Quarterly report pursuant to Section 13 or 15(d)

Crude Oil and Natural Gas Properties and Equipment (Narrative) (Details)

v3.21.2
Crude Oil and Natural Gas Properties and Equipment (Narrative) (Details)
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jun. 20, 2026
Apr. 12, 2021
Feb. 25, 2021
Sep. 26, 2018
USD ($)
Sep. 17, 2018
USD ($)
item
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
item
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
Feb. 24, 2021
Mar. 31, 2020
USD ($)
Dec. 31, 2012
Property, Plant and Equipment [Line Items]                            
Reduction in VAT receivable                 $ (1,339,000) $ (919,000)        
Impairment of proved crude oil and natural gas properties             $ 0 $ 0 0 30,625,000        
Property, net             $ 74,102,000   $ 74,102,000   $ 37,036,000      
Etame Marine Block [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage     58.80%                 31.10%    
Impairment of proved crude oil and natural gas properties               30,600,000            
Property, net           $ 15,600,000   $ 15,600,000   $ 15,600,000        
Undeveloped acreage                         $ 2,300,000  
Undeveloped leasehold value                         $ 11,500,000  
Etame Marine Block [Member] | VAALCO Gabon S.A. [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage             63.575%   63.575%          
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Etame Marine Block [Member] | Consortium [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage             7.50%   7.50%          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member]                            
Property, Plant and Equipment [Line Items]                            
Deferred tax assets, basis difference in fixed assets             $ 18,600,000   $ 18,600,000          
Estimated costs of technical studies           500,000                
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Consortium [Member]                            
Property, Plant and Equipment [Line Items]                            
Number of wells drilled | item                 2          
Number of wellbores drilled | item                 2          
Number of technical studies required | item                 2          
Estimated costs of technical studies           $ 1,500,000                
Entitled percent for consortium after initial royalty percentage                 80.00%          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Signing Bonus [Member]                            
Property, Plant and Equipment [Line Items]                            
Contractual obligation         $ 21,800,000                  
Payment of signing bonus, allocated to proved and unproved property       $ 11,800,000                    
Reduction in VAT receivable       8,400,000                    
Other accrued liabilities       1,700,000                    
Allocated to unproved leasehold cost             6,700,000   $ 6,700,000          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Signing Bonus [Member] | Consortium [Member]                            
Property, Plant and Equipment [Line Items]                            
Contractual obligation         $ 65,000,000.0                  
Payment of signing bonus, allocated to proved and unproved property       35,000,000.0                    
Reduction in VAT receivable       25,000,000.0                    
Other accrued liabilities       $ 5,000,000.0                    
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Tax Impact [Member]                            
Property, Plant and Equipment [Line Items]                            
Allocated to unproved leasehold cost             $ 7,100,000   $ 7,100,000          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Etame Marine Block [Member]                            
Property, Plant and Equipment [Line Items]                            
Number of exploitation areas | item         3                  
Period of agreement for exploitation areas         10 years       10 years          
Number of contract extension periods | item         2                  
Production license agreement term extended by government         5 years                  
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Etame Marine Block [Member] | Government Of Gabon [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage             7.50%   7.50%          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Scenario, Forecast [Member] | Etame Marine Block [Member]                            
Property, Plant and Equipment [Line Items]                            
Increase (decrease) in working interest ownership percentage (1.60%)                          
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Scenario, Forecast [Member] | Etame Marine Block [Member] | Government Of Gabon [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage 10.00%                          
Increase (decrease) in working interest ownership percentage 2.50%                          
Production Sharing Contract, After September 16, 2028 [Member] | Consortium [Member]                            
Property, Plant and Equipment [Line Items]                            
Entitled percent for consortium after initial royalty percentage                 70.00%          
Sasol Gabon S.A. [Member]                            
Property, Plant and Equipment [Line Items]                            
Undeveloped acreage             $ 2,200,000   $ 2,200,000          
Sasol Gabon S.A. [Member] | Etame Marine Block [Member]                            
Property, Plant and Equipment [Line Items]                            
Increase (decrease) in working interest ownership percentage     27.80%                      
Undeveloped leasehold value             13,700,000   13,700,000          
Block P Offshore Equatorial Guinea [Member]                            
Property, Plant and Equipment [Line Items]                            
Working interest ownership, percentage                     43.00%     31.00%
Increase (decrease) in working interest ownership percentage   45.90%                 12.00%      
Undeveloped acreage             $ 10,000,000.0   $ 10,000,000.0          
Potential payment                     $ 3,100,000      
Period of development                 25 years