the provisions of Section 310(b) of the Trust
Indenture Act.

                 SECTION 6.09.   Corporate Trustee Required; Eligibility.
There shall at all times be a Trustee hereunder which shall be a corporation or
a national banking association organized and doing business under the laws of
the United States of America or any state thereof, authorized under such laws
to exercise corporate trust powers, and subject to supervision or examination
by Federal or state authority, having a combined capital and surplus of at
least $50,000,000.  If such Person publishes reports of condition at least
annually, pursuant to law or to the requirements of the aforesaid supervising
or examining authority, then for the purposes of this Section, the combined
capital and surplus of such corporation shall be deemed to be its combined
capital and surplus as set forth in its most recent report of condition so
published.  Neither the Company nor any Affiliate of the Company shall serve as
Trustee hereunder. If at any time the Trustee shall cease to be eligible to
serve as Trustee hereunder pursuant to the provisions of this Section, it shall
resign immediately upon obtaining knowledge thereof in the manner and with the
effect hereinafter specified in this Article.

                 SECTION 6.10.   Resignation and Removal; Appointment of
Successor. (a) No resignation or removal of the Trustee and no appointment of a
successor Trustee pursuant to this Article shall become effective until the
acceptance of appointment by the successor Trustee under Section 6.11.





                                      -57-
<PAGE>   64
                 (b)      The Trustee may resign at any time by giving written
notice thereof to the Company.  If an instrument of acceptance by a successor
Trustee shall not have been delivered to the Trustee within 30 days after the
giving of such notice of resignation, the resigning Trustee may petition any
court of competent jurisdiction for the appointment of a successor Trustee.

                 (c)      The Trustee may be removed at any time by Act of the
Holders of a majority in principal amount of the Outstanding Notes, delivered
to the Trustee and to the Company.

                 (d)      If at any time:

                 (1)      the Trustee shall fail to comply with Section 310(b)
         of the Trust Indenture Act pursuant to Section 6.08 hereof after
         written request therefor by the Company or by any Holder who has been
         a bona fide Holder of a Note for at least six months, unless the
         Trustee's duty to resign is stayed in accordance with the provisions
         of Section 310(b) of the Trust Indenture Act, or

                 (2)      the Trustee shall cease to be eligible under Section
         6.09 hereof and shall fail to resign after written request therefor by
         the Company or by any such Holder, or

                 (3)      the Trustee shall become incapable of acting or a
         decree or order for relief by a court having jurisdiction in the
         premises shall have been entered in respect of the Trustee in an
         involuntary case under the Federal bankruptcy laws, as now or
         hereafter constituted, or any other applicable Federal or state
         bankruptcy, insolvency or similar law; or a decree or order by a court
         having jurisdiction in the premises shall have been entered for the
         appointment of a receiver, custodian, liquidator, assignee, trustee,
         sequestrator (or other similar official) of the Trustee or of its
         property or affairs, or any public officer shall take charge or
         control of the Trustee or of its property or affairs for the purpose
         of rehabilitation, conservation, winding up or liquidation, or

                 (4)      the Trustee shall commence a voluntary case under the
         Federal bankruptcy laws, as now or hereafter constituted, or any other
         applicable Federal or state bankruptcy, insolvency or similar law or
         shall consent to the appointment of or taking possession by a
         receiver, custodian, liquidator, assignee, trustee, sequestrator (or
         other similar official) of the Trustee or its property or affairs, or
         shall make an assignment for the benefit of creditors, or shall admit
         in writing its inability to pay its debts generally as they become
         due, or shall take corporate action in furtherance of any such action,

then, (i) the Company by a Board Resolution may remove the Trustee with respect
to the Notes, or (ii) subject to Section 5.14, any Holder who has been a bona
fide Holder of a Note for at least six months may, on behalf of such Holder and
all others similarly situated, petition any court of competent jurisdiction for
the removal of the Trustee and the appointment of a successor Trustee for the
Notes.





                                      -58-
<PAGE>   65
                 (e)      If the Trustee shall resign, be removed or become
incapable of acting, or if a vacancy shall occur in the office of Trustee for
any cause, the Company, by or pursuant to a Board Resolution, shall promptly
appoint a successor Trustee.  Within one year after such resignation, removal
or incapability, or the occurrence of such vacancy, a successor Trustee may be
appointed by Act of the Holders of a majority in principal amount of the Notes
delivered to the Company and the retiring Trustee and the successor Trustee so
appointed shall, forthwith upon its acceptance of such appointment in
accordance with Section 6.11, become the successor Trustee and to that extent
replace the successor Trustee appointed by the Company.  If no successor
Trustee shall have been so appointed by the Company or the Holders and shall
have accepted appointment in the manner hereinafter provided, any Holder that
has been a bona fide Holder of a Note for at least six months may, subject to
Section 5.14, on behalf of himself and all others similarly situated, petition
any court of competent jurisdiction for the appointment of a successor Trustee.

                 (f)      The Company shall give notice of each resignation and
each removal of the Trustee and each appointment of a successor Trustee by
mailing written notice of such resignation, removal and appointment by
first-class mail, postage prepaid, to the Holders as their names and addresses
appear in the Security Register.  Each notice shall include the name of the
successor Trustee with respect to the Notes and the address of its Corporate
Trust Office.

                 SECTION 6.11.   Acceptance of Appointment by Successor.  (a)
In the event of an appointment hereunder of a successor Trustee, each such
successor Trustee so appointed shall execute, acknowledge and deliver to the
Company and to the retiring Trustee an instrument accepting such appointment,
and thereupon the resignation or removal of the retiring Trustee shall become
effective and such successor Trustee, without any further act, deed or
conveyance, shall become vested with all the rights, powers, trusts and duties
of the retiring Trustee but, on request of the Company or the successor
Trustee, such retiring Trustee shall, upon payment of its charges, execute and
deliver an instrument transferring to such successor Trustee all the rights,
powers and trusts of the retiring Trustee, and shall duly assign, transfer and
deliver to such successor Trustee all property and money held by such former
Trustee hereunder, subject to its lien, if any, provided for in Section 6.07.

                 (b)      Upon request of any such successor Trustee, the
Company shall execute any and all instruments for more fully and certainly
vesting in and confirming to such successor Trustee all such rights, powers and
trusts referred to in paragraph (a) of this Section.

                 (c)      No successor Trustee shall accept its appointment
unless at the time of such acceptance such successor Trustee shall be qualified
and eligible under this Article and under the Trust Indenture Act.

                 SECTION 6.12.   Merger, Conversion, Consolidation or
Succession to Business.  Any corporation into which the Trustee may be merged
or converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which the Trustee shall be a
party, or any corporation succeeding to all or substantially all of the
corporate





                                      -59-
<PAGE>   66
trust business of the Trustee, shall be the successor of the Trustee hereunder,
provided that such corporation shall be otherwise qualified and eligible under
this Article and under the Trust Indenture Act, without the execution or filing
of any paper or any further act on the part of any of the parties hereto.  In
case any Notes shall have been authenticated, but not delivered, by the Trustee
then in office, any successor by merger, conversion or consolidation to such
authenticating Trustee may adopt such authentication and deliver the Notes so
authenticated with the same effect as if such successor Trustee had itself
authenticated such Notes.  In the event that any Notes shall not have been
authenticated by such predecessor Trustee, any such successor Trustee may
authenticate and deliver such Notes, in either its own name or that of its
predecessor Trustee, with the full force and effect which this Indenture
provides for the certificate of authentication of the Trustee.

                 SECTION 6.13.   Preferential Collection of Claims Against
Company.  The Trustee shall comply with Section 311(a) of the Trust Indenture
Act, excluding any creditor relationship described in Section 311(b) of the
Trust Indenture Act.  A Trustee who has resigned or been removed shall be
subject to Section 311(a) of the Trust Indenture Act to the extent indicated
therein.


                                  ARTICLE VII

               Holders' Lists and Reports by Trustee and Company

                 SECTION 7.01.   Company To Furnish Trustee Names and Addresses
of Holders.  The Company shall furnish or cause to be furnished to the Trustee:

                 (a)      semiannually, not less than ten days prior to each
         Interest Payment Date, a list, in such form as the Trustee may
         reasonably require, of the names and addresses of the Holders as of
         the Record Date immediately preceding such Interest Payment Date, and

                 (b)      at such other times as the Trustee may request in
         writing, within 30 days after the receipt by the Company of any such
         request, a list of similar form and content as of a date not more than
         15 days prior to the time such list is furnished;

provided, however, that if and so long as the Trustee shall be the Registrar
for the Notes, no such list need be furnished with respect to the Notes.

                 SECTION 7.02.   Preservation of Information; Communications to
Holders.  (a) The Trustee shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders contained in the most recent
list furnished to the Trustee as provided in Section 7.01 and the names and
addresses of Holders received by the Trustee in its capacity as Registrar, if
so acting.  The Trustee may destroy any list furnished to it as provided in
Section 7.01 upon receipt of a new list so furnished.





                                      -60-
<PAGE>   67
                 (b)      Holders may communicate as provided in Section 312(b)
of the Trust Indenture Act with other Holders with respect to their rights
under this Indenture or under the Notes.

                 (c)      Each Holder of Notes, by receiving and holding the
same, agrees with the Company and the Trustee that neither the Company nor the
Trustee shall be held accountable by reason of the disclosure of any such
information as to the names and addresses of the Holders in accordance with
Section 7.02(b), regardless of the source from which such information was
derived, and that the Trustee shall not be held accountable by reason of
mailing any material pursuant to a request made under Section 7.02(b).

                 SECTION 7.03.   Reports by the Trustee.  (a) Within 60 days
after April 15 of each year commencing with the year 1997, the Trustee shall
transmit by mail to all Holders of Notes, as provided in Section 1.07, a brief
report dated as of such April 15 and with respect to the previous 12 months if
and to the extent required under Section 313(a) of the Trust Indenture Act.

                 (b)      The Trustee shall comply with Sections 313(b) and
313(c) of the Trust Indenture Act.

                 (c)      A copy of each such report shall, at the time of its
transmission to Holders, be filed by the Trustee with each stock exchange, if
any, upon which the Notes are then listed, with the Commission and also with
the Company.  The Company shall promptly notify the Trustee of the listing of
the Notes on any stock exchange.

                 SECTION 7.04.   Reports by the Company.  The Company shall
file with the Trustee, within 15 days after the Company is required to file the
same with the Commission, copies of the annual reports and of the information,
documents and other reports (or copies of such portions of any of the foregoing
as the Commission may from time to time by rules and regulations prescribe)
which the Company may be required to file with the Commission pursuant to
Section 13 or Section 15(d) of the Exchange Act; provided, however, that if the
Company is not subject to Section 13 or Section 15(d) of the Exchange Act, the
Company shall nevertheless file with the Commission and the Trustee on the same
timely basis such reports, information and other documents as the Company would
file if the Company were subject to the requirements of Section 13 or Section
15(d) of the Exchange Act.  The Company and any other obligor on the Notes
shall also comply with the other provisions of Section 314(a) of the Trust
Indenture Act.


                                  ARTICLE VIII

              Consolidation, Merger, Conveyance, Lease or Transfer

                 SECTION 8.01.   Company May Consolidate, etc., Only on Certain
Terms.  The Company shall not in any transaction or series of transactions,
consolidate with or merge with or into any other Person (other than a merger of
a Subsidiary into the Company in which the Company is





                                      -61-
<PAGE>   68
the continuing corporation), or sell, convey, assign, transfer, lease or
otherwise dispose of all or substantially all of the Property and assets of the
Company and the Subsidiaries, taken as a whole, to any Person, unless:

                 (1)      either (a) the Company shall be the continuing
         corporation or (b) if other than the Company, the corporation formed
         by such consolidation or into which the Company is merged or the
         Person which acquires by sale, assignment, conveyance, transfer, lease
         or disposition, all or substantially all of the Property and assets of
         the Company and the Subsidiaries, taken as a whole (any such
         corporation or Person being the "Surviving Entity"), shall be a
         corporation organized and existing under the laws of the United States
         of America, any political subdivision thereof or any state thereof or
         the District of Columbia and shall expressly assume, by an indenture
         supplemental hereto, executed and delivered to the Trustee, in form
         satisfactory to the Trustee, the due and punctual payment of the
         principal of (and premium, if any) and interest on all the Notes and
         the performance of every covenant and obligation in this Indenture on
         the part of the Company to be performed or observed;

                 (2)      immediately before and after giving effect to such
         transaction or series of transactions on a pro forma basis (including,
         without limitation, any Indebtedness incurred or anticipated to be
         incurred in connection with or in respect of such transaction or
         series of transactions) no Default or Event of Default shall have
         occurred and be continuing or would result therefrom;

                 (3)      immediately after giving effect to such transaction
         or series of transactions on a pro forma basis (including, without
         limitation, any Indebtedness incurred or anticipated to be incurred in
         connection with or in respect of such transaction or series of
         transactions), the Consolidated Net Worth of the Company (or the
         Surviving Entity if the Company is not continuing) is equal to or
         greater than the Consolidated Net Worth of the Company immediately
         prior to such transaction or series of transactions; and

                 (4)      immediately after giving effect to such transaction
         or series of transactions on a pro forma basis as if such transaction
         or series of transactions had occurred on the first day of the
         Determination Period, the Company (or the Surviving Entity if the
         Company is not continuing) would be permitted to incur $1.00 of
         additional Indebtedness under the provisions of Section 10.09(a).

                 In connection with any consolidation, merger, sale,
conveyance, lease, assignment, transfer or other disposition contemplated by
this Section 8.01, the Company shall deliver, or cause to be delivered, to the
Trustee, in form and substance reasonably satisfactory to the Trustee, an
Officers' Certificate and an Opinion of Counsel, each stating that such
consolidation, merger, sale, conveyance, lease, assignment, transfer or
disposition and the supplemental indenture in respect thereto comply with this
Article and that all conditions precedent herein provided for relating to such
transaction have been complied with.





                                      -62-
<PAGE>   69
                 SECTION 8.02.   Successor Corporation Substituted.  Upon any
consolidation with or merger by the Company with or into any other corporation,
or any sale, conveyance, lease, assignment, transfer or other disposition of
all or substantially all of the Property and assets of the Company and the
Subsidiaries, taken as a whole, in accordance with Section 8.01, the successor
corporation formed by such consolidation or into which the Company is merged or
the successor Person to which such sale, conveyance, lease, assignment,
transfer or disposition is made shall succeed to, and be substituted for, and
may exercise every right and power of, the Company under this Indenture with
the same effect as if such successor had been named as the Company herein, and
thereafter the predecessor corporation shall be relieved of all obligations and
covenants under this Indenture and the Notes.


                                   ARTICLE IX

                            Supplemental Indentures

                 SECTION 9.01.   Supplemental Indentures without Consent of
Holders.  Without the consent of any of the Holders, the Company, when
authorized by a Board Resolution, and the Trustee, at any time and from time to
time, may enter into one or more indentures supplemental hereto, in form
satisfactory to the Trustee, for any of the following purposes:

                 (1)      to evidence the succession of another Person to the
         Company and the assumption by such successor of the covenants of the
         Company herein and contained in the Notes; or

                 (2)      to add to the covenants of the Company, for the
         benefit of the Holders of all of the Notes, or to surrender any right
         or power herein conferred upon the Company; or

                 (3)      to add any additional Events of Default; or

                 (4)      to provide for uncertificated Notes in addition to or
         in place of certificated Notes; or

                 (5)      to change or eliminate any of the provisions of this
         Indenture, provided that any such change or elimination shall become
         effective only when there is no Note Outstanding created prior to the
         execution of such supplemental indenture which is entitled to the
         benefit of such provision; or

                 (6)      to evidence and provide for the acceptance of
         appointment hereunder by a successor Trustee pursuant to the
         requirements of Section 6.11(b); or

                 (7)      to secure the Notes; or





                                      -63-
<PAGE>   70
                 (8)      to cure any ambiguity, to correct or supplement any
         provision herein which may be inconsistent with any other provision
         herein or to add any other provisions with respect to matters or
         questions arising under this Indenture, provided such actions shall
         not adversely affect the interests of the Holders in any material
         respect; or

                 (9)      to comply with the requirements of the Commission in
         order to effect or maintain the qualification of this Indenture under
         the Trust Indenture Act.

                 SECTION 9.02.   Supplemental Indentures with Consent of
Holders.  With the consent of the Holders of not less than a majority in
principal amount of the Outstanding Notes, by Act of said Holders delivered to
the Company and the Trustee, the Company, when authorized by a Board
Resolution, and the Trustee may enter into an indenture or indentures
supplemental hereto for the purpose of adding any provisions to or changing in
any manner or eliminating any of the provisions of this Indenture or of
modifying in any manner the rights of the Holders; provided, however, that no
such supplemental indenture shall, without the consent of the Holder of each
Outstanding Note,

                 (1)      change the Stated Maturity of the principal of, or
         any installment of interest on, any Note, or reduce the principal
         amount thereof (or any premium, if any) or the interest thereon, that
         would be due and payable upon Maturity thereof, or change the place of
         payment where, or the coin or currency in which, any Note or the
         interest thereon is payable, or impair the right to institute suit for
         the enforcement of any such payment on or after the Stated Maturity
         thereof, or

                 (2)      reduce the percentage in principal amount of the
         Outstanding Notes, the consent of whose Holders is required for any
         such supplemental indenture, or the consent of whose Holders is
         required for any waiver of compliance with certain provisions of this
         Indenture, or certain Defaults hereunder and their consequences,
         provided for in this Indenture, or

                 (3)      modify in any manner the obligation of the Company to
         make an offer to purchase Notes pursuant to Section 10.12 or 10.13, or

                 (4)      subordinate in right of payment, or otherwise
         subordinate, the Notes to any other Indebtedness, or

                 (5)      modify any of the provisions of this Section or
         Section 5.13, except to increase any percentage set forth therein or
         to provide that certain other provisions of this Indenture cannot be
         modified or waived without the consent of the Holder of each
         Outstanding Note affected thereby.





                                      -64-
<PAGE>   71
                 It shall not be necessary for any Act of Holders under this
Section to approve the particular form of any proposed supplemental indenture,
but it shall be sufficient if such Act shall approve the substance thereof.

                 SECTION 9.03.   Execution of Supplemental Indentures.  In
executing, or accepting the additional trusts created by, any supplemental
indenture permitted by this Article or the modifications thereby of the trusts
created by this Indenture, the Trustee shall be entitled to receive, and
(subject to Section 6.01) shall be fully protected in relying upon, an Opinion
of Counsel stating that the execution of such supplemental indenture is
authorized or permitted by this Indenture.  The Trustee may, but shall not be
obligated to, enter into any such supplemental indenture which affects the
Trustee's own rights, duties or immunities under this Indenture or otherwise.

                 SECTION 9.04.   Effect of Supplemental Indentures.  Upon the
execution of any supplemental indenture under this Article, this Indenture
shall be modified in accordance therewith, and such supplemental indenture
shall form a part of this Indenture for all purposes; and every Holder of Notes
theretofore or thereafter authenticated and delivered hereunder shall be bound
thereby.  Promptly after the effectiveness of any such supplemental indenture,
the Trustee shall give written notice thereof to the Holders at the Company's
expense.

                 SECTION 9.05.   Conformity with Trust Indenture Act.  Every
supplemental indenture executed pursuant to this Article shall conform to the
requirements of the Trust Indenture Act as then in effect.

                 SECTION 9.06.   Reference in Notes to Supplemental Indentures.
Notes authenticated and delivered after the execution of any supplemental
indenture pursuant to this Article may, and shall if required by the Trustee,
bear a notation in form approved by the Trustee as to any matter provided for
in such supplemental indenture.  If the Company shall so determine, new Notes
so modified as to conform, in the opinion of the Trustee and the Board of
Directors, to any such supplemental indenture may be prepared and executed by
the Company and authenticated and delivered by the Trustee in exchange for
Outstanding Notes.


                                   ARTICLE X

                                   Covenants

                 SECTION 10.01.   Payment of Principal, Premium and Interest.
The Company covenants and agrees for the benefit of the Holders that it shall
duly and punctually pay the principal of (and premium, if any) and interest on
the Notes in accordance with the terms of the Notes and this Indenture.

                 SECTION 10.02.   Maintenance of Office or Agency.  The Company
shall maintain in the Borough of Manhattan, The City of New York, an office or
agency where Notes may be





                                      -65-
<PAGE>   72
presented or surrendered for payment, where Notes may be surrendered for
registration of transfer or exchange and where notices and demands to or upon
the Company in respect of the Notes and this Indenture may be served.  The
Company shall give prompt written notice to the Trustee of the location, and
any change in the location, of such office or agency.  If at any time the
Company shall fail to maintain any such required office or agency or shall fail
to furnish the Trustee with the address thereof, such presentations,
surrenders, notices and demands may be made or served at the Corporate Trust
Office of the Trustee, and the Company hereby appoints the Trustee its agent to
receive all presentations, surrenders, notices and demands.

                 The Company may also from time to time designate one or more
other offices or agencies (in or outside of The City of New York) where the
Notes may be presented or surrendered for any or all of such purposes, and may
from time to time rescind such designations; provided, however, that no such
designation or rescission shall in any manner relieve the Company of its
obligation to maintain an office or agency in The City of New York, for such
purposes.  The Company shall give prompt written notice to the Trustee of any
such designation and any change in the location of any such other office or
agency.

                 SECTION 10.03.   Money for the Note Payments to Be Held in
Trust.  If the Company, any Subsidiary or any of their respective Affiliates
shall at any time act as Paying Agent with respect to the Notes, such Paying
Agent shall, on or before each due date of the principal of (and premium, if
any) or interest on any of the Notes, segregate and hold in trust for the
benefit of the Persons entitled thereto money sufficient to pay the principal
(and premium, if any) or interest so becoming due until such money shall be
paid to such Persons or otherwise disposed of as herein provided, and shall
promptly notify the Trustee of its action or failure so to act.

                 Whenever the Company shall have one or more Paying Agents with
respect to the Notes, it shall, prior to or on each due date of the principal
of (and premium, if any) or interest on any of the Notes, deposit with a Paying
Agent a sum sufficient to pay the principal (and premium, if any) or interest
so becoming due, such sum to be held in trust for the benefit of the Persons
entitled to such principal, premium or interest, and (unless such Paying Agent
is the Trustee) the Company shall promptly notify the Trustee of its action or
failure so to act.

                 SECTION 10.04.   Corporate Existence.  Subject to Article
VIII, the Company shall do or cause to be done all things necessary to preserve
and keep in full force and effect the corporate existence, rights (charter and
statutory) and franchises of the Company and each Material Subsidiary;
provided, however, that the Company and any Material Subsidiary shall not be
required to preserve any such right or franchise if the Board of Directors
shall determine that the preservation thereof is no longer desirable in the
conduct of the business of the Company and that the loss thereof is not
disadvantageous in any material respect to the Holders.

                 SECTION 10.05.   Maintenance of Property.  The Company shall
cause all Property used or useful in the conduct of its business or the
business of any Subsidiary to be maintained and kept in good condition, repair
and working order and supplied with all necessary equipment and shall





                                      -66-
<PAGE>   73
cause to be made all necessary repairs, renewals, replacements, betterments and
improvements thereof, all as in the judgment of the Company may be necessary so
that the business carried on in connection therewith may be properly and
advantageously conducted at all times; provided, however, that nothing in this
Section shall prevent the Company from discontinuing the operation or
maintenance of any of such Property if such discontinuance is, in the judgment
of the Company, desirable in the conduct of its business or the business of any
Subsidiary and not disadvantageous in any material respect to the Holders.

                 SECTION 10.06.   Payment of Taxes and Other Claims.  The
Company shall pay or discharge or cause to be paid or discharged, before the
same shall become delinquent, (i) all taxes, assessments and governmental
charges levied or imposed upon the Company or any Subsidiary or upon the
income, profits or property of the Company or any Subsidiary and (ii) all
lawful claims for labor, materials and supplies which, if unpaid, might by law
become a Lien upon the property of the Company or any Subsidiary; provided,
however, that the Company shall not be required to pay or discharge or cause to
be paid or discharged any such tax, assessment, charge or claim whose amount,
applicability or validity is being contested in good faith by appropriate
proceedings upon stay of execution or the enforcement thereof and for which
adequate reserves in accordance with GAAP or other appropriate provision has
been made.

                 SECTION 10.07.   Transactions with Affiliates.  Subsequent to
the Issue Date, the Company shall not, and shall not permit any Subsidiary to,
directly or indirectly, enter into or permit to exist any transaction or series
of related transactions (including, but not limited to, the purchase, sale,
lease or exchange of Property, the making of any Investment, the giving of any
Guarantee or the rendering of any service) with any Affiliate of the Company
other than the Company or a Wholly Owned Subsidiary except a Non-Recourse
Subsidiary unless (i) such transaction or series of related transactions is on
terms no less favorable to the Company or such Subsidiary than those that could
be obtained in a comparable arm's length transaction with a Person that is not
such an Affiliate and (ii) (a) with respect to a transaction or series of
related transactions that has a Fair Market Value in excess of $2,000,000 but
less than $5,000,000, the Company delivers an Officers' Certificate to the
Trustee certifying that such transaction or series of related transactions
complies with clause (i) above and (b) with respect to a transaction or series
of related transactions that has a Fair Market Value equal to, or in excess of,
$5,000,000, the transaction or series of related transactions is approved by a
majority of the Board of Directors (including a majority of the disinterested
directors), which approval is set forth in a Board Resolution certifying that
such transaction or series of related transactions complies with clause (i)
above.

                 SECTION 10.08.   Limitation on Restricted Payments.  (a) The
Company shall not, nor shall it permit any of its Subsidiaries (other than
Non-Recourse Subsidiaries) to, make any Restricted Payment if at the time
thereof, and after giving effect thereto (the amount of any such payment to be
made other than in cash to be determined by the Board of Directors, which
determination shall be conclusive and evidenced by a Board Resolution), (i) any
Default shall have occurred and be continuing or would result therefrom, (ii)
the incurrence of at least $1.00 of additional Indebtedness would not be
permitted under Section 10.09(a) or (iii) the aggregate amount





                                      -67-
<PAGE>   74
of all Restricted Payments declared or made on or subsequent to the Issue Date
by the Company or any Subsidiary (other than a Non-Recourse Subsidiary) would
exceed the sum of (A) 50% (or if Consolidated Net Income of the Company shall
be a deficit, minus 100% of such deficit) of the aggregate Consolidated Net
Income of the Company accrued during the period beginning on October 1, 1993
and ending on the last day of the fiscal quarter immediately preceding the date
of such proposed Restricted Payment, (B) an amount equal to (x) the aggregate
net cash proceeds received by the Company, subsequent to October 7, 1993, from
the issuance or sale (other than to a Subsidiary), subsequent to October 7,
1993, of shares of its Capital Stock (excluding Redeemable Stock, but including
Capital Stock of the Company issued upon the exercise of options, warrants or
rights to purchase Capital Stock (other than Redeemable Stock) of the Company
and including the Equity Offerings), and (y) the liability (expressed as a
positive number) in accordance with GAAP of any Indebtedness of the Company, or
the carrying value of any Redeemable Stock or the Preferred Stock, which has
been converted into, exchanged for or satisfied by the issuance of shares of
Capital Stock (other than Redeemable Stock) of the Company, subsequent to
October 7, 1993, (C) in the case of the disposition or repayment of any
Investment constituting a Restricted Payment made after the Issue Date in
compliance with this Section 10.08 and the other provisions of this Indenture,
an amount equal to the lesser of the return of capital with respect to such
Investment and the initial amount of such Investment, in either case, minus the
cost of the disposition of such Investment and (D) $10,000,000.

                 (b)      The provisions of this Section 10.08 shall not
prevent the Company or any Subsidiary from paying a dividend on Capital Stock
of any class within 60 days after the declaration thereof if, on the date of
declaration, the Company or such Subsidiary could have paid such dividend in
compliance with the other provisions of this Section 10.08 and the other
provisions of this Indenture.  The aggregate amount of dividends paid by the
Company or any Subsidiary pursuant to this subsection shall be included in all
subsequent computations under subsection (a) above.

                 (c)      The provisions of this Section 10.08 shall not
prevent the Company from paying regular dividends on the Preferred Stock.  The
aggregate amount of dividends paid by the Company pursuant to this subsection
shall not be included in subsequent computations under subsection (a) above.

                 (d)      The provisions of this Section 10.08 shall not
prevent the Company or any Subsidiary from repurchasing or redeeming shares of
Capital Stock or Subordinated Indebtedness of the Company out of the net cash
proceeds from the substantially concurrent issuance or sale (other than to a
Subsidiary except a Non-Recourse Subsidiary) of Capital Stock of the Company
(other than Redeemable Stock); provided, that the net cash proceeds from such
sale are excluded from clause (iii)(B) of subsection (a) above to the extent
such proceeds are applied to purchase or redeem such Capital Stock or
Subordinated Indebtedness.  The aggregate amount of Restricted Payments made by
the Company or any Subsidiary pursuant to this subsection shall not be included
in subsequent computations under subsection (a) above.





                                      -68-
<PAGE>   75
                 (e)      The provisions of this Section 10.08 shall not
prevent the Company or any Subsidiary from exchanging, repurchasing or
redeeming Subordinated Indebtedness of the Company (the "Retired Indebtedness")
solely in exchange for, or out of the net cash proceeds from the substantially
concurrent sale of, new Subordinated Indebtedness of the Company, so long as
such Subordinated Indebtedness (i) is subordinated to the Notes at least to the
same extent as the Retired Indebtedness, (ii) is scheduled to mature no earlier
than the scheduled maturity of the Retired Indebtedness and (iii) has an
Average Life at the time incurred that is greater than the Average Life of the
Retired Indebtedness.  The aggregate amount of consideration paid by the
Company pursuant to this subsection shall not be included in subsequent
computations under subsection (a) above.

                 SECTION 10.09.   Limitation on Indebtedness.  (a) The Company
shall not, and shall not permit any Subsidiary (other than a Non-Recourse
Subsidiary) to, directly or indirectly, create, incur, assume, suffer to exist,
Guarantee or otherwise become liable with respect to the payment of
(collectively, "incur"), any Indebtedness unless immediately after the date of
such transaction and after giving effect to the incurrence of such Indebtedness
and the receipt and application of the proceeds thereof as if such Indebtedness
had been incurred and the proceeds thereof applied on the first day of the
Determination Period, the Consolidated Interest Coverage Ratio of the Company
at such date is at least 2.50 to 1.0.

                 (b)      Notwithstanding Section 10.09(a), the Company or any
Subsidiary may incur any Permitted Indebtedness.

                 SECTION 10.10.   Limitation on Subsidiary Indebtedness and
Preferred Stock.  The Company shall not permit any Subsidiary to, directly or
indirectly, create, incur, assume, Guarantee or otherwise become liable with
respect to the payment of (collectively, "incur"), any Indebtedness or to issue
or suffer to exist any preferred stock, other than:

                 (i)      Indebtedness described in clauses (ii), (iii), (iv),
         (v), (vi), (viii), (ix), (xi), (xii), (xiii) and (xiv) of the
         definition of "Permitted Indebtedness" set forth in Section 1.01;

                 (ii)     Indebtedness of a Subsidiary which represents the
         assumption by such Subsidiary of Indebtedness (other than Non-Recourse
         Indebtedness) of another Subsidiary in connection with a merger of
         such Subsidiaries; provided that no Subsidiary or any successor (by
         way of merger) thereto existing on the Issue Date shall assume or
         otherwise incur any Indebtedness of an entity which is not a
         Subsidiary on the Issue Date, except to the extent that such
         Subsidiary would be permitted to incur such Indebtedness under this
         Indenture;

                 (iii)    Indebtedness or preferred stock of any Person
         existing at the time such Person becomes a Subsidiary; provided, that
         such Indebtedness was not incurred in anticipation of such corporation
         becoming a Subsidiary and would otherwise be permitted pursuant to
         Section 10.09(a);





                                      -69-
<PAGE>   76
                 (iv)     Indebtedness or preferred stock issued to and held by
         the Company or a Wholly Owned Subsidiary other than a Non-Recourse
         Subsidiary, so long as the transfer of such Indebtedness or preferred
         stock to a Person other than the Company or any Wholly Owned
         Subsidiary would be deemed to constitute the issuance of such
         Indebtedness or preferred stock by the issuer thereof;

                 (v)      Indebtedness or preferred stock issued in exchange
         for, or the proceeds of which are used to refinance, repurchase or
         redeem, Indebtedness or preferred stock described in clause (iii) of
         this Section 10.10 or in clause (ii) of the definition of "Permitted
         Liens" set forth in Section 1.01 (the "Retired Indebtedness or
         Stock"), provided that the Indebtedness or the preferred stock so
         issued has (A) a principal amount or liquidation value, as the case
         may be, not in excess of the principal amount or liquidation value of
         the Retired Indebtedness or Stock, (B) a final redemption date later
         than the stated maturity or final redemption date (if any) of the
         Retired Indebtedness or Stock and (C) an Average Life at the time of
         issuance of such Indebtedness or preferred stock that is greater than
         the Average Life of the Retired Indebtedness or Stock; or

                 (vi)     Indebtedness or preferred stock of a Subsidiary,
         which, when combined with (A) the aggregate amount of all other
         outstanding Indebtedness of the Subsidiaries plus the aggregate
         liquidation value of all preferred stock of any Subsidiary, in either
         case excluding any Non-Recourse Subsidiary (other than Indebtedness
         secured by Liens described under clauses (iii), (x), (xv) and (xix) of
         the definition of "Permitted Liens" set forth in Section 1.01), plus
         (B) the aggregate amount of all Indebtedness of the Company secured by
         Liens (other than such Indebtedness secured by Liens described under
         clauses (ii), (iii), (x), (xv) and (xix) of the definition of
         "Permitted Liens" set forth in Section 1.01), plus (C) the aggregate
         amount of all Capital Lease Obligations of the Company and the
         Subsidiaries, shall not exceed 10% of the Company's Consolidated Net
         Tangible Assets.

                 SECTION 10.11.   Limitation on Dividends and Other Payment
Restrictions Affecting Subsidiaries.  The Company shall not, and shall not
permit any Subsidiary (other than a Non-Recourse Subsidiary) to, directly or
indirectly, create, enter into any agreement with any Person, or otherwise
cause or suffer to exist or become effective any consensual encumbrance or
restriction which by its terms expressly restricts the ability of any
Subsidiary (other than a Non-Recourse Subsidiary) to (i) pay dividends, in cash
or otherwise, or make any other distributions on its Capital Stock, (ii) pay
any Indebtedness owed to the Company or any Subsidiary (other than a
Non-Recourse Subsidiary), (iii) make loans or advances to the Company or any
Subsidiary or (iv) transfer any of its Property or any assets to the Company or
any Subsidiary (other than a Non-Recourse Subsidiary), except encumbrances or
restrictions contained in any agreement or instrument (a) existing on the Issue
Date and listed on Schedule 10.11; (b) relating to any Property acquired by the
Company or any of the Subsidiaries after the date of this Indenture, provided
that such encumbrance or restriction relates only to the Property which is
acquired; (c) relating to any Indebtedness of any Subsidiary at the date of
acquisition of such Subsidiary by the Company or any Subsidiary; provided that
such Indebtedness was not incurred in connection with or anticipation of





                                      -70-
<PAGE>   77
such acquisition; (d) arising pursuant to an agreement effecting a refinancing
of Indebtedness issued pursuant to an agreement referred to in the foregoing
clauses (a) through (c), so long as the encumbrances and restrictions contained
in any such refinancing agreement are no more restrictive than the encumbrances
and restrictions contained in such agreements; (e) which constitute customary
provisions restricting subletting or assignment of any lease of the Company or
any Subsidiary or provisions in agreements that restrict the assignment of such
agreement or any rights thereunder; and (f) which constitute restrictions on
the sale or other disposition of any Property securing Indebtedness as a result
of a Permitted Lien on such Property.

                 SECTION 10.12.   Change of Control.  (a) Upon the occurrence
of a Change of Control, each Holder shall have the right to require the Company
to repurchase all of such Holder's Notes in whole or in part pursuant to the
offer described in paragraph (b) below (the "Change of Control Offer") at a
purchase price (the "Repurchase Price") in cash equal to 101% of the aggregate
principal amount of such Notes (or portions thereof) plus accrued and unpaid
interest thereon, if any, to the Change of Control Payment Date (as defined
below).  References in this Section 10.12 to Notes shall be deemed to refer to
portions of Notes, if such Notes are tendered in part.

                 (b)      Within 30 calendar days subsequent to the date of any
Change of Control, the Company shall mail a notice to each Holder and to the
Trustee stating:

                 (i)      that a Change of Control has occurred and a Change of
         Control Offer is being made pursuant to this Section 10.12, and that,
         although Holders are not required to tender their Notes, all Notes
         that are timely tendered will be accepted for payment;

                 (ii)     the Repurchase Price and the repurchase date, which
         shall be a date occurring no earlier than 30 days and no later than 60
         days subsequent to the date on which such notice is mailed (the
         "Change of Control Payment Date");

                 (iii)    that any Note not tendered will continue to accrue
         interest;

                 (iv)     that any Note accepted for payment pursuant to the
         Change of Control Offer will cease to accrue interest on and after the
         Change of Control Payment Date;

                 (v)      that any Holder electing to have a Note repurchased
         pursuant to a Change of Control Offer will be required to surrender
         the Note, with the form entitled "Election of Holder to Require
         Repurchase" on the reverse of the Note completed, to the Paying Agent
         at the address specified in the notice on or prior to the close of
         business on the Change of Control Payment Date;

                 (vi)     that any Holder will be entitled to withdraw such
         election if the Paying Agent receives, not later than the close of
         business on the third Business Day preceding the Change of Control
         Payment Date, a letter setting forth the name of the Holder, the
         principal amount





                                      -71-
<PAGE>   78
         of Notes the Holder delivered for repurchase and a statement that such
         Holder is withdrawing the Holder's election to have such Notes
         repurchased;

                 (vii)    that any Holder may elect to have such Holder's
         Notes repurchased in whole or in part, and if in part, in principal
         amounts equal to $1,000 or any integral  multiple thereof; and

                 (viii)   any other information necessary to enable Holders to
         tender their Notes and to have such Notes repurchased pursuant to this
         Section 10.12.

                 (c)      On the Change of Control Payment Date, the Company
shall (i) accept for payment any Note tendered pursuant to the Change of
Control Offer, (ii) deposit with the Paying Agent money sufficient to pay the
Repurchase Price of any Note so tendered and (iii) deliver to the Trustee an
Officers' Certificate that states the aggregate principal amount of Notes
accepted by the Company for payment.  The Paying Agent shall promptly mail to
each Holder of Notes so accepted payment in an amount equal to the Repurchase
Price therefor.  The Company shall publicly announce the results of the Change
of Control Offer on or as soon as practicable after the Change of Control
Payment Date.  For purposes of this Section 10.12, the Trustee shall act as the
Paying Agent.

                 (d)      Notwithstanding the foregoing, if any Note accepted
for payment shall not be so paid pursuant to the provisions of this Section
10.12, then, from the Change of Control Payment Date until the principal of
(and premium) and interest on such Note is paid, interest shall be paid on the
unpaid principal (and premium) and, to the extent permitted by law, on any
accrued but unpaid interest thereon, in each case at the rate or rates
prescribed therefor in the Notes.

                 (e)      Upon surrender of a Note that is tendered in part,
the Company shall issue and the Trustee shall authenticate a new Note equal in
principal amount to the untendered portion of the Note surrendered.

                 (f)      The Company shall comply with any applicable tender
offer rules (including, without limitation, any applicable requirements of Rule
14e-1 under the Exchange Act) in the event that the repurchase offer is
triggered under the circumstances described herein.

                 SECTION 10.13.   Limitation on Asset Sales.  (a) The Company
shall not engage in, and shall not permit any Subsidiary (other than a
Non-Recourse Subsidiary) to engage in, any Asset Sale unless:

                 (i)      except in the case of an Asset Sale resulting from
         the requisition of title to, seizure or forfeiture of any Property or
         assets or any actual or constructive total loss or an agreed or
         compromised total loss, the consideration received by the Company or
         such Subsidiary for such Asset Sale at the time thereof is at least
         equal to the Fair Market Value of the Property; and





                                      -72-
<PAGE>   79
                 (ii)     at least 75% of the consideration from such Asset
         Sale consists of Cash Proceeds (or the assumption of Indebtedness of
         the Company or such Subsidiary relating to the Capital Stock or
         Property that was the subject of such Asset Sale and the release of
         the Company or such Subsidiary from such Indebtedness).

                 (b)      The Company or a Subsidiary, as the case may be, may
apply the Net Available Proceeds of an Asset Sale engaged in by such Person to
(i) the acquisition of one or more Replacement Assets, provided that such Net
Available Proceeds are so applied within 365 days after the related Asset Sale,
(ii) repay Indebtedness described under clause (ii) of the definition of
"Permitted Indebtedness" set forth in Section 1.01 (but only if the related
commitments or amounts available to be reborrowed thereunder are permanently
reduced by the amount of such payment) or (iii) purchase and retire, or
otherwise repay, in whole or in part the Company's 9-1/4% Senior Notes Due 2003
originally issued under an Indenture dated as of October 1, 1993.  The amount
of Net Available Proceeds not applied in accordance with the foregoing sentence
shall constitute "Excess Proceeds."  When the aggregate amount of outstanding
Excess Proceeds from all Asset Sales exceeds $15,000,000 (the "Trigger Date"),
the Company shall make a pro rata offer (an "Asset Sale Offer") to purchase,
from all Holders and holders of any then outstanding Pari Passu Indebtedness
required to be repurchased or repaid on a permanent basis in connection with an
Asset Sale, an aggregate principal amount (expressed as a multiple of $1,000)
of Notes and any such Pari Passu Indebtedness equal to such Excess Proceeds as
follows:

                 (1)      Not later than the 30th day following the Trigger
         Date, the Company shall (i) give a written notice to the Trustee at
         its Corporate Trust Office and to each Holder, as such Holder's name
         and address appear in the Security Register, in each case by
         first-class postage prepaid mail (a "Purchase Notice") offering to
         purchase (a "Net Proceeds Offer") from all Holders the maximum
         principal amount (expressed as a multiple of $1,000) of Notes that may
         be purchased out of an amount (the "Payment Amount") equal to the
         product of such Excess Proceeds multiplied by a fraction, the
         numerator of which is the outstanding principal amount of the Notes
         and the denominator of which is the sum of the outstanding principal
         amount of the Notes and any such Pari Passu Indebtedness, if any
         (subject to proration in the event the Payment Amount is less than the
         aggregate Offered Price (as hereinafter defined) of all Notes
         tendered), and (ii) to the extent required by any Pari Passu
         Indebtedness and provided there is a permanent reduction in the
         principal amount of such Pari Passu Indebtedness, the Company shall
         make an offer to purchase such Pari Passu Indebtedness (a "Pari Passu
         Offer") in an amount (the "Pari Passu Indebtedness Amount") equal to
         the excess of the Excess Proceeds over the Payment Amount.

                 (2)      The offer price for the Notes shall be payable in
         cash in an amount equal to 100% of the aggregate principal amount of
         the Notes tendered pursuant to a Net Proceeds Offer, plus accrued and
         unpaid interest, if any, to the date such Net Proceeds Offer is
         consummated (the "Offered Price"), in accordance with Section
         10.13(c).  To the extent that the aggregate Offered Price of the Notes
         tendered pursuant to a Net Proceeds Offer is less than the Payment
         Amount relating thereto or the aggregate amount of the Pari Passu





                                      -73-
<PAGE>   80
         Indebtedness that is purchased or repaid pursuant to the Pari Passu
         Offer is less than the Pari Passu Indebtedness Amount (such shortfall
         constituting a "Net Proceeds Deficiency"), the Company may use such
         Net Proceeds Deficiency, or a portion thereof, for general corporate
         purposes, subject to the limitations of Section 10.08 and the amount
         of Excess Proceeds shall be reset to zero.

                 (3)      If the aggregate Offered Price of Notes validly
         tendered and not withdrawn by Holders thereof exceeds the Payment
         Amount, Notes to be purchased will be selected on a pro rata basis by
         the Trustee based on the aggregate principal amount of Notes so
         tendered.  Upon completion of a Net Proceeds Offer and a Pari Passu
         Offer, the amount of Excess Proceeds shall be reset to zero.

                 (4)      The Purchase Notice shall set forth a purchase date
         (the "Net Proceeds Payment Date"), which shall be on a Business Day no
         earlier than 30 days nor later than 60 days from the Trigger Date.
         The Purchase Notice shall also state (i) that a Trigger Date with
         respect to one or more Asset Sales has occurred and that such Holder
         has the right to require the Company to repurchase such Holder's Notes
         at the Offered Price, subject to the limitations described in the
         forgoing paragraph (3), (ii) any information regarding such Net
         Proceeds Offer required to be furnished pursuant to Rule 14e-1 under
         the Exchange Act and any other securities laws and regulations
         thereunder, (iii) that any Note, or portion thereof, not tendered or
         accepted for payment will continue to accrue interest, (iv) that,
         unless the Company defaults in depositing money with the Paying Agent
         in accordance with the last paragraph of Section 10.13(c), or payment
         is otherwise prevented, any Note, or portion thereof, accepted for
         payment pursuant to the Net Proceeds Offer shall cease to accrue
         interest after the Net Proceeds Payment Date, and (v) the instructions
         a Holder must follow in order to have its Notes repurchased in
         accordance with Section 10.13(c).

                 (c)      Holders electing to have Notes purchased will be
required to surrender such Notes, with the section entitled "Election of
Holders to Require Repurchase" on the reverse of the Notes completed, to the
Trustee at the address specified in the notice at least five Business Days
prior to the Net Proceeds Payment Date.  Holders will be entitled to withdraw
their election if the Trustee receives, not later than three Business Days
prior to the Net Proceeds Payment Date, a telegram or letter setting forth the
name of the Holder, the principal amount of the Notes delivered for purchase by
the Holder as to which such election is to be withdrawn and a statement that
such Holder is withdrawing its election to have such Notes purchased.  Holders
whose Notes are purchased only in part shall be issued new Notes equal in
principal amount to the unpurchased portion of the Notes surrendered.

                 (d)      On the Net Proceeds Payment Date, the Company shall
(i) accept for payment any Note tendered pursuant to the Net Proceeds Offer,
(ii) deposit with the Trustee money sufficient to pay the repurchase price of
any Note or portion thereof so tendered in an aggregate amount equal to the
Payment Amount or such lesser amount and (iii) deliver to the Trustee an
Officers' Certificate that states the aggregate principal amount of Notes
accepted by the Company for payment.  The





                                      -74-
<PAGE>   81
Paying Agent shall promptly mail to each Holder of Notes so accepted payment in
an amount equal to the purchase price therefor.

                 (e)      Notwithstanding the foregoing, if any Note accepted
for payment shall not be so paid pursuant to the provisions of this Section
10.13, then, from the Net Proceeds Payment Date until the principal of and
interest on such Note is paid, interest shall be paid on the unpaid principal
and, to the extent permitted by law, on any accrued but unpaid interest
thereon, in each case at the rate or rates prescribed therefor in the Notes.

                 (f)      Upon surrender of a Note that is tendered in part,
the Company shall issue and the Trustee shall authenticate a new Note equal in
principal amount to the untendered portion of the Note surrendered.

                 (g)      The Company shall comply with any applicable tender
offer rules (including, without limitation, any applicable requirements of Rule
14e-1 under the Exchange Act) in the event that an offer to purchase is made
under the circumstances described in this Section 10.13.

                 SECTION 10.14.   Limitation on Sale and Lease-Back
Transactions. The Company shall not, and shall not permit any Subsidiary (other
than a Non-Recourse Subsidiary) to, directly or indirectly, enter into, assume,
Guarantee or otherwise become liable with respect to any Sale and Lease-Back
Transaction if the lease obligations of the Company or any such Subsidiary
created or incurred in connection with such Sale and Lease-Back Transaction
constitute Capital Lease Obligations, unless the Company or such Subsidiary
would have been permitted to enter into such transaction under (i) Section
10.09(a), (ii) clause (vi) of Section 10.10 (in the case of a Subsidiary) and
(iii) Section 10.15.  Any Sale and Lease-Back Transaction that the Company or
any Subsidiary enters into and does not result in the creation or incurrence of
any Capital Lease Obligation of the Company or any Subsidiary, shall be deemed
to constitute an Asset Sale.

                 SECTION 10.15.   Limitation on Liens.  The Company shall not,
and shall not permit any Subsidiary to, directly or indirectly, create, affirm,
incur, assume or suffer to exist (collectively, "suffer to exist") any Lien on
or with respect to any Property of the Company or such Subsidiary or any
interest therein or any income or profits therefrom, whether owned at the date
hereof or hereafter acquired, without effectively providing that the Notes
shall be secured equally and ratably with (or prior to) the Indebtedness so
secured, other than Permitted Liens.

                 SECTION 10.16.   Certificate as to Default.  The Company shall
deliver to the Trustee within 120 days after the end of each fiscal year of the
Company ending after the date hereof, a certificate from the principal
executive officer, principal financial officer or principal accounting officer
of the Company, stating whether or not, to the best knowledge of such officer,
the Company has complied with all conditions and covenants under this
Indenture, and, if the Company shall be in Default, specifying all such
Defaults and the nature thereof of which such officer may have knowledge.





                                      -75-
<PAGE>   82
                 For the purposes of this Section 10.16, compliance shall be
determined without regard to any period of grace or requirement of notice under
this Indenture.

                 The Company shall deliver written notice to the Trustee five
days after any executive officer of the Company has knowledge of the occurrence
of any event which with the giving of notice or the lapse of time or both would
become an Event of Default under subsection (3), (4), (5), (6), (7) or (8) of
Section 5.01.

                 SECTION 10.17. Insurance.  The Company will at all times keep
all its and the Subsidiaries' Properties which are of an insurable nature
insured with insurers, reasonably believed by the Company to be responsible,
against loss or damage to the extent that property of similar character is
usually so insured by corporations similarly situated and owning like
properties.

                 SECTION 10.18. Changes to NN-1 Agreement of Limited
Partnership.  The Company shall not, and shall not permit any Subsidiary to,
amend, modify or waive Section 5.1(c) of the Agreement of Limited Partnership
of the NN-1 Limited Partnership.

                 SECTION 10.19.  Certain Covenants Suspended.  The covenants
set forth in this Article X will be applicable to the Company, except that
during any period of time that:

                 (i)      the ratings assigned to the Notes by both S&P and
         Moody's (collectively, the "Rating Agencies") are equal to or higher
         than BBB- and Baa3, or the equivalents thereof, respectively (the
         "Investment Grade Ratings"); and

                 (ii)     no Event of Default or Default has occurred and is
         continuing,

the Company and its Subsidiaries will not be subject to the provisions of
Section 10.08, Section 10.09 and Section 10.13 and clauses (3) and (4) of
Section 8.01 of this Indenture (collectively, the "Suspended Covenants").

                 In the event that the Company is not subject to the Suspended
Covenants for any period of time as a result of the preceding sentence and,
subsequently, one or both Rating Agencies withdraws its ratings or downgrades
the ratings assigned to the Securities below the required Investment Grade
Ratings, then the Company and its Subsidiaries will again be subject to the
Suspended Covenants and compliance with the Suspended Covenants with respect to
Restricted Payments made after the time of such withdrawal or downgrade will be
calculated in accordance with the terms of Section 10.08 as if such Section had
been in effect during the entire period of time from the date of this
Indenture.





                                      -76-
<PAGE>   83
                                   ARTICLE XI

                                  Redemptions

                 SECTION 11.01.  Notice to Trustee.  The Company may at its
option redeem Notes pursuant to paragraph 4 of the reverse of the Notes.  In
order to effect any such redemption, the Company shall notify the Trustee at
least 45 days prior to the Redemption Date (unless a shorter period is
acceptable to the Trustee) of the Redemption Date and the principal amount of
Notes to be redeemed and it shall deliver to the Trustee an Officers'
Certificate, a Board Resolution authorizing the redemption and an Opinion of
Counsel with respect to the due authorization of such redemption and to the
effect that such redemption is being made in accordance with this Indenture and
the Notes.

                 SECTION 11.02.  Selection of the Notes To Be Redeemed.  If
less than all the Notes are to be redeemed, the Trustee shall select, subject
to the remainder of this Section, the Notes to be redeemed by any manner that
is acceptable to the Trustee.  The Trustee shall make the selection not more
than 60 days and not less than 30 days before each Redemption Date from Notes
outstanding not previously called for redemption.  The Trustee may select for
redemption portions of the principal of Notes that have denominations larger
than $1,000.  Notes and portions of them it selects shall be in amounts of
$1,000 or integral multiples of $1,000.  Provisions of this Indenture that
apply to Notes called for redemption shall also apply to portions of Notes
called for redemption.  The Trustee shall notify the Company promptly of the
Notes or portions of Notes to be called for redemption.

                 SECTION 11.03. Notice of Redemption.  At least 30 but not more
than 60 days before a Redemption Date, the Company shall mail a notice of
redemption by first-class mail to each Holder whose Notes are to be redeemed.

                 The notice shall identify the Notes to be redeemed and shall
state:

                          (1)     the Redemption Date;

                          (2)     the Redemption Price and the amount of
                 accrued interest to be paid;

                          (3)     the name and address of the Paying Agent;

                          (4)     that the Notes called for redemption must be
                 surrendered to the Paying Agent to collect the Redemption
                 Price and accrued interest, if any;

                          (5)     whether such redemption is made pursuant to
                 the sinking fund provisions of Article XII;





                                      -77-
<PAGE>   84
                          (6)     that, unless the Company defaults in making
                 the redemption payment, interest on the Notes called for
                 redemption ceases to accrue on and after the specified
                 Redemption Date; and

                          (7)     if any Note is being redeemed in part, the
                 portion of the principal amount (equal to $1,000 or any
                 integral multiple thereof) of such Note to be redeemed and
                 that, on or after the Redemption Date, upon surrender of such
                 Note, a new Note or Notes in principal amount equal to the
                 unredeemed portion thereof will be issued.

                 At the Company's request, the Trustee shall give the notice of
redemption in the Company's name and at its expense.

                 SECTION 11.04.  Effect of Notice of Redemption.  Once notice
of redemption is mailed, the Notes called for redemption become due and payable
on the specified Redemption Date at the Redemption Price.

                 SECTION 11.05.  Deposit of Redemption Price on Redemption.  On
or before each Redemption Date the Company shall deposit with the Paying Agent
money (which shall be immediately available funds if deposited on the
Redemption Date and which must be received by such Paying Agent prior to 10:00
a.m. New York City time) sufficient to pay the Redemption Price of and accrued
interest on all Notes to be redeemed on that date.  The Paying Agent shall
return to the Company any money not required for that purpose.

                 SECTION 11.06. Notes Redeemed in Part. Upon surrender of a
Note that is redeemed in part, the Company shall issue and the Trustee shall
authenticate a new Note equal in principal amount to the unredeemed portion of
the Note surrendered.

                 This instrument may be executed in any number of counterparts,
each of which so executed shall be deemed to be an original, but all such
counterparts shall together constitute but one and the same instrument.





                                      -78-
<PAGE>   85
                 IN WITNESS WHEREOF, the parties hereto have caused this
Indenture to be duly executed, and the corporate seal of the Company to be
hereunto affixed and attested, all as of the day and year first above written.


                                    NOBLE DRILLING CORPORATION

                                  
                                  
                                    By /s/ BYRON L. WELLIVER
                                       ----------------------------------------
                                    Name:  BYRON L. WELLIVER
                                    Title: SENIOR VICE PRESIDENT-FINANCE
                                  
[Corporate Seal]

Attest:


/s/ JULIE J. ROBERTSON                     
- ------------------------------------
Assistant-Secretary

                                    TEXAS COMMERCE BANK NATIONAL
                                    ASSOCIATION, as Trustee
                                    
                                    
                                    
                                    By /s/ TERRY L. STEWART                  
                                       ----------------------------------------
                                    Name:  TERRY L. STEWART
                                    Title: ASSISTANT VICE PRESIDENT





                                      -79-
<PAGE>   86
STATE OF TEXAS          )
                        )      
COUNTY OF DALLAS        )      


          On the day of June 28, 1996, before me personally came to me known
Byron L. Welliver, who, being by me duly sworn, did depose and say that he is
Sr. VP-Finance of Noble Drilling Corporation, one of the corporations
described in and which executed the foregoing instrument; that he knows the
seal of said corporation; that the seal affixed to said instrument is such
corporate seal; that it was so affixed by authority of the Board of Directors
of said corporation, and that he signed his name thereto by like authority.



                                             /s/ MARILYN KITTELSON             
                                    -------------------------------------------
                                                   Notary Public

                                    Qualified in
                                    Commission Expires

                                    MARILYN KITTELSON           
[Seal]                              Notary Public, State of Texas      
                                    My Commission Expires 8-3-96        





                                      -80-
<PAGE>   87
STATE OF TEXAS          )      
                        )         
COUNTY OF HARRIS        )      


          On the day of June 27, 1996, before me personally came to me known
Terry L. Stewart, who, being by me duly sworn, did depose and say that he is
Assistant Vice President of Texas Commerce Bank National Association, one of
the corporations described in and which executed the foregoing instrument; that
he knows the seal of said corporation; that the seal affixed to said instrument
is such corporate seal; that it was so affixed by authority of the Board of
Directors of said corporation, and that he signed his name thereto by like
authority.



                                                 /s/ PAT WAGNER          
                                    -------------------------------------------
                                                   Notary Public


                                    Qualified in
                                    Commission Expires


                                    PAT WAGNER         
[Seal]                              Notary Public, State of Texas       
                                    My Commission Expires March 22, 2000     





                                      -81-
<PAGE>   88
                           NOBLE DRILLING CORPORATION
                                 SCHEDULE 1.01A
                   INDEBTEDNESS OUTSTANDING ON THE ISSUE DATE



<TABLE>
<CAPTION>

                                               Interest       Interest       Amount           Amount          Amount
                                                Basis           Rate       Outstanding      Due Within      Available
Loan Description                                                                             One Year
                                                                              (000)           (000)           (000)   
- ------------------------------------------    ----------    -----------    -----------    ------------    ------------
<S>                                            <C>             <C>          <C>              <C>           <C>         
9-1/4% Senior Notes Due 2003                   9-1/4%          9.25%        $ 125,000             0               0
    Obligor: Noble Drilling Corporation

Wells Fargo Bank
  US Line of Credit                              (a)           5.75%                0             0         $22,500(2)
    Obligor: Noble Drilling Corporation

Transamerica                                    6.23%          6.23%            8,766        $5,844               0
    Obligor: Noble Drilling Services Inc.

Royal Bank of Canada:
  Canadian Line of Credit                    RB Prime+.75     8.95%                0             0           1,000(1)
    Obligor: Noble Drilling (Canada) Ltd.

U.S. Government - Guaranteed Ship               8.95%          8.95%            1,286           520               0
  Financial Sinking Fund Bonds
    Obligor: NN-1 Limited Partnership
</TABLE>



(1)   Margined to 75% of receivables outstanding less than ninety days.
(2)   Margined to 75% of Noble Drilling U.K. Ltd., Noble Drilling U.S. Inc.,
      Noble Drilling (Mexico) Inc., Noble Drilling (West Africa) Ltd., Noble
      Drilling (West Africa) Inc., Noble Drilling de Venezuela, Noble Offshore
      Corporation, Noble International Ltd. receivables outstanding less than
      90 days.  Noble Drilling de Venezuela and Noble Drilling (West Africa)
      Ltd. receivables limited to US$ portion only.

(a)   Greater of the prime rate as set by the Agent in Houston, Texas, and the
      sum of the Federal Funds rate and 0.5%.

Guarantees

None

Letters of Credit

1.    Noble International Ltd. - Mexico:  $1,360,100 performance bond in favor
      of Fianzas Monterrey Aetna.
2.    Noble International Ltd. - Qatar:  $1,690,630 performance bond in favor
      of QGPC.
3.    Noble International Ltd. - Qatar:  $2,082,231 performance bond in favor
      of QGPC.
4.    Noble Drilling de Venezuela:  $689,655 promissory note in favor of Banco
      Provincial.
5.    Noble International Ltd. - Mexico:  $1,600,000 bid bond in favor of
      Fianzas Monterrey Aetna.
<PAGE>   89

                           NOBLE DRILLING CORPORATION
                                 SCHEDULE 1.01B
                      LIENS IN EXISTENCE ON THE ISSUE DATE



Liens in favor of Royal Bank of Canada
      Noble Drilling (Canada) Ltd. - U.S. $1,000,000 line of credit:

      Land and buildings in Nisku Industrial Park in Edmonton
      Assignment of accounts receivable of Noble Drilling (Canada) Ltd.

Liens in favor of United States Government:
      NN-1, jackup rig

<PAGE>   90

                           NOBLE DRILLING CORPORATION
                                 SCHEDULE 10.11
        CERTAIN ENCUMBRANCES OR RESTRICTIONS CONTAINED IN ANY AGREEMENT
                  OR INSTRUMENT AND EXISTING ON THE ISSUE DATE



Limited Partnership Agreement dated as of January 16, 1992, between Noble
Drilling Corporation and National Enerdrill Corporation relating to NN-1
Limited Partnership, a Texas limited partnership.



<PAGE>   1

                                                                    EXHIBIT 99.1


 
                DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS
 
     This Prospectus includes "forward-looking statements" within the meaning of
Section 27A of the Securities Act of 1933, as amended (the "Securities Act"),
and Section 21E of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"). All statements other than statements of historical facts
included in this Prospectus, including without limitation, statements under
"Risk Factors -- Intense Competition; Industry Conditions," "The
Company -- Offshore Contract Drilling Operations -- Offshore Drilling Rigs" and
"Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Outlook" and "-- Liquidity and Capital Resources," regarding the
Company's financial position, business strategy, plans and objectives of
management of the Company for future operations and indebtedness covenant
compliance, are forward-looking statements. Although the Company believes that
the expectations reflected in such forward-looking statements are reasonable, it
can give no assurance that such expectations will prove to have been correct.
Important factors that could cause actual results to differ materially from the
Company's expectations ("Cautionary Statements") are disclosed under "Risk
Factors" and elsewhere in this Prospectus, including without limitation in
conjunction with the forward-looking statements included in this Prospectus. All
subsequent written and oral forward-looking statements attributable to the
Company or persons acting on its behalf are expressly qualified in their
entirety by the Cautionary Statements.
 
                                USE OF PROCEEDS
 
   
     The net proceeds from the sale of the shares of Common Stock offered in the
Equity Offerings will be approximately $236,000,000 ($271,400,000 if the
Underwriters' over-allotment options are exercised in full), after deducting the
underwriting discount and estimated expenses of the Equity Offerings payable by
the Company.
    
 
   
     The net proceeds to the Company from the Debt Offering being made
concurrently herewith, after deducting the underwriting discount and estimated
expenses of the Debt Offering payable by the Company, are expected to be
approximately $122,000,000. The closing of each Offering is conditioned upon the
simultaneous closing of the other Offerings and upon the simultaneous closing of
the Acquisition.
    
 
   
     Of the net proceeds from the Offerings, $300,000,000 will be used to fund
the cash portion of the purchase price of the Acquisition (see "The
Acquisition"). The net proceeds from the Offerings remaining after payment of
the purchase price of the Acquisition of approximately $58,000,000 will be added
to the Company's working capital and will be available for general corporate
purposes. Such general corporate purposes are expected to include planned
upgrade and refurbishment capital expenditures for several of the Company's and
Neddrill's drilling rigs and may include the purchase of other capital assets.
See "Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Liquidity and Capital Resources -- Capital Expenditures and
Commitments."
    
 
                                     -14-
<PAGE>   2
 
The Company's land drilling operations have become less significant as the
Company has emphasized its offshore and international operations.
 
RECENT DEVELOPMENTS
 
  Asset Rationalization Program
 
   
     Consistent with the Company's strategic objectives to enhance the deepwater
capability of its fleet, the Company has sold two of its posted barges (the Gus
Androes and Gene Rosser) and, at March 31, 1996, reclassified its two remaining
posted barges (the Lewis Dugger and Chuck Syring) as assets held for sale. On
June 21, 1996, the Company entered into an asset purchase agreement to sell the
Lewis Dugger and Chuck Syring to Mallard Bay Drilling, Inc., a subsidiary of
Energy Ventures, Inc., for $32,000,000, composed of $24,500,000 in cash and
$7,500,000 in drill pipe credit. Closing is subject to U.S. Department of
Transportation, Maritime Administration approval and certain other closing
conditions. The net proceeds from the sale of the four barges, together with
working capital, have been used to purchase the two jackup rigs described in the
next paragraph and are planned to be used to enhance the deepwater capability of
the Company's fleet.
    
 
     On February 26, 1996, the Company purchased the Odin Explorer, renamed the
Gus Androes, a 300-foot independent leg cantilevered jackup rig located in the
United Arab Emirates. The rig is currently undergoing refurbishment and is
scheduled to be available for work in the third quarter of 1996. In addition, on
March 20, 1996, the Company purchased the Dana, a 250-foot independent leg
cantilevered jackup rig located offshore Qatar.
 
                                THE ACQUISITION
 
     On April 25, 1996, the Company entered into an Agreement of Sale and
Purchase (the "Acquisition Agreement") with Nedlloyd and Neddrill Holding B.V.
to acquire the assets of Neddrill utilized in its offshore contract drilling,
accommodation and other oil and gas exploration and production related service
businesses, $25,000,000 in net working capital and the personnel employed by
Neddrill. The purchase price is $300,000,000 in cash plus 5,000,000 shares of
Common Stock.
 
     The Acquisition promotes the Company's historic and long-term strategic
goals of expanding its international presence and enhancing its deepwater
drilling capabilities. The Acquisition adds deepwater and harsh environment
capabilities to the Company's fleet, diversifies the fleet to include drillships
and a semisubmersible and increases the Company's geographic diversification by
providing entry into the Brazilian offshore market and expanding its presence in
the North Sea.
 
   
     Neddrill's operations are managed from its headquarters in Rotterdam, The
Netherlands. Its fleet includes two dynamically positioned drillships (one of
which is currently operating offshore West Africa, the second offshore Brazil);
one second generation semisubmersible rig operating in the North Sea; and six
harsh environment jackup drilling rigs (five operating in the North Sea and one
offshore Argentina). Neddrill also owns a 41 percent interest in a third
dynamically positioned drillship through a joint venture for which Neddrill will
operate the drillship. In addition, Neddrill operates under a bareboat charter a
seventh harsh environment jackup rig as a hotel accommodation unit in the North
Sea. Neddrill's semisubmersible and jackup rigs are all currently under
contract, with commitments extending through August 1996 to 2001, depending on
the rig. All three drillships are committed under five to six year contracts to
work for Petrobras offshore Brazil. In addition to the one drillship already on
location, the other two are scheduled to arrive in late 1996 or early 1997.
    
 
     Neddrill currently employs approximately 615 personnel in offshore/field
positions and 60 employees in shorebase and administrative positions. Depending
on location, some employees are covered by a labor agreement or are represented
by labor unions. Neddrill's employees will initially receive the same pay rates
and benefits package as they received prior to closing of the Acquisition,
although the Acquisition Agreement does not bind the Company to continue to
provide pay or benefits except as required by applicable law and existing
employment agreements. Neddrill maintains shorebase facilities in Argentina,
Brazil, Denmark, the United Kingdom and The Netherlands.
 

                                     -23-
<PAGE>   3
 
     The Acquisition will expand the types of rigs comprising the Company's
offshore fleet to include drillships and a semisubmersible. Each of these types
of rigs is described further below.
 
     Drillships. Drillships are ships that are equipped for drilling and are
typically self-propelled and move from one location to another under their own
power. Drillships are positioned over the well through use of either an
anchoring system or a computer controlled thruster system (dynamic positioning).
Neddrill's two wholly owned drillships are capable of drilling in water depths
of up to 4,500 feet. Upon completion of a scheduled substantial upgrade, the
Neddrill Muravlenko will be capable of drilling in water depths of up to 4,000
feet. Drillships are typically more expensive to construct and operate than
jackup rigs.
 
     Semisubmersible Rigs. Semisubmersible rigs are floating platforms which, by
means of a water ballasting system, can be submerged to a predetermined depth so
that a substantial portion of the hull is below the water surface during
drilling operations. Neddrill's semisubmersible rig maintains its position over
the well through the use of dynamic positioning. Neddrill's semisubmersible rig
is designed to work in water depths of up to 1,500 feet and can drill in many
areas where the Company's jackup rigs can also drill. However, semisubmersible
rigs normally require water depth of at least 200 feet in order to conduct
operations. Semisubmersible rigs are typically more expensive to construct and
operate than jackup rigs.
 
     The following table sets forth certain information concerning Neddrill's
owned and operated offshore drilling fleet at March 31, 1996. Unless otherwise
indicated, Neddrill wholly owns and operates the units listed in the table.
 
                        NEDDRILL OFFSHORE DRILLING RIGS
 
<TABLE>
<CAPTION>
                                                                   YEAR       WATER     MAXIMUM
                                                                 BUILT OR     DEPTH     DRILLING 
           NAME                       MAKE           TYPE(1)    REBUILT(2)    RATING     DEPTH        LOCATION     STATUS(3)
- --------------------------  ------------------------ -------    ----------    ------    -------     ------------   ---------
                                                                              (FEET)    (FEET)
<S>                         <C>                      <C>        <C>           <C>       <C>        <C>            <C>
DYNAMICALLY POSITIONED
  DRILLSHIPS-3
Neddrill 1................  Gusto Engineering                     1995R       4,500     20,000     West Africa    Active
                            Pelican Class (enhanced)
Neddrill Muravlenko (4)...  Gusto Engineering                      1982         984     21,000     Norway         Docked
                            Pelican Class
Neddrill 2 (5)............  Neddrill                               1977       4,500     25,000     Brazil         Active
SEMISUBMERSIBLE-1
Neddrill 6 (6)(7).........  Offshore Co. SCP III                  1991R       1,500     25,000     U.K.           Active
JACKUP RIGS-7
Neddrill Trigon             CFEM T-2005C
  (6)(7)(8)...............                            IC           1982         360     25,000     Argentina      Active
Neddrill 10 (6)(7)........  CFEM T-2005C              IC           1982         300     25,000     Denmark        Active
Neddrill 3 (6)(7).........  Marine Structure CJ-46    IC           1982         250     20,000     Netherlands    Active
Neddrill 9 (6)(7).........  Marine Structure CJ-46    IC           1982         230     20,000     France         Active
Neddrill 7 (6)(7).........  Marine Structure CJ-46    IC           1981         205     25,000     U.K.           Active
Neddrill 4 (6)(7).........  Neddrill                  IC           1982         250     20,000     Netherlands    Active
Neddrill Kolskaya           Gusto Engineering
  (6)(9)..................                            IC           1983         330        N/A     Denmark        Active
</TABLE>
 
- ---------------
 
(1) Type code is defined as follows:
 
    IC . . . . Independent Leg Cantilevered jackup rig
 
(2) Rigs designated with an "R" were modified, refurbished or otherwise upgraded
    in such year by capital expenditures in an amount material to the net book
    value of the rig.
 
(3) Rigs listed as active were operating under contract as of March 31, 1996.
 
   
(4) Neddrill owns a 41 percent interest in the drillship through a joint venture
    arrangement. The drillship is scheduled to be upgraded in Gibraltar in the
    second half of 1996 to increase water depth rating to 4,000 feet at a
    projected total cost of $36,000,000 (one-half to be paid by Neddrill). See
    "Management's
    
 

                                     -24-
<PAGE>   4
 
    Discussion and Analysis of Financial Condition and Results of
    Operations -- Liquidity and Capital Resources."
 
(5) Scheduled to be upgraded in the second half of 1996 to increase water depth
    rating to 6,000 feet at a projected cost of $26,000,000. See "Management's
    Discussion and Analysis of Financial Condition and Results of
    Operations -- Liquidity and Capital Resources."
 
(6) Harsh environment capability.
 
(7) Equipped with a top drive unit.
 
(8) Scheduled to be returned to the North Sea in the second half of 1996 and
    upgraded to increase leg holding capacity, repair spudcans and extend
    cantilever reach at a projected cost of approximately $14,000,000. See
    "Management's Discussion and Analysis of Financial Condition and Results of
    Operations -- Liquidity and Capital Resources."
 
(9) Neddrill operates this unit, which is presently used in offshore hotel
    accommodation mode (at a capacity of 250 bunks) instead of drilling mode,
    under a bareboat charter terminating in August 1996, with an option to
    extend through April 1997.
 
     The Neddrill 2 is currently operating under contract for Petrobras offshore
Brazil. The Neddrill 1, which is currently operating under contract offshore
West Africa, was upgraded in 1995 from moored-only positioning to a rated water
depth of 4,500 with dynamic positioning. The Neddrill 1 is scheduled during the
second half of 1996 for mobilization to Brazil to substitute for the Neddrill 2
while it undergoes a scheduled upgrade during the fourth quarter of 1996 to a
rated water depth of 6,000 feet, after which the Neddrill 2 is scheduled to
continue in a renewed long-term contract with Petrobras. Upon the return
offshore Brazil of the Neddrill 2, the Neddrill 1 is scheduled for certain
refurbishments upon conclusion of which it also is scheduled to commence a
long-term contract with Petrobras. Each of the contracts with Petrobras contains
provisions that permit Petrobras to terminate the contract without further
obligation under certain circumstances, including the failure of Neddrill to
perform its obligations under the contract. Generally, Neddrill's other drilling
contracts permit the operator to terminate the contracts without further
obligation upon relatively short prior notice (in one contract, 10 days) to
Neddrill. Such provisions are common in oil and gas offshore drilling contracts.
 
     The closing of the Acquisition is contingent upon the simultaneous closing
of the Equity Offerings and the Debt Offering. The closing of the Acquisition is
also subject to certain other conditions, including a condition to the
obligation of the Company to proceed with the closing that no actual,
constructive, arranged or compromised total loss of the Neddrill 1, Neddrill 2
or Neddrill 6 or of two or more of Neddrill's other rigs shall have occurred or
that there not have been the cancellation, termination or rescission by
Petrobras of either of the current drilling contracts with Petrobras regarding
the Neddrill 1 or Neddrill 2. If an actual, constructive, arranged or
compromised total loss of only one of the rigs not specified occurs, there will
be a reduction to the purchase price based on an amount scheduled for each
drilling unit in the Acquisition Agreement. There can be no assurance that such
other conditions will be satisfied or that the Acquisition will be completed.
 
     The closing of the Equity Offerings and the Debt Offering is contingent
upon the simultaneous closing of the Acquisition. If the Acquisition is not
completed for any reason, the Offerings will not be consummated.
 

                                     -25-


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