v3.8.0.1

Disclosures About Oil and Gas Producing Activities - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017 MBoe MMcf | Dec. 31, 2016 MBoe MMcf | Dec. 31, 2015 MBoe MMcf
Extractive Industries [Abstract] |  |  |
Extensions and discoveries | 33,307 | 16,651 | 34,895
Acquisition of proved reserves | 1,572 |  |
Economic revisions | 17,700 | 22,400 | 11,900
Increased revisions due to cost reduction, updated well Performance and technical parameters | 9,400 | 2,100 | 13,000
Significant changes in reserves | Extensions and discoveries for 2017 were 33.3 MMBoe, primarily attributable to our development project in the Wolfcamp shale oil resource play in the Permian Basin. During 2017, we acquired 1.6 MMBoe of proved reserves through the Bolt-On Acquisition, and we reclassified 17.7 MMBoe of proved undeveloped reserves to unproved reserves. The reserves reclassified are attributable to horizontal well locations in Project Pangea that are no longer expected to be developed within five years from their initial booking, as required by SEC rules. Revisions included an increase of 9.4 MMBoe resulting from updated well performance and technical parameters and an increase of 3.1 MMBoe due to higher commodity prices | Extensions and discoveries for 2016 were 16.7 MMBoe, primarily attributable to our development project in the Wolfcamp shale oil resource play in the Permian Basin. During 2016, we reclassified 22.4 MMBoe of proved undeveloped reserves to unproved reserves. The reserves reclassified are attributable to horizontal well locations in Project Pangea that are no longer expected to be developed within five years from their initial booking, as required by SEC rules. Revisions included an increase of 2.1 MMBoe resulting from cost reductions, updated well performance and technical parameters, offset by a decrease of 1.9 MMBoe due to lower commodity prices. | Extensions and discoveries for 2015 were 34.9 MMBoe, primarily attributable to our development project in the Wolfcamp shale oil resource play in the Permian Basin. During 2015, we reclassified 11.9 MMBoe of proved reserves to unproved reserves. The reserves reclassified are attributable to horizontal and vertical well locations in Project Pangea that are no longer expected to be developed within five years from their initial booking, as required by SEC rules. Revisions included an increase of 13 MMBoe resulting from cost reductions, updated well performance and technical parameters, offset by a decrease of 9.8 MMBoe due to lower commodity prices.
Period for reclassification of proved reserves to unproved reserves | 5 years | 5 years | 5 years
Increased revisions due to higher commodity prices | 3,100 |  |
Production | 4,500 | 4,800 | 5,800
Field fuel | MMcf | 1,319 | 1,330 | 1,530
Decreased revisions due to lower commodity prices |  | 1,900 | 9,800

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