Digital Data Series 69-GG
The main objective of the U.S. Geological Survey’s (USGS) National and Global Petroleum Assessment Project is to assess the potential for undiscovered, technically recoverable oil and natural gas resources of the United States and the world. The USGS updated assessments that were completed during the USGS World Petroleum Assessment 2000 and conducted new assessments in areas around the world that were not previously examined. These assessments used the latest geology-based assessment methodology for conventional oil and gas resources.
As part of this project, the USGS assessed 13 geologic provinces located in sub-Saharan Africa. Coastal provinces were extended offshore to water depths ranging from 2,000 to 4,000 meters (m). Within these 13 geologic provinces, 18 assessment units were identified.
The west Africa provinces are (1) the Senegal, containing the passive-margin Senegal Basin of Middle Jurassic to Holocene age; (2) the West African Coastal, characterized by rift, passive-margin, and transform tectonics; (3) the Gulf of Guinea, characterized by transform tectonics; (4) the Niger Delta, containing more than 9,100 m of sedimentary rock and recent sediments; (5) the West-Central Coastal, which contains the Aptian salt basin and is dominated by both rift and sag tectonics, and which includes the Congo Basin; and (6) the Orange River Coastal, containing more than 7,000 m of syn-rift and post-rift sedimentary rock. The West African Coastal Province was assessed for the first time, whereas the other five west Africa provinces were reassessed for the 2012 World Oil and Gas Resource Assessment. More than 275 new oil and gas fields have been discovered in the six west Africa provinces since the USGS World Petroleum Assessment in 2000. These provinces were assessed because of increased energy exploration activity and new oil and gas discoveries within the provinces.
Seven provinces not assessed as part of the World Petroleum Assessment 2000 were assessed by the USGS as part of the World Assessment 2012. These provinces are (1) the Chad Province, containing Cretaceous and Cenozoic-age lacustrine, continental, and minor marine rocks; (2) the Sud Province, containing Cretaceous and Paleogene age lacustrine, continental, and minor marine rocks; (3) the South Africa Coastal Province, which contains rift, transform, and passive-margin rocks; (4) the Mozambique Coastal Province, containing rift, drift, and passive-margin rocks; (5) the Morondava Province, which contains failed rift, drift, and passive-margin rocks; (6) the Tanzania Coastal Province, containing rift, drift, and passive-margin rocks; and (7) the Seychelles Province, which contains rift and drift rocks. At the time of this assessment 157 oil and gas fields had been discovered in the seven provinces. These provinces were assessed because of increased interest and new oil and gas discoveries within the provinces.
The assessment was geology based and used the total petroleum system (TPS) concept. The geologic elements of a TPS are hydrocarbon source rocks (source rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and distribution), and traps where hydrocarbon accumulates. By using these geologic criteria, 16 conventional total petroleum systems and 18 assessment units in the 13 provinces were defined. The undiscovered, technically recoverable oil and gas resources were assessed for all assessment units.
Brownfield, M.E., comp., 2016, Assessment of undiscovered hydrocarbon resources of Sub-Saharan Africa: U.S. Geological Survey Digital Data Series 69–GG, 16 chap., variously paged, https://dx.doi.org/10.3133/ds69GG.
ISSN 2327-638X (online)
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