Understanding the evolution of Offshore Basins: Southern and Central Somalia and Implications for Hydrocarbon Exploration
October 19, 2017

Spectrum, alongside the University of Leeds and the Federal Government of Somalia, have developed a new understanding of the crustal architecture beneath offshore Somalia and proposed a number of exciting unexplored exploration plays in this truly frontier region.

Before 2014, understanding of the evolution of the Somalian passive margin had been dependent on low fold legacy 2D seismic and satellite-derived regional potential field data. Newly acquired seismic, gravity and magnetic data have facilitated the development of new theories on the evolution of the Somali passive margin.

Offshore Somalia has three main basins: Obbia Basin in the north, Coriole Basin in the centre, and Juba-Lamu Basin extending into Kenya. We note a marked difference in the crustal architecture between the Obbia and Juba-Lamu Basins, and relate these to variations in structural deformation styles generated by the fabric of the rift and ocean-plate transforms. Rift-related normal faulting, creating the basin geometry and accommodation space for deposition of Jurassic source rocks, is followed by drift, strike-slip movement, compression and inversion during multiple plate reorganisations. The variation in nature and distribution of sediments along the margin can be attributed to differences in sediment supply, depositional style, accommodation space and sub-basin tectonics.

Offshore Somalia

Figure: Crustal structure of offshore Somalia supported by gravity modelling

To the south, oceanic crust underlies a thick clastic sequence in the Juba-Lamu Basin; a lower heat flow puts the more deeply buried Late Cretaceous, Early Cretaceous and Late Jurassic source rocks in the oil-generating window. Clastic plays are identified in a series of Cretaceous folds nearshore, which are overlain by deep water fold and thrust belt complexes displaying numerous potential traps. Further offshore, large basin floor fan complexes are identified above Early Cretaceous source rock. The modelling of oil generation in this hydrocarbon system is supported by satellite optical slick analysis.

This new understanding of the crustal architecture beneath offshore Somalia is guiding our interpretation and allows us to propose a number of exciting unexplored exploration plays in this truly frontier region.

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Understanding the Evolution of Offshore Basins: Southern and Central Somalia and Implications for Hydrocarbon Exploration