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9. Asset Retirement Obligation (Tables)
 12 Months Ended
Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]  
Asset retirement obligation
   Years ended December 31, 
   2015   2014 
Beginning asset retirement obligation  $286,804   $160,665 
Liabilities incurred for new wells placed in production   48,711    103,778 
Accretion of discount on asset retirement obligations   32,574    22,361 
Ending asset retirement obligation  $368,089   $286,804