5. Property, Plant and Equipment

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

	2015		2014
	(In millions)
Exploration and Production
Unproved properties	$	958	$	1,468
Proved properties		4,202		4,211
Wells, equipment and related facilities		38,738		38,263
		43,898		43,942
Bakken Midstream		2,757		2,386
Corporate, Interest and Other		171		194
Total — at cost		46,826		46,522
Less: Reserves for depreciation, depletion, amortization and lease impairment		20,474		19,005
Property, plant and equipment — net	$	26,352	$	27,517

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:

	2015			2014			2013
	(In millions)
Balance at January 1	$	1,416		$	2,045		$	2,259
Additions to capitalized exploratory well costs pending the determination of proved reserves		424			292			237
Reclassifications to wells, facilities and equipment based on the determination of proved reserves		(72	)		(629	)		(106	)
Capitalized exploratory well costs charged to expense		(356	)		(235	)		(267	)
Dispositions and other		3			(57	)		(78	)
Ending balance at December 31	$	1,415		$	1,416		$	2,045
Number of wells at end of year		35			37			50

In 2015, exploratory drilling activity primarily related to the Gulf of Mexico and the offshore Stabroek license in Guyana. For the years ended December 31, 2015, 2014 and 2013, reclassifications to wells, facilities and equipment based on the determination of proved reserves primarily related to Equatorial Guinea, the Stampede project in the Gulf of Mexico, (which the co-owners sanctioned for development in 2014) and the Shenzi project in the Gulf of Mexico, respectively. In 2015, capitalized exploratory well costs charged to expense related to the Dinarta Block in the Kurdistan Region of Iraq resulting from our and our partners’ decision to cease further drilling and relinquish the block, gas discoveries offshore Ghana that have not sufficiently progressed appraisal negotiations with the regulator, and three wells with discovered resources offshore Australia that we determined will not be included in the current development concept for the Equus project. In 2014 capitalized well costs charged to expense included a previously capitalized exploration well in Green Canyon Block 469 in the Gulf of Mexico where it was determined no further development activities were planned, and in 2013, two previously capitalized exploration wells in Area 54, offshore Libya, were expensed due to civil unrest in the country. The preceding table excludes exploratory dry hole costs of $54 million (2014: $66 million; 2013: $77 million), which were incurred and subsequently expensed in the same year.

Exploratory well costs capitalized for greater than one year following completion of drilling were $1,053 million at December 31, 2015, separated by year of completion as follows (in millions):

2014	$	79
2013		43
2012		336
2011		207
2010 and prior		388
	$	1,053

Approximately 75% of the capitalized well costs in excess of one year relates to Block WA-390-P, offshore Western Australia, where development planning and commercial activities for our natural gas discoveries are ongoing. In December 2014, we executed a non-binding letter of intent with the North West Shelf (NWS), a third-party joint venture with existing natural gas processing and liquefaction facilities. In 2015, we initiated joint front-end engineering studies with NWS and we also commenced discussions with potential long-term purchasers of liquefied natural gas. In addition, at our adjacent WA-474-P Block which could become part of the Equus project, we plan to drill a commitment well in 2016. Successful execution of binding agreements with NWS is necessary before we can execute a gas sales agreement and sanction development of the project.

Approximately 25% of the capitalized well costs in excess of one year relates to offshore Ghana. Appraisal plans for the seven discoveries on the block were submitted to the Ghanaian government in May 2013 for approval. Five of the plans were approved and discussions continue with the government on the two remaining appraisal plans. In 2014, we completed three appraisal wells and subsurface evaluation, and development planning progressed in 2015. The government of Côte d’Ivoire has challenged the maritime border between it and the country of Ghana, which includes a portion of our Deepwater Tano/Cape Three Points license. We are unable to proceed with development of this license until there is a resolution of this matter, which may also impact our ability to develop the license. The International Tribunal for Law of the Sea is expected to render a final ruling on the maritime border dispute in 2017. Under terms of our license, the deadline to declare commerciality for the Pecan Field, which would be the primary development hub for the block, is in March 2016, and the deadline to submit a plan of development is in September 2016. We have requested an extension of the submission deadline for a plan of development for the Pecan Field, and will continue to work with the government on how best to progress work on the block given the maritime border dispute.