Geodynamic evolution and hydrocarbon potential of sedimentary basins of northern Somalia

Seismic reflection profiles, gravity, deep exploratory well and outcrop data have provided the key subsurface information needed to better understand the tectonic subsidence, uplift history and hydrocarbon potential of the rifted basins (Guban, Nogal and Daroor) in the northern Somalia. Regional seismic reflection profiles show that the northern Somalia sedimentary basins can be divided into five main stratigraphic sequences: (1) Middle- Late Jurassic syn-rift sequences (Adigrat Group), (2) ?Cenomanian-Campanian syn-rift sequences (Gumburo Group), (3) Campanian-Maastrichtian syn-rift sequences (Jesomma Sandstones), (4) Palaeocene post-rift sequences (Auradu Limestones), (5) Early-Middle Eocene post-rift sequences (Taleh Formation) and (6) Oligocene-Miocene (Nogal Group) syn-rift sequences. Backstripping of deep exploration wells suggests three rifting events in northern Somalia that are interrupted by periods of uplift and erosion. The first rifting event was initiated in the Kimmeridgian and resulted in the deposition of synrift sequences of Bihendula Group. Both clastic and carbonate reservoirs and significant source rocks are developed in this group, sealed either by intraformational shale or by overlying salt. Rifting resulted in the development of structural traps in the form of horsts and tilted fault blocks. The initial rifting phase is interpreted as result of the late-stage breakup of the Gondwana when Africa and Madagascar separated. The second rifting event was initiated during the Campanian-Maastrichtian duration and resulted synrift sediments comprising Jessoma formation and Gumburo sandstones. These reservoir facies provide the primary exploration target in the Guban, Nogal and Daroor basins. The final rifting event was in the Oligocene-Miocene and is related to the opening of the Gulf of Aden. Reactivation of faults during the Oligocene-Miocene is known to have modified pre-existing traps throughout northern Somalia, in particular Guban basin along the Gulf of Aden. In the northern Somalia, Jurassic rift basins form the main exploration plays. Secondary exploration targets include Oligocene-Miocene rift sequence of the Gulf of Aden together with underlying pre-rift Eocene carbonates. The main seals for the different plays are various shales, some of which are also source rocks, but the Early Eocene evaporates of the Taleh formations can also perform a sealing role for Paleogene or older generated hydrocarbons migrating vertically.