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)	2014			2013
Asset Retirement Obligations, Beginning Balance	$	586		$	402
Liabilities Incurred	75			90
Liabilities Settled	(101		)	(41		)
Revision of Estimate	155			156
Accretion Expense	36			28
Other	—			(49		)
Asset Retirement Obligations, Ending Balance	$	751		$	586

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 a 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 and included $33 million for DJ Basin, $29 million for the 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&A expense in the consolidated statements of operations.

For the year ended December 31, 2013

Liabilities incurred were due to new wells and facilities and included $15 million for onshore US development, $68 million for deepwater Gulf of Mexico, and $7 million for Eastern Mediterranean.

Liabilities settled of $41 million primarily related to deepwater Gulf of Mexico abandonment activities and non-core, onshore US assets sold.

Revisions were primarily due to changes in estimated costs for future abandonment activities and acceleration of timing and included $86 million for DJ Basin, $36 million for deepwater Gulf of Mexico, $10 million for Equatorial Guinea, and $7 million for Eastern Mediterranean. Increased US costs are due primarily to more stringent abandonment standards impacting procedures and materials.

Other includes $17 million for non-core, onshore US, and $32 million for China ARO liabilities transferred to liabilities associated with assets held for sale.

See Note 2. Additional Financial Statement Information and Note 3. Property Transactions.

Accretion expense is included in DD&A expense in the consolidated statements of operations.