Properties and Equipment (Tables)

6 Months Ended

Jun. 30, 2018

The following table presents the components of properties and equipment, net of accumulated depreciation, depletion and amortization ("DD&A"):



	June 30, 2018			December 31, 2017
	(in thousands)
Properties and equipment, net:
Crude oil and natural gas properties
Proved	$	4,944,476		$	4,356,922
Unproved	908,271			1,097,317
Total crude oil and natural gas properties	5,852,747			5,454,239
Infrastructure, pipeline and other	127,799			109,359
Land and buildings	12,724			10,960
Construction in progress	294,669			196,024
Properties and equipment, at cost	6,287,939			5,770,582
Accumulated DD&A	(2,095,331		)	(1,837,115		)
Properties and equipment, net	$	4,192,608		$	3,933,467

Impairment of natural gas and crude oil properties

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



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(in thousands)

Impairment of proved and unproved properties	$	159,528	$	27,463	$	192,658	$	29,565
Amortization of individually insignificant unproved properties	26		103		84		194
Impairment of crude oil and natural gas properties	$	159,554	$	27,566	$	192,742	$	29,759

Schedule of Aging of Capitalized Exploratory Well Costs [Table Text Block]

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



	Six Months Ended June 30, 2018			Year Ended December 31, 2017
	(in thousands, except for number of wells)

Beginning balance	$	15,448		$	—
Additions to capitalized exploratory well costs pending the determination of proved reserves	23,443			51,776
Reclassifications to proved properties	(29,883		)	(36,328		)
Capitalized exploratory well costs charged to expense	—			—
Ending balance	$	9,008		$	15,448

Number of wells pending determination at period end	1			3