Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Oil and Gas Reserves (Details)

v3.20.4
Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Oil and Gas Reserves (Details)
bbl in Thousands, Bcf in Thousands
 12 Months Ended
Dec. 31, 2020
bbl
Bcf
Dec. 31, 2019
bbl
Bcf
Dec. 31, 2018
bbl
Bcf
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period | Bcf 4,528,000 4,743,000 5,395,000
Purchases of reserves | Bcf 0 0 0
Extensions and discoveries | Bcf 240,000 1,097,000 711,000
Sales of reserves | Bcf (75,000) (77,000) (45,000)
Revisions of prior reserve estimates | Bcf (1,725,000) (734,000) (821,000)
Current production | Bcf (380,000) (502,000) (497,000)
End of period | Bcf 2,588,000 4,528,000 4,743,000
Proved developed reserves (Volume) | Bcf 1,527,000 1,984,000 2,115,000
Proved undeveloped reserves (Volume) | Bcf 1,061,000 2,544,000 2,628,000
Oil      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period | bbl 18,000 21,000 19,000
Purchases of reserves | bbl 0 0 0
Extensions and discoveries | bbl 1,000 4,000 5,000
Sales of reserves | bbl 0 (2,000) 0
Revisions of prior reserve estimates | bbl (4,000) (2,000) 0
Current production | bbl (2,000) (2,000) (3,000)
End of period | bbl 13,000 18,000 21,000
Proved developed reserves (Volume) | bbl 7,000 8,000 10,000
Proved undeveloped reserves (Volume) | bbl 7,000 10,000 11,000
Natural Gas      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period | Bcf 4,048,000 4,134,000 4,825,000
Purchases of reserves | Bcf 0 0 0
Extensions and discoveries | Bcf 216,000 997,000 622,000
Sales of reserves | Bcf (74,000) (63,000) (43,000)
Revisions of prior reserve estimates | Bcf (1,564,000) (562,000) (827,000)
Current production | Bcf (345,000) (458,000) (444,000)
End of period | Bcf 2,281,000 4,048,000 4,134,000
Proved developed reserves (Volume) | Bcf 1,358,000 1,757,000 1,813,000
Proved undeveloped reserves (Volume) | Bcf 923,000 2,291,000 2,321,000
Natural Gas Liquids      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period | bbl 62,000 81,000 76,000
Purchases of reserves | bbl 0 0 0
Extensions and discoveries | bbl 3,000 13,000 10,000
Sales of reserves | bbl 0 0 0
Revisions of prior reserve estimates | bbl (23,000) (27,000) 1,000
Current production | bbl (4,000) (5,000) (6,000)
End of period | bbl 38,000 62,000 81,000
Proved developed reserves (Volume) | bbl 22,000 30,000 41,000
Proved undeveloped reserves (Volume) | bbl 16,000 32,000 40,000