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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2013
Asset Retirement Obligations  
Asset Retirement Obligations

(7) Asset Retirement Obligations

        The following is a reconciliation of the Company's asset retirement obligations for the years ended December 31, 2012 and 2013 (in thousands).

 
   2012   2013  

Asset retirement obligations—beginning of year

   $ 6,715   $ 10,552  

Obligations incurred for wells drilled or on properties acquired

     9,440     242  

Obligations related to assets sold

     (6,107 )   —  

Accretion expense

     504     1,065  
           
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Asset retirement obligations—end of year

   $ 10,552   $ 11,859  
           
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