Hydrocarbon generation potentials of the EzeAku Shale, Southern Benue Trough, Nigeria

This study is a contribution to our understanding of the hydrocarbon potentials of the EzeAku Shale in the Lower Benue Trough, Nigeria. It assessed the hydrocarbon generation potentials and timing of the EzeAku Shale—source horizon encountered in Amansiodo-1 well drilled in the basin using one-dimensional Genesis Zetaware basin modelling software. This software allowed the integration of burial and thermal effects on EzeAku source rock with kinetic inputs. The result of the model indicates that the EzeAku source horizon encountered at 3,490 m in Amansiodo-1 well expelled 285 mg/gTOC of oil and 80 mg/gTOC of gas. The hydrocarbon generation began in Early Santonian but was breached as remote uplift was still taking place. Maximum expulsion occurred at the end of Santonian (83 My) at the rate of 90 mg/gTOC/My. Hydrocarbon expulsion resumed later after the Santonian inversion in the Campanian (80 My) and Palaeocene (61 My) at the rate of 30 mg/gTOC/My and 10 mg/gTOC/My, respectively. The huge volume of hydrocarbons expelled at the end of Santonian from this source horizon could be due to early maturation under increased heat during the inversion. Subsequent expulsions occurred as the uplift gave way to subsidence in the Campano–Maastrichtian time. The current seepages observed in the basin at the nose of the anticlinorium could suggest a possible migration of the generated hydrocarbons through the open unconformity and fault planes.