<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM JUNE 30,
1997 FORM 10-Q AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL
STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
                             
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               JUN-30-1997
<CASH>                                           3,008
<SECURITIES>                                         0
<RECEIVABLES>                                   55,867
<ALLOWANCES>                                         0
<INVENTORY>                                          0
<CURRENT-ASSETS>                                14,773
<PP&E>                                       1,161,957
<DEPRECIATION>                                 320,498
<TOTAL-ASSETS>                                 935,851
<CURRENT-LIABILITIES>                           75,360
<BONDS>                                        445,983
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           129
<OTHER-SE>                                     348,389
<TOTAL-LIABILITY-AND-EQUITY>                   935,851
<SALES>                                        199,415
<TOTAL-REVENUES>                               199,077
<CGS>                                           80,986
<TOTAL-COSTS>                                   80,986
<OTHER-EXPENSES>                                54,502
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              17,952
<INCOME-PRETAX>                                 45,637
<INCOME-TAX>                                    10,212
<INCOME-CONTINUING>                             35,222
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    35,222
<EPS-PRIMARY>                                     1.36
<EPS-DILUTED>                                     1.36