Seismic stratigraphic framework, dispersal of depocenters, and helium reservoirs in the Rukwa Rift Basin, Tanzania

The Rukwa Rift Basin (RRB) in the southwestern Tanzania presents favourable geological conditions for the occurrence and accumulation of helium gas. However, the evolution and dynamics of these favourable conditions in relation to helium remain complex. In this study, laboratory- cored samples, 2D seismic reflection data, Digital Elevation Model (DEM) and well data are integrated to map the distribution of sediment accumulation and potential helium reservoirs. The isochron and time-thickness maps unveil that the RRB experienced a shift in depocenter location and progressive strata dispersal in space and time during each of the rifting phases from the late Paleozoic to the late Cenozoic. The results reveal a change in morphology while distribution of depocenters is defined by topographic highs related to footwall uplift during a multiphase rifting history that modulated the deposition, differential erosional patterns, drainage system and sediment routing in the RRB. The depocenters to the south of the Saza shear zone might have been isolated initially during Karoo rifting, contiguous during Cretaceous and linked into a single main depocenter during the latter stages of rifting between late Miocene and Pleistocene. Petrophysical analysis reveal high porosity and permeability ranges, that is ∼26–30 % and ∼ 272.7–660.6 mD respectively. These petrophysical parameters are high enough for potential helium reservoirs comprising sandstone sequences mainly in the Karoo and Red Sandstone formations.