Property Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2011

Property, Plant and Equipment [Abstract]

Components of property, plant and equipment

	2011		2010
	(Millions of dollars)
Exploration and Production
Unproved properties	$	4,064	$	3,796
Proved properties		3,975		3,496
Wells, equipment and related facilities		29,239		26,064
		37,278		33,356
Marketing, Refining and Corporate		2,432		2,347
Total — at cost		39,710		35,703
Less: reserves for depreciation, depletion, amortization and lease impairment		14,998		14,576
Property, plant and equipment — net	$	24,712	$	21,127

Net changes in capitalized exploratory well costs

	2011			2010			2009
	(Millions of dollars)
Beginning balance at January 1	$	1,783		$	1,437		$	1,094
Additions to capitalized exploratory well costs pending the determination of proved reserves		512			675			433
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves		(171	)		(87	)		(16	)
Capitalized exploratory well costs charged to expense		(90	)		(110	)		(74	)
Dispositions		(12	)		(132	)		—
Ending balance at December 31	$	2,022		$	1,783		$	1,437
Number of wells at end of year		59			77			53

Exploratory drilling costs capitalized

2010	$	423
2009		448
2008		392
2007		72
2006		168
	$	1,503