PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consisted of the following:



	As of December 31,
	2013			2012

	(In thousands)
Oil and gas properties
Subject to depletion	$	5,687,557		$	5,770,913
Unevaluated costs	221,605			307,267
Accumulated depletion	(5,268,719		)	(5,297,220		)
Net oil and gas properties	640,443			780,960
Other property and equipment
Pipelines and processing facilities	347,093			375,248
General properties	72,125			75,147
Accumulated depreciation	(198,856		)	(202,297		)
Net other property and equipment	220,362			248,098
Property, plant and equipment, net of accumulated depletion and depreciation	$	860,805		$	1,029,058

Ceiling Test Analysis and Impairment

The charges for impairment are summarized below:



		Pre-tax Charges for Impairment
	Segment	2013		2012		2011

		(in thousands)
U.S.
Oil and gas properties	Exploration and production	$	—	$	2,152,128	$	—
Other property and equipment	Midstream	54		7,328		57,996
Other property and equipment	Exploration and production	1,809		537		—
Canada
Oil and gas properties	Exploration and production	—		465,935		49,063
		$	1,863	$	2,625,928	$	107,059

As described in Note 2, we are required to perform a quarterly ceiling test for impairment of our oil and gas properties in each of our cost centers. We did not recognize impairment in 2013 during our quarterly ceiling tests. We did recognize other property and equipment impairment charges in 2013 for surface land and pipeline in Texas.

In 2012, we recognized impairment expense each quarter as the average of the first of month prices for the preceding 12 months declined each quarter. For our U.S. oil and gas properties, the Henry Hub price declined 33% from the price used at December 31, 2011 and the pricing used for NGLs declined 28% from the price used at December 31, 2011. For our Canadian oil and gas properties, the AECO price declined 36% from the price used at December 31, 2011. In 2012, the impairment on our oil and gas properties in both the U.S. and Canada was impacted by the exclusion of our derivatives from the ceiling test due to the discontinuance of hedge accounting. Other property and equipment impairment charges during 2012 were a result of reduced anticipated utilization of pipelines and facilities in Colorado and Texas and reduced use of a compressed natural gas facility in Texas.

The charge for impairment of our oil and gas properties in Canada in 2011 was recognized as a result of a 12% decrease in AECO natural gas price utilized in our Canadian ceiling test from December 31, 2010 to March 31, 2011.

We also recognized an impairment charge of $58.0 million in 2011 related to certain Barnett Shale midstream assets to reduce their carrying value to estimated fair value as a result of decreased development by us and others in response to decreased natural gas prices during the fourth quarter of 2011.

Unevaluated Natural Gas and Oil Properties Not Subject to Depletion

Under full cost accounting, we may exclude certain unevaluated property costs from the amortization base pending determination of whether proved reserves have been discovered or impairment has occurred. A summary of the unevaluated properties not subject to depletion at December 31, 2013 and 2012 and the year in which they were incurred follows:



	December 31, 2013 Costs Incurred During										December 31, 2012 Costs Incurred During
	2013		2012		2011		Prior		Total		2012		2011		2010		Prior		Total

	(In thousands)										(In thousands)
U.S.
Acquisition costs	$	—	$	3,013	$	13,484	$	—	$	16,497	$	6,844	$	42,339	$	1,447	$	32,429	$	83,059
Exploration costs	14		364		—		—		378		2,676		207		—		—		2,883
Capitalized interest	1,093		1,374		—		—		2,467		4,093		—		—		—		4,093
Total U.S.	$	1,107	$	4,751	$	13,484	$	—	$	19,342	$	13,613	$	42,546	$	1,447	$	32,429	$	90,035
Canada
Acquisition costs	$	—	$	2,956	$	1,300	$	68,586	$	72,842	$	333	$	—	$	643	$	80,488	$	81,464
Exploration costs	$	7,044	$	31,746	$	41,092	$	30,413	$	110,295	$	36,356	$	44,837	$	18,500	$	20,171	$	119,864
Capitalized interest	$	3,947	$	2,724	$	3,522	$	8,933	$	19,126	$	2,796	$	3,614	$	2,830	$	6,664	$	15,904
Total Canada	$	10,991	$	37,426	$	45,914	$	107,932	$	202,263	$	39,485	$	48,451	$	21,973	$	107,323	$	217,232
Total	$	12,098	$	42,177	$	59,398	$	107,932	$	221,605	$	53,098	$	90,997	$	23,420	$	139,752	$	307,267

The following table summarizes the regions where we have unevaluated property costs not subject to depletion.



	As of December 31,
	2013		2012

	(In thousands)
Barnett Shale	$	—	$	40,716
West Texas	19,343		49,318
Horn River Basin	202,262		217,233
Total	$	221,605	$	307,267

Costs are transferred into the amortization base on an ongoing basis, as projects are evaluated and proved reserves established or impairment determined. Pending determination of proved reserves attributable to the above costs, we cannot assess the future impact on the amortization rate. Unevaluated acquisition costs in our Horn River Asset will require up to an estimated nine more years of exploration and development activity before evaluation is complete, which is covered by the remaining primary term of the underlying leases. Unevaluated acquisition costs in our West Texas Asset will require up to an estimated three more years of exploration and development activity before evaluation is complete, which is covered by the remaining primary term and the renewal term of the underlying leases.

Other Matters

Capitalized overhead costs that directly relate to exploration and development activities were $13.6 million, $16.8 million and $18.3 million for 2013, 2012 and 2011, respectively. For 2013, depletion per Mcfe was $0.51 and $0.14 for the U.S. and Canada, respectively. For 2012, depletion per Mcfe was $1.14 and $0.83 for the U.S. and Canada, respectively. For 2011, consolidated depletion per Mcfe was $1.35. Depreciation expense was $17.1 million, $18.6 million and $20.3 million for 2013, 2012 and 2011, respectively.