Review of Hydrocarbon Prospectivity and Source Rock Evaluation of the Abakaliki Trough, South East Nigeria

The Abakaliki Trough in South East Nigeria forms part of the southern Benue Trough system and contains Cretaceous sedimentary sequences with documented organic matter that merits systematic source rock evaluation to assess hydrocarbon prospectivity. This study reviews the hydrocarbon prospectivity of the Abakaliki Trough using published geochemical analyses of outcrop samples, borehole data, and petroleum system modelling results. Total organic carbon measurements from Albian to Campanian age mudstones compiled from published literature range from 0.5 to 4.2 weight percent, with Turonian black shales recording the highest values. Rock-Eval pyrolysis data indicate predominantly Type II and mixed Type II/III kerogen in the Turonian intervals, with the remaining sequences dominated by Type III terrestrial organic matter. Vitrinite reflectance data from boreholes indicate that the Turonian source rocks have reached early to mid-oil window maturity levels at depths exceeding 2,500 metres in the deepest part of the trough. Basin modelling using PetroMod 2D software with an assumed heat flow history constrained by maturity profiles indicates that peak hydrocarbon generation commenced in the late Oligocene and continues to the present day. The study identifies the eastern Abakaliki sub-basin as the highest-priority exploration area for further evaluation, based on the combination of adequate source rock richness, favourable maturity window, and proximity to documented structural traps. Keywords: hydrocarbon prospectivity, source rock, Abakaliki Trough, South East Nigeria, petroleum system.