Asset Retirement Obligation (Tables)

12 Months Ended

Dec. 31, 2014

Asset Retirement Obligation Disclosure [Abstract]

Our asset retirement obligations primarily represent the estimated present value of the amounts we will incur to plug, abandon and remediate our producing properties at the end of their productive lives. Significant inputs used in determining such obligations include estimates of plugging and abandonment costs, estimated future inflation rates and well life. The inputs are calculated based on historical data as well as current estimated costs. A reconciliation of our liability for plugging and abandonment costs for the years ended December 31, 2014 and 2013 are as follows (in thousands):


	2014			2013
Beginning of period	$	230,077		$	146,478
Liabilities incurred		8,602			8,731
Acquisitions		11,927			¾
Liability released		(8,309	)		¾
Liabilities settled		(4,442	)		(424	)
Disposition of wells		(13,951	)		(3,129	)
Accretion expense		15,226			10,778
Change in estimate		48,333			67,643
End of period		287,463			230,077
Less current portion		(15,067	)		(5,037	)
Long-term asset retirement obligations	$	272,396		$	225,040