Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, plant and equipment consists of the following (in thousands):



	December 31,
	2017			2016
Oil and natural gas properties
Proved	$	1,056,806		$	840,201
Unproved	100,884			74,937
Total oil and natural gas properties	1,157,690			915,138
Less accumulated depreciation, depletion and impairment	(460,431		)	(353,030		)
Net oil and natural gas properties capitalized costs	697,259			562,108

Land	4,500			5,100
Electrical infrastructure	131,010			130,242
Non-oil and natural gas equipment	26,809			35,768
Buildings and structures	79,548			88,603
Total	241,867			259,713
Less accumulated depreciation and amortization	(15,886		)	(3,889		)
Other property, plant and equipment, net	225,981			255,824
Total property, plant and equipment, net	$	923,240		$	817,932

The net carrying value of the Company’s oil and natural gas properties was reduced by $319.1 million during the Successor 2016 Period, $657.4 million during the Predecessor 2016 Period and $4.5 billion during 2015, as a result of quarterly full cost ceiling analyses in the respective periods. No full cost ceiling impairments were recorded in the 2017 period. See Note 10 for discussion of impairment of other property, plant and equipment.

The average rates used for depreciation and depletion of oil and natural gas properties were $7.92 per Boe in 2017, $8.31 per Boe for the Successor 2016 Period, $6.05 per Boe in the Predecessor 2016 Period and $10.81 per Boe in 2015.

The Company has approximately $10.6 million in assets classified as held for sale in the other current assets line of the accompanying consolidated balance sheet at December 31, 2017. Approximately $9.3 million of this total is related to one of the Company’s properties located in downtown Oklahoma City, OK, which was classified as held for sale in the fourth quarter of 2017 and is expected to be sold during the first half of 2018. The remaining balance largely consists of the Company’s remaining drilling and oilfield services assets. These assets had a carrying value of $6.9 million which exceeded the net realizable value of $2.9 million determined by expected sales prices obtained from third parties. As a result, the Company recorded an impairment of $4.0 million for the year ended December 31, 2017. The Company disposed of approximately $1.7 million of these assets during the year ended December 31, 2017, and recorded an insignificant gain on sale of assets which is included in other operating expenses in the accompanying consolidated statement of operations. The Company expects to dispose of the majority of the remaining assets within the next year.

Costs Excluded from Amortization

The following table summarizes the costs, by year incurred, related to unproved properties, which were excluded from oil and natural gas properties subject to amortization at December 31, 2017 (in thousands):



			Year Cost Incurred
	Total		2017		2016		2015		2014 and Prior
Property acquisition	$	96,450	$	42,827	$	15,610	$	19,481	$	18,532
Exploration	4,434		1,904		678		1,453		399
Total costs incurred	$	100,884	$	44,731	$	16,288	$	20,934	$	18,931

The Company expects to complete the majority of the evaluation activities within 10 years from the applicable date of acquisition, contingent on the Company’s capital expenditures and drilling program. In addition, the Company’s internal engineers evaluate all properties on a quarterly basis.