<ARTICLE> 5 <MULTIPLIER> 1,000 <CURRENCY> U.S. DOLLARS <PERIOD-TYPE> 6-MOS <FISCAL-YEAR-END> DEC-31-1997 <PERIOD-START> JAN-01-1997 <PERIOD-END> JUN-30-1997 <EXCHANGE-RATE> 1 <CASH> 23,584 <SECURITIES> 0 <RECEIVABLES> 20,018 <ALLOWANCES> 0 <INVENTORY> 0 <CURRENT-ASSETS> 47,316 <PP&E> 238,299 <DEPRECIATION> 116,645 <TOTAL-ASSETS> 190,519 <CURRENT-LIABILITIES> 24,563 <BONDS> 0 <PREFERRED-MANDATORY> 0 <PREFERRED> 0 <COMMON> 110 <OTHER-SE> 142,829 <TOTAL-LIABILITY-AND-EQUITY> 190,519 <SALES> 36,332 <TOTAL-REVENUES> 50,698 <CGS> 7,101 <TOTAL-COSTS> 7,101 <OTHER-EXPENSES> 36 <LOSS-PROVISION> 0 <INTEREST-EXPENSE> 725 <INCOME-PRETAX> 26,678 <INCOME-TAX> 9,490 <INCOME-CONTINUING> 17,188 <DISCONTINUED> 296 <EXTRAORDINARY> 0 <CHANGES> 0 <NET-INCOME> 17,484 <EPS-PRIMARY> 1.69 <EPS-DILUTED> 1.69