Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Summary of net property and equipment balances

The following table presents a summary of our net property and equipment balances as of December 31, 2015 and 2014:



	December 31,
In thousands	2015			2014
Oil and natural gas properties
Proved properties	$	10,245,195		$	9,782,337
Unevaluated properties	894,948			918,406
Total	11,140,143			10,700,743
Accumulated depletion, depreciation and impairment	(9,022,823		)	(3,679,883		)
Net oil and natural gas properties	2,117,320			7,020,860
CO₂ properties
CO₂ properties	1,187,458			1,162,538
Accumulated depletion and depreciation	(213,106		)	(183,646		)
Net CO₂ properties	974,352			978,892
Pipelines and plants
CO₂ pipelines ⁽¹⁾	1,749,538			1,733,562
Plants	543,681			536,002
Total	2,293,219			2,269,564
Accumulated depletion and depreciation	(230,297		)	(182,385		)
Net plants and pipelines	2,062,922			2,087,179
Other property and equipment
Other property and equipment	408,194			468,051
Accumulated depletion and depreciation	(186,979		)	(202,738		)
Net other property and equipment	221,215			265,313
Net property and equipment	$	5,375,809		$	10,352,244


(1)	Amount includes $114.3 million of CO₂ pipelines at December 31, 2015, that were under construction and not subject to depreciation during 2015.

Summary of unevaluated properties excluded from oil and natural gas properties being amortized

A summary of the unevaluated property costs excluded from oil and natural gas properties being amortized at December 31, 2015, and the year in which the costs were incurred follows:



	December 31, 2015
	Costs Incurred During:
In thousands	2015		2014		2013		2012 and Prior		Total
Property acquisition costs	$	—	$	6,500	$	215,660	$	395,752	$	617,912
Exploration and development	24,814		95,397		40,090		30,206		190,507
Capitalized interest	28,302		21,179		22,916		14,132		86,529
Total	$	53,116	$	123,076	$	278,666	$	440,090	$	894,948