Etude stratigraphique, pétrographique et diagénétique des grès d'âge Crétacé-Paléogène de la région ouest du bassin du lac Turkana, Kenya. Conséquences sur leurs caractéristiques réservoir et l'évaluation du potentiel pétrolier du nord-ouest du Kenya.

摘要

Because they offer the oldest and longest-lived sedimentary basins and they are a cross-over area between Cenozoic and Cretaceous rifts, the Northern (NKR) and Central (CKR) Kenya Rifts are among the most important areas of the East African Rift for hydrocarbon prospecting. During the 70s and 80s, the interest of oil companies focussed in the Turkana depression and the northeastern region of Kenya. Seismic refiection surveys and several exploration wells allowed the identification of several deep buried basins: 1) In the NKR, 3 strings of N-S oriented half-grabens, the oldest known basins being of Cretaceous(?)-Paieogene to middle Miocene age; 2) In the CKR, two N-S half-grabens, the Baringo Basin (Paieogene-Present) and the Kerio Basin (Paleogene-upper Miocene). All basins are filled by up to 8-km thick of alluvial, fluvio-deltaic or lacustrine sediments and volcanics of late Eocene to Neogene age. New sedimentological studies have focussed'on reservoirtsource rock quality in several of these basins. In terms of hydrocarbon potential, arkosic sandstones in CKRlNKR such as the Lapur Sandstone Formation or the Muruanachok Sandstone Formation demonstrate a good reservoir quaiity with porosity up to 25 %.Strong changes in terms of diagenetic aiteration relate to deformation events (burialtupiif!) or change in sediment source. High quaiity source rocks relate to freshwater lake environments under tropical climate. Such environments have been identified during Cretaceous-Paleogene in the NKR and iower Neogene in the CKR and can be envisaged to occur in basins of same age that are highly under-explored.