SUPPLEMENTAL INFORMATION ON OIL AND NATURAL GAS OPERATIONS - UNAUDITED - Summary of Estimated Proved Oil and Natural Gas Reserve (Details) MMcf in Thousands, MBbls in Thousands	2 Months Ended	10 Months Ended	12 Months Ended
Feb. 28, 2017 MMcf MBbls	Dec. 31, 2017 MMcf MBbls	Dec. 31, 2016 MMcf MBbls	Dec. 31, 2015 MMcf MBbls
Oil (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Revisions of previous estimates \| MBbls		3,769
Production \| MBbls		(4,169)
Estimated proved reserves, ending balance \| MBbls		21,876
Estimated proved developed reserves: \| MBbls		20,275
Estimated proved undeveloped reserves: \| MBbls		1,601
NGLs (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Revisions of previous estimates \| MBbls		(94)
Production \| MBbls		(403)
Estimated proved reserves, ending balance \| MBbls		2,305
Estimated proved developed reserves: \| MBbls		1,689
Estimated proved undeveloped reserves: \| MBbls		616
Natural Gas (MMcf)
Oil and gas properties – United States, proved and unevaluated:
Revisions of previous estimates \| MMcf		(2,801)
Production \| MMcf		(7,616)
Estimated proved reserves, ending balance \| MMcf		50,116
Estimated proved developed reserves: \| MMcf		37,946
Estimated proved undeveloped reserves: \| MMcf		12,170
Oil, Natural Gas and NGLs (MBoe)
Oil and gas properties – United States, proved and unevaluated:
Revisions of previous estimates \| MMcf		3,208
Production \| MMcf		(5,841)
Estimated proved reserves, ending balance \| MMcf		32,533
Estimated proved developed reserves: \| MMcf		28,288
Estimated proved undeveloped reserves: \| MMcf		4,245
Predecessor \| Oil (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance \| MBbls	23,280	22,276	30,276	42,397
Revisions of previous estimates \| MBbls	730		(751)	(6,818)
Extensions, discoveries and other additions \| MBbls			63	862
Purchase of producing properties \| MBbls				685
Sale of reserves \| MBbls	(826)			(859)
Production \| MBbls	(908)		(6,308)	(5,991)
Estimated proved reserves, ending balance \| MBbls	22,276		23,280	30,276
Estimated proved developed reserves: \| MBbls	18,344		18,269	21,734
Estimated proved undeveloped reserves: \| MBbls	3,932		5,011	8,542
Predecessor \| NGLs (MBbls)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance \| MBbls	10,629	2,802	6,458	27,817
Revisions of previous estimates \| MBbls	(2)		6,352	(20,777)
Extensions, discoveries and other additions \| MBbls			2	11
Purchase of producing properties \| MBbls				1,808
Sale of reserves \| MBbls	(7,417)			0
Production \| MBbls	(408)		(2,183)	(2,401)
Estimated proved reserves, ending balance \| MBbls	2,802		10,629	6,458
Estimated proved developed reserves: \| MBbls	1,515		9,255	4,784
Estimated proved undeveloped reserves: \| MBbls	1,287		1,374	1,674
Predecessor \| Natural Gas (MMcf)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance \| MMcf	117,320	60,533	121,858	493,843
Revisions of previous estimates \| MMcf	1,242		24,858	(362,102)
Extensions, discoveries and other additions \| MMcf			45	1,499
Purchase of producing properties \| MMcf				26,136
Sale of reserves \| MMcf	(52,992)			(1,061)
Production \| MMcf	(5,037)		(29,441)	(36,457)
Estimated proved reserves, ending balance \| MMcf	60,533		117,320	121,858
Estimated proved developed reserves: \| MMcf	35,865		90,741	90,262
Estimated proved undeveloped reserves: \| MMcf	24,668		26,579	31,596
Predecessor \| Oil, Natural Gas and NGLs (MBoe)
Oil and gas properties – United States, proved and unevaluated:
Estimated proved reserves, beginning balance \| MMcf	53,462	35,166	57,043	152,520
Revisions of previous estimates \| MMcf	935		9,744	(87,945)
Extensions, discoveries and other additions \| MMcf			73	1,123
Purchase of producing properties \| MMcf				6,849
Sale of reserves \| MMcf	(17,075)			(1,036)
Production \| MMcf	(2,156)		(13,398)	(14,468)
Estimated proved reserves, ending balance \| MMcf	35,166		53,462	57,043
Estimated proved developed reserves: \| MMcf	25,836		42,647	41,562
Estimated proved undeveloped reserves: \| MMcf	9,330		10,815	15,481

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

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-Publisher FASB
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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

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Production of proved reserves.

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- Definition

Purchase of minerals in place.

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- Definition

Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

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Sales of minerals in place.

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- Definition

Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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Net quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other renewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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