<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>
<MULTIPLIER> 1,000
       
<S>                             <C>                <C>               <C>               <C>              <C> 
<PERIOD-TYPE>                   9-MOS              6-MOS             3-MOS             YEAR             YEAR
<FISCAL-YEAR-END>             DEC-31-1996       DEC-31-1996       DEC-31-1996       DEC-31-1995     DEC-31-1994
<PERIOD-END>                  SEP-30-1996       JUN-30-1996       MAR-31-1996       DEC-31-1995     DEC-31-1994  
<CASH>                              1,485             1,873             7,064             1,565             269
<SECURITIES>                            0                 0                 0                 0               0
<RECEIVABLES>                      60,201            88,234            92,539            75,476         118,532  
<ALLOWANCES>                            0                 0                 0             1,814             670  
<INVENTORY>                             0                 0                 0                 0               0
<CURRENT-ASSETS>                   76,508           104,589           117,634            91,927         124,060  
<PP&E>                          1,878,188         1,907,317         1,853,119         1,855,408       1,368,695  
<DEPRECIATION>                   (911,230)         (860,796)         (819,975)         (791,459)       (687,172)  
<TOTAL-ASSETS>                  1,070,109         1,177,173         1,179,523         1,180,238         812,171  
<CURRENT-LIABILITIES>             109,201           114,070           109,430           136,827         180,604   
<BONDS>                           220,771           313,935           288,084           254,184         151,095  
<PREFERRED-MANDATORY>             150,000           150,000           150,000           150,000               0   
<PREFERRED>                             0                 0                 0                 0               0  
<COMMON>                          126,714           126,625           126,620           126,575         106,513  
<OTHER-SE>                        373,945           377,390           390,447           399,417         258,315  
<TOTAL-LIABILITY-AND-EQUITY>    1,070,109         1,177,173         1,179,523         1,180,238         812,871  
<SALES>                                 0                 0                 0                 0               0   
<TOTAL-REVENUES>                  248,480           163,941            76,972           237,358         191,866  
<CGS>                                   0                 0                 0                 0               0  
<TOTAL-COSTS>                     268,090           184,353            84,415           286,224         219,576  
<OTHER-EXPENSES>                      (42)              (84)              (57)             (161)            314  
<LOSS-PROVISION>                        0                 0                 0                 0               0  
<INTEREST-EXPENSE>                 21,015            14,098             6,793            18,149          23,124  
<INCOME-PRETAX>                   (40,583)          (34,426)          (14,179)          (65,827)        (50,477)  
<INCOME-TAX>                      (14,309)          (12,094)           (4,986)          (23,242)            256 
<INCOME-CONTINUING>               (26,274)          (22,331)           (9,192)          (42,585)        (50,733)  
<DISCONTINUED>                          0                 0                 0                 0               0  
<EXTRAORDINARY>                         0                 0                 0                 0               0   
<CHANGES>                               0                 0                 0                 0               0   
<NET-INCOME>                      (26,274)          (22,331)           (9,192)          (42,585)        (50,733)  
<EPS-PRIMARY>                        (.21)             (.18)             (.07)             (.38)           (.31)  
<EPS-DILUTED>                        (.21)             (.18)             (.07)             (.38)           (.31)  
        

</TABLE>