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:



	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

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

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

Carla/Diega Carla is a 2011 crude oil discovery on Block O, Diega (formerly Carmen) is a 2008 condensate and crude oil discovery on Blocks O and I. We are continuing our appraisal program for our Carla discovery. During first quarter of 2013, we spud the Carla I-7 well and continue to review the drilling results of the Carla O-7 well. Further appraisal drilling of Diega is planned for the second half of 2013. We are currently evaluating regional development scenarios for these two discoveries, which includes possible sanctioning of Carla during 2013.

Felicita/Yolanda Felicita is a 2008 condensate and natural gas discovery on Block O. Yolanda is a 2008 condensate and natural gas discovery on Block I. We are currently evaluating regional natural gas development options for these discoveries.

YoYo YoYo is a 2007 natural gas and condensate discovery. During 2011 we acquired and processed additional 3D seismic information and are continuing evaluations for future drilling potential. We are also working with the government of Cameroon to assess gas commercialization options.

Leviathan Leviathan is a 2010 natural gas discovery. During 2012, we continued to evaluate the discovery with the successful drilling of both the Leviathan-3 and Leviathan-4 appraisal wells. We have project and commercial teams in place and are in the process of screening multiple development concepts. In 2012, we announced that the partners in the Leviathan Project had agreed in principle on a proposal to sell a 30% working interest in the Leviathan licenses to Woodside Energy Ltd. (Woodside).

Leviathan-1 Deep In January 2012, we returned to the Leviathan-1 well and began drilling toward two deeper intervals in order to evaluate them for the existence of crude oil (Leviathan-1 Deep). We are continuing our evaluation of Leviathan-1 Deep and will integrate the data from the Leviathan-1 Deep well into our model to update our analysis and design a drilling plan specifically to test the deep oil concept. We have secured a drillship with the capabilities necessary to reach the target objective. The drillship is scheduled to arrive in the Eastern Mediterranean at the end of 2013, and we plan to begin drilling an exploratory well shortly after its arrival.

Tanin 1 Tanin 1 is a 2011 natural gas discovery located in the Alon A block, offshore Israel. We and our partners are currently reviewing alternatives for the development of reserves from this asset.

Dolphin 1 Dolphin 1 is a 2011 natural gas discovery located in the Hanna license, southwest of the Tamar gas field. We and our partners are currently reviewing alternatives for the development of reserves from this asset.

Dalit Dalit is a 2009 natural gas discovery. We and our partners are working on a development plan which would include tie-in to the Tamar platform and have submitted a development plan to the Israeli government.

Cyprus During the fourth quarter of 2011, we drilled a successful natural gas exploration well (A-1) in Block 12. We submitted an appraisal plan to the Cyprus government and are reviewing locations for appraisal drilling activities. We plan to drill the A-2 appraisal well during the second half of 2013.

Gunflint Gunflint (Mississippi Canyon Block 948) is a 2008 crude oil discovery. In July 2012, we drilled a successful Gunflint appraisal well. We have commenced drilling the second Gunflint appraisal well and continue to proceed towards sanctioning a scalable development project in the second half of 2013. First production from Gunflint is targeted for 2015 if we utilize a subsea tieback to an existing host facility or 2017 if a standalone facility is required.