UNAUDITED CRUDE OIL AND NATURAL GAS RESERVES INFORMATION - Standardized Measure of Discounted Future Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
UNAUDITED CRUDE OIL AND NATURAL GAS RESERVES INFORMATION
Future cash inflows	$ 208,459	$ 148,596	$ 5
Future cash outflows:
Production cost	(48,929)	(35,038)	(3)
Development cost	(58,784)	(37,667)
Future income tax	(16,006)	(5,802)
Future net cash flows	84,740	70,089	2
Adjustment to discount future annual net cash flows at 10%	(35,054)	(29,925)	$ (2)
Standardized measure of discounted future net cash flows	$ 49,686	$ 40,164		$ 5
Percentage of discount on future annual net cash flows (as a percent)	10.00%	10.00%	10.00%

N/A.

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The percentage of discount relating to future annual net cash flows relating to oil and gas.

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Amount of estimated future accumulated cash inflow from the sale of proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for costs to be incurred in developing proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for income tax, based on the future income less future expense derived from production and sale of proved oil and gas reserves.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 235
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Amount, after future accumulated cash outflow for development and production costs and future income tax, of estimated future accumulated cash inflow from the sale of proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for costs to be incurred in producing proved oil and gas reserves.

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Amount of discount on future accumulated cash inflow, after deducting future accumulated cash outflow for development and production costs and future income tax, from sale of proved oil and gas reserves, using a discount rate of ten percent a year.

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Amount of discounted future accumulated cash inflow relating to proved oil and gas reserves.

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