<ARTICLE>                     5
                    
<MULTIPLIER>                                   1,000
       
                             
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                              Dec-31-1997
<PERIOD-END>                                   Jun-30-1997
<CASH>                                         3,587
<SECURITIES>                                   0
<RECEIVABLES>                                  151,726
<ALLOWANCES>                                   3,483
<INVENTORY>                                    6,908
<CURRENT-ASSETS>                               161,228
<PP&E>                                         2,006,060
<DEPRECIATION>                                 1,107,764
<TOTAL-ASSETS>                                 1,152,528
<CURRENT-LIABILITIES>                          257,332
<BONDS>                                        198,719
<PREFERRED-MANDATORY>                          0
<PREFERRED>                                    0
<COMMON>                                       72,540
<OTHER-SE>                                     459,653
<TOTAL-LIABILITY-AND-EQUITY>                   1,152,528
<SALES>                                        0
<TOTAL-REVENUES>                               420,349
<CGS>                                          0
<TOTAL-COSTS>                                  234,156
<OTHER-EXPENSES>                               0
<LOSS-PROVISION>                               0
<INTEREST-EXPENSE>                             10,804
<INCOME-PRETAX>                                102,542
<INCOME-TAX>                                   38,324
<INCOME-CONTINUING>                            64,218
<DISCONTINUED>                                 0
<EXTRAORDINARY>                                0
<CHANGES>                                      0
<NET-INCOME>                                   64,218
<EPS-PRIMARY>                                  0.00
<EPS-DILUTED>                                  0.00