Annual report pursuant to Section 13 and 15(d)

SUPPLEMENTAL DISCLOSURES ABOUT NATURAL GAS PRODUCING ACTIVITIES - Additional Information (Details)

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SUPPLEMENTAL DISCLOSURES ABOUT NATURAL GAS PRODUCING ACTIVITIES - Additional Information (Details) - Bcfe
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Extractive Industries [Abstract]      
Revisions of previous estimates 152 4 22
Proved developed and undeveloped reserves, positive (negative) revision due to change of prices (in Bcfe) (149) (4) 1
Proved developed and undeveloped reserves, revisions due to loss of leases (in Bcfe) 17   12
Proved developed and undeveloped, revision from well performance (in Bcfe) 14 9 59
Proved undeveloped reserve, revision of previous estimate (in Bcfe) 165    
Proved undeveloped reserves, negative revision due to change of prices (in Bcfe) 148 2  
Proved undeveloped reserves, revision from lease expirations (in Bcfe) 17    
Extensions, discoveries and other additions   13 85
Additional proved undeveloped locations, discoveries (in Bcfe)   12 19
Additional proved undeveloped locations, drilling activities (in Bcfe)   1 3
Proved developed and undeveloped reserves negative revision in operating expenses (in Bcfe)   2  
Proved developed and undeveloped, revision from changes in ownership (in Bcfe)   1  
Proved undeveloped reserves converted (in Bcfe)   29  
Proved undeveloped reserves, added from additional locations (in Bcfe)   12  
Proved undeveloped reserves, revision of previous estimate (in Bcfe)   8  
Proved undeveloped reserves, revision from performance (in Bcfe)   9  
Proved undeveloped reverses, revision from changes in ownership (in Bcfe)   1  
Proved undeveloped reserves, revision of previous estimates (in Bcfe)     14
Purchases of reserves-in-place     1