Asset Retirement Obligations

3 Months Ended

Mar. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

Note 7. 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:

	Three Months Ended March 31,
(millions)	2020			2019
Asset Retirement Obligations, Beginning Balance	$	814		$	880
Liabilities Incurred	3			2
Liabilities Settled	(27		)	(27		)
Revisions of Estimates	(8		)	—
Accretion Expense	11			12
Asset Retirement Obligations, Ending Balance	$	793		$	867

Three Months Ended March 31, 2020 Liabilities settled primarily relate to abandonment of US onshore properties, with $21 million 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. The revision of estimates is due to changes in the timing of spend in the DJ Basin.

Three Months Ended March 31, 2019 Liabilities settled of $27 million relate to abandonment of US onshore properties, primarily 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.