Asset Retirement Obligations

12 Months Ended

Dec. 31, 2019

Asset Retirement Obligation [Abstract]

The Company's asset retirement obligations primarily relate to the future plugging and abandonment of wells and related facilities. Market risk premiums associated with asset retirement obligations are estimated to represent a component of the Company's credit-adjusted risk-free rate that is utilized in the calculations of asset retirement obligations.

Asset retirement obligations activity is as follows:


	Year Ended December 31,
	2019		2018
	(in millions)
Beginning asset retirement obligations	$	183	$	271

New wells placed on production	5		1
Changes in estimates (a)	82		16
Dispositions	(37)		(89)
Liabilities settled	(52)		(30)
Accretion of discount	10		14


Ending asset retirement obligations	191		183
Less current portion of asset retirement obligations	73		25
Asset retirement obligations, long term	$	118	$	158

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(a)Changes in estimates are determined based on several factors, including abandonment cost estimates based on recent actual costs incurred to abandon wells, credit-adjusted risk-free discount rates and well life estimates. The 2019 change in estimate is primarily due to accelerating the forecasted timing of abandoning certain of the Company's vertical oil and

gas wells, which had the effect of increasing the present value and current portion of the abandonment obligation attributable to those wells.