The Tectonic Framework and Regional Hydrocarbon Prospectivity of the Gulf of Aden

The Gulf of Aden rifting predates that in the Red Sea. Isolated sub‐basins developed during the earliest Oligocene following a major emergent (erosional) period during the latest Eocene. Marine sedimentation began in the middle‐to‐late Oligocene and progressed upwards from marginal marine to bathyal environments with significant turbidite input (primarily on the Yemen side). Stretched and dike‐invaded continental crust exists in water depths greater than 1,000 m in some areas. Sea‐floor spreading began in the late Miocene and progressed westward into the Afar region. Only limited faulting has affected the post‐rift, uppermost Miocene to Recent section, which is primarily dominated by prograding sequences and thermal subsidence. With over 40,600 square kilometres of continental shelf in less than 300 m of water, the Gulf of Aden is a frontier exploration area. Only minimal exploration work has been carried out in the offshore, including twelve wells resulting in one sub‐commercial discovery and numerous indications of hydrocarbons. Thw wells drilled to‐date have encountered source, reservoir and seals in both the pre‐rift and syn‐rift section. Heat flow and thermal modelling has shown that the Gulf of Aden continental margins are not areas of excessive heat flow, and hydrocarbon generative “kitchens” can be mapped in the pre‐rift sequence. The hydrocarbon prospectivity of the Gulf of Aden differs from that in the Red Sea in that the primary hydrocarbon plays are found in the pre‐rift exploration plays exist in horst and rotated fault‐blocks within NW‐SE trending sub‐basins controlled by Upper Jurassic to Lower Cretaceous tensional tectonies. A combination structural‐stratigraphic trap has proved hydrocarbons beneath the pre‐Oligocene erosional unconformity. Syn‐rift exploration for clastic reservoirs sealed by anhydrites exists in early Oligocene transtensional sub‐basinse. The primary structure traps are rollover anticlines associated with listric growth faults. Source maturity is a significant risk for syn‐rift plays.