Annual report pursuant to Section 13 and 15(d)

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

v3.20.1
Crude Oil and Natural Gas Properties and Equipment (Narrative) (Details)
$ in Thousands, in Billions
 12 Months Ended
Sep. 26, 2018
USD ($)
Sep. 17, 2018
USD ($)
Sep. 17, 2018
XAF ( )
Dec. 31, 2019
USD ($)
item
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 25, 2018
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Production license agreement term extended by government       5 years      
Deferred tax assets, basis difference in fixed assets       $ 26,590 $ 38,479    
Deferred tax liabilities, basis difference in fixed assets       18,600      
Reduction in VAT receivable       275 (777) $ (3,025)  
VAT receivable, net of valuation allowance       4,200      
Allocated to proved leasehold cost       22,500      
Allocated to unproved leasehold cost       13,700      
Estimated costs of technical studies       1,300      
Estimated costs of technical studies, net       400      
Undeveloped Acreage       $ 23,771 23,771    
Monthly royalty rate, based on production at the published price       13.00%      
Additional increase to working interest ownership, percent       0.80%      
Inventory write-off       $ 0   0  
Etame Field [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Percent of participating interest       33.575%      
Number of exploitation areas | item       3      
Period of agreement for exploitation areas       10 years      
Number of contract extension periods | item       2      
Production license agreement term extended by government       5 years      
Number of drilled wells required by agreement | item       2      
Number of appraisal wells required by agreement | item       2      
Block P Offshore Equatorial Guinea [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Deferred tax assets, basis difference in fixed assets       $ 18,600      
Working interest ownership, percentage       31.00%      
Undeveloped Acreage       $ 10,000      
Period of development       25 years      
Capitalized costs, signing bonus       $ 6,700      
Capitalized costs, tax impact       7,100      
Undeveloped leasehold value       10,000      
Gabon [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Contractual commitment, gross             $ 65,000
Contractual obligation       1,200 $ 1,100 $ 1,200 $ 21,800
Cash paid for signing bonus, gross amount $ 35,000            
Payment of signing bonus, allocated to proved and unproved property 11,800            
Reduction in VAT receivable, gross amount 25,000   14.1        
Reduction in VAT receivable $ 8,400 $ 4,200 4.7        
Accrued liabilities, end of drilling activities, gross amount       5,000      
Accrued liabilities, end of drilling activities       $ 1,700      
Number of drilled wells required by agreement | item       2      
Number of appraisal wells required by agreement | item       2      
Working interest ownership, percentage         7.50%    
Additional increase to working interest ownership, percent       2.50%      
Inventory write-off         $ 400    
Gabon DMO [Member] | Gabon [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Contractual obligation       $ 1,100 1,200    
PID And PIH [Member] | Gabon [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Contractual obligation       $ 2,200 $ 1,900    
Prior Production Sharing Contract, Through September 17, 2018 [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Entitled percent for consortium after initial royalty percentage       70.00%      
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Entitled percent for consortium after initial royalty percentage       80.00%      
Production Sharing Contract, After September 16, 2028 [Member]              
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]              
Entitled percent for consortium after initial royalty percentage       70.00%