CARRIZO OIL & GAS INC
8-K, 1999-12-03
CRUDE PETROLEUM & NATURAL GAS
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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): December 1, 1999


                             CARRIZO OIL & GAS, INC.
             (Exact name of registrant as specified in its charter)


         TEXAS                               000-22915           76-0415919
(State or other jurisdiction of            (Commission        (I.R.S. Employer
incorporation)                             File Number)      Identification No.)


                              14811 ST. MARY'S LANE
                                    SUITE 148
                              HOUSTON, TEXAS 77079
              (Address of principal executive offices and zip code)


       Registrant's telephone number, including area code: (281) 496-1352





<PAGE>   2




ITEM 5.  OTHER EVENTS.

                  On December 1, 1999, Carrizo Oil & Gas, Inc., a Texas
corporation (the "Company"), signed a commitment letter (the "Commitment
Letter") with an investor group led by Chase Capital Partners (the "Investors")
whereby the Investors will purchase $30,000,000 of the Company's securities.
Under the terms of the Commitment Letter, the Investors will purchase
$22,000,000 aggregate principal amount of Senior Subordinated Notes due 2007,
along with warrants to purchase up to 2,760,189 shares of the Company's Common
Stock at the exercise price of $2.20 per share, subject to adjustments, and
purchase 3,636,364 shares of the Company's Common Stock for $2.20 per share (the
"Financing").

                  The Financing contemplates a shareholders' agreement among the
Investors and the Company's five current directors that will allow Chase Capital
Partners, among other things, to elect up to two directors to the Company's
current Board of Directors. As required by Chase Capital Partners under the
Commitment Letter, three of the Company's directors, Paul B. Loyd, Jr., Steven
A. Webster, and Douglas A. P. Hamilton, will be included among the Investors and
will invest an aggregate of at least $3 million in the Financing.

                  The Company also signed a Stock and Warrant Purchase Agreement
(the "Purchase Agreement") among the Company, Enron North America Corp.,
Sundance Assets, L.P. ("Sundance") and Joint Energy Development Investments II
Limited Partnership ("JEDI II") (collectively, the "Enron Parties"), providing
for the repurchase of all the outstanding shares of the Company's 9% Series A
Preferred Stock, the repurchase of 750,000 currently outstanding warrants to
purchase the Company's Common Stock held by the Enron Parties and the amendment
of the terms of 250,000 warrants to purchase the Company's Common Stock retained
by the Enron Parties, for the total purchase price of $12,000,000 (the "Enron
Repurchase"). The exercise price of these retained warrants will be reduced from
$11.50 per share to $4 per share.

                  The proceeds of the Financing will be used to fund the Enron
Repurchase and repay a total of approximately $5 million of the Company's senior
debt, with the remaining proceeds of approximately $12 million being available
to fund the Company's exploration and development program, working capital and
general corporate purposes.

                  The Company has also reached an agreement with Compass Bank,
subject to closing the Financing, whereby the $9 million of maturities due in
the year 2000 under the existing Term Loan facility would be extended. The
revised maturities under the Term Loan provide for a $2 million principal
payment at closing, $1.74 million of principal payments during the second half
of the year 2000, $2.64 million of principal payments during the first half of
the year 2001 and the remaining balance due in July 2001. In addition, the
maturity date for the remaining bank loan borrowing base facility will be
extended from June 2000 until January 2002, subject to interim borrowing base
reviews.


                                       2
<PAGE>   3


                  The funding of the Financing is subject to certain conditions,
including the Enron Repurchase, the extension of the bank debt and the execution
of definitive agreements. The closing of the Enron Repurchase and debt extension
are subject to certain conditions, including the Financing. The closings of the
Enron Repurchase, the Financing, and the debt extension are expected to occur
simultaneously on or before December 15, 1999.

                  The descriptions of the Purchase Agreement and the Commitment
Letter do not purport to be complete and are qualified in their entirety by
provisions of each such agreement, copies of which have been filed as Exhibits
99.1 and 99.2, respectively, and which are incorporated by reference herein.

                  Statements in this document, including but not limited to
those relating to the effects, results and timing of closing of the Financing,
Enron Repurchase and Compass Bank agreement, use and amount of proceeds, and
other statements that are not historical facts are forward looking statements
that are based on current expectations. Although the Company believes that its
expectations are based on reasonable assumptions, it can give no assurance that
these expectations will prove correct. Important factors that could cause actual
results to differ materially from those in the forward looking statements
include possible failure of the Company to close the Enron Repurchase, or the
Financing, and the agreement with Compass Bank and other risks described in the
Company's filings with the Securities and Exchange Commission. There can be no
assurance as to the completion of any transaction described herein.

ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS.

         (c)      Exhibits.

         99.1     Stock and Warrant Purchase Agreement dated December 1, 1999
                  among the Company, Enron North America Corp., Sundance Assets,
                  L.P. and Joint Energy Development Investments II Limited
                  Partnership.

         99.2     Commitment Letter dated December 1, 1999 between Carrizo Oil &
                  Gas, Inc. and Chase Capital Partners.

         99.3     Press Release of the Company dated December 2, 1999.



                                       3
<PAGE>   4


                                   SIGNATURES


                  Pursuant to the requirements 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.


                                        CARRIZO OIL & GAS, INC.



                                        By: /s/ FRANK A. WOJTEK
                                           -------------------------------------
                                           Name: Frank A. Wojtek
                                           Title: Chief Financial Officer,
                                                  Vice President, Secretary
                                                  and Treasurer


Date:  December 3, 1999


                                       4
<PAGE>   5


                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>

 EXHIBIT
 NUMBER                               DESCRIPTION
 -------                              -----------
<S>               <C>
  99.1            Stock and Warrant Purchase Agreement dated December 1, 1999
                  among the Company, Enron North America Corp., Sundance Assets,
                  L.P. and Joint Energy Development Investments II Limited
                  Partnership.

  99.2            Commitment Letter dated December 1, 1999 between Carrizo Oil &
                  Gas, Inc. and Chase Capital Partners.

  99.3            Press Release of the Company dated December 2, 1999.
</TABLE>


<PAGE>   1
                                                                    EXHIBIT 99.1





                      STOCK AND WARRANT PURCHASE AGREEMENT



                                      among



                            CARRIZO OIL & GAS, INC.,



                           ENRON NORTH AMERICA CORP.,

                              SUNDANCE ASSETS, L.P.



                                       and



                            JOINT ENERGY DEVELOPMENT
                       INVESTMENTS II LIMITED PARTNERSHIP




                                      dated


                                December 1, 1999



<PAGE>   2



                                TABLE OF CONTENTS

<TABLE>


<S>                 <C>                                                                                                <C>
ARTICLE I.          Definitions...................................................................................1
         1.1        Definitions...................................................................................1

ARTICLE II.         Sale and Purchase of Shares and Warrants; Closing.............................................2
         2.1        Sale and Purchase of Shares and Repurchased Warrants..........................................2
         2.2        Closing.......................................................................................3
         2.3        Delivery......................................................................................3
         2.4        Payment.......................................................................................3
         2.5        Amendment of Retained Warrants................................................................3
         2.6        Other Closing Matters.........................................................................5

ARTICLE III.        Representations and Warranties of Issuer......................................................6
         3.1        Corporate Existence...........................................................................6
         3.2        Power and Authorization.......................................................................6
         3.3        Binding Obligations...........................................................................6
         3.4        No Violation..................................................................................6
         3.5        Consents......................................................................................6

ARTICLE IV.         Representations and Warranties of Sellers.....................................................7
         4.1        Corporate; Partnership Existence..............................................................7
         4.2        Power and Authorization.......................................................................7
         4.3        Binding Obligations...........................................................................7
         4.4        No Violation..................................................................................8
         4.5        Consents......................................................................................8
         4.6        Title to Shares and Warrants..................................................................8

ARTICLE V.          Closing Conditions      ......................................................................8
         5.1        Conditions to Obligation of Sellers...........................................................8
         5.2        Conditions to Obligation of Issuer............................................................9

ARTICLE VI.         Other Provisions.............................................................................10
         6.1        Other Action.................................................................................10
         6.2        Survival; Failure to Close...................................................................10

ARTICLE VII.        Indemnification..............................................................................10
         7.1         ........................................................................................... 10

ARTICLE VIII.       Miscellaneous................................................................................10
         8.1        Amendments; Waivers..........................................................................10
         8.2        Successors and Assigns.......................................................................10

</TABLE>

<PAGE>   3

<TABLE>
<S>      <C>        <C>                                                                                          <C>

         8.3        Severability.................................................................................10
         8.4        Descriptive Headings.........................................................................11
         8.5        Governing Law................................................................................11
         8.6        Entire Agreement.............................................................................11
         8.7        Execution in Counterparts....................................................................11
         8.8        Further Cooperation..........................................................................11
         8.9        Notices......................................................................................11
         8.10       No Waiver; Remedies Cumulative...............................................................11
         8.11       [Intentionally Left Blank]...................................................................12
         8.12       Dispute Resolution...........................................................................12


EXHIBITS

A                   Opinion of Baker & Botts, L.L.P
B                   Commitment Letter

</TABLE>


<PAGE>   4



                      STOCK AND WARRANT PURCHASE AGREEMENT

         This STOCK AND WARRANT PURCHASE AGREEMENT (this "Agreement") is made as
of December 1, 1999, by and between Carrizo Oil & Gas, Inc., a Texas corporation
("Issuer"), and Enron North America Corp., a Delaware corporation ("ENA"),
formerly known as Enron Capital & Trade Resources Corp., Sundance Assets, L.P.,
a Delaware limited partnership ("Sundance") and Joint Energy Development
Investments II Limited Partnership, a Delaware limited partnership ("JEDI II").
JEDI II and the Applicable Enron Entity (as defined below) are hereinafter
individually referred to as a "Seller" and collectively as "Sellers". ENA,
Sundance and JEDI II are sometimes referred to herein as "the Enron Parties."

                                    RECITALS

         The Enron Parties desire to sell to Purchaser and Purchaser desires to
repurchase, subject to the terms and conditions set forth herein, all the
outstanding shares of Preferred Stock (as herein defined) owned by them and the
Repurchased Warrants (as defined herein) in consideration for the sum of
$12,000,000 and the amendment of the terms of the Retained Warrants (as defined
herein).

                                   AGREEMENTS

         In consideration of the recitals and the mutual covenants herein
contained and other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto hereby agree as follows:

                                   ARTICLE I.

                                   DEFINITIONS

         1.1 DEFINITIONS. In addition to the capitalized terms defined elsewhere
in this Agreement, the following capitalized terms shall have the following
respective meanings when used in this Agreement. Any capitalized term used, but
not defined herein shall have the meaning given to it in the Original Agreement
unless the context requires otherwise.

                  "APPLICABLE ENRON ENTITY" shall mean either or both of
         Sundance and ENA, to be determined in each case prior to Closing.

                  "BOARD OF DIRECTORS" shall mean the Board of Directors of
         Issuer or any committee thereof duly authorized to act on behalf of the
         Board of Directors.

                  "CLAIMS" shall have the meaning assigned to such term in
         Section 8.1.

                  "CLOSING" shall have the meaning assigned to such term in
         Section 2.2.


                                       1
<PAGE>   5



                  "CLOSING DATE" shall have the meaning assigned to such term in
         Section 2.2.

                  "COMMON STOCK" shall mean the common stock, par value $.01 per
         share, of Issuer.

                  "LIEN" shall mean, with respect to any Person, any mortgage,
         deed of trust, lien, security interest, pledge, lease, conditional sale
         contract, claim, charge, easement, right of way, assessment,
         restriction and other encumbrance of any kind.

                  "ORIGINAL AGREEMENT" shall  mean  the  Stock  Purchase
         Agreement dated as of January 8, 1998 among the Issuer, Enron Capital &
         Trade Resources Corp. and Joint Energy Development Investments II
         Limited Partnership.

                  "PREFERRED STOCK" shall mean the 9% Series A Preferred Stock,
         par value $0.01, having the relative rights, preferences, privileges
         and limitations set forth in the Statement of Resolution.

                  "REPURCHASED WARRANTS" shall mean all Warrants other than the
         Retained Warrants.

                  "RETAINED WARRANTS" shall mean the Warrants to purchase
         187,500 shares of Common Stock, to be retained by the Applicable Enron
         Entity, and the Warrants to purchase 62,500 shares of Common Stock, to
         be retained by JEDI II, in each case in accordance with Section 2.5.

                  "SECURITIES ACT" shall mean the Securities Act of 1933, as
         amended.

                  "SHARES" shall mean all the shares of Preferred Stock owned by
         the Sellers.

                  "STATEMENT OF RESOLUTION" shall mean the Statement of
         Resolution relating to the Preferred Stock dated January 8, 1998 as
         filed with the Secretary of State of the State of Texas.

                  "WARRANTS" shall mean the warrants which are exercisable into
         1,000,000 shares of Common Stock issued in connection with the Original
         Agreement.

                                   ARTICLE II.

                SALE AND PURCHASE OF SHARES AND WARRANTS; CLOSING

         2.1 SALE AND PURCHASE OF SHARES AND REPURCHASED WARRANTS.

                  (a) Subject to the satisfaction of the terms and conditions
         herein set forth and in reliance upon the respective representations,
         warranties, and covenants of the parties set forth herein or in any
         document delivered pursuant hereto, at the Closing Sellers agree to
         sell,


                                       2

<PAGE>   6

         assign and deliver to Issuer, and Issuer agrees to purchase from
         Sellers all of the Enron Parties' right, title and interest in, to and
         in respect of the Shares and the Repurchased Warrants.

                  (b) Either or both of the Shares and Warrants (or any portion
         of such Shares and Warrants) owned as of the date hereof by Sundance
         may be transferred to ENA prior to the Closing Date (as defined below).

         2.2      CLOSING. The closing of the sale and purchase of the Shares
and the Repurchased Warrants (the "Closing") will occur at 9:30 a.m. on the
Closing Date (as defined below) at the offices of Baker & Botts, L.L.P., 910
Louisiana, Houston, Texas 77002. The "Closing Date" shall mean the Business Day
immediately following the date on which all the conditions to the obligations of
each party hereto to consummate the transactions under this Agreement shall have
been satisfied or waived in writing by such party.

         2.3      DELIVERY. Delivery of the Shares and the Repurchased Warrants
pursuant to this Agreement shall be made at the Closing by Sellers delivering
against payment therefor and delivery of certificates representing the Retained
Warrants as provided below, (a) certificates from the Applicable Enron Entity
representing an aggregate of 87,448.75 Shares and (b) certificates from JEDI II
representing an aggregate of 262,346.17 Shares and delivery of Warrant
Certificates representing the Warrants.

         2.4      PAYMENT. Payment in the amount of $12,000,000 for the Shares
and Repurchased Warrants shall be made by a wire transfer of $3 million to the
Applicable Enron Entity (divided between Sundance and ENA as they shall request)
and a wire transfer of $9 million to JEDI II, both in immediately available
funds to an account of each at a commercial bank, which accounts shall have been
designated by them prior to the Closing Date.

         2.5      AMENDMENT OF RETAINED WARRANTS. Additionally, at the Closing,
Issuer and the Sellers will amend

                  (a) both of the Retained Warrants by (i) replacing the
         existing definitions of "Exercise Price" with the following:

                  "Exercise Price" means an amount, per share, equal to $4.00.
                  The Exercise Price shall be subject to adjustment, as forth in
                  Section 4.

         and (ii) adding as a new final sentence to Section 4(b) of each
         Retained Warrant:


                  Notwithstanding anything to the contrary contained herein, no
                  adjustments shall be made under this paragraph in connection
                  with any private placement of securities or exercise of
                  warrants issued in such private placement, to the extent that
                  a portion of the proceeds


                                       3
<PAGE>   7


                  thereof are used by the Company to fund the payment under the
                  Stock Purchase Agreement among the Company, Sundance Assets,
                  L.P., Joint Energy Development Investments II Limited
                  Partnership and Enron North America Corp. dated December 1,
                  1999.

                  (b) the Retained Warrant to be issued to the Applicable Enron
         Entity by replacing the existing definitions of "JEDI II Warrant" and
         "Warrant Shares" with the following:

                           "JEDI II Warrant" means the Warrant issued to Joint
         Energy Development Investments II Limited Partnership on the Date of
         Issuance which originally upon exercise entitled the holder thereof to
         purchase from the Company 750,000 shares of Common Stock and which
         following amendment of such Warrant in December 1999 entitled the
         holder to purchase from the Company 187,500 shares of Common Stock.

                           "Warrant Shares" means the shares of Common Stock (or
         amount of other property) equal to the number of shares of Common
         Stock, as adjusted from time to time pursuant to the terms hereof,
         which would be received upon the exercise of all or any portion of this
         Warrant, which, at the Date of Issuance, was equal to 250,000 shares of
         Common Stock and which following amendment of this Warrant in December
         1999, was equal to 62,500 shares of Common Stock.

                  (c) the Retained Warrant to be issued to JEDI II by replacing
         the existing definitions of "ECT Warrant" and "Warrant Shares" with the
         following:

                           "ECT Warrant" means the Warrant issued to Enron
         Capital & Trade Resources Corp. on the Date of Issuance which
         originally upon exercise entitled the holder thereof to purchase from
         the Company 250,000 shares of Common Stock and which following
         amendment of such Warrant in December 1999 entitled the holder to
         purchase from the Company 62,500 shares of Common Stock.

                           "Warrant Shares" means the shares of Common Stock (or
         amount of other property) equal to the number of shares of Common
         Stock, as adjusted from time to time pursuant to the terms hereof,
         which would be received upon the exercise of all or any portion of this
         Warrant, which, at the Date of Issuance, was equal to 750,000 shares of
         Common Stock and which following amendment of this Warrant in December
         1999, was equal to 187,500 shares of Common Stock.

Issuer shall issue new certificates representing the Retained Warrants as
amended in accordance with this Agreement.


                                       4
<PAGE>   8


         2.6     OTHER CLOSING MATTERS.

                  (a) Effective upon the Closing, all agreements between Issuer,
         on the one hand, and the Enron Parties, on the other hand, shall
         terminate, including, without limitation, the Basic Documents (as
         defined in the Original Agreement) (collectively, subject to the
         following proviso, the "Terminated Agreements"); provided that (i)
         Section 8.3, Section 8.5, Section 9.1 (as amended below), Section
         9.3(b), (c) and (d) and Section 10.12 of the Original Agreement shall
         expressly survive such termination and (ii) the foregoing shall not
         terminate this Agreement, the Retained Warrants or the Confidentiality
         Agreement between ENA and Issuer dated as of June 8, 1999 (the "1999
         Confidentiality Agreement"). Effective upon the Closing, the Enron
         Parties hereby release Issuer and its current and former officers,
         directors, employees, shareholders and agents and Issuer hereby
         releases the Enron Parties and their current and former officers,
         directors, employees, shareholders and agents from any obligation,
         liability or claim arising out of, in connection with or otherwise in
         respect of the Terminated Agreements or in respect of the Enron
         Parties' investment or securities holdings in the Issuer (INCLUDING ANY
         ACT OR FAILURE TO ACT THAT CONSTITUTES ORDINARY OR GROSS NEGLIGENCE OR
         RECKLESS OR WILLFUL, WANTON MISCONDUCT).

                  (b) Section 9.1 shall be replaced by the following:

                  ISSUER INDEMNIFICATION. Issuer agrees to indemnify, defend,
and hold harmless Purchasers and each Affiliate of either of the Purchasers (a
"Purchasers' Indemnified Person") from, against, and in respect of any and all
claims, demands, losses, reasonable costs and expenses, obligations,
liabilities, damages, recoveries, and deficiencies, including interest,
penalties and reasonable attorneys' fees (collectively, "Claims") but only to
the extent such Claims are based on Claims against such Purchasers' Indemnified
Persons by third parties not affiliated with the Purchasers (as used in this
Article IX, "Third Party Claims"), that such Purchasers' Indemnified Party shall
incur or suffer, which arise, result from, or relate to (a) any breach of, or
failure by Issuer to perform, any of its representations, warranties, covenants,
or agreements in this Agreement or in any schedule, certificate, exhibit, or
other instrument furnished or to be furnished by Issuer in connection with the
transactions contemplated by this Agreement, or in the Charter of Issuer or (b)
any claims of any applicable Governmental Authority or other Person arising
under any Governmental Requirement applicable to the Issuer (including without
limitation any Environmental Law or regulation under ERISA). WITHOUT LIMITATION,
THE FOREGOING INDEMNITY SHALL APPLY TO EACH PURCHASER INDEMNIFIED PERSON WITH
RESPECT TO LOSSES WHICH IN WHOLE OR IN PART ARE CAUSED BY OR ARISE OUT OF THE
CONCURRENT OR COMPARATIVE NEGLIGENCE OR THE STRICT LIABILITY OF SUCH PURCHASER
INDEMNIFIED PERSON; PROVIDED, HOWEVER, NO PURCHASER INDEMNIFIED PARTY SHALL BE
INDEMNIFIED FOR ITS OWN NEGLIGENCE OR WILFUL MISCONDUCT.




                                       5
<PAGE>   9


                                  ARTICLE III.

                    REPRESENTATIONS AND WARRANTIES OF ISSUER

         Issuer represents and warrants to Sellers as follows:

         3.1 CORPORATE EXISTENCE. Issuer is a corporation duly organized,
validly existing and in good standing under the laws of the State of Texas.

         3.2 POWER AND AUTHORIZATION. Issuer has all requisite power and
authority to execute, deliver, and perform this Agreement, and to consummate the
transactions contemplated hereby. The execution and delivery of this Agreement
and the consummation of the transactions to be performed by Issuer have been
duly and validly authorized by all necessary action on the part of the Board of
Directors, and no other corporate proceedings are necessary to authorize the
execution, delivery and performance of this Agreement by Issuer.

         3.3 BINDING OBLIGATIONS. This Agreement when executed and delivered
by Issuer, shall constitute a legal, valid and binding obligation of Issuer
enforceable in accordance with its terms, except insofar as the enforceability
thereof may be limited (i) by applicable bankruptcy, insolvency, reorganization,
moratorium or other similar laws affecting the enforcement of creditors' rights
generally and (ii) by general principles of equity and public policy (regardless
of whether considered at law or in equity).

         3.4 NO VIOLATION. The execution and delivery by Issuer of this
Agreement, and the consummation of the transactions contemplated hereby, will
not, upon receipt of the consents of its lenders (a) conflict with or result in
a breach of any provision of the Charter or bylaws of Issuer, (b) result in any
default or in any material modification of the terms of any material instrument
or agreement of Issuer, or (c) violate any Governmental Requirement applicable
to Issuer.

         3.5 CONSENTS. All consents, approvals, qualifications, orders or
authorizations of, or filings with, any Governmental Authority, and all consents
under any material contracts, agreements, or instruments by which Issuer is
bound or to which it is subject, and required in connection with Issuer's valid
execution, delivery, or performance of this Agreement, and the consummation of
the transactions contemplated hereby, has been obtained or made, other than the
consent of Compass Bank.


                                       6
<PAGE>   10




                                   ARTICLE IV.

                    REPRESENTATIONS AND WARRANTIES OF SELLERS

         ENA, Sundance and JEDI II, as applicable, represent and warrant to
Issuer as follows (each Enron Party's representations and warranties are being
made as to that Enron Party only and not the other):

         4.1     CORPORATE; PARTNERSHIP EXISTENCE.

                  (a) ENA is a corporation duly organized, validly existing and
         in good standing under the laws of the State of Delaware.

                  (b) JEDI II and Sundance are limited partnerships duly formed
         and validly existing under the laws of the State of Delaware.

         4.2     POWER AND AUTHORIZATION.

                 (a) ENA has all requisite power and authority to execute,
         deliver and perform this Agreement and to consummate the transactions
         contemplated hereby. All action on the part of ENA requisite for the
         due execution, delivery and performance of this Agreement has been duly
         and effectively taken. The execution and delivery of and the
         consummation of the transactions to be performed by ENA hereunder has
         been duly and validly authorized by all necessary action on the part of
         the board of directors of ENA hereunder, and no other corporate
         proceedings are necessary to authorize the execution and delivery by
         ENA.

                 (b) JEDI II and Sundance have all requisite power and
         authority to execute, deliver and perform this Agreement and to
         consummate the transactions contemplated hereby. All action on the part
         of JEDI II and Sundance requisite for the due execution, delivery and
         performance of this Agreement has been duly and effectively taken. The
         execution and delivery of this Agreement and the consummation of the
         transactions to be performed by JEDI II and Sundance hereunder have
         been duly and validly authorized by all necessary action on the part of
         JEDI II and Sundance, their respective partners and any shareholder of
         or partner in any of their respective partners, and no other
         partnership or corporate proceedings, as the case may be, are necessary
         to authorize the execution and delivery by JEDI II or Sundance of this
         Agreement.

         4.3 BINDING OBLIGATIONS. This Agreement when executed and delivered by
it, shall constitute legal, valid and binding obligations of each Enron Party
enforceable in accordance with its terms, except insofar as the enforceability
thereof may be limited (i) by applicable bankruptcy, insolvency, reorganization,
moratorium or other similar laws affecting the enforcement of creditors' rights
generally and (ii) by general principles of equity (regardless of whether
considered at law or in equity).


                                       7
<PAGE>   11



         4.4 NO VIOLATION. The execution and delivery by each Enron Party of
this Agreement and the consummation of the transactions contemplated hereby will
not (a) conflict with or result in a breach of any provision of the Charter or
bylaws or other organizational document of any Enron Party, (b) result in any
default or in any material modification of the terms of any material instrument
or agreement of any Enron Party, or (c) violate any Governmental Requirement
applicable to any Enron Party.

         4.5 CONSENTS. All consents, approvals, qualifications, orders or
authorizations of, or filings with, any Governmental Authority, and all consents
under any material contracts, agreements, or instruments by which any Enron
Party is bound or to which it is subject, and required in connection with such
Enron Party's valid execution, delivery, or performance of this Agreement, and
the consummation of the transactions contemplated hereby, has been obtained or
made.

         4.6 TITLE TO SHARES AND WARRANTS. As of the date of this Agreement
each Enron Party owns beneficially and of record the number of Shares and
Warrants set forth on Schedule I attached hereto, free and clear of all Liens.
At Closing, JEDI II and the Applicable Enron Entity will own beneficially and of
record the number of Shares and Warrants set forth on Schedule I attached hereto
free and clear of all Liens. ENA has transferred and assigned to Sundance all of
its right, title and interest in, to and in respect of the Shares and Warrants
purchased by ENA under the Original Agreement. Prior to Closing, Sundance may
transfer and assign to ENA, all or a portion of its rights, title and interest
in, to and in respect of the Shares and/or Warrants previously transferred from
ENA to Sundance. The Shares and the Warrants constitute all of the equity
securities of Issuer owned by each of the Enron Parties, and except as described
herein such Shares and Warrants are not subject to any agreements or
understandings with respect to the transfer of any of the Shares or Warrants
other than those with the Issuer. No Enron Party has granted to any third party
any option, right of first refusal or other rights with respect to the Shares or
the Warrants except as described herein. Sundance has full legal right to sell,
assign and transfer the Shares and Repurchased Warrants to ENA. Each Seller has
full legal right to sell, assign and transfer the Shares and Repurchased
Warrants owned by it to Issuer and will, upon delivery of certificates
representing such Shares and Repurchased Warrants to Issuer pursuant to the
terms hereof, transfer to Issuer title to such Shares and Repurchased Warrants,
free and clear of any Liens.

                                   ARTICLE V.

                               CLOSING CONDITIONS

         5.1 CONDITIONS TO OBLIGATION OF SELLERS. The obligation of Sellers to
consummate the transactions contemplated hereby is subject to satisfaction of
the following conditions at the time of Closing:

                  (a) the representations and warranties contained in Article
         III, shall be accurate in all respects, as of the time of Closing on
         the Closing Date (provided that this provision


                                       8
<PAGE>   12


         shall not require the text of any representation that refers to a
         specific date to be changed with respect to such reference);

                  (b) no action, suit or proceeding shall be pending before any
         Governmental Authority wherein an unfavorable injunction, judgment,
         order, decree, ruling, charge, penalty or onerous condition would
         prevent consummation of any of the transactions contemplated by this
         Agreement, and no such injunction, judgment, order, decree, ruling,
         charge; penalty or onerous condition shall be in effect;

                  (c) all material notices, consents and approvals required for
         the consummation of the transactions contemplated hereby shall have
         been given or obtained;

                  (d) the Enron Parties shall have received an opinion of Baker
         & Botts, L.L.P, dated as of the Closing Date in substantially the form
         attached as Exhibit A;

                  (e) the Company shall have made payment for all outstanding
         legal fees owed by it to any Enron Party.

         5.2 CONDITIONS TO OBLIGATION OF ISSUER. The obligations of Issuer to
consummate the transactions contemplated hereby are subject to satisfaction of
the following conditions:

                  (a) the representations and warranties contained in Article IV
         shall be accurate in all respects as of the time of Closing on the
         Closing Date (provided that this provision shall not require the text
         of any representation that refers to a specific date to be changed with
         respect to such reference);

                  (b) no action, suit, or proceeding shall be pending before any
         Governmental Authority wherein an unfavorable injunction, judgment,
         order, decree, ruling, charge, penalty or onerous condition would
         prevent consummation of any of the transactions contemplated by this
         Agreement and no such injunction, judgment, order, decree, ruling,
         charge, penalty or onerous condition shall be in effect;

                  (c) all material notices, consents and approvals required for
         the consummation of the transactions contemplated hereby shall have
         been given or obtained, including, without limitation, the consent of
         Compass Bank;

                  (d) Issuer shall have completed the financing contemplated by
         the draft of commitment letter attached hereto as Exhibit B or shall
         have otherwise obtained funds in an amount at least equal to the amount
         contemplated by such commitment letter in either case, pursuant to
         definitive agreements that are satisfactory to Issuer in its sole
         discretion.



                                       9
<PAGE>   13



                                   ARTICLE VI.

                                OTHER PROVISIONS

         6.1  OTHER ACTION. Each of the parties shall use its reasonable best
efforts to cause the Closing Date to occur as soon as is reasonably practicable.

         6.2 SURVIVAL; FAILURE TO CLOSE. All representations, warranties,
indemnities, and covenants contained herein or made in writing by any party in
connection herewith will survive the execution and delivery of this Agreement.
Notwithstanding anything herein to the contrary, if the Closing has not occurred
on or before December 15, 1999, then either party may terminate its obligations
under this Agreement by written notice to the other; provided, that no party may
terminate this Agreement if Closing has failed to occur because such party (or
any Affiliate thereof) willfully or negligently fail to perform or observe its
material agreements and covenants hereunder.

                                  ARTICLE VII.

                                 INDEMNIFICATION

         7.1 The scope and the procedure for indemnification for any Claims
arising out of a breach of this Agreement shall be as specified in Article IX of
the Original Agreement as originally executed (notwithstanding the fact that
portions of Article IX of the Original Agreement have been amended or terminated
hereby) with the Enron Parties having the correlative rights and obligations of
the Purchasers under the Original Agreement.

                                  ARTICLE VIII.

                                  MISCELLANEOUS

         8.1 AMENDMENTS; WAIVERS. No amendment or waiver of any provision of
this Agreement, nor consent to any departure by Issuer or the Enron Parties
therefrom, shall in any event be effective unless the same shall be in writing
and signed by the Enron Parties and Issuer in the case of amendments, and the
Enron Parties or Issuer, as the case may be, in the case of waivers.

         8.2 SUCCESSORS AND ASSIGNS. All of the respective rights, obligations
and interests of the parties hereto shall be binding upon and inure to the
benefit of the respective successors of the parties hereto. This Agreement and
the rights and obligations of each party thereunder shall not be assigned
without the prior written consent of the other party.

         8.3 SEVERABILITY. Whenever possible, each provision of this
Agreement will be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be prohibited
by or invalid under applicable law, such provision will be ineffective only to
the extent of such prohibition or invalidity, without invalidating the remainder


                                       10
<PAGE>   14

of this Agreement unless the consummation of the transaction contemplated hereby
is materially and adversely affected thereby.

         8.4 DESCRIPTIVE HEADINGS. The descriptive headings of this Agreement
are inserted for convenience of reference only and do not constitute a part of
and shall not be utilized in interpreting this Agreement.

         8.5 GOVERNING LAW. This Agreement shall be deemed a contract and
instrument made under the laws of the State of Texas and shall be construed and
enforced in accordance with and governed by the laws of the State of Texas,
without regard to principles of conflicts of law.

         8.6 ENTIRE AGREEMENT. This Agreement (together with the Retained
Warrants and the provisions of the Original Agreement which survive termination
of the Terminated Agreements pursuant to Section 2.6) and the 1999
Confidentiality Agreement to the extent not amended hereby constitute the entire
agreement among Issuer and the Enron Parties concerning the matters referred to
herein and therein, and supersede all prior agreements and understandings among
Issuer and the Enron Parties relating to the subject matter hereof and thereof.
There are no unwritten oral agreements between or among the parties.

         8.7 EXECUTION IN COUNTERPARTS. This Agreement may be executed in any
number of counterparts, each of which when so executed and delivered shall be
deemed an original, and such counterparts together shall constitute one
instrument.

         8.8 FURTHER COOPERATION. At any time and from time to time, and at
its own expense, each party shall promptly execute and deliver all such
documents and instruments, and do all such acts and things, as the other may
reasonably request in order to further effect the purposes of this Agreement.

         8.9 NOTICES. All notices, requests, and other communications to any
party hereunder shall be in writing (including telecopy) and shall be given to
such party at its address or telecopy number set forth on the signature pages
hereof or such other address or telecopy number as such party may hereafter
specify by notice to the other parties.

         8.10 NO WAIVER; REMEDIES CUMULATIVE. No failure or delay on the part
of a party in exercising any right or remedy under this Agreement and no course
of dealing among Issuer and either of the Sellers shall operate as a waiver
thereof, nor shall any single or partial exercise of any right or remedy under
this Agreement preclude any other or further exercise thereof or the exercise of
any other right or remedy under this Agreement. The rights and remedies
expressly provided are cumulative and not exclusive of any rights or remedies
that a party would otherwise have. No notice to or demand on a party not
otherwise required by this Agreement or shall entitle that party to any other or
further notice or demand in similar or other circumstances or constitute a
waiver of the rights of that Party to any other or further action in any
circumstances without notice or demand.


                                       11
<PAGE>   15



         8.11  [Intentionally Left Blank]

         8.12 DISPUTE RESOLUTION. (a) Any controversy, dispute or claim
arising out of or relating to this Agreement, or the transactions contemplated
thereby shall be resolved in accordance with Section 10.12 of the Original
Agreement, with the Enron Parties having the correlative rights and obligations
of the Purchasers under such provision.


                                       12
<PAGE>   16


         IN WITNESS WHEREOF, the parties hereto have executed this Agreement on
the date first set forth above.

                             CARRIZO OIL & GAS, INC.



                             By:      /s/ S.P. JOHNSON IV
                                  ---------------------------------------------
                                  Name:   S.P. Johnson IV
                                  Title:  President/CEO

                             Address for Notice:

                             14811 St. Mary's Lane, Suite 148
                             Houston, Texas 77079
                             Attention: S.P. Johnson IV
                             Telecopy: 281-496-0884

                             with a copy to:

                             Baker & Botts, L.L.P.
                             3000 One Shell Plaza
                             Houston, TX 77002
                             Attn: Gene Oshman, Esq.
                             Telecopy: 713-229-1522


                                       13
<PAGE>   17




                            ENRON NORTH AMERICA CORP.


                            By:       /s/ JOHN S. HOPLEY
                                  ---------------------------------------------
                                  Name:   John S. Hopley
                                  Title:  Vice President

                            Address for Notice:

                            Enron North America Corp.
                            Attn:
                            1400 Smith Street
                            Houston, Texas 77002
                            Phone:  (713) 853-1939
                            Fax:  (713) 646-4039 or (713) 646-4946


                            JOINT ENERGY DEVELOPMENT INVESTMENTS II
                            LIMITED PARTNERSHIP

                            By: ENRON CAPITAL MANAGEMENT II
                                LIMITED PARTNERSHIP,
                                its sole general partner

                                  By:  ENRON CAPITAL II CORP., its sole general
                                          partner


                                       By:     /s/ RAYMOND M. BOWEN
                                            -----------------------------------
                                            Name:  Raymond M. Bowen
                                            Title: Vice President

                             Address for Notice:

                             1400 Smith Street
                             Houston, Texas 77002
                             Attn:  Donna W. Lowry
                             Phone:  713/853-1939
                             Fax:  713/646-4029 or 713/646-4946


                                       14
<PAGE>   18



                             SUNDANCE ASSETS, L.P.

                             By:      PONDEROSA ASSETS, L.P., its General
                                      Partner

                                      By:  ENRON PONDEROSA
                                           MANAGEMENT HOLDINGS, INC.,
                                           its General Partner


                                           By:  /s/ RAYMOND M. BOWEN
                                                -------------------------------
                                                Name: Raymond M. Bowen
                                                Title: Vice President

                             Address:

                             Sundance Assets, L.P.
                             c/o Wilmington Trust Company
                             Rodney Square North
                             1100 North Market Street
                             Wilmington, Delaware  19899
                             Attention:  Corporate Trust Administration

                             With a copy to:

                             Ponderosa Assets, L.P.
                             c/o Enron Ponderosa Management Holdings, Inc.
                             1400 Smith Street
                             Houston, Texas  77002

                                       15
<PAGE>   19



                                   Schedule 1




<TABLE>
<CAPTION>

          Current Ownership                             Shares                               Warrants
          -----------------                             ------                               --------
          <S>                                          <C>                                   <C>
              Sundance                                 87,448.75                              250,000

               JEDI II                                262,346.17                              750,000

                 ENA                                       0                                     0

</TABLE>

<TABLE>
<CAPTION>
       Closing Date Ownership                           Shares                               Warrants
       ----------------------                           ------                               --------
       <S>                                             <C>                                   <C>
       Applicable Enron Entity                         87,448.75                              250,000

               JEDI II                                262,346.17                              750,000

</TABLE>


                                       16
<PAGE>   20
                                                                       Exhibit A




                                                               December __, 1999




Enron North America Corp.
Joint Energy Development
    Investments II Limited Partnership
Sundance Assets, L.P.
1400 Smith Street
Houston, Texas 77002

Ladies and Gentlemen:

                  This opinion is being furnished to you at the request of
Carrizo Oil & Gas, Inc., a Texas corporation (the "Company"), pursuant to
Section 5.1(c) of the Stock and Warrant Purchase Agreement dated as of December
__, 1999 (the "Purchase Agreement" among the Company, Enron North America
Corp., a Delaware corporation ("ENA"), and Joint Energy Development Investments
II Limited Partnership, a Delaware limited partnership ("JEDI II"), and Sundance
Assets, L.P. a Delaware limited partnership ("Sundance") providing among other
things (i) the purchase by Carrizo of 349,794.92 of the outstanding shares of 9%
Series A Preferred Stock of the Company, (ii) the repurchase of warrants to
purchase 750,000 shares of the common stock, par value $.01 per share, of the
Company (the "Common Stock"), and (iii) the amendment of warrants to purchase
250,000 shares of Common Stock (the "Retained Warrants"). The terms of the
Retained Warrants are set forth in Warrant Certificates (the "Amended Warrant
Certificates") to be issued to each of the Applicable Enron Entity and JEDI II.
The Purchase Agreement and the Amended Warrant Certificates are referred to
herein as the "Agreements."

                  We have examined the originals, or copies certified or
otherwise identified, of the Company's Amended and Restated Articles of
Incorporation (the "Charter") and the Company's Amended and Restated Bylaws (the
"Bylaws"), each as amended to date, corporate records of the Company,
certificates of public officials and of representatives of the Company, statutes
and other instruments and documents as a basis for the opinions hereinafter
expressed. In giving such opinions, we have relied upon certificates of officers
of the Company with respect to the accuracy of the factual matters contained in
such certificates. In making our examination, we have assumed that all
signatures on documents examined by us are genuine, all documents submitted to
us as originals are authentic and all documents submitted to us as certified or
photostatic copies conformed with the originals of such documents, and have
assumed the truth and accuracy of all representations

                                       17
<PAGE>   21


Enron North America Corp.                                    December __, 1999
Joint Energy Development
    Investments II Limited Partnership
Sundance Assets, L.P.




and warranties of each party and that each party will comply with all of their
respective agreements, but have conducted no independent investigation with
respect to the foregoing.

                  On the basis of the foregoing, and subject to the limitations
and qualifications hereinafter set forth, we are of the opinion that
(capitalized terms used but not defined herein shall have the meaning assigned
to such terms in the Purchase Agreement):

                  1. The Company is a corporation duly incorporated, validly
         existing and in good standing under the laws of the State of Texas.

                  2. The Company has all requisite corporate power and authority
         to issue the Amended Warrant Certificates. The execution and delivery
         of the Amended Warrant Certificates have been duly and validly
         authorized by all necessary action on the part of the Board of
         Directors, and no other corporate proceedings are necessary to
         authorize the execution and delivery of the Amended Warrant
         Certificates by the Company.

                  3. Each of the Amended Warrant Certificates when executed and
         delivered, shall constitute a legal, valid and binding obligation of
         the Company enforceable in accordance with its terms, except insofar as
         the enforceability thereof may be limited (i) by applicable bankruptcy,
         insolvency, reorganization, moratorium or other similar laws affecting
         the enforcement of creditors' rights generally and (ii) by general
         principles of equity and public policy (regardless of whether
         considered at law or in equity).

                  4. There have been reserved for issuance, out of the
         authorized and unissued shares of the Company's Common Stock, a number
         of shares sufficient to provide for the exercise of the rights of
         purchase represented by the Amended Warrant Certificates, and such
         shares, when issued upon receipt of payment therefor or upon a net
         exercise in accordance with the terms of the Amended Warrant
         Certificates, will be duly authorized, validly issued, fully paid and
         nonassessable.


                                       18
<PAGE>   22



Enron North America Corp.                                   December __, 1999
Joint Energy Development
    Investments II Limited Partnership
Sundance Assets, L.P.



                  5. The execution and delivery of the Agreements, and the
         consummation of the transactions contemplated thereby will not to our
         knowledge, after due inquiry, violate any Governmental Requirement of
         the United States or the State of Texas applicable to the Company;
         which conflict, breach, violation, default or creation of a lien would,
         singularly or in the aggregate, be reasonably expected to have a
         Material Adverse Effect.

                  6. All consents, approvals, qualifications, orders or
         authorizations of, or filings with, any Governmental Authority of the
         United States or the State of Texas, required in connection with the
         Company's valid execution, delivery, or performance of the Agreements,
         and the consummation by the Company of the transactions contemplated
         thereby (other than such consents, approvals, qualifications,
         authorizations or filings not customarily obtained at the time of
         entering into agreements like the Agreements, but instead, customarily
         undertaken at an appropriate later date for future transactions), has,
         to our knowledge, after due inquiry been obtained or made.

                  We express no opinion with respect to the legality, validity,
binding nature or enforceability of any provisions of the Agreements (i)
purporting to release or exculpate any party from liability for the acts or
omissions of such party proximately causing damages or injuries as result of
such party's negligence, willful misconduct or strict liability, or purporting
to impose a duty upon any party to indemnify, or make contribution to, any other
party when any claimed damages or liability result from the negligence, strict
liability, willful misconduct of, or the violation of federal or state
securities or anti-fraud laws by, the party seeking such indemnity or
contribution, (ii) relating to waivers of rights or precluding any party from
asserting claims or defenses or for obtaining certain rights or remedies, (iii)
requiring the resolution of any controversies, disputes or claims by arbitration
or by reference to a third-party expert, (iv) restricting access to courts or to
legal or equitable remedies or affecting the jurisdiction or venue of courts or
(v) relating to the severability of invalid terms, the reformation of contracts
and similar provisions.

                  Whenever our opinion is based on circumstances "known to us
after due inquiry" or "to our knowledge after due inquiry," we have relied on
certificates of officers (after the discussion of the contents thereof with such
officers) of the Company or certificates of others as to the existence or
nonexistence of the circumstances upon which such opinion is predicted. We have
no reason to believe, however, that any such certificate is untrue or inaccurate
in any material respect.

                  In the foregoing opinions, phrases such as "to our knowledge,"
"known to us" and those with equivalent wording refer to the conscious awareness
of information by the lawyers of this



                                       19
<PAGE>   23



Enron North America Corp.                                    December __, 1999
Joint Energy Development
    Investments II Limited Partnership
Sundance Assets, L.P.



firm who have prepared this opinion, signed this opinion or been actively
involved in assisting and advising the Company in connection with the execution
and delivery of the Agreements.

                  The foregoing opinions are limited in all respects to the laws
of the State of Texas and applicable federal law, in each case as in effect on
the date hereof. The opinions expressed herein are for your benefit and may be
relied upon only by you and may not be given or described to any other person
without our prior written consent. The opinions given are strictly limited to
the matters stated herein and no implied opinions are to be inferred from
anything stated herein, and without limiting the generality of the foregoing we
express no opinion with respect to any bankruptcy or creditors rights laws or
any federal or state securities or antifraud law, rule or regulation except as
otherwise specifically stated herein.

                                            Very truly yours,





                                       20

<PAGE>   24
                                                                      EXHIBIT 2

                                                                [DRAFT 11/30/99]


                                                               November __, 1999


Carrizo Oil & Gas, Inc.
14811 St. Mary's Lane, Suite 148
Houston, Texas  77079
Attention: Chip Johnson

                             Carrizo Oil & Gas, Inc.
                             $30,000,000 Investment


Gentlemen:

          You have advised Chase Capital Partners (together with one or more of
its affiliated investment funds, "CCP") that Carrizo Oil & Gas, Inc. (the
"Company") intends to purchase (the "Redemption") from Enron Corp. and its
affiliates (collectively, "Enron"), pursuant to a definitive purchase agreement
with Enron (the "Enron Purchase Agreement") with respect to the Redemption with
terms and conditions satisfactory to CCP, all of the Company's outstanding 9%
Series A Preferred Stock, par value $0.01 per share (liquidation amount of
approximately $34,000,000) and warrants to purchase 750,000 shares of the
Company's common stock (collectively, the "Enron Equity"), which to your
knowledge represents all of the securities of the Company held by Enron other
than warrants to purchase 250,000 shares of the Company's common stock which
will be retained by Enron (and the terms of which will be amended), for an
aggregate redemption price of up to $12,000,000 in cash. In connection
therewith, the Company intends to issue (a) $22,000,000 aggregate principal
amount of its senior subordinated notes (the "Notes"), together with warrants to
purchase common stock (the "Common Stock") of the Company (the "Warrants") and
(b) aggregate consideration of $8,000,000 in Common Stock.

          CCP is pleased to advise you of its commitment to purchase up to
$22,000,000 aggregate principal amount of the Notes, the Warrants and up to
$8,000,000 of the Common Stock (collectively, the "Investment"), upon the terms
and subject to the conditions set forth or referred to in this letter
("Commitment Letter") and in the Term Sheet (the "Term Sheet") annexed hereto;
provided, however that the foregoing amounts will be reduced to the extent of
the investment by the non-management directors as described herein and in the
Term Sheet.

          You agree promptly to prepare and provide to CCP all information
reasonably requested by CCP with respect to the Company, the Redemption and the
other transactions contemplated hereby, including all financial information and
projections (the "Projections"). You hereby represent and covenant that (a) all
information other than the Projections (the "Information") that has been or will
be made available to CCP by or on behalf of you or any of



<PAGE>   25

your authorized representatives, when taken as a whole, is or will be, when
furnished, complete and correct in all material respects and does not or will
not, when furnished, contain any untrue statement of a material fact or omit to
state a material fact necessary in order to make the statements contained
therein not materially misleading in light of the circumstances under which such
statements are made and (b) the Projections that have been or will be made
available to CCP by or on behalf of you or any of your authorized
representatives have been or will be prepared in good faith based upon
assumptions that are reasonable at the time made and at the time the related
Projections are made available to CCP. You agree that if at any time from and
including the date hereof until the closing of the Investment, any of the
representations in the preceding sentence would be incorrect, then you will
promptly supplement the Information and the Projections so that such
representations will be correct. You agree that CCP will be entitled to use and
rely primarily on the Information and the Projections without responsibility for
independent verification thereof.

          As consideration for CCP's commitment hereunder, you agree to pay to
CCP, conditioned upon the closing, a fee (the "Closing Fee") in an amount equal
to one and one-half percent (1 1/2%) of the aggregate amount of CCP's portion of
the total Investment. The Closing Fee shall be payable on the Closing Date,
shall be paid in immediately available funds and, once paid, shall not be
refundable under any circumstances. The Closing Fee shall be in addition to
reimbursement of the reasonable out-of-pocket fees and expenses of CCP.

          CCP's commitment hereunder is subject to (a) CCP's not having
discovered or otherwise becoming aware of information not previously disclosed
to CCP that CCP believes to be materially inconsistent with its understanding,
based on information provided to CCP prior to the date hereof, of the business,
operations, properties, assets, liabilities, prospects or financial condition of
Company, (b) there not having occurred any event, condition or circumstance that
has had or is reasonably likely to have a material adverse effect on the
business, operations, properties, assets, liabilities, prospects or financial
condition of Company, (c) there not having occurred and being continuing a
material disruption of or material adverse change in financial, banking or
capital market conditions, (d) the negotiation, execution and delivery of
definitive documentation with respect to the Investment reasonably satisfactory
to CCP and its counsel, (e) the closing of the Redemption on the terms set forth
in the Enron Purchase Agreement and or other terms satisfactory to CCP
simultaneously with the closing of the Investment, (f) the negotiation,
execution and delivery of an amendment to your credit facility with Compass Bank
or a new credit facility with Shell Capital on terms reasonably satisfactory to
CCP, (g) evidence reasonbly satisfactory to CCP that the transactions
contemplated by the Investment do not require shareholder approval under NASDAQ
rules and are not in violation of NASDAQ's voting rights policy and (h) the
other conditions set forth or referred to herein and in the Term Sheet. In
addition to the foregoing, certain non-management directors of the Company will
be required to purchase at least 10% of the total amount of the Investment as a
condition to closing. The terms and conditions of CCP's commitment hereunder and
of the Investment are not limited to the terms and conditions set forth herein
or in the Term Sheet. Those matters that are not covered by or made clear under
the provisions hereof or of the Term Sheet are subject to the reasonable
approval and reasonable agreement of CCP and you.

          By executing this Commitment Letter, you agree (a) to indemnify and
hold harmless CCP, its affiliates and their respective officers, partners,
directors, managers,



                                       2
<PAGE>   26

employees, affiliates, agents and controlling persons from and against any and
all losses, claims, damages, liabilities and expenses, joint or several, to
which any such persons may become subject arising out of or in connection with
this Commitment Letter, the Term Sheet, the Redemption, the Investment or any
related transaction or any claim, litigation, investigation or proceeding
relating to any of the foregoing, regardless of whether any of such indemnified
parties is a party thereto, and to reimburse each of such indemnified parties
upon demand for any reasonable legal or other expenses incurred in connection
with investigating or defending any of the foregoing, provided that the
foregoing indemnity will not, as to any indemnified party, apply to losses,
claims, damages, liabilities or related expenses to the extent they are found in
a final judgment of a court to have resulted from the willful misconduct or
gross negligence of such indemnified party, and (b) to reimburse CCP and its
affiliates on demand for all reasonable out-of-pocket expenses (including but
not limited to expenses of CCP's due diligence investigation, consultants' fees,
syndication expenses, travel expenses and reasonable fees, disbursements and
other charges of counsel), in each case incurred in connection with the
Commitment Letter, the Term Sheet, the Redemption, the Investment and any
related documentation (whether or not the transactions contemplated hereby are
consummated) and the administration, enforcement, amendment, modification or
waiver thereof; provided, that CCP shall notify you when out-of pocket expenses
(other than fees, disbursements and other charges of counsel) exceeds $20,000.
Notwithstanding any other provision of this Commitment Letter, no indemnified
person shall be liable for any indirect or consequential damages in connection
with its activities related to the Investment.

          In consideration of the substantial expenditure of time, effort and
expense to be undertaken by CCP immediately upon the execution and delivery of
this Commitment Letter, you hereby undertake and agree that in the absence of
CCP's prior written consent, for the period from the date hereof until December
15, 1999 (the "Termination Date"), you will not, nor will you permit any of your
affiliates (or authorize or permit any of their respective representatives) to
take, directly or indirectly, any action to initiate, assist, solicit, receive,
negotiate, encourage or accept any offer or inquiry from any person to (a)
provide any debt or equity financing other than financings under your credit
agreement, arrangements relating to certain oil and gas financings and other
financings of the type not described herein (a "Financing") or purchase all or
substantially all of the assets or capital stock of the Company (whether through
a purchase of stock, merger, asset sale or related transaction) (a "Sale of the
Company"), (b) reach any agreement or understanding (whether or not such
agreement or understanding is absolute, revocable, contingent or conditional)
for, or otherwise attempt to consummate, any Financing or Sale of the Company or
(c) furnish or cause to be furnished any information with respect to the Company
or any of its affiliates to any person (other than as contemplated by this
Commitment Letter) who you, or any of your representatives, know or have reason
to believe is in the process of considering any Financing or Sale of the
Company, except in each case, solely with respect to a Sale of the Company, to
the extent that the foregoing restrictions are inconsistent with the exercise of
the fiduciary duties of your officers or directors. The obligations under this
paragraph shall terminate and be of no further force and effect in the event
that this Commitment Letter is terminated by CCP in accordance with its terms.

          This Commitment Letter is delivered to you on the understanding that
neither the existence of this Commitment Letter or the Term Sheet nor any of
their terms or substance shall be disclosed, directly or indirectly, except (a)
as may be compelled to be disclosed in a judicial



                                       3
<PAGE>   27

or administrative proceeding or as otherwise required by law, (b) on a
confidential and "need-to-know" basis, to your officers, directors, employees,
agents and advisors who are directly involved in the consideration of this
matter, (c) on a confidential basis to Nasdaq and its agents and (d) on a
confidential basis to Enron and its advisors and agents in connection with the
Redemption.

          You acknowledge that CCP and its affiliates may be providing debt
financing, equity capital or other services (including financial advisory
services) to other companies in respect of which you may have conflicting
interests regarding the transactions described herein and otherwise. CCP will
not use confidential information obtained from you by virtue of the transactions
contemplated by this Commitment Letter or its other relationships with you in
connection with the performance by CCP or any of its affiliates of services for
other companies, and CCP will not furnish any such information to other
companies. You also acknowledge that CCP and its affiliates have no obligation
to use in connection with the transactions contemplated by this Commitment
Letter, or to furnish to you, confidential information obtained by CCP or any of
its affiliates from other companies.

          This Commitment Letter and CCP's commitment hereunder shall not be
assignable by you without the prior written consent of CCP, and any attempted
assignment without such consent shall be void. This Commitment Letter and CCP's
commitment hereunder may be assigned in whole or in part by CCP to its
affiliates or other financial institutions acceptable to CCP and reasonably
acceptable to you. This Commitment Letter may not be amended or any provision
hereof waived or modified except by an instrument in writing signed by CCP and
you. This Commitment Letter may be executed in any number of counterparts, each
of which shall be an original and all of which, when taken together, shall
constitute one agreement. Delivery of an executed counterpart of a signature
page of this Commitment Letter by facsimile transmission shall be effective as
delivery of a manually executed counterpart of this Commitment Letter. This
Commitment Letter is intended to be solely for the benefit of the parties hereto
and is not intended to confer any benefits upon, or create any rights in favor
of, any person other than the parties hereto. This Commitment Letter shall be
governed by, and construed in accordance with, the laws of the State of New
York.

          Please indicate your acceptance of the terms hereof and of the Term
Sheet by signing in the appropriate space below and returning to CCP the
enclosed duplicate originals (or facsimiles) of this Commitment Letter not later
than 5:00 p.m., New York City time, on December 3, 1999. CCP's commitment
hereunder will expire at such time in the event that CCP has not received such
executed duplicate originals (or facsimiles) in accordance with the immediately
preceding sentence. In the event that the closing in respect of the Investment
does not occur on or before the Termination Date, then this Commitment Letter
and CCP's commitment hereunder shall automatically terminate unless CCP shall,
in its discretion, agree to an extension. The compensation, reimbursement,
indemnification and confidentiality provisions contained herein shall remain in
full force and effect regardless of whether definitive documentation for the
Investment shall be executed and delivered and notwithstanding the termination
of this Commitment Letter or CCP's commitment hereunder.

          CCP is pleased to have been given the opportunity to assist you in
connection with this transaction and we look forward to working with you to
complete this transaction.



                                       4
<PAGE>   28

                                               Very truly yours,

                                               CHASE CAPITAL PARTNERS



                                               By:______________________________
                                                  Name:
                                                  Title:


Accepted and agreed to as of
the date first above written:


CARRIZO OIL & GAS, INC.



By:________________________________
   Name:
   Title:



                                       5
<PAGE>   29




                             CARRIZO OIL & GAS, INC.
             $22,000,000 SENIOR SUBORDINATED NOTES WITH WARRANTS AND
                       $8,000,000 COMMON STOCK INVESTMENT
                                   TERM SHEET

                            SENIOR SUBORDINATED NOTES

ISSUER:                           Carrizo Oil & Gas, Inc. (the "Issuer").

HOLDERS:                          Affiliates of Chase Capital Partners
                                  (collectively, "CCP"), certain non-management
                                  directors of the Issuer (as described under
                                  "Conditions Precedent" below) and, at the
                                  option of CCP, other investors acceptable to
                                  CCP and reasonably acceptable to the Issuer.

ISSUE:                            Senior Subordinated Notes (the "Notes") with
                                  warrants to purchase 15.4% of the Issuer's
                                  fully-diluted common stock.

PRINCIPAL AMOUNT:                 $22,000,000.

ISSUE PRICE:                      Par.

CLOSING DATE:                     To be no later than December 15, 1999.

CLOSING FEE:                      Payable in accordance with the Commitment
                                  Letter to which this Term Sheet is attached.

SECURITY:                         The Notes will be unsecured.

RANKING:                          The Notes will be subordinated obligations of
                                  the Issuer ranking junior in right of payment
                                  to all Senior Indebtedness (to be defined) of
                                  the Issuer and senior in right of payment to
                                  all existing and future subordinated
                                  indebtedness of the Issuer.

USE OF PROCEEDS:                  The proceeds of the Notes shall be used to
                                  retire all of the Issuer's 9% Series A
                                  Preferred Stock, par value $0.01 (liquidation
                                  amount of approximately $34,000,000) and
                                  warrants to purchase 750,000 shares of the
                                  Issuer's common stock held by affiliates of
                                  Enron Corp. collectively, "Enron"), which to
                                  the Issuer's knowledge represents all of the
                                  securities of the Issuer held by Enron other
                                  than warrants to purchase up to 250,000 shares
                                  of the Issuer's common stock which Enron will
                                  retain (and the terms of which will be
                                  amended), at an aggregate redemption price
                                  equal to $12,000,000 in cash, to fund the
                                  Issuer's ongoing drilling program, to fund
                                  working capital and for general corporate
                                  purposes.
<PAGE>   30

COUPON:                           The Notes will bear  interest at a fixed rate
                                  of 9% per annum, payable quarterly in arrears,
                                  calculated on the basis of a 360-day year.
                                  Until the fifth anniversary of the Closing
                                  Date, interest on the Notes may, at the option
                                  of the Issuer, be paid in cash, or may accrue
                                  and be added to the principal amount of the
                                  Notes, in each case, pro rata among the Notes,
                                  provided, however, that at least 40% of each
                                  such interest payment shall be paid in cash.
                                  On and after the fifth anniversary of the
                                  Closing Date, all interest on the Notes shall
                                  be payable in cash. During the existence of
                                  any event of default under the definitive Note
                                  documentation, the interest rate will be 2.0%
                                  p.a. above the stated coupon rate.

MATURITY DATE:                    The eighth anniversary of the Closing Date.

REDEMPTION PROVISIONS:            MANDATORY:

                                  The Notes shall be amortized in one annual
                                  installment on the Maturity Date.

                                  Upon the occurrence of a change of control (to
                                  be defined, but to include a substantial asset
                                  sale, merger and liquidation as well as other
                                  customary change of control events), each
                                  holder of the Notes may require the Issuer to
                                  redeem the Notes at the applicable Optional
                                  Redemption Price.


                                  OPTIONAL:

                                  The Notes may be prepaid in whole or in part,
                                  at any time upon 30 days' notice, at the
                                  following premium (expressed as a percentage
                                  of the principal amount prepaid), plus accrued
                                  and unpaid interest (the "Optional Redemption
                                  Price"):

                                         Year 1                 109%
                                         Year 2                 107%
                                         Year 3                 105%
                                         Year 4                 104%
                                         Year 5                 103%
                                         Year 6                 102%
                                         Year 7                 101%
                                         Thereafter             100%

                                  Any offer to redeem or repurchase any Notes
                                  shall be made to all holders of the Notes on
                                  the same terms and conditions and any
                                  redemption or repurchase shall be made on a
                                  pro rata basis among the holders of the



                                       2
<PAGE>   31

                                  Notes.

DOCUMENTATION:                    The issuance of the Notes and the related
                                  warrants will be subject to the negotiation,
                                  execution and delivery of definitive
                                  documentation reasonably acceptable to all
                                  parties, including warrant agreement,
                                  shareholders' agreement and registration
                                  rights agreement, and shall contain
                                  representations, warranties, covenants and
                                  events of default customary for a transaction
                                  of this type and other terms deemed
                                  appropriate by CCP (including but not limited
                                  to those specified herein).

CONDITIONS PRECEDENT:             Customary for a financing of this type,
                                  including but not limited to (i) reasonably
                                  satisfactory documentation, (ii) due
                                  authorization, (iii) absence of default, (iv)
                                  truth and accuracy of representations and
                                  warranties, (v) requisite authorizations,
                                  approvals and consents; (vi) satisfactory
                                  legal opinions and (vii) satisfactory evidence
                                  that the issuance of the Notes, Warrants and
                                  Common Stock does not require shareholder
                                  approval under NASDAQ rules and is not in
                                  violation of NASDAQ's voting rights policy. In
                                  addition to the foregoing, certain
                                  non-management directors of the Issuer will be
                                  required to purchase, on a pro rata basis, at
                                  least 10% of the total amount of the Notes,
                                  Warrants and Common Stock as a condition to
                                  closing.

REPRESENTATIONS AND
WARRANTIES:                       Customary for a financing of this type.

AFFIRMATIVE COVENANTS:            Customary for a financing of this type.

FINANCIAL COVENANTS:              Customary for a financing of this type.

INFORMATION RIGHTS:               Customary for a financing of this type,
                                  subject to third-party confidentiality
                                  provisions and attorney-client privilege
                                  exceptions. The holders of the Notes will
                                  agree to maintain the confidentiality of all
                                  non-public information received from the
                                  Issuer, subject to customary exceptions.

NEGATIVE COVENANTS:               Customary for a financing of this type and to
                                  be consistent with the Senior Facilities. The
                                  definitive Note documentation will contain
                                  certain restrictions on modifications to the
                                  Senior Facilities without the prior written
                                  consent of the holders of the Notes.

EVENTS OF DEFAULT:                Customary for a financing of this
                                  type, which will include: nonpayment of
                                  principal; nonpayment of interest, fees or
                                  other amounts after a grace period to be
                                  agreed upon; material inaccuracy of
                                  representations and warranties; violation of
                                  covenants (subject to grace periods to be
                                  agreed upon); cross-acceleration; bankruptcy
                                  events; and material judgments.


                                       3
<PAGE>   32

                                  Upon the occurrence of an event of default,
                                  the holders of a majority of the aggregate
                                  principal amount of the Notes then outstanding
                                  may, at their option, by written notice to the
                                  Issuer, declare all the Notes due and payable.
                                  The Notes shall become automatically
                                  accelerated in the case of any bankruptcy
                                  event of default of the Issuer.

EXPENSES AND                      The Issuer shall pay (a) all reasonable
INDEMNIFICATION:                  out-of-pocket expenses of CCP and its
                                  affiliates associated with the provision of
                                  the Notes and the preparation, negotiation,
                                  execution and delivery of the definitive Note
                                  documentation, whether or not the transaction
                                  closes, and any amendment or waiver with
                                  respect thereto (including the reasonable
                                  fees, disbursements and other charges of
                                  counsel) and (b) all reasonable out-of-pocket
                                  expenses of the holders of the Notes
                                  (including fees, disbursements and other
                                  charges of counsel) in connection with the
                                  enforcement of the Notes.

TRANSFER RESTRICTIONS:            The Notes shall be freely transferable,
                                  subject only to compliance with applicable
                                  securities law; provided, however that no
                                  Notes shall be transferred to a competitor of
                                  the Issuer.

GOVERNING LAW:                    State of New York.



                                       4
<PAGE>   33



                                    WARRANTS

ISSUER:                           Carrizo Oil & Gas, Inc. (the "Issuer").

WARRANTS:                         Warrants  to  purchase  15.4% of the
                                  fully-diluted  common  stock of the
                                  Issuer (the "Warrant Stock").

EXERCISE PERIOD:                  Exercisable  at any time prior to the
                                  eighth anniversary of the Closing Date.

PURCHASE PRICE:                   The Warrants will be issued in conjunction
                                  with the Notes for no additional
                                  consideration and will be detachable.

EXERCISE PRICE:                   $2.20 per share.

PAYMENT OF EXERCISE PRICE:        Cash or surrender of Warrants equal to the
                                  Exercise Price.

METHOD OF EXERCISE:               Full or partial.

LIQUIDITY OPPORTUNITY:            From and after the fifth anniversary of
                                  the Closing Date and for so long as CCP owns
                                  at least 15% of the Issuer's fully-diluted
                                  common equity and CCP has not been given a
                                  liquidity opportunity (to be defined, but to
                                  include (i) a sale of the Issuer which
                                  includes the sale of CCP's equity or (ii) the
                                  Issuer reaching a specified minimum public
                                  float), then CCP shall have the right to
                                  appoint two additional members to the Issuer's
                                  Board of Directors and the Issuer will
                                  increase the size of its Board of Directors to
                                  provide for such additional Board members.

TAG-ALONG RIGHTS:                 Each holder of Warrants or Warrant Stock that
                                  is a Significant Holder shall have the right
                                  to participate in any sale of common stock by
                                  any principal shareholders to any third party
                                  (other than (i) sales to other principal
                                  shareholders with a value of less than $3
                                  million, (ii) sales in the public market or
                                  (iii) sales pursuant to the exercise of
                                  registration rights), such participation to be
                                  pro rata with such shareholders. A
                                  "Significant Holder" is a holder of Warrants,
                                  Warrant Stock or Common Stock representing not
                                  less than 10% of the Issuer's fully-diluted
                                  common equity.


                                       5
<PAGE>   34

PREEMPTIVE RIGHTS:                Each holder of Warrants or Warrant Stock that
                                  is a Significant Holder will be entitled to
                                  participate pro rata (assuming exercise of all
                                  Warrants) as purchasers in private equity
                                  offerings by the Issuer (including
                                  appreciation rights and other securities or
                                  rights having equity features).

ANTI-DILUTION PROVISIONS:         Customary weighted-average anti-dilution
                                  provisions. The Issuer will not be permitted
                                  to enter into any transaction that would
                                  result in an adjustment under the antidilution
                                  provisions that would cause Warrants to become
                                  exercisable for at least 2,075,000 shares at a
                                  price less than $1.77 unless the Issuer has
                                  previously obtained shareholder approval for
                                  the issuance of the Warrants. The Issuer will
                                  submit the issuance of the Warrants as a
                                  matter to be approved by the shareholders at
                                  the Issuer's next shareholders meeting and the
                                  principal shareholders and CCP will agree in
                                  the shareholders agreement to vote to approve
                                  such issuance.

INFORMATION RIGHTS:               The holders of the Warrants or Warrant Stock
                                  will be entitled to receive the same
                                  information as holders of the Notes. The
                                  holders of the Warrants and Warrant Stock will
                                  agree to maintain the confidentiality of all
                                  non-public information received from the
                                  Issuer, subject to customary exceptions.

REGISTRATION RIGHTS:              The holders of Warrants, Warrant Stock and/or
                                  Common Stock will have the following
                                  registration rights:

                                  (i)   Three demand registrations at any time,
                                        and

                                  (ii)  Unlimited piggyback rights.

                                  The Issuer will pay the expenses of the
                                  holders of Warrant Stock in all demand and
                                  piggyback registrations (including the
                                  fees and expenses of one counsel for such
                                  holders, but excluding underwriting discounts
                                  and selling commissions).

                                  The Issuer will not grant other registration
                                  rights inconsistent with the rights of the
                                  holders of Warrants, Warrant Stock and Common
                                  Stock.



                                       6
<PAGE>   35

                                  If any other holder or group of holders of the
                                  Issuer's equity exercises a demand
                                  registration right and the holders of
                                  Warrants, Warrant Stock and/or Common Stock,
                                  promptly after receiving notice of such
                                  exercise, exercise one of their demand
                                  registration rights, then all such holders
                                  shall be entitled to include shares in such
                                  registration on a pro rata basis with priority
                                  over any holder entitled to piggyback
                                  registration rights with respect to such
                                  demand registration. Any existing registration
                                  rights granted by the Issuer shall be amended
                                  to give effect to the foregoing arrangement.

                                  The Issuer, its principal shareholders
                                  (including the holders of the Warrant Stock
                                  and the Common Stock) and the holders of
                                  Warrants will agree to customary holdback
                                  restrictions with respect to any offering
                                  which includes common stock issued upon
                                  exercise of the Warrants.

DOCUMENTATION:                    The terms with respect to the Warrants will be
                                  set forth in definitive documentation
                                  reasonably acceptable to all parties and
                                  containing other terms and provisions
                                  customary for a transaction of this type,
                                  including a shareholders agreement among the
                                  holders of the Warrants and the Common Stock,
                                  the Issuer and the principal shareholders.

TRANSFERABILITY:                  The Warrants shall be freely transferable in
                                  whole or in part to accredited investors,
                                  subject only to compliance with applicable
                                  securities laws; provided, however that no
                                  Warrants shall be transferred to a competitor
                                  of the Issuer.




<PAGE>   36



                                  COMMON STOCK

ISSUER:                           Carrizo Oil & Gas, Inc. (the "Issuer").

TYPE OF SECURITY:                 Common Stock, par value $0.01 per share (the
                                  "Common Stock").

NUMBER OF SHARES:                 3,636,364 shares.

PURCHASE PRICE:                   $2.20 per share.

CLOSING FEE:                      Payable in accordance with the Commitment
                                  Letter to which this Term Sheet is attached.

LIQUIDITY OPPORTUNITY:            From and after the fifth anniversary of the
                                  Closing Date and for so long as CCP owns at
                                  least 15% of the Issuer's fully-diluted common
                                  equity and CCP has not been given a liquidity
                                  opportunity (to be defined, but to include (i)
                                  a sale of the Issuer which includes the sale
                                  of CCP's equity or (ii) the Issuer reaching a
                                  specified minimum public float), then CCP
                                  shall have the right to appoint two additional
                                  members to the Issuer's Board of Directors and
                                  the Issuer will increase the size of its Board
                                  of Directors to provide for such additional
                                  Board members.

TAG-ALONG RIGHTS:                 Each holder of Common Stock that is a
                                  Significant Holder shall have the right to
                                  participate in any sale of common stock by any
                                  principal shareholders to any third party
                                  (other than (i) sales to other principal
                                  shareholders with a value of less than $3
                                  million, (ii) sales in the public market or
                                  (iii) sales pursuant to the exercise of
                                  registration rights), such participation to be
                                  pro rata with such shareholders.

PREEMPTIVE RIGHTS:                Each holder of Common Stock that is a
                                  Significant Holder will be entitled to
                                  participate pro rata as purchasers in private
                                  equity offerings by the Issuer (including
                                  appreciation rights and other securities or
                                  rights having equity features).



                                       8
<PAGE>   37

BOARD REPRESENTATION:             For so long as CCP owns at least 15% of the
                                  Issuer's fully-diluted equity, CCP will have
                                  the right to appoint 2 members to the Issuer's
                                  Board of Directors. For so long as CCP owns at
                                  least 7 1/2% but less than 15% of the Issuer's
                                  fully-diluted equity, CCP will have the right
                                  to appoint 1 member to the Issuer's Board of
                                  Directors. The Issuer will increase the size
                                  of its Board of Directors from 5 to 7 to
                                  provide for the Board members to be appointed
                                  by CCP.

INFORMATION RIGHTS:               The holders of the Common Stock will be
                                  entitled to receive the same information as
                                  holders of the Notes. The holders of the
                                  Common Stock will agree to maintain the
                                  confidentiality of all non-public information
                                  received from the Issuer, subject to customary
                                  exceptions.


                                       9
<PAGE>   38

REGISTRATION RIGHTS:              The holders of the Common Stock, Warrants
                                  and/or Warrant Stock will have the following
                                  registration rights:

                                  (i)  Three demand registrations at any time,
                                       and

                                  (ii) Unlimited piggyback rights.

                                  The Issuer will pay the expenses of the
                                  holders of Common Stock in all demand and
                                  piggyback registrations (including the fees
                                  and expenses of one counsel for such holders,
                                  but excluding underwriting discounts and
                                  selling commissions).

                                  The Issuer will not grant other registration
                                  rights inconsistent with the rights of the
                                  holders of Common Stock, Warrants and Warrant
                                  Stock.

                                  If any other holder or group of holders of the
                                  Issuer's equity exercises a demand
                                  registration right and the holders of
                                  Warrants, Warrant Stock and/or Common Stock,
                                  promptly after receiving notice of such
                                  exercise, exercise one of their demand
                                  registration rights, then all such holders
                                  shall be entitled to include shares in such
                                  registration on a pro rata basis with priority
                                  over any holder entitled to piggyback
                                  registration rights with respect to such
                                  demand registration. Any existing registration
                                  rights granted by the Issuer shall be amended
                                  to give effect to the foregoing arrangement.

                                  The Issuer, its principal shareholders
                                  (including the holders of the Warrant Stock
                                  and the Common Stock) and the holders of
                                  Warrants will agree to customary holdback
                                  restrictions with respect to any offering
                                  which includes any Common Stock.

DOCUMENTATION:                    The terms with respect to the purchase of the
                                  Common Stock will be set forth in definitive
                                  documentation reasonably acceptable to all
                                  parties and containing other terms and
                                  provisions customary for a transaction of this
                                  type, including a shareholders agreement among
                                  the holders of the Common Stock and the
                                  Warrants, the Issuer and the principal
                                  shareholders.

TRANSFERABILITY:                  The Common Stock shall be freely transferable
                                  in whole or in part, subject only to
                                  compliance with applicable securities laws;
                                  provided, however that no Common Stock shall
                                  be transferred to a competitor of the Issuer.


                                       10

<PAGE>   1

                                                                    EXHIBIT 99.2


                                                                December 1, 1999



Carrizo Oil & Gas, Inc.
14811 St. Mary's Lane, Suite 148
Houston, Texas  77079
Attention: Chip Johnson

                             Carrizo Oil & Gas, Inc.
                             $30,000,000 Investment


Gentlemen:

                  You have advised Chase Capital Partners (together with one or
more of its affiliated investment funds, "CCP") that Carrizo Oil & Gas, Inc.
(the "Company") intends to purchase (the "Redemption") from Enron Corp. and its
affiliates (collectively, "Enron"), pursuant to a definitive purchase agreement
with Enron (the "Enron Purchase Agreement") with respect to the Redemption with
terms and conditions satisfactory to CCP, all of the Company's outstanding 9%
Series A Preferred Stock, par value $0.01 per share (liquidation amount of
approximately $34,000,000) and warrants to purchase 750,000 shares of the
Company's common stock (collectively, the "Enron Equity"), which to your
knowledge represents all of the securities of the Company held by Enron other
than warrants to purchase 250,000 shares of the Company's common stock which
will be retained by Enron (and the terms of which will be amended), for an
aggregate redemption price of up to $12,000,000 in cash. In connection
therewith, the Company intends to issue (a) $22,000,000 aggregate principal
amount of its senior subordinated notes (the "Notes"), together with warrants to
purchase common stock (the "Common Stock") of the Company (the "Warrants") and
(b) aggregate consideration of $8,000,000 in Common Stock.

                  CCP is pleased to advise you of its commitment to purchase up
to $22,000,000 aggregate principal amount of the Notes, the Warrants and up to
$8,000,000 of the Common Stock (collectively, the "Investment"), upon the terms
and subject to the conditions set forth or referred to in this letter
("Commitment Letter") and in the Term Sheet (the "Term Sheet") annexed hereto;
provided, however that the foregoing amounts will be reduced to the extent of
the investment by the non-management directors as described herein and in the
Term Sheet.

                  You agree promptly to prepare and provide to CCP all
information reasonably requested by CCP with respect to the Company, the
Redemption and the other transactions contemplated hereby, including all
financial information and projections (the "Projections"). You hereby represent
and covenant that (a) all information other than the Projections (the
"Information") that has been or will be made available to CCP by or on behalf of
you or any of

<PAGE>   2


your authorized representatives, when taken as a whole, is or will be, when
furnished, complete and correct in all material respects and does not or will
not, when furnished, contain any untrue statement of a material fact or omit to
state a material fact necessary in order to make the statements contained
therein not materially misleading in light of the circumstances under which such
statements are made and (b) the Projections that have been or will be made
available to CCP by or on behalf of you or any of your authorized
representatives have been or will be prepared in good faith based upon
assumptions that are reasonable at the time made and at the time the related
Projections are made available to CCP. You agree that if at any time from and
including the date hereof until the closing of the Investment, any of the
representations in the preceding sentence would be incorrect, then you will
promptly supplement the Information and the Projections so that such
representations will be correct. You agree that CCP will be entitled to use and
rely primarily on the Information and the Projections without responsibility for
independent verification thereof.

                  As consideration for CCP's commitment hereunder, you agree to
pay to CCP, conditioned upon the closing, a fee (the "Closing Fee") in an amount
equal to one and one-half percent (1 1/2%) of the aggregate amount of CCP's
portion of the total Investment. The Closing Fee shall be payable on the Closing
Date, shall be paid in immediately available funds and, once paid, shall not be
refundable under any circumstances. The Closing Fee shall be in addition to
reimbursement of the reasonable out-of-pocket fees and expenses of CCP.

                  CCP's commitment hereunder is subject to (a) CCP's not having
discovered or otherwise becoming aware of information not previously disclosed
to CCP that CCP believes to be materially inconsistent with its understanding,
based on information provided to CCP prior to the date hereof, of the business,
operations, properties, assets, liabilities, prospects or financial condition of
Company, (b) there not having occurred any event, condition or circumstance that
has had or is reasonably likely to have a material adverse effect on the
business, operations, properties, assets, liabilities, prospects or financial
condition of Company, (c) there not having occurred and being continuing a
material disruption of or material adverse change in financial, banking or
capital market conditions, (d) the negotiation, execution and delivery of
definitive documentation with respect to the Investment reasonably satisfactory
to CCP and its counsel, (e) the closing of the Redemption on the terms set forth
in the Enron Purchase Agreement and or other terms satisfactory to CCP
simultaneously with the closing of the Investment, (f) the negotiation,
execution and delivery of an amendment to your credit facility with Compass Bank
or a new credit facility with Shell Capital on terms reasonably satisfactory to
CCP, (g) evidence reasonably satisfactory to CCP that the transactions
contemplated by the Investment do not require shareholder approval under NASDAQ
rules and are not in violation of NASDAQ's voting rights policy and (h) the
other conditions set forth or referred to herein and in the Term Sheet. In
addition to the foregoing, certain non-management directors of the Company will
be required to purchase at least 10% of the total amount of the Investment as a
condition to closing. The terms and conditions of CCP's commitment hereunder and
of the Investment are not limited to the terms and conditions set forth herein
or in the Term Sheet. Those matters that are not covered by or made clear under
the provisions hereof or of the Term Sheet are subject to the reasonable
approval and reasonable agreement of CCP and you.

                  By executing this Commitment Letter, you agree (a) to
indemnify and hold harmless CCP, its affiliates and their respective officers,
partners, directors, managers,

                                        2

<PAGE>   3


employees, affiliates, agents and controlling persons from and against any and
all losses, claims, damages, liabilities and expenses, joint or several, to
which any such persons may become subject arising out of or in connection with
this Commitment Letter, the Term Sheet, the Redemption, the Investment or any
related transaction or any claim, litigation, investigation or proceeding
relating to any of the foregoing, regardless of whether any of such indemnified
parties is a party thereto, and to reimburse each of such indemnified parties
upon demand for any reasonable legal or other expenses incurred in connection
with investigating or defending any of the foregoing, provided that the
foregoing indemnity will not, as to any indemnified party, apply to losses,
claims, damages, liabilities or related expenses to the extent they are found in
a final judgment of a court to have resulted from the willful misconduct or
gross negligence of such indemnified party, and (b) to reimburse CCP and its
affiliates on demand for all reasonable out-of-pocket expenses (including but
not limited to expenses of CCP's due diligence investigation, consultants' fees,
syndication expenses, travel expenses and reasonable fees, disbursements and
other charges of counsel), in each case incurred in connection with the
Commitment Letter, the Term Sheet, the Redemption, the Investment and any
related documentation (whether or not the transactions contemplated hereby are
consummated) and the administration, enforcement, amendment, modification or
waiver thereof; provided, that CCP shall notify you when out-of pocket expenses
(other than fees, disbursements and other charges of counsel) exceeds $20,000.
Notwithstanding any other provision of this Commitment Letter, no indemnified
person shall be liable for any indirect or consequential damages in connection
with its activities related to the Investment.

                  In consideration of the substantial expenditure of time,
effort and expense to be undertaken by CCP immediately upon the execution and
delivery of this Commitment Letter, you hereby undertake and agree that in the
absence of CCP's prior written consent, for the period from the date hereof
until December 15, 1999 (the "Termination Date"), you will not, nor will you
permit any of your affiliates (or authorize or permit any of their respective
representatives) to take, directly or indirectly, any action to initiate,
assist, solicit, receive, negotiate, encourage or accept any offer or inquiry
from any person to (a) provide any debt or equity financing other than
financings under your credit agreement, arrangements relating to certain oil and
gas financings and other financings of the type not described herein (a
"Financing") or purchase all or substantially all of the assets or capital stock
of the Company (whether through a purchase of stock, merger, asset sale or
related transaction) (a "Sale of the Company"), (b) reach any agreement or
understanding (whether or not such agreement or understanding is absolute,
revocable, contingent or conditional) for, or otherwise attempt to consummate,
any Financing or Sale of the Company or (c) furnish or cause to be furnished any
information with respect to the Company or any of its affiliates to any person
(other than as contemplated by this Commitment Letter) who you, or any of your
representatives, know or have reason to believe is in the process of considering
any Financing or Sale of the Company, except in each case, solely with respect
to a Sale of the Company, to the extent that the foregoing restrictions are
inconsistent with the exercise of the fiduciary duties of your officers or
directors. The obligations under this paragraph shall terminate and be of no
further force and effect in the event that this Commitment Letter is terminated
by CCP in accordance with its terms.

                  This Commitment Letter is delivered to you on the
understanding that neither the existence of this Commitment Letter or the Term
Sheet nor any of their terms or substance shall be disclosed, directly or
indirectly, except (a) as may be compelled to be disclosed in a judicial

                                        3

<PAGE>   4


or administrative proceeding or as otherwise required by law, (b) on a
confidential and "need-to-know" basis, to your officers, directors, employees,
agents and advisors who are directly involved in the consideration of this
matter, (c) on a confidential basis to Nasdaq and its agents and (d) on a
confidential basis to Enron and its advisors and agents in connection with the
Redemption.

                  You acknowledge that CCP and its affiliates may be providing
debt financing, equity capital or other services (including financial advisory
services) to other companies in respect of which you may have conflicting
interests regarding the transactions described herein and otherwise. CCP will
not use confidential information obtained from you by virtue of the transactions
contemplated by this Commitment Letter or its other relationships with you in
connection with the performance by CCP or any of its affiliates of services for
other companies, and CCP will not furnish any such information to other
companies. You also acknowledge that CCP and its affiliates have no obligation
to use in connection with the transactions contemplated by this Commitment
Letter, or to furnish to you, confidential information obtained by CCP or any of
its affiliates from other companies.

                  This Commitment Letter and CCP's commitment hereunder shall
not be assignable by you without the prior written consent of CCP, and any
attempted assignment without such consent shall be void. This Commitment Letter
and CCP's commitment hereunder may be assigned in whole or in part by CCP to its
affiliates or other financial institutions acceptable to CCP and reasonably
acceptable to you. This Commitment Letter may not be amended or any provision
hereof waived or modified except by an instrument in writing signed by CCP and
you. This Commitment Letter may be executed in any number of counterparts, each
of which shall be an original and all of which, when taken together, shall
constitute one agreement. Delivery of an executed counterpart of a signature
page of this Commitment Letter by facsimile transmission shall be effective as
delivery of a manually executed counterpart of this Commitment Letter. This
Commitment Letter is intended to be solely for the benefit of the parties hereto
and is not intended to confer any benefits upon, or create any rights in favor
of, any person other than the parties hereto. This Commitment Letter shall be
governed by, and construed in accordance with, the laws of the State of New
York.

                  Please indicate your acceptance of the terms hereof and of the
Term Sheet by signing in the appropriate space below and returning to CCP the
enclosed duplicate originals (or facsimiles) of this Commitment Letter not later
than 5:00 p.m., New York City time, on December 3, 1999. CCP's commitment
hereunder will expire at such time in the event that CCP has not received such
executed duplicate originals (or facsimiles) in accordance with the immediately
preceding sentence. In the event that the closing in respect of the Investment
does not occur on or before the Termination Date, then this Commitment Letter
and CCP's commitment hereunder shall automatically terminate unless CCP shall,
in its discretion, agree to an extension. The compensation, reimbursement,
indemnification and confidentiality provisions contained herein shall remain in
full force and effect regardless of whether definitive documentation for the
Investment shall be executed and delivered and notwithstanding the termination
of this Commitment Letter or CCP's commitment hereunder.

                                        4

<PAGE>   5

                  CCP is pleased to have been given the opportunity to assist
you in connection with this transaction and we look forward to working with you
to complete this transaction.


                                            Very truly yours,

                                            CHASE CAPITAL PARTNERS



                                            By: /s/ CHRIS BEHRENS
                                               --------------------------------
                                               Name: Chris Behrens
                                               Title: General Partner


Accepted and agreed to as of
the date first above written:


CARRIZO OIL & GAS, INC.



By: /s/ S.P. JOHNSON IV
   --------------------------------------
   Name: S.P. Johnson IV
   Title: President/CEO



                                        5
<PAGE>   6
                             CARRIZO OIL & GAS, INC.
             $22,000,000 SENIOR SUBORDINATED NOTES WITH WARRANTS AND
                       $8,000,000 COMMON STOCK INVESTMENT
                                   TERM SHEET

                                         SENIOR SUBORDINATED NOTES
                                         -------------------------

ISSUER:                             Carrizo Oil & Gas, Inc. (the "Issuer").

HOLDERS:                            Affiliates of Chase Capital Partners
                                    (collectively, "CCP"), certain
                                    non-management directors of the Issuer (as
                                    described under "Conditions Precedent"
                                    below) and, at the option of CCP, other
                                    investors acceptable to CCP and reasonably
                                    acceptable to the Issuer.

ISSUE:                              Senior Subordinated Notes (the "Notes") with
                                    warrants to purchase 15.4% of the Issuer's
                                    fully-diluted common stock.

PRINCIPAL AMOUNT:                   $22,000,000.

ISSUE PRICE:                        Par.

CLOSING DATE:                       To be no later than December 15, 1999.

CLOSING FEE:                        Payable in accordance with the Commitment
                                    Letter to which this Term Sheet is attached.

SECURITY:                           The Notes will be unsecured.

RANKING:                            The Notes will be subordinated obligations
                                    of the Issuer ranking junior in right of
                                    payment to all Senior Indebtedness (to be
                                    defined) of the Issuer and senior in right
                                    of payment to all existing and future
                                    subordinated indebtedness of the Issuer.

USE OF PROCEEDS:                    The proceeds of the Notes shall be used to
                                    retire all of the Issuer's 9% Series A
                                    Preferred Stock, par value $0.01
                                    (liquidation amount of approximately
                                    $34,000,000) and warrants to purchase
                                    750,000 shares of the Issuer's common stock
                                    held by affiliates of Enron Corp.
                                    collectively, "Enron"), which to the
                                    Issuer's knowledge represents all of the
                                    securities of the Issuer held by Enron other
                                    than warrants to purchase up to 250,000
                                    shares of the Issuer's common stock which
                                    Enron will retain (and the terms of which
                                    will be amended), at an aggregate redemption
                                    price equal to $12,000,000 in cash, to fund
                                    the Issuer's ongoing drilling program, to
                                    fund working capital and for general
                                    corporate purposes.

<PAGE>   7


COUPON:                             The Notes will bear interest at a fixed rate
                                    of 9% per annum, payable quarterly in
                                    arrears, calculated on the basis of a
                                    360-day year. Until the fifth anniversary of
                                    the Closing Date, interest on the Notes may,
                                    at the option of the Issuer, be paid in
                                    cash, or may accrue and be added to the
                                    principal amount of the Notes, in each case,
                                    pro rata among the Notes, provided, however,
                                    that at least 40% of each such interest
                                    payment shall be paid in cash. On and after
                                    the fifth anniversary of the Closing Date,
                                    all interest on the Notes shall be payable
                                    in cash. During the existence of any event
                                    of default under the definitive Note
                                    documentation, the interest rate will be
                                    2.0% p.a. above the stated coupon rate.

MATURITY DATE:                      The eighth anniversary of the Closing Date.

REDEMPTION PROVISIONS:              MANDATORY:

                                    The Notes shall be amortized in one annual
                                    installment on the Maturity Date.

                                    Upon the occurrence of a change of control
                                    (to be defined, but to include a substantial
                                    asset sale, merger and liquidation as well
                                    as other customary change of control
                                    events), each holder of the Notes may
                                    require the Issuer to redeem the Notes at
                                    the applicable Optional Redemption Price.


                                    OPTIONAL:

                                    The Notes may be prepaid in whole or in
                                    part, at any time upon 30 days' notice, at
                                    the following premium (expressed as a
                                    percentage of the principal amount prepaid),
                                    plus accrued and unpaid interest (the
                                    "Optional Redemption Price"):

                                                Year 1            109%
                                                Year 2            107%
                                                Year 3            105%
                                                Year 4            104%
                                                Year 5            103%
                                                Year 6            102%
                                                Year 7            101%
                                                Thereafter        100%

                                    Any offer to redeem or repurchase any Notes
                                    shall be made to all holders of the Notes on
                                    the same terms and conditions and any
                                    redemption or repurchase shall be made on a
                                    pro rata basis among the holders of the
                                    Notes.


                                       2
<PAGE>   8


DOCUMENTATION:                      The issuance of the Notes and the related
                                    warrants will be subject to the negotiation,
                                    execution and delivery of definitive
                                    documentation reasonably acceptable to all
                                    parties, including warrant agreement,
                                    shareholders' agreement and registration
                                    rights agreement, and shall contain
                                    representations, warranties, covenants and
                                    events of default customary for a
                                    transaction of this type and other terms
                                    deemed appropriate by CCP (including but not
                                    limited to those specified herein).

CONDITIONS PRECEDENT:               Customary for a financing of this type,
                                    including but not limited to (i) reasonably
                                    satisfactory documentation, (ii) due
                                    authorization, (iii) absence of default,
                                    (iv) truth and accuracy of representations
                                    and warranties, (v) requisite
                                    authorizations, approvals and consents; (vi)
                                    satisfactory legal opinions and (vii)
                                    satisfactory evidence that the issuance of
                                    the Notes, Warrants and Common Stock does
                                    not require shareholder approval under
                                    NASDAQ rules and is not in violation of
                                    NASDAQ's voting rights policy. In addition
                                    to the foregoing, certain non-management
                                    directors of the Issuer will be required to
                                    purchase, on a pro rata basis, at least 10%
                                    of the total amount of the Notes, Warrants
                                    and Common Stock as a condition to closing.

REPRESENTATIONS AND
WARRANTIES:                         Customary for a financing of this type.

AFFIRMATIVE COVENANTS:              Customary for a financing of this type.

FINANCIAL COVENANTS:                Customary for a financing of this type.

INFORMATION RIGHTS:                 Customary for a financing of this type,
                                    subject to third-party confidentiality
                                    provisions and attorney-client privilege
                                    exceptions. The holders of the Notes will
                                    agree to maintain the confidentiality of all
                                    non-public information received from the
                                    Issuer, subject to customary exceptions.

NEGATIVE COVENANTS:                 Customary for a financing of this type and
                                    to be consistent with the Senior Facilities.
                                    The definitive Note documentation will
                                    contain certain restrictions on
                                    modifications to the Senior Facilities
                                    without the prior written consent of the
                                    holders of the Notes.

EVENTS OF DEFAULT:                  Customary for a financing of this type,
                                    which will include: nonpayment of principal;
                                    nonpayment of interest, fees or other
                                    amounts after a grace period to be agreed
                                    upon; material inaccuracy of representations
                                    and warranties; violation of covenants
                                    (subject to grace periods to be agreed
                                    upon); cross-acceleration; bankruptcy
                                    events; and material judgments.


                                       3
<PAGE>   9


                                    Upon the occurrence of an event of default,
                                    the holders of a majority of the aggregate
                                    principal amount of the Notes then
                                    outstanding may, at their option, by written
                                    notice to the Issuer, declare all the Notes
                                    due and payable. The Notes shall become
                                    automatically accelerated in the case of any
                                    bankruptcy event of default of the Issuer.

EXPENSES AND INDEMNIFICATION:       The Issuer shall pay (a) all reasonable
                                    out-of-pocket expenses of CCP and its
                                    affiliates associated with the provision of
                                    the Notes and the preparation, negotiation,
                                    execution and delivery of the definitive
                                    Note documentation, whether or not the
                                    transaction closes, and any amendment or
                                    waiver with respect thereto (including the
                                    reasonable fees, disbursements and other
                                    charges of counsel) and (b) all reasonable
                                    out-of-pocket expenses of the holders of the
                                    Notes (including fees, disbursements and
                                    other charges of counsel) in connection with
                                    the enforcement of the Notes.

TRANSFER RESTRICTIONS:              The Notes shall be freely transferable,
                                    subject only to compliance with applicable
                                    securities law; provided, however that no
                                    Notes shall be transferred to a competitor
                                    of the Issuer.

GOVERNING LAW:                      State of New York.


                                       4
<PAGE>   10




                                                    WARRANTS
                                                    --------

ISSUER:                             Carrizo Oil & Gas, Inc. (the "Issuer").

WARRANTS:                           Warrants to purchase 15.4% of the
                                    fully-diluted common stock of the Issuer
                                    (the "Warrant Stock").

EXERCISE PERIOD:                    Exercisable at any time prior to the eighth
                                    anniversary of the Closing Date.

PURCHASE PRICE:                     The Warrants will be issued in conjunction
                                    with the Notes for no additional
                                    consideration and will be detachable.

EXERCISE PRICE:                     $2.20 per share.

PAYMENT OF EXERCISE PRICE:          Cash or surrender of Warrants equal to the
                                    Exercise Price.

METHOD OF EXERCISE:                 Full or partial.

LIQUIDITY OPPORTUNITY:              From and after the fifth anniversary of the
                                    Closing Date and for so long as CCP owns at
                                    least 15% of the Issuer's fully-diluted
                                    common equity and CCP has not been given a
                                    liquidity opportunity (to be defined, but to
                                    include (i) a sale of the Issuer which
                                    includes the sale of CCP's equity or (ii)
                                    the Issuer reaching a specified minimum
                                    public float), then CCP shall have the right
                                    to appoint two additional members to the
                                    Issuer's Board of Directors and the Issuer
                                    will increase the size of its Board of
                                    Directors to provide for such additional
                                    Board members.

TAG-ALONG RIGHTS:                   Each holder of Warrants or Warrant Stock
                                    that is a Significant Holder shall have the
                                    right to participate in any sale of common
                                    stock by any principal shareholders to any
                                    third party (other than (i) sales to other
                                    principal shareholders with a value of less
                                    than $3 million, (ii) sales in the public
                                    market or (iii) sales pursuant to the
                                    exercise of registration rights), such
                                    participation to be pro rata with such
                                    shareholders. A "Significant Holder" is a
                                    holder of Warrants, Warrant Stock or Common
                                    Stock representing not less than 10% of the
                                    Issuer's fully-diluted common equity.


                                       5
<PAGE>   11


PREEMPTIVE RIGHTS:                  Each holder of Warrants or Warrant Stock
                                    that is a Significant Holder will be
                                    entitled to participate pro rata (assuming
                                    exercise of all Warrants) as purchasers in
                                    private equity offerings by the Issuer
                                    (including appreciation rights and other
                                    securities or rights having equity
                                    features).

ANTI-DILUTION PROVISIONS:           Customary weighted-average anti-dilution
                                    provisions. The Issuer will not be permitted
                                    to enter into any transaction that would
                                    result in an adjustment under the
                                    antidilution provisions that would cause
                                    Warrants to become exercisable for at least
                                    2,075,000 shares at a price less than $1.73
                                    unless the Issuer has previously obtained
                                    shareholder approval for the issuance of the
                                    Warrants. The Issuer will submit the
                                    issuance of the Warrants as a matter to be
                                    approved by the shareholders at the Issuer's
                                    next shareholders meeting and the principal
                                    shareholders and CCP will agree in the
                                    shareholders agreement to vote to approve
                                    such issuance.

INFORMATION RIGHTS:                 The holders of the Warrants or Warrant Stock
                                    will be entitled to receive the same
                                    information as holders of the Notes. The
                                    holders of the Warrants and Warrant Stock
                                    will agree to maintain the confidentiality
                                    of all non-public information received from
                                    the Issuer, subject to customary exceptions.

REGISTRATION RIGHTS:                The holders of Warrants, Warrant Stock
                                    and/or Common Stock will have the following
                                    registration rights:

                                    (i)  Three demand registrations at any time,
                                         and

                                    (ii) Unlimited piggyback rights.

                                    The Issuer will pay the expenses of the
                                    holders of Warrant Stock in all demand and
                                    piggyback registrations (including the fees
                                    and expenses of one counsel for such
                                    holders, but excluding underwriting
                                    discounts and selling commissions).

                                    The Issuer will not grant other registration
                                    rights inconsistent with the rights of the
                                    holders of Warrants, Warrant Stock and
                                    Common Stock.


                                       6
<PAGE>   12


                                    If any other holder or group of holders of
                                    the Issuer's equity exercises a demand
                                    registration right and the holders of
                                    Warrants, Warrant Stock and/or Common Stock,
                                    promptly after receiving notice of such
                                    exercise, exercise one of their demand
                                    registration rights, then all such holders
                                    shall be entitled to include shares in such
                                    registration on a pro rata basis with
                                    priority over any holder entitled to
                                    piggyback registration rights with respect
                                    to such demand registration. Any existing
                                    registration rights granted by the Issuer
                                    shall be amended to give effect to the
                                    foregoing arrangement.

                                    The Issuer, its principal shareholders
                                    (including the holders of the Warrant Stock
                                    and the Common Stock) and the holders of
                                    Warrants will agree to customary holdback
                                    restrictions with respect to any offering
                                    which includes common stock issued upon
                                    exercise of the Warrants.

DOCUMENTATION:                      The terms with respect to the Warrants will
                                    be set forth in definitive documentation
                                    reasonably acceptable to all parties and
                                    containing other terms and provisions
                                    customary for a transaction of this type,
                                    including a shareholders agreement among the
                                    holders of the Warrants and the Common
                                    Stock, the Issuer and the principal
                                    shareholders.

TRANSFERABILITY:                    The Warrants shall be freely transferable in
                                    whole or in part to accredited investors,
                                    subject only to compliance with applicable
                                    securities laws; provided, however that no
                                    Warrants shall be transferred to a
                                    competitor of the Issuer.


                                       7
<PAGE>   13




                                                  COMMON STOCK
                                                  ------------

ISSUER:                             Carrizo Oil & Gas, Inc. (the "Issuer").

TYPE OF SECURITY:                   Common Stock, par value $0.01 per share (the
                                    "Common Stock").

NUMBER OF SHARES:                   3,636,364 shares.

PURCHASE PRICE:                     $2.20 per share.

CLOSING FEE:                        Payable in accordance with the Commitment
                                    Letter to which this Term Sheet is attached.

LIQUIDITY OPPORTUNITY:              From and after the fifth anniversary of the
                                    Closing Date and for so long as CCP owns at
                                    least 15% of the Issuer's fully-diluted
                                    common equity and CCP has not been given a
                                    liquidity opportunity (to be defined, but to
                                    include (i) a sale of the Issuer which
                                    includes the sale of CCP's equity or (ii)
                                    the Issuer reaching a specified minimum
                                    public float), then CCP shall have the right
                                    to appoint two additional members to the
                                    Issuer's Board of Directors and the Issuer
                                    will increase the size of its Board of
                                    Directors to provide for such additional
                                    Board members.

TAG-ALONG RIGHTS:                   Each holder of Common Stock that is a
                                    Significant Holder shall have the right to
                                    participate in any sale of common stock by
                                    any principal shareholders to any third
                                    party (other than (i) sales to other
                                    principal shareholders with a value of less
                                    than $3 million, (ii) sales in the public
                                    market or (iii) sales pursuant to the
                                    exercise of registration rights), such
                                    participation to be pro rata with such
                                    shareholders.

PREEMPTIVE RIGHTS:                  Each holder of Common Stock that is a
                                    Significant Holder will be entitled to
                                    participate pro rata as purchasers in
                                    private equity offerings by the Issuer
                                    (including appreciation rights and other
                                    securities or rights having equity
                                    features).


                                       8
<PAGE>   14


BOARD REPRESENTATION:               For so long as CCP owns at least 15% of the
                                    Issuer's fully-diluted equity, CCP will have
                                    the right to appoint 2 members to the
                                    Issuer's Board of Directors. For so long as
                                    CCP owns at least 7 1/2% but less than 15%
                                    of the Issuer's fully-diluted equity, CCP
                                    will have the right to appoint 1 member to
                                    the Issuer's Board of Directors. The Issuer
                                    will increase the size of its Board of
                                    Directors from 5 to 7 to provide for the
                                    Board members to be appointed by CCP.

INFORMATION RIGHTS:                 The holders of the Common Stock will be
                                    entitled to receive the same information as
                                    holders of the Notes. The holders of the
                                    Common Stock will agree to maintain the
                                    confidentiality of all non-public
                                    information received from the Issuer,
                                    subject to customary exceptions.


                                       9
<PAGE>   15


REGISTRATION RIGHTS:                The holders of the Common Stock, Warrants
                                    and/or Warrant Stock will have the following
                                    registration rights:

                                    (i)  Three demand registrations at any time,
                                         and

                                    (ii) Unlimited piggyback rights.

                                    The Issuer will pay the expenses of the
                                    holders of Common Stock in all demand and
                                    piggyback registrations (including the fees
                                    and expenses of one counsel for such
                                    holders, but excluding underwriting
                                    discounts and selling commissions).

                                    The Issuer will not grant other registration
                                    rights inconsistent with the rights of the
                                    holders of Common Stock, Warrants and
                                    Warrant Stock.

                                    If any other holder or group of holders of
                                    the Issuer's equity exercises a demand
                                    registration right and the holders of
                                    Warrants, Warrant Stock and/or Common Stock,
                                    promptly after receiving notice of such
                                    exercise, exercise one of their demand
                                    registration rights, then all such holders
                                    shall be entitled to include shares in such
                                    registration on a pro rata basis with
                                    priority over any holder entitled to
                                    piggyback registration rights with respect
                                    to such demand registration. Any existing
                                    registration rights granted by the Issuer
                                    shall be amended to give effect to the
                                    foregoing arrangement.

                                    The Issuer, its principal shareholders
                                    (including the holders of the Warrant Stock
                                    and the Common Stock) and the holders of
                                    Warrants will agree to customary holdback
                                    restrictions with respect to any offering
                                    which includes any Common Stock.

DOCUMENTATION:                      The terms with respect to the purchase of
                                    the Common Stock will be set forth in
                                    definitive documentation reasonably
                                    acceptable to all parties and containing
                                    other terms and provisions customary for a
                                    transaction of this type, including a
                                    shareholders agreement among the holders of
                                    the Common Stock and the Warrants, the
                                    Issuer and the principal shareholders.

TRANSFERABILITY:                    The Common Stock shall be freely
                                    transferable in whole or in part, subject
                                    only to compliance with applicable
                                    securities laws; provided, however that no
                                    Common Stock shall be transferred to a
                                    competitor of the Issuer.


                                       10


<PAGE>   1
                                                                    EXHIBIT 99.3


                     [CARRIZO OIL AND GAS, INC. LETTERHEAD]

                                                                            NEWS
- --------------------------------------------------------------------------------
PRESS RELEASE                 Contact: CARRIZO OIL AND GAS, INC.
                                       FRANK A. WOJTEK, CHIEF FINANCIAL OFFICER
                                       (281) 496-1352

CARRIZO OIL AND GAS, INC. ANNOUNCES SIGNIFICANT FINANCING, REPURCHASE OF
PREFERRED STOCK AND EXTENSION OF MATURITY OF BANK DEBT

HOUSTON, DECEMBER 2, 1999--CARRIZO OIL AND GAS, INC. (NASDAQ:CRZO) today
announced (1) the signing of a commitment letter whereby an investor group led
by Chase Capital Partners has committed to purchase $30 million of the Company's
securities, (2) an agreement with affiliates of Enron Corp. to repurchase all of
the outstanding shares of the Company's 9% Series A Preferred Stock (the "Enron
Repurchase") and (3) an agreement to extend the maturities due under the
Company's bank facility.

Under the terms of the commitment letter, the Investors will purchase $22
million aggregate principal amount of Senior Subordinated Notes due 2007 (the
"Notes") with detachable warrants to purchase Carrizo Common Stock, and will
purchase $8 million of Carrizo's Common Stock, (the "Financing"). The Notes will
bear interest at 9% per annum. At the Company's option, up to 60% of the
interest payments can be satisfied through payment-in-kind in additional Notes
for up to five years. The Notes will be unsecured obligations ranking junior to
the Company's bank debt and certain other future senior debt. The Notes will
have an eight-year maturity, are redeemable in advance at a premium at Carrizo's
option and are required to be redeemed earlier upon certain specified events.

Pursuant to the Financing, the Company has agreed to sell 3,636,364 shares of
Common Stock to the Investors at a price of $2.20 per share and will issue new
warrants with an eight-year term which will entitle the holders to purchase up
to an additional 2,760,189 shares of Carrizo's Common Stock at a price of $2.20
per share, subject to adjustments, exercisable any time after issuance. The
Investors will be entitled to registration rights relating to the Common Stock
and the Common Stock underlying the new warrants.

"We welcome Chase Capital Partners to our team", commented Steven A. Webster,
Carrizo's Chairman of the Board. "This Financing is being made possible because
of the success of Carrizo's drilling program this past year and what we believe
is one of the largest and most attractive prospect inventories in the Gulf Coast
area for a company of this size. We believe these transactions will be very
accretive to our shareholders in that they reduce the Company's level of senior
obligations and provide significant additional capital for the continuation of
Carrizo's exploration activities."


<PAGE>   2

"Chase Capital Partners is very excited about the opportunity to invest in
Carrizo," said Christopher Behrens, General Partner of Chase Capital Partners.
"Chase Capital Partners has known Carrizo's management team for some time and is
impressed with the business they have built and their successes to date. With
this financing, Carrizo will be well positioned to capitalize on the
significant investments that it has made in 3-D seismic and lease acquisition
over the last few years. Carrizo fits well with our strategy of focusing on the
energy sector, an industry that we know well through numerous investments over
the years."

The Financing contemplates a shareholders' agreement among the Investors and the
Company's five current directors that will allow Chase Capital Partners, among
other things, to elect up to two directors to Carrizo's current Board of
Directors. Three of the Company's directors, Paul B. Loyd Jr., Steven A.
Webster, and Douglas A. P. Hamilton, will invest an aggregate of at least $3
million in the Financing.

The proceeds of the Financing will be used to fund the Enron Repurchase and
repay a total of approximately $5 million of the Company's senior debt, with the
remaining proceeds of approximately $12 million being available to fund the
Company's exploration and development program, working capital and general
corporate purposes.

Pursuant to the terms of the Enron Repurchase, the Company will repurchase from
the affiliates of Enron Corp., for $12 million, all the outstanding shares of
Carrizo's 9% Series A Preferred Stock and 750,000 currently outstanding warrants
to purchase Carrizo's Common Stock. The Enron affiliates will retain 250,000 of
the currently outstanding warrants, the exercise price of which will be reduced
from $11.50 per share to $4 per share.

The Company has also reached an agreement with Compass Bank, subject to closing
the Financing, whereby the $9 million of maturities due in the year 2000 under
the existing Term Loan facility would be extended. The revised maturities under
the Term Loan provide for a $2 million principal payment at closing, $1.74
million of principal payments during the second half of the year 2000, $2.64
million of principal payments during the first half of the year 2001 and the
remaining balance due in July 2001. In addition, the maturity date for the
remaining bank loan borrowing base facility will be extended from June 2000
until January 2002, subject to interim borrowing base reviews.

The funding of the Financing is subject to certain conditions, including the
Enron Repurchase, the extension of the bank debt and the execution of definitive
agreements. The closings of the Enron Repurchase, the Financing, and the debt
extension are expected to occur simultaneously on or before December 15, 1999.

"We are very excited about the added financial capability this transaction gives
Carrizo", commented S.P. Johnson IV, President and Chief Executive Officer. "In
turn, this will allow us to prudently exploit the significant drilling potential
we have developed through our aggressive program of 3-D seismic and lease
acquisition in recent years. We have now reached the point where most of our
near term capital spending will be devoted directly to drilling, which we
believe will have an immediate impact on the growth of production and reserves.
We expect to

<PAGE>   3

continue to build on the momentum developed through the success of the 1999
drilling program."

"This is a significant financial event for Carrizo", commented Frank A. Wojtek,
Chief Financial Officer. "Not only will the Financing provide approximately $12
million in cash for exploration activities and working capital, the simultaneous
debt repayment and deferral will eliminate or defer over $12 million of current
liabilities that were previously to come due in the next 12 months, thus
providing over $24 million in increased working capital. Further, while the
Financing will add $22 million of subordinated debt, the simultaneous Enron
Repurchase will eliminate approximately $34 million of Redeemable Preferred
Stock. The Enron Repurchase combined with the stock sale will result in over $29
million of increased common shareholders' equity."

Carrizo Oil and Gas, Inc., is a Houston based energy company engaged in the
exploration, development, exploitation and production of oil and natural gas in
proved onshore trends along the Texas and Louisiana Gulf Coast regions. Carrizo
controls significant prospective acreage blocks and utilizes advanced 3-D
seismic techniques to identify potential oil and gas reserves and drilling
opportunities.

Chase Capital Partners (www.chasecapital.com) is a global private equity
organization with over $12 billion under management, including $450 million
committed in 25 investments in the energy and power sector. In energy, Chase
Capital Partners invests in exploration and production, midstream and downstream
businesses, and in the power sector, Chase Capital Partners invests in
traditional generation and distribution, as well as in companies that are
focused in the rapidly deregulating electricity industry. Chase Capital
Partners' primary limited partner is the Chase Manhattan Corporation, one of the
largest bank holding companies in the United States. Since its inception in
1984, Chase Capital Partners has closed more than 900 individual transactions in
North America, Europe, Asia and Latin America.

Statements in this news release, including but not limited to those relating to
the effects, results and timing of closing of the Financing, Enron Repurchase
and Compass Bank agreement, future capital spending, future momentum, use and
amount of proceeds, continued drilling and exploration success, growth of
production or reserves, the effects and potential of any prospects or wells, and
other statements that are not historical facts are forward looking statements
that are based on current expectations. Although the Company believes that its
expectations are based on reasonable assumptions, it can give no assurance that
these expectations will prove correct. Important factors that could cause actual
results to differ materially from those in the forward looking statements
include possible failure of the Company to close the Enron Repurchase, or the
Financing, and the agreement with Compass Bank, the results of and dependence on
exploratory drilling activities, operating risks, regulatory and environmental
matters, capital requirements and availability, dependence on key personnel, oil
and gas price levels, availability of drilling rigs, weather, land issues,
matters outside the Company's control and other risks described in the Company's
filings with the Securities and Exchange Commission. There can be no assurance
as to the completion of any transaction described herein.


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