Assessment of Undiscovered Oil and Gas Resources of the Sud Province, Central- East Africa By Michael E. Brownfield M ED ATLANTIC ITE RRAN OCEAN EAN SEA Sud Province INDIAN OCEAN Central African Rifts Assessment Unit SOUTH ATLANTIC OCEAN Click here to return to Volume Title Page Chapter 14 of Geologic Assessment of Undiscovered Hydrocarbon Resources of Sub-Saharan Africa Compiled by Michael E. Brownfield \\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch14_figures\ch14_figures\ch14_cover.aiDigital Data Series 69–GG U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Director U.S. Geological Survey, Reston, Virginia: 2016 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS. 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ISSN 2327-638X (online) iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Tectonic History and Geology of the Sud Province and Central African Rifts Assessment Unit, Central-East Africa .................................................................................................................4 Source Rocks.........................................................................................................................................4 Reservoir, Traps, and Seals .................................................................................................................4 Exploration ....................................................................................................................................................10 Geologic Model ............................................................................................................................................10 Summary........................................................................................................................................................10 For Additional Information ..........................................................................................................................10 Acknowledgments .......................................................................................................................................10 References ....................................................................................................................................................12 Figures 1. Map showing the Sud Province, Central African Rifts Assessment Unit, central- east Africa ......................................................................................................................................2 2. Map showing generalized geology of central-east Africa ....................................................3 3. Map showing western and central African rift system, and West African rift subsystem and central African rift subsystem ........................................................................5 4. Geologic cross sections of the western part of the Bongor and Doseo Basins, in western Sud Province, central-east Africa .........................................................................6 5. Generalized stratigraphic columns of the Doba, Doseo, and Salamat Basins, Central African Republic and Chad, central-east Africa .......................................................7 6. Generalized stratigraphic columns of the Muglad and Melut Basins, southern Sudan .............................................................................................................................8 7. Geologic cross sections of the Muglad and Melut Basins ....................................................9 8. Events chart for the eastern part of the Cretaceous-Tertiary Composite Total Petroleum System (704601) and the Central African Rifts Assessment Unit (70460101) .....................................................................................................................................11 9. Events chart for the western part of the Cretaceous-Tertiary Composite Total Petroleum System (704601) and the Central African Rifts Assessment Unit (70460101) .....................................................................................................................................11 Table 1. Sud Province and Central African Rifts Assessment Unit assessment results for undiscovered, technically recoverable oil, gas, and natural gas liquids ....................12 iv Abbreviations Used in This Report km2 square kilometers m meter mD millidarcy mg/g milligrams per gram AU assessment unit D darcy HI hydrogen index TOC total organic carbon TPS total petroleum system USGS U.S. Geological Survey Assessment of Undiscovered Oil and Gas Resources of the Sud Province, Central-East Africa By Michael E. Brownfield Abstract The U.S. Geological Survey estimated mean volumes of undiscovered, technically recoverable conventional oil The main objective of the U.S. Geological Survey’s and gas resources for the Central African Rifts Assessment National and Global Petroleum Assessment Project is to assess Unit in the Sud Province. The mean volumes are estimated the potential for undiscovered, technically recoverable oil at 7,310 million barrels of oil, 13,218 billion cubic feet and natural gas resources of the United States and the world. of gas, and 353 million barrels of natural gas liquids. The As part of this project, the U.S Geological Survey recently estimated mean size of the largest oil field that is expected to completed an assessment of the Sud Province, an area of be discovered is 1,112 million barrels of oil, and the estimated approximately 978,800 square kilometers that covers parts of mean size of the expected largest gas field is 3,677 billion the of Central African Republic, Chad, Ethiopia, and Sudan. cubic feet of gas. For this assessment, a minimum undiscov- This assessment was based on data from oil and gas wells, ered field size of 1 million barrels of oil equivalent was field production records, and published geologic reports. used. No attempt was made to estimate economically The Sud Province was assessed because of increased recoverable reserves. exploratory activity and interest in its future oil and gas potential. The assessment was geology based and used the total petroleum system concept. The geologic elements of a Introduction total petroleum system consist of hydrocarbon source rocks (source-rock maturation and hydrocarbon generation and The main objective of the U.S. Geological Survey’s migration), reservoir rocks (quality and distribution), and traps (USGS) National and Global Petroleum Assessment Project is (for hydrocarbon accumulation). Using these geologic criteria, to assess the potential for undiscovered, technically recover- the U.S. Geological Survey defined the Cretaceous-Tertiary able oil and natural gas resources of the United States and the Composite Total Petroleum System with one assessment world (U.S. Geological Survey World Conventional Resources unit, the Central African Rifts Assessment Unit, encompass- Assessment Team, 2012). As part of this project, the USGS ing about 848,825 square kilometers, that extends beyond the in 2012 completed an assessment of the Sud Province (fig. 1), Sud Province boundary. The assessment unit contains parts of an area of approximately 978,800 square kilometers (km2) that the Central African Republic, Chad, Ethiopia, Kenya, Sudan, covers parts of the of Central African Republic, Chad, Ethiopia, and Tanzania. and Sudan. This assessment was based on data from oil and gas Hydrocarbons were generated from Cretaceous and wells, field production records, and published geologic reports. Paleogene lacustrine rocks in the rift basins and from A geologic map of central-east Africa is shown in figure 2. Paleogene lacustrine source rocks and possibly from The Sud Province was assessed because of increased Cretaceous marine source rocks in the Kenyan Anza rift energy exploration activity and interest in its future oil and basin. Generation most likely began in the Late Cretaceous gas potential. The assessment was geology based and used the and continues to the present. Hydrocarbons migrated into total petroleum system concept. The geologic elements of a Cretaceous and Paleogene reservoirs and structural traps. total petroleum system consist of hydrocarbon source rocks Traps include