An overview of the geology of Tanga onshore basin: implication for hydrocarbon potential, Tanzania, East Africa

Abstract

Tanzania, like other East African countries, is seeking to increase its hydrocarbon discoveries from both onshore and offshore sedimentary basins. Although the Tanga onshore basin has the potential of adding to the hydrocarbon reserve of the country, it has very scanty literature to guide preliminary investigations into the basin prospectivity. This review seeks to highlight the petroleum system elements within the basin and how worthy it is exploring for its hydrocarbons potential. The general geology of the basin seems to have characteristics of a complete petroleum system with dolomitic limestone as source rocks and an obvious shale source rock and evidences of fossils and oil seepage around Kivundo River, although further research is needed to validate this assumption. Feldspathic sandstones are present to serve as a reservoir to economic hydrocarbon reserves. The basin has suitable thickness to provide the needed temperature and pressure for thermal maturity of any existing organic matter (OM) and to expel them from their various ‘kitchens’. Brittle structures are available to facilitate the migration of expelled kerogens. Structural straps are available via micro-folds and faults, to ensure accumulation of economic quantities that could be explored and exploited at profit. Also, the Tanga onshore basin has geological analogies that are similar to other basins’ hydrocarbon discoveries including that in Rovuma, Morondava and Songo Songo basins which are to the south of Tanga onshore basin.