PETROLEUM GEOLOGICAL CHARACTERISTICS AND EXPLORATION PROSPECTS IN TANZANIA BASIN, EAST AFRICA

In recent years, a total of fourteen large and medium gas fields have been discovered in the Tanzania basin, along the East African coast, which makes Tanzania the focus of deepwater hydrocarbon exploration in the world. On the basis of regional geologic information and the previous researches, we made a brief summarization of the tectono-sedimentary evolution of the basin and the assemblage of petroleum systems in it. Prediction of exploration prospects is also made on the basic data. It is suggested that there occur three sets of source rocks in the basin, i.e. the Middle-Upper Jurassic restricted marine shale, Lower Cretaceous deltaic shale and Upper Cretaceous marine shale. The main reservoirs are consisting of the lower Cretaceous fluvial sandstone and Upper Cretaceous, Paleocene and Oligocene deep channel sandstone with the Middle Jurassic sandstone and limestone as potential reservoirs. In the basin, the Jurassic-Neogene shale and clay deposits occur as excellent regional and interlayer seals. The gas pools are dominated by structural traps both onshore and offshore, and in deep-water they are dominated by structural and stratigraphic traps. Further exploration targets should be put on the slope fans and submarine fans formed by gravity current and channel filling sediments since Cretaceous.