Deltaic sedimentation mechanisms in the southern Tanzania continental margin and their influence on reservoir occurrence

The Mandawa and Ruvuma deltaic depositional systems are part of the Cretaceous and Cenozoic successions, respectively, of the coastal Tanzania Basin. The two systems have not been extensively investigated from both sedimentological and geophysical perspectives. Their similarities and differences, depositional characteristics, and evolution are poorly understood. A detailed understanding of the Mandawa and Ruvuma deltaic systems will be of interest to the scientific community and hydrocarbon exploration companies working in the region. Remote sensing and seismic interpretation methods were used in this study to characterize these systems. Remote sensing mapping showed that the Ruvuma Delta overprinted the Mandawa Delta, confirming that the former is younger than the latter. Seismic data interpretation from the Mandawa and Ruvuma deltaic systems have revealed that the two contain Cretaceous and Cenozoic reservoirs of the southern Tanzania continental margin, respectively. These reservoirs have similar characteristic seismic expressions and are included in the migrating channel complexes and sheet sands enclosed by thick channel levee/drift successions. The reservoirs were deposited following an interplay of tectonics, sedimentation mechanisms, and sea-level changes. This study demonstrates that deltaic sedimentation is crucial for hydrocarbon occurrence in the Tanzania continental margin. The remote sensing method applied in this study effectively identified the locations of deltaic lobes relative to hydrocarbon discoveries in the study area. The method may be used to assess petroleum prospectivity and allow further exploration of other hydrocarbon fields where similar depositional systems are present.