Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property Plant And Equipment [Abstract]

Components of Property, Plant and Equipment

Property, plant and equipment at December 31 were as follows:

	2017		2016
	(In millions)
Exploration and Production
Unproved properties	$	520	$	710
Proved properties		3,162		4,249
Wells, equipment and related facilities		25,550		38,250
		29,232		43,209
Midstream		3,219		3,598
Corporate and Other		53		100
Total — at cost		32,504		46,907
Less: Reserves for depreciation, depletion, amortization and lease impairment		16,312		23,312
Property, Plant and Equipment — Net	$	16,192	$	23,595

Net Changes in Capitalized Exploratory Well Costs

Capitalized Exploratory Well Costs:  The following table discloses the amount of capitalized exploratory well costs pending determination of proved reserves at December 31, and the changes therein during the respective years:

	2017			2016			2015
	(In millions)
Balance at January 1	$	597		$	1,415		$	1,416
Additions to capitalized exploratory well costs pending the determination of proved reserves		116			79			424
Reclassifications to wells, facilities and equipment based on the determination of proved reserves		(165	)		—			(72	)
Capitalized exploratory well costs charged to expense		(268	)		(897	)		(356	)
Dispositions and other		24			—			3
Balance at December 31	$	304		$	597		$	1,415
Number of Wells at December 31		12			17			35

Exploratory Drilling Costs Capitalized in Excess of One Year After Completion of Drilling

Exploratory well costs capitalized for greater than one year following completion of drilling were $170 million at December 31, 2017, separated by year of completion as follows (in millions):

2016	$	—
2015		166
2014		—
2013		4
	$	170