Different roles of tectonic events in the development history of the coastal Tanzania basin: remote sensing mapping and seismic interpretation results, and their implications for petroleum prospectivity.

The northern and southern parts of the coastal Tanzania basin have different petroleum potentials. This difference may be attributed to several local factors including tectonic influences, orientation of different tectonic structures, and sedimentation mechanism. These aspects have not been the focus of the previous studies, thus making it difficult to have a full understanding of key factors for different petroleum potentials between the northern and southern parts of the study area. We used remote sensing mapping and 2D seismic interpretation to assess possible differences in sedimentation mechanism, occurrence, and orientation of tectonic features along the coastal Tanzania basin. Results of this work have shown that the coastal Tanzania basin contains NNE-SSW trending tectonic zones characterized by several tectonic blocks with multiple trends and dip directions. Orientations of these tectonic blocks and the associated bounding faults are believed to be one of the factors for different petroleum potentials between the northern and southern coastal Tanzania basin. The associated tectonic events created structures that influenced sedimentary and structural development of the basin. The created structures allowed deposition of fine-grained deposits with source and seal potential, coarse-grained deposits with reservoir potential, and formation of fault systems and localized folds that controlled migration, and trapping and seepage of the generated hydrocarbons. These structural features also form potential petroleum prospects in the basin. The post-Miocene faulting and the associated negative flower structures have fragmented the Pliocene–Quaternary potential prospects and created possible seepage pathways. This might be the reason behind limited petroleum potential for the Pliocene–Quaternary reservoirs compared to the Cretaceous and the Paleocene-Miocene reservoirs of the coastal Tanzania basin. Remote sensing mapping has also allowed demarcation of the Ruvuma and Mandawa deltaic systems that were the dominant sedimentation mechanisms during the Jurassic-Tertiary period. These systems are not mapped further north of the study area, and may also be used to explain significant gas discoveries in the southern coastal Tanzania basin. Therefore, we conclude that different in sedimentation mechanism, orientation of the mapped tectonic blocks, and localized tectonic events are the main reasons for differences in the hydrocarbon potential between northern and southern regions, and for different parts of the studied sedimentary cover. [ABSTRACT FROM AUTHOR]