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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
14. Asset Retirement Obligations

The majority of Anadarko’s AROs relate to the plugging of wells and the related abandonment of oil and gas properties. Revisions in estimated liabilities during the period relate primarily to changes in estimates of asset retirement costs and include, but are not limited to, revisions of estimated inflation rates, changes in property lives, and the expected timing of settlement. The following summarizes changes in the Company’s AROs:
millions
2017
 
2016
Carrying amount at January 1
$
2,931

 
$
2,059

Liabilities acquired (1)
4

 
813

Liabilities incurred
191

 
93

Property dispositions
(154
)
 
(88
)
Liabilities settled
(135
)
 
(225
)
Accretion expense
144

 
100

Revisions in estimated liabilities
(187
)
 
179

Carrying amount at December 31
$
2,794

 
$
2,931

__________________________________________________________________
(1) 
In December 2016, the Company closed the GOM Acquisition. See Note 3—Acquisitions, Divestitures, and Assets Held for Sale for additional information.