Structural Mapping and Prospect Risking of Hydrocarbon Traps in the Sokoto-Rima Basin, Zamfara State, North West Nigeria

The Sokoto-Rima Basin in Zamfara State, North West Nigeria, is an underexplored sedimentary province with documented surface hydrocarbon seeps and favourable structural elements that have not been systematically evaluated for petroleum prospectivity. This study presents a structural mapping exercise and applies a systematic prospect risking methodology to identified hydrocarbon traps within the basin. Gravity and magnetic anomaly data from federal government geophysical surveys, combined with satellite imagery structural lineament mapping, were used to delineate subsurface structural elements including anticlines, half-grabens, and fault-bounded closures. Three prospective trap types were identified: simple compressional anticlines in the north-western portion, inversion anticlines related to Eocene compressional reactivation of extensional faults, and basement-cored structural highs in the east. A probabilistic risking workflow was applied to each trap, evaluating geological chance factors for reservoir presence, seal integrity, charge adequacy, and structural closure. The geologic probability of success for the highest-ranked prospect is estimated at 18 percent based on calibration of analogous basin risks in West Africa. The study recommends acquisition of a regional seismic reflection programme as the minimum data acquisition needed to convert these gravity-defined structures to drillable prospects and to confirm the presence of porous Cretaceous reservoir facies at drilling depths below 1,500 metres. Keywords: structural mapping, prospect risking, Sokoto-Rima Basin, Zamfara State, hydrocarbon trap.