PROPERTIES AND EQUIPMENT

The following table presents the components of properties and equipment, net of accumulated DD&A:



	As of December 31,
	2013			2012
	(in thousands)
Properties and equipment, net:
Crude oil and natural gas properties
Proved	$	1,781,681		$	2,075,924
Unproved	307,203			319,327
Total crude oil and natural gas properties	2,088,884			2,395,251
Pipelines and related facilities	21,781			47,786
Equipment and other	29,246			34,858
Land and buildings	13,617			14,935
Construction in progress	53,810			67,217
Gross properties and equipment	2,207,338			2,560,047
Accumulated DD&A	(553,893		)	(943,341		)
Properties and equipment, net	$	1,653,445		$	1,616,706

The following table presents impairment charges recorded for crude oil and natural gas properties:



	Year Ended December 31,
	2013		2012		2011
	(in thousands)
Continuing operations:
Impairment of proved properties	$	48,750	$	—	$	—
Impairment of individually significant unproved properties	1,082		1,629		1,108
Amortization of individually insignificant unproved properties	3,603		4,266		1,193
Total continuing operations	53,435		5,895		2,301
Discontinued operations:
Impairment of proved properties	—		161,185		22,460
Impairment of individually significant unproved properties	—		313		—
Amortization of individually insignificant unproved properties	3		756		398
Total discontinued operations	3		162,254		22,858
Total impairment of crude oil and natural gas properties	$	53,438	$	168,149	$	25,159

In the first quarter of 2013, we recognized an impairment charge of approximately $45.0 million related to all of our shallow Upper Devonian (non-Marcellus Shale) Appalachian Basin producing properties located in West Virginia and Pennsylvania owned directly by us, as well as through our proportionate share of PDCM. The impairment charge represented the excess of the carrying value of the assets over the estimated fair value, less cost to sell. The fair value of the assets was determined based upon estimated future cash flows from unrelated third-party bids, a Level 3 input. Pursuant to a purchase and sale agreement entered into in October 2013, we determined that the carrying value of the above-mentioned properties exceeded the transaction sales price, a Level 3 input, less costs to sell. As a result, we recognized an additional impairment charge of approximately $3.8 million in the third quarter of 2013 to reduce the carrying value of the net assets to reflect the current net sales price. The impairment charge was included in the consolidated statement of operations line item impairment of crude oil and natural gas properties. See Note 14, Assets Held for Sale, Divestitures and Discontinued Operations, for additional information regarding these properties.

In 2012, we recognized an impairment charge of $161.2 million to write-down our Piceance Basin proved oil and natural gas properties to fair value. The fair value was based on estimated future cash flows from an unrelated third-party bid, a Level 3 input. The impairment charge was included in the consolidated statement of operations line item impairment of crude oil and natural gas properties.

In 2011, we recognized an impairment charge of $22.5 million to write-down our NECO assets to fair value. The fair value was based on unrelated third-party bids, a Level 3 input. The impairment charge was included in the consolidated statement of operations line item impairment of crude oil and natural gas properties.

Suspended Well Costs

The following table presents the capitalized exploratory well costs pending determination of proved reserves, and included in properties and equipment on the consolidated balance sheets:



	2013			2012			2011
	(in thousands, except for number of wells)

Balance beginning of year, January 1,	$	19,567		$	4,432		$	2,297
Additions to capitalized exploratory well costs pending the determination of proved reserves	13,424			30,482			3,692
Reclassifications to wells, facilities and equipment based on the determination of proved reserves	(32,991		)	—			(1,557		)
Capitalized exploratory well costs charged to expense	—			(15,347		)	—
Balance end of year, December 31,	$	—		$	19,567		$	4,432

Number of wells pending determination at December 31,	—			2			6

As of December 31, 2013, none of our wells pending determination were classified as exploratory wells.

Additions to capitalized exploratory well costs pending determination of proved reserves increased in 2012 as compared to 2011 as we increased our exploratory drilling activities in the Utica Shale play. In 2012, capitalized well costs related to two vertical stratigraphic test wells in southeastern Ohio were expensed at a cost of $12.2 million. Additionally, three Rose Run test wells in Ohio and a well in southeast Colorado were determined to have noncommercial quantities of hydrocarbons and were expensed at a cost of $1.2 million and $0.9 million, respectively.

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



	As of December 31,
	2012		2011
	(in thousands)

Exploratory well costs capitalized for a period of one year or less	$	19,567	$	3,587
Exploratory well costs capitalized for a period greater than one year since commencement of drilling	—		845
Balance end of year, December 31,	$	19,567	$	4,432
Number of projects with exploratory well costs that have been capitalized for a period greater than one year since commencement of drilling	—		2