Asset Retirement Obligations

12 Months Ended

Dec. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

(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 lives. 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, 2018 and 2017 (in thousands):

	2018			2017
Beginning of period	$	276,855		$	257,943
Liabilities incurred		3,376			7,724
Acquisitions		13,438			—
Liabilities settled		(5,052	)		(7,965	)
Disposition of wells		(13,332	)		(8,078	)
Accretion expense		25,456			14,711
Change in estimate		12,013			12,520
End of period		312,754			276,855
Less current portion		(5,485	)		(6,327	)
Long-term asset retirement obligations	$	307,269		$	270,528

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