Asset Retirement Obligations

9 Months Ended

Sep. 30, 2019

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

Note 6. Asset Retirement Obligations

Asset retirement obligations (ARO) consist primarily of estimated costs of dismantlement, removal, site reclamation and similar activities associated with our oil and gas properties. Changes in ARO are as follows:

	Nine Months Ended September 30,
(millions)	2019			2018
Asset Retirement Obligations, Beginning Balance	$	880		$	875
Liabilities Incurred	17			16
Liabilities Settled	(82		)	(309		)
Revisions of Estimates	(60		)	67
Accretion Expense	33			25
Asset Retirement Obligations, Ending Balance	$	788		$	674

Nine Months Ended September 30, 2019 Liabilities settled relate primarily to abandonment of US onshore properties, principally in the DJ Basin where we have engaged in a program to plug and abandon older vertical wells. Costs associated with these abandonment activities will be incurred over several years. Revisions of estimates relate primarily to a decrease of $73 million in the DJ Basin as a result of improved cycle times and cost reductions for vertical wells, partially offset by acceleration of timing estimates of $13 million for wells offshore Israel.

Nine Months Ended September 30, 2018 Liabilities settled include $216 million and $24 million of liabilities assumed by the purchasers of the Gulf of Mexico properties and Greeley Crescent assets, respectively, and $69 million related to abandonment of US onshore properties, primarily in the DJ Basin. Revisions of estimates relate primarily to increases in cost and timing of estimates of $84 million for US onshore, primarily in the DJ Basin, partially offset by decreases in cost and timing estimates of $11 million associated with the North Sea abandonment project and $6 million for Eastern Mediterranean.