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02 October 2010 @ 07:33 pm
Assessment of Undiscovered Oil and Gas Resources of Four West Africa Geologic Provinces  
Introduction
The main objective of the U.S. Geological Survey’s (USGS) World Petroleum Resources Project is to assess the potential for undiscovered, technically recoverable oil and natural gas resources of the world, exclusive of the United States. As part of this program, the USGS recently completed an assessment of four geologic provinces located along the northwest and west-central African coast and extending offshore to a water depth of 4,000  meters (m) (fig. 1). From  north  to  south,  the  provinces  are:  (1)  the  Senegal, containing the passive-marginal Senegal Basin of Middle Jurassic to Holocene age; (2)   the Gulf of Guinea, characterized by transform tectonics; (3) the Niger Delta, containing  more  than  9,100 m  of  sediments;  and  (4)  the  West-Central Coastal, containing the Aptian salt basin and dominated by both rift and sag tectonics including the Congo Basin.
These provinces were assessed previously as part of the USGS World Assessment 2000 (U.S. Geological Survey World Energy Assessment Team, 2000), resulting in estimated  mean  volumes  of  71.5  billion  barrels  of  oil  (BBO),  235.2 trillion  cubic  feet   of  gas  (TCFG),  and  10.8 billion  barrels of natural gas liquids (BBNGL).

More  than  275  new  fields  have  been  discovered  in  the  four western Africa provinces since the 2000 assessment.
The provinces were reassessed because of increased activity and because of new oil and gas discoveries within the provinces. The assessment was based on geology and used the total petroleum system (TPS) concept. The geologic elements of a TPS include hydrocarbon source rocks (source rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and distribution), and traps for hydrocarbon accumulation. Using these geologic criteria, seven conventional total petroleum systems and nine assessment  units  (AU)  in  the  four  provinces  were  defined,  and the undiscovered, technically recoverable oil and gas resources  were  assessed  (table  1).



Resource Summary
The results of the USGS assessment of undiscovered, technically recoverable
conventional oil and gas resources in the west African provinces are given in  table  1.  The  mean  volumes  are  estimated  at  (1)  2,350  million  barrels  of  oil  (MMBO),  18,706  billion  cubic  feet  of  gas  (BCFG),  and  567 million  barrels  of  natural  gas  liquids  (MMBNGL)  for  the  Coastal  Plain  and  Offshore  AU  in  the  Senegal  Province;  (2)  4,071  MMBO,  34,451  BCFG,  and  1,145 MMBNGL  for  the  Coastal  Plain  and  Offshore  AU  in  the  Gulf  of  Guinea Province; and (3)  15,534  MMBO,  58,221  BCFG,  and  6,326  MMBNGL  for  the  Agbada  Reservoirs and Akata Reservoirs Aus in the Niger Delta Province. The West-Central Coastal Province was divided into the Gabon Subsalt, Gabon Suprasalt, Central Congo Delta and Carbonate Platform, Central Congo Turbidites, and Kwanza-Namibe  AUs.  The  estimated  mean  volumes  for  these  five  AUs  are  49,736  MMBO,  75,8790  BCFG,  and  2,877  MMNGL.  
This  assessment for the west Africa provinces indicates that most of the oil and gas potential remains in the offshore waters.


http://pubs.usgs.gov/fs/2010/3006/