Hydrocarbon Prospectivity in Mesozoic and Early–Middle Cenozoic Rift Basins of Central and Northern Kenya, Eastern Africa
Jean-Jacques Tiercelin, Thierry Nalpas, Peter Thuo, Jean-Luc Potdevin, 2013. "Hydrocarbon Prospectivity in Mesozoic and Early–Middle Cenozoic Rift Basins of Central and Northern Kenya, Eastern Africa", Tectonics and Sedimentation: Implications for Petroleum Systems, Dengliang Gao
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The northern (NKR) and central (CKR) segments of the Kenya Rift are among the most important areas of the East African rift system for hydrocarbon prospecting because they offer the oldest and longest lived sedimentary basins and they are a crossover area between Ce-nozoic and Cretaceous rifts. During the 1970s and 1980s, the interest of oil companies focused in the Turkana depression and the northeastern region of Kenya. Seismic reflection surveys and several exploration wells enabled the identification of several deeply buried basins: (1) In the NKR, three strings of north–south-oriented half grabens, the oldest known basins being of Cretaceous?–Paleogene to middle Miocene age; (2) In the CKR, two north–south half grabens, the Baringo-Bogoria Basin (Paleogene–Present), and the Kerio Basin (Paleogene–upper Miocene). All basins are filled by up to 8 km (5 mi) thick sediments of alluvial, fluviodeltaic, or lacustrine origin and volcanics of late Eocene to Neogene age.
New studies have focused on reservoir and/or source rock quality in several of these basins. In terms of hydrocarbon potential, arkosic sand stones in CKR or NKR demonstrate a fair to good reservoir quality, with porosity up to 25%. Strong changes in terms of diagenetic alteration relate to deformation events or change in sediment source as a result of tectonic activity and hydrothermal fluid circulation associated with volcanism. High-quality source rocks were deposited in freshwater lake environments under a tropical climate. Such environments have been identified during the Paleogene in the NKR and lower Neogene in the CKR. The combination of reservoir and source rock characteristics results in a provisional classification of each studied basin, in terms of very high to medium potential for hydrocarbons.
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The influence of tectonics on sedimentation and hydrocarbon accumulation is different among extensional, strike-slip, and contractional structural styles. Addressing the role of different structural styles and syntectonic sedimentation in petroleum systems is essential to assess the hydrocarbon potential of sedimentary basins. This 18-chapter volume is small enough to focus on the interplay among tectonics, sedimentation, and petroleum systems. Yet it is big enough to cover the diversity of structural styles in important petroliferous sedimentary basins around the globe, including those in west Africa, east Africa, east Brazil, east United States of America, Gulf of Mexico, South China Sea, the Russian Arctic, and the Mediterranean Sea.