<ARTICLE> 5                     
<LEGEND>                        
THIS SCHEDULE  CONTAINS SUMMARY FINANCIAL  INFORMATION  EXTRACTED FROM FORM 10-Q
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>                       
<MULTIPLIER> 1,000
                        
       

<PERIOD-TYPE>                                3-MOS
<FISCAL-YEAR-END>                      DEC-31-1998
<PERIOD-END>                           MAR-31-1998
<CASH>                                       12605
<SECURITIES>                                     0
<RECEIVABLES>                               149822
<ALLOWANCES>                                     0
<INVENTORY>                                  60226
<CURRENT-ASSETS>                            255762
<PP&E>                                     1800805
<DEPRECIATION>                              700858
<TOTAL-ASSETS>                             1629614
<CURRENT-LIABILITIES>                       205341
<BONDS>                                          0
<PREFERRED-MANDATORY>                            0
<PREFERRED>                                      0
<COMMON>                                       397
<OTHER-SE>                                  622867
<TOTAL-LIABILITY-AND-EQUITY>               1629614
<SALES>                                     298964
<TOTAL-REVENUES>                            312564
<CGS>                                       270905
<TOTAL-COSTS>                               290205
<OTHER-EXPENSES>                                 0
<LOSS-PROVISION>                                 0
<INTEREST-EXPENSE>                            3804
<INCOME-PRETAX>                              18621
<INCOME-TAX>                                  2800
<INCOME-CONTINUING>                          15821
<DISCONTINUED>                                   0
<EXTRAORDINARY>                                  0
<CHANGES>                                        0
<NET-INCOME>                                 15821
<EPS-PRIMARY>                                  0.4
<EPS-DILUTED>                                  0.4