Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves (Details)

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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Extractive Industries [Abstract]      
Sales and transfers of oil and gas produced, net of production costs $ (264) $ (734) $ (1,063)
Net changes in prices, production costs, and development costs (954) (1,372) 591
Acquisition of oil and gas reserves in place 0 0 0
Extensions and discoveries 38 388 519
Previously estimated development costs incurred during the period 215 406 402
Revisions of previous quantity estimates, less related production costs (255) (321) (357)
Sales of oil and gas reserves in place (6) (49) (26)
Accretion of discount 170 298 264
Net changes in income taxes 0 425 (185)
Change in production rates and other (109) (319) 194
Total change in standardized measure of discounted future net cash flows $ (1,165) $ (1,278) $ 339