Capitalized Exploratory Well Costs (Tables)

12 Months Ended

Dec. 31, 2012

Capitalized Exploratory Well Costs [Abstract]

Changes in Capitalized Exploratory Well Costs

We capitalize exploratory well costs until a determination is made that the well has found proved reserves or is deemed noncommercial. If a well is deemed to be noncommercial, the well costs are immediately charged to exploration expense as dry hole cost.

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

	Year Ended December 31,
	2012			2011			2010
(millions)
Capitalized Exploratory Well Costs, Beginning of Period	$	696		$	466		$	463
Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves	360			322			161
Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves	(18		)	(55		)	(155		)
Capitalized Exploratory Well Costs Charged to Expense (1)	(114		)	(37		)	(3		)
Other (2)	(24		)	—			—
Capitalized Exploratory Well Costs, End of Period	$	900		$	696		$	466

⁽¹⁾  Amount primarily represents Deep Blue (deepwater Gulf of Mexico) exploratory well costs capitalized prior to December 31, 2012. Although hydrocarbons were found in both the initial exploration well and subsequent sidetrack, we and our partners decided not to proceed with additional appraisal activities.

⁽²⁾  Amount relates to Selkirk (North Sea) exploratory well costs capitalized prior to December 31, 2012. During the fourth quarter of 2012, our Selkirk field, which is included in discontinued operations, was determined to be uneconomic for joint development and was charged to exploration expense. See Note 3.  Acquisitions and Divestitures

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: 

	December 31,
	2012		2011		2010
(millions)
Exploratory Well Costs Capitalized for a Period of One Year or Less	$	355	$	318	$	166
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	545		378		300
Balance at End of Period	$	900	$	696	$	466
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling	14		13		13

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 December 31, 2012:

			Suspended Since
	Total		2011		2010		2009 & Prior
(millions)
Country/Project:
Offshore Equatorial Guinea
Carla	$	12	$	12	$	—	$	—
Carmen	22		1		1		20
Diega	82		45		2		35
Felicita	35		2		2		31
Yolanda	18		1		1		16
Offshore Cameroon
YoYo	45		5		2		38
Offshore Israel
Leviathan	108		67		41		—
Leviathan-1 Deep	28		28		—		—
Tanin 1	31		31		—		—
Dolphin 1	22		22		—		—
Dalit	22		—		1		21
Offshore Cyprus
Cyprus A-1	57		57		—		—
Deepwater Gulf of Mexico
Gunflint	54		—		—		54
Other
Projects of $10 million or less each	9		—		5		4
Total	$	545	$	271	$	55	$	219