Quarterly report pursuant to Section 13 or 15(d)

Asset Retirement Obligations (Details)

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Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Asset Retirement Obligations        
Asset retirement obligations - beginning of period     $ 30,612  
Obligations incurred for wells drilled     2,665  
Accretion expense $ 620 $ 408 1,218 $ 808
Asset retirement obligations - end of period $ 34,495   $ 34,495