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Asset Retirement Obligation
12 Months Ended
Dec. 31, 2012
Asset Retirement Obligation  
Asset Retirement Obligation

9. Asset Retirement Obligation

        Activity related to the Company's asset retirement obligation during the year ended December 31, 2012 is as follows:

(In thousands)
   
 

Balance at December 31, 2011

  $ 60,142  

Liabilities incurred

    2,685  

Liabilities settled

    (1,259 )

Liabilities divested

    (4,463 )

Accretion expense

    3,165  

Change in Estimate

    6,746  
       

Balance at December 31, 2012

  $ 67,016  
       

        The change in estimate during 2012 is attributable to increased costs for materials and services to plug and abandon wells in certain areas of our operations.