<ARTICLE>         5
<RESTATED>
<MULTIPLIER>  1,000
       
                                                                                         
<PERIOD-TYPE>                                12-MOS            3-MOS             6-MOS              9-MOS
<FISCAL-YEAR-END>                                DEC-31-1996       DEC-31-1997       DEC-31-1997        DEC-31-1997
<PERIOD-END>                                     DEC-31-1996       MAR-31-1997       JUN-30-1997        SEP-30-1997
<CASH>                                                13,161            19,873            14,182             25,596
<SECURITIES>                                               0                 0                 0                  0
<RECEIVABLES>                                        234,646           199,166           201,431            220,820
<ALLOWANCES>                                               0                 0                 0                  0
<INVENTORY>                                           13,963            16,047            17,664             30,191
<CURRENT-ASSETS>                                     268,156           248,155           249,250            287,798
<PP&E>                                             5,381,313         5,551,657         5,750,873          5,937,101
<DEPRECIATION>                                     2,281,252         2,366,731         2,458,790          2,554,317
<TOTAL-ASSETS>                                     3,432,430         3,493,616         3,599,782          3,726,414
<CURRENT-LIABILITIES>                                309,657           288,509           268,680            282,851
<BONDS>                                            1,235,706         1,248,686         1,349,099          1,312,595
<COMMON>                                             114,030           114,282           114,369            114,522
<PREFERRED-MANDATORY>                                      0                 0                 0                  0
<PREFERRED>                                                0                 0                 0                  0
<OTHER-SE>                                         1,404,486         1,453,022         1,474,279          1,501,539
<TOTAL-LIABILITY-AND-EQUITY>                       3,432,430         3,493,616         3,599,782          3,726,414
<SALES>                                              976,032           322,489           481,128            714,196
<TOTAL-REVENUES>                                     977,151           321,828           580,669            857,417
<CGS>                                                679,439           208,644           398,774            596,352
<TOTAL-COSTS>                                        679,439           208,644           398,774            596,352
<OTHER-EXPENSES>                                      35,911             9,142            18,083             26,790
<LOSS-PROVISION>                                           0                 0                 0                  0
<INTEREST-EXPENSE>                                    61,606            15,960            32,101             51,048
<INCOME-PRETAX>                                      200,195            88,082           131,711            183,227
<INCOME-TAX>                                          78,768            35,205            53,088             73,819
<INCOME-CONTINUING>                                  121,427            52,877            78,623            109,408
<DISCONTINUED>                                             0                 0                 0                  0
<EXTRAORDINARY>                                            0                 0                 0                  0
<CHANGES>                                                  0                 0                 0                  0
<NET-INCOME>                                         121,427            52,877            78,623            109,408
<EPS-PRIMARY>                                           1.42               .59               .88              1.22
<EPS-DILUTED>                                           1.38               .56               .84              1.17