<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED FINANCIAL STATEMENTS AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE
TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 2,290
<SECURITIES> 0
<RECEIVABLES> 39,304
<ALLOWANCES> 0
<INVENTORY> 0
<CURRENT-ASSETS> 42,965
<PP&E> 1,119,002
<DEPRECIATION> (561,066)
<TOTAL-ASSETS> 632,312
<CURRENT-LIABILITIES> 55,680
<BONDS> 0
0
0
<COMMON> 500
<OTHER-SE> 329,663
<TOTAL-LIABILITY-AND-EQUITY> 632,312
<SALES> 98,121
<TOTAL-REVENUES> 98,301
<CGS> 0
<TOTAL-COSTS> 50,250
<OTHER-EXPENSES> 1,446
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 661
<INCOME-PRETAX> 47,226
<INCOME-TAX> (16,530)
<INCOME-CONTINUING> 30,696
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 30,696
<EPS-BASIC> 0.86
<EPS-DILUTED> 0.86
</TABLE>