Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Components of Property, Plant and Equipment

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

	2018		2017
	(In millions)
Exploration and Production
Unproved properties	$	394	$	520
Proved properties		3,124		3,162
Wells, equipment and related facilities		26,173		25,550
		29,691		29,232
Midstream		3,492		3,219
Corporate and Other		39		53
Total — at cost		33,222		32,504
Less: Reserves for depreciation, depletion, amortization and lease impairment		17,139		16,312
Property, Plant and Equipment — Net	$	16,083	$	16,192

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:

	2018			2017			2016
	(In millions)
Balance at January 1	$	304		$	597		$	1,415
Additions to capitalized exploratory well costs pending the determination of proved reserves		128			116			79
Reclassifications to wells, facilities and equipment based on the determination of proved reserves		—			(165	)		—
Capitalized exploratory well costs charged to expense		(14	)		(268	)		(897	)
Dispositions and other		—			24			—
Balance at December 31	$	418		$	304		$	597
Number of Wells at December 31		24			12			17

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 $267 million at December 31, 2018, separated by year of completion as follows (in millions):

2017	$	97
2016		—
2015		166
2014		—
2013		4
	$	267