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, 2019
Dec. 31, 2018
Dec. 31, 2017
Extractive Industries [Abstract]      
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  
Revisions of previous estimates 4 22  
Proved developed and undeveloped reserves, revision due to change of prices (in Bcfe) (4) 1  
Proved developed and undeveloped reserves negative revision in operating expenses (in Bcfe) 2    
Proved developed and undeveloped, revision from performance (in Bcfe) 9 59  
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 reserves, revision due to change of prices (in Bcfe) (2)    
Proved undeveloped reverses, revision from changes in ownership 1    
Proved undeveloped reserves, revision of previous estimates (in Bcfe)   14  
Proved developed and undeveloped reserves, revisions due to loss of leases (in Bcfe)   12  
Purchases of reserves-in-place   1 327