Asset Retirement Obligations

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

(9)	Asset Retirement Obligations

Our asset retirement obligations primarily represent the present value of the estimated 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. The following is a reconciliation of our liability for plugging and abandonment costs as of December 31, 2017 and 2016 (in thousands):


	2017			2016
Beginning of period	$	257,943		$	264,137
Liabilities incurred		7,724			2,694
Acquisitions		—			21,900
Liabilities settled		(7,965	)		(11,511	)
Disposition of wells		(8,078	)		(10,540	)
Accretion expense		14,711			18,021
Change in estimate		12,520			(26,758	)
End of period		276,855			257,943
Less current portion		(6,327	)		(7,271	)
Long-term asset retirement obligations	$	270,528		$	250,672

Accretion expense is recognized as an increase to depreciation, depletion and amortization expense in the accompanying consolidated statements of operations.