<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
COMPANY'S SEC FORM 10-Q FOR THE PERIOD ENDING MARCH 31, 1997 AND IS QUALIFIED IN
ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
                             
<PERIOD-TYPE>                   3-MOS
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-END>                               MAR-31-1997
<CASH>                                          24,380
<SECURITIES>                                         0
<RECEIVABLES>                                   91,178
<ALLOWANCES>                                         0
<INVENTORY>                                     34,714
<CURRENT-ASSETS>                               182,808
<PP&E>                                       3,143,998
<DEPRECIATION>                               1,586,326
<TOTAL-ASSETS>                               1,845,931
<CURRENT-LIABILITIES>                          243,440
<BONDS>                                        517,485
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         4,391
<OTHER-SE>                                     585,692
<TOTAL-LIABILITY-AND-EQUITY>                 1,845,931
<SALES>                                        282,021
<TOTAL-REVENUES>                               292,430
<CGS>                                           81,360
<TOTAL-COSTS>                                  145,373
<OTHER-EXPENSES>                                10,420
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                               3,984
<INCOME-PRETAX>                                132,653
<INCOME-TAX>                                    68,883
<INCOME-CONTINUING>                             63,770
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    63,770
<EPS-PRIMARY>                                      .74
<EPS-DILUTED>                                        0