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Assessment of the undiscovered oil and gas of the Senegal province, Mauritania, Senegal, the Gambia, and Guinea-Bissau, northwest Africa

December 1, 2003

Undiscovered, conventional oil and gas resources were assessed in the Senegal Province as part of the U.S. Geological Survey World Petroleum Assessment 2000 (U.S. Geological Survey World Energy Assessment Team, 2000). Although
several total petroleum systems may exist in the province,
only one composite total petroleum system, the Cretaceous-Tertiary Composite Total Petroleum System, was defined
with one assessment unit, the Coastal Plain and Offshore Assessment Unit, having sufficient data to allow quantitative assessment.
The primary source rocks for the Cretaceous-Tertiary Composite Total Petroleum System are the Cenomanian-Turonian marine shales. The Turonian shales can be as much
as 150 meters thick and contain Type II organic carbon ranging from 3 to 10 weight percent. In the Senegal Province, source rocks are mature even when situated at depths relatively shallow
for continental passive margin basins. Reservoir rocks consist
of Upper Cretaceous sandstones and lower Tertiary clastic and carbonate rocks. The Lower Cretaceous platform carbonate rocks (sealed by Cenomanian shales) have porosities ranging from 10 to 23 percent. Oligocene carbonate rock reservoirs exist, such as the Dome Flore field, which contains as much
as 1 billion barrels of heavy oil (10? API, 1.6 percent sulfur)
in place. The traps are a combination of structural closures
and stratigraphic pinch-outs.
Hydrocarbon production in the Senegal Province to date has been limited to several small oil and gas fields around
Cape Verde (also known as the Dakar Peninsula) from Upper Cretaceous sandstone reservoirs bounded by normal faults, of which three fields (two gas and one oil) exceed the minimum size assessed in this study (1 MMBO; 6 BCFG). Discovered known oil resources in the Senegal Province are 10 MMBO, with known gas resources of 49 BCFG (Petroconsultants, 1996).
This study estimates that 10 percent of the total number of potential oil and gas fields (both discovered and undiscovered) of at least the minimum size have been discovered. The estimated
mean size and number of assessed, undiscovered oil fields are 13 MMBO and 13 fields, respectively, whereas the mean size and number of undiscovered gas fields are estimated to be 50 BCFG and 11 fields.
The mean estimates for undiscovered conventional petroleum
resources are 157 MMBO, 856 BCFG, and 43 MMBNGL (table 2). The mean sizes of the largest anticipated undiscovered oil and gas fields are 66 MMBO and 208 BCFG, respectively.
The Senegal Province is underexplored considering its large size. The province has hydrocarbon potential in both the offshore and onshore, and undiscovered gas resources may be significant and accessible in areas where the zone of oil generation
is relatively shallow.

Citation Information

Publication Year 2003
Title Assessment of the undiscovered oil and gas of the Senegal province, Mauritania, Senegal, the Gambia, and Guinea-Bissau, northwest Africa
DOI 10.3133/b2207A
Authors Michael E. Brownfield, Ronald R. Charpentier
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Bulletin
Series Number 2207
Index ID b2207A
Record Source USGS Publications Warehouse
USGS Organization Central Energy Resources Science Center