In February 2010 the USGS published: Assessment of Undiscovered Oil and Gas Resources of Four West Africa Geologic Provinces (USGS Fact Sheet 2010-3006)
Four geologic provinces located along the northwest and west-central coast of Africa recently were assessed for undiscovered oil, natural gas, and natural gas liquids resources as part of the U.S. Geological Survey’s (USGS) World Oil and Gas Assessment. Using a geology-based assessment methodology, the USGS estimated mean volumes of 71.7 billion barrels of oil, 187.2 trillion cubic feet of natural gas, and 10.9 billion barrels of natural gas liquids.
Figure 1: Locations of four assessed geologic provinces located along the northwest and west-central coast of Africa.
Table 1. West Africa Provinces assessment results for undiscovered, technically recoverable oil, gas, and natural gas liquids.
Largest expected mean field size in million barrels of oil and billion cubic feet of gas; MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas accumulations, all liquids are included as natural gas liquids (NGL). Undiscovered gas resources are the sum of nonassociated and associated gas. F95 represents a 95 percent chance of at least the amount tabulated; other fractiles are defined similarly. AU, assessment unit; AU probability is the chance of at least one accumulation of minimum size within the AU. NGL, natural gas liquids. TPS, total petroleum system. Gray shading indicates not applicable.
The entire document is 2 pages, linked from here: Assessment of Undiscovered Oil and Gas Resources of Four West Africa Geologic Provinces. Due mostly to the odd way they have handled fairly simple graphics, the 2 page document is 7.5MB. I’ve made the map and the chart into web graphics here. You can click on them here to enlarge.
When you read about US foreign policy in West African countries, or about US Africa Command activities in West Africa, keep the map above in mind.
NOTE: The figures above refer only to undiscovered oil. They do not include fields that have already been discovered and whose size is known, and do not include fields already in production.
The areas marked on the map do include fields that have already been discovered, and fields already in production, since many discoveries and production are in those same geologic provinces where there are estimates of undiscovered oil.