Capitalized Exploratory Well Costs (Tables)

3 Months Ended

Mar. 31, 2013

Capitalized Exploratory Well Costs [Abstract]

Changes in Capitalized Exploratory Well Costs

Changes in capitalized exploratory well costs are as follows and exclude amounts that were capitalized and subsequently expensed in the same period: 

	Three Months Ended March 31, 2013
(millions)
Capitalized Exploratory Well Costs, Beginning of Period	$	900
Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves	178
Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves	(8		)
Capitalized Exploratory Well Costs, End of Period	$	1,070

Aging of Capitalized Well Costs

The following table provides an aging of capitalized exploratory well costs based on the date that drilling commenced, and the number of projects that have been capitalized for a period greater than one year: 

	March 31, 2013		December 31, 2012
(millions)
Exploratory Well Costs Capitalized for a Period of One Year or Less	$	453	$	355
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	617		545
Balance at End of Period	$	1,070	$	900
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling	13		14

Aging of Exploratory Well Costs

The following table provides a further aging of those exploratory well costs that have been capitalized for a period greater than one year since the commencement of drilling as of March 31, 2013:

			Suspended Since
	Total		2012		2011		2010 & Prior
(millions)
Country/Project:
Offshore Equatorial Guinea
Carla	$	12	$	—	$	12	$	—
Diega	106		1		46		59
Felicita	36		1		2		33
Yolanda	18		—		1		17
Offshore Cameroon
YoYo	47		2		5		40
Offshore Israel
Leviathan	113		5		67		41
Leviathan-1 Deep	55		27		28		—
Tanin 1	33		2		31		—
Dolphin 1	22		—		22		—
Dalit	22		—		—		22
Offshore Cyprus
Cyprus A-1	64		7		57		—
Deepwater Gulf of Mexico
Gunflint	77		23		—		54
Other
Projects of $10 million or less each	12		3		—		9
Total	$	617	$	71	$	271	$	275