Development of a Novel Enhanced Geothermal System Conceptual Model for Petroleum Wellbore Repurposing in the Benue Trough Deep Thermal Province, North Central Nigeria

The global energy transition creates new engineering challenges for petroleum engineers, including the conceptual development of geothermal energy systems that leverage existing petroleum well infrastructure in geothermally favourable sedimentary basins. The Benue Trough represents a regionally elevated heat flow province where depleted or abandoned petroleum wells could potentially be repurposed for enhanced geothermal system energy extraction. This study develops a novel Enhanced Geothermal System conceptual model for petroleum wellbore repurposing in the Benue Trough deep thermal province, North Central Nigeria. The theoretical model framework integrates geological characterisation of heat flow, geothermal gradient, and reservoir rock thermal properties from compiled borehole measurements with hydraulic fracturing design considerations for EGS permeability creation at depths between 3,000 and 5,000 metres. An original thermodynamic efficiency model is derived for a doublet wellbore configuration repurposing one petroleum injector and one producer, incorporating wellbore heat exchange, fluid viscosity-temperature effects, and thermal drawdown prediction using an analytical cylindrical heat source model. Coupled thermal reservoir simulation using TOUGH2 quantifies thermal energy production over a twenty-year operational life for the conceptual system under base and optimistic permeability assumptions. Results indicate a theoretical sustainable power output of 2.4 to 8.7 megawatts electric from a single doublet, sufficient to supply distributed power needs for rural communities in the Benue Trough area. Regulatory and environmental considerations for EGS development under Nigerian mining law are discussed. Keywords: enhanced geothermal system, wellbore repurposing, Benue Trough, energy transition, North Central Nigeria.