Asset Retirement Obligations

12 Months Ended

Dec. 31, 2015

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

Note 9. 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 asset retirement obligations were as follows:

	Year Ended December 31,
(millions)	2015			2014
Asset Retirement Obligations, Beginning Balance	$	751		$	586
Liabilities Incurred	67			75
Liabilities Settled	(38		)	(101		)
Revision of Estimate	166			155
Accretion Expense	43			36
Asset Retirement Obligations, Ending Balance	$	989		$	751

For the year ended December 31, 2015

Liabilities incurred were due to new wells and facilities and included $22 million primarily for onshore US, $16 million for deepwater Gulf of Mexico and $29 million for Rosetta Merger related assets.

We settled liabilities of $23 million for the DJ Basin, $2 million for deepwater Gulf of Mexico and $13 million for the North Sea.

Revisions were primarily due to changes in estimated costs for future abandonment activities and acceleration of timing of abandonment and included $96 million for the DJ Basin, $48 million for Eastern Mediterranean, $35 million for deepwater Gulf of Mexico, and decreases of $10 million for Equatorial Guinea and $3 million for other non-core, onshore US developments.

For the year ended December 31, 2014

Liabilities incurred were due to new wells and facilities and included $20 million for onshore US, $25 million for deepwater Gulf of Mexico, $2 million for Cameroon, and $10 million for Eastern Mediterranean. Additional liabilities of $18 million were incurred for wells in Equatorial Guinea.

We settled liabilities of $33 million for the DJ Basin, $62 million for deepwater Gulf of Mexico, and $28 million for other non-core, onshore US developments and $1 million for China. At December 31, 2013, our non-operated North Sea fields were classified as held for sale, which included the related ARO for these fields. During 2014, the unsold North Sea properties were reclassified as held and used, resulting in an offset of $23 million to the balance of liabilities settled.

Revisions were primarily due to changes in estimated costs for future abandonment activities and acceleration of timing of abandonment and included $33 million for DJ Basin, $29 million for deepwater Gulf of Mexico, $16 million for Equatorial Guinea, $8 million for Eastern Mediterranean, and $69 million related to a non-operated North Sea field.

Accretion expense is included in DD&Aexpense in the consolidated statements ofoperations.