<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM APPLICABLE
FINANCIAL STATEMENTS AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED> 
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>                     <C>                     <C>                     
<PERIOD-TYPE>                                9-MOS                   6-MOS                   3-MOS                    YEAR      
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1997             DEC-31-1996  
<PERIOD-END>                               SEP-30-1997             JUN-30-1997             MAR-31-1997             DEC-31-1996  
<CASH>                                           1,551                   3,591                   6,706                   1,358  
<SECURITIES>                                         0                       0                       0                       0  
<RECEIVABLES>                                   65,407                  52,340                  60,466                  95,803  
<ALLOWANCES>                                         0                       0                       0                   1,351  
<INVENTORY>                                          0                       0                       0                       0  
<CURRENT-ASSETS>                                87,701                  62,979                  75,868                 115,427  
<PP&E>                                       1,987,752               2,044,133               2,017,947               2,006,425  
<DEPRECIATION>                              (1,221,234)             (1,008,883)               (970,761)               (941,052) 
<TOTAL-ASSETS>                                 895,728               1,113,688               1,133,980               1,195,454  
<CURRENT-LIABILITIES>                          136,201                  99,117                 110,920                 120,500  
<BONDS>                                        268,694                 322,826                 312,204                 356,735  
<PREFERRED-MANDATORY>                                0                 150,000                 150,000                 150,000  
<PREFERRED>                                          0                       0                       0                       0  
<COMMON>                                         1,269                 126,920                 126,870                 126,736  
<OTHER-SE>                                     292,083                 348,084                 361,459                 363,670  
<TOTAL-LIABILITY-AND-EQUITY>                   895,278               1,113,688               1,133,980               1,195,454  
<SALES>                                              0                       0                       0                       0  
<TOTAL-REVENUES>                               240,294                 162,064                  86,807                 338,146  
<CGS>                                                0                       0                       0                       0  
<TOTAL-COSTS>                                  487,041                 169,586                  82,599                 370,192  
<OTHER-EXPENSES>                                   150                      71                      21                  (2,092)  
<LOSS-PROVISION>                                     0                       0                       0                       0  
<INTEREST-EXPENSE>                              25,502                  16,698                   7,744                  27,149  
<INCOME-PRETAX>                               (271,930)                (24,205)                 (3,505)                (56,837) 
<INCOME-TAX>                                   (74,665)                 (8,475)                 (1,304)                (20,306) 
<INCOME-CONTINUING>                           (197,338)                (15,730)                 (2,201)                (36,801) 
<DISCONTINUED>                                       0                       0                       0                       0  
<EXTRAORDINARY>                                      0                       0                       0                       0  
<CHANGES>                                            0                       0                       0                       0  
<NET-INCOME>                                  (197,338)                (15,730)                 (2,201)                (36,801) 
<EPS-PRIMARY>                                    (1.56)                   (.12)                   (.02)                   (.29) 
<EPS-DILUTED>                                    (1.56)                   (.12)                   (.02)                   (.29) 
        

</TABLE>