Asset Retirement Obligations

12 Months Ended

Dec. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

8. Asset Retirement Obligations

The following table describes changes to our asset retirement obligations:


	2020		2019

	(In millions)
Balance at January 1	$	1,024	$	857
Liabilities incurred	36		72
Liabilities settled or disposed of	(161)		(75)
Accretion expense	46		40
Revisions of estimated liabilities	52		129
Foreign currency remeasurement	2		1
Balance at December 31	$	999	$	1,024

Total Asset Retirement Obligations at December 31:
Current portion of asset retirement obligations	$	105	$	127
Long-term asset retirement obligations	894		897
Total at December 31	$	999	$	1,024

The liabilities incurred in 2020 and 2019 primarily relate to operations in Guyana, the U.S. and Malaysia. The liabilities settled or disposed of in 2020 primarily reflect an asset sale in the Gulf of Mexico and abandonment activity completed in the Gulf of Mexico, the Bakken and the U.K. North Sea, while 2019 primarily relates to abandonment activity in the Gulf of Mexico and the Bakken. Revisions of estimated liabilities in 2020 and 2019 reflect an acceleration of planned abandonment activity in the Gulf of Mexico and changes in service and equipment rates.

Sinking fund deposits that are legally restricted for purposes of settling asset retirement obligations, which are reported in non-current Other assets in the Consolidated Balance Sheet, were $207 million at December 31, 2020 (2019: $178 million).