5. Impairments

Impairments of proved properties are included in impairment expense in the Company’s Consolidated Statements of Income. The following summarizes impairments of proved properties and the related post-impairment fair values by segment at December 31:



	2015				2014				2013
millions	Impairment		Fair Value⁽¹⁾		Impairment		Fair Value⁽¹⁾		Impairment		Fair Value⁽¹⁾
Oil and gas exploration and production
Long-lived assets held for use
U.S. onshore properties	$	3,684	$	1,253	$	545	$	552	$	142	$	271
Gulf of Mexico properties	349		65		276		223		562		242
Cost-method investment ⁽²⁾	3		32		3		32		11		32
Midstream
Long-lived assets held for use	1,039		212		12		—		79		36
Total impairments	$	5,075	$	1,562	$	836	$	807	$	794	$	581

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⁽¹⁾	Measured as of the impairment date using the income approach and Level 3 inputs.


⁽²⁾	Represents the after-tax net investment.

2015 Impairments In 2015, impairments were primarily related to the Company’s Greater Natural Buttes oil and gas and midstream properties in the Rockies, other U.S. onshore oil and gas properties primarily in the Southern and Appalachia Region, other midstream properties primarily in the Rockies, and oil and gas properties in the Gulf of Mexico, all of which were impaired due to lower forecasted commodity prices.

2014 Impairments In 2014, certain U.S. onshore and Gulf of Mexico oil and gas properties were impaired primarily due to lower forecasted commodity prices.

2013 Impairments In 2013, certain Gulf of Mexico properties were impaired due to a reduction in estimated future net cash flows and downward revisions of reserves resulting from changes to the Company’s development plans. Also in 2013, certain U.S. onshore properties and related midstream assets were impaired due to downward revisions of reserves resulting from changes to the Company’s development plans. In addition, a midstream property was impaired during 2013 due to a reduction in estimated future cash flows.

Impairments of Unproved Properties Impairments of unproved properties are included in exploration expense in the Company’s Consolidated Statements of Income. In 2015, the Company recognized a $935 million impairment of unproved Greater Natural Buttes properties and a $66 million impairment of an unproved Gulf of Mexico property as a result of lower commodity prices. Also in 2015, the Company recognized a $109 million impairment of unproved Utica properties resulting from an assignment of mineral interests in settlement of a legal matter.

5. Impairments (Continued)

Potential for Future Impairments During 2015, the Company recognized significant impairments of proved oil and gas and midstream properties and impairments of unproved oil and gas properties, primarily as a result of lower forecasted commodity prices and changes to the Company’s drilling plans. At December 31, 2015, the Company’s estimate of undiscounted future cash flows attributable to a certain depletion group with a net book value of approximately $2.2 billion indicated that the carrying amount was expected to be recovered; however, this depletion group may be at risk for impairment if the estimates of future cash flows decline. The Company estimates that, if this depletion group becomes impaired in a future period, the Company could recognize non-cash impairments in that period in excess of $800 million. It is also reasonably possible that prolonged low or further declines in commodity prices, further changes to the Company’s drilling plans in response to lower prices, or increases in drilling or operating costs could result in other additional impairments.