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The sum of the capitalized costs incurred, as of the balance sheet date, of unproved properties excluded from amortization including acquisition costs, exploration costs, development costs, and production costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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.

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Volume increase (decrease) of proved reserves of oil and gas.

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Purchase of minerals in place.

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

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