OIL AND NATURAL GAS PROPERTIES - Summary of oil and natural gas property costs (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Oil and natural gas properties:
Proved	$ 484,433	$ 478,569
Unproved	86,028	109,590
Total oil and natural gas properties	570,461	588,159
Accumulated depletion, depreciation, amortization and impairment	(362,495)	(359,304)
Oil and natural gas properties, net	$ 207,966	$ 228,855

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Amount of accumulated depreciation, depletion and amortization of oil and gas property carried under the successful effort method. Oil and gas property include, but not limited to, the entity's wells and related equipment and facilities.

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Oil and Gas properties, gross, carried under the successful effort method.

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Oil and gas properties net of accumulated depreciation, depletion, amortization, impairment, and abandonment, carried under the successful effort method.

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Oil and Gas properties with proved reserves under the successful effort method.

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Oil and Gas properties with unproved reserves under the successful effort method.

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