Leveraging Abandoned Oil Wells for Geothermal Energy: A Techno-Economic Pathway to Nigeria's Energy Transition

Abstract The oil and gas industry remains Nigeria's dominant energy provider; however, global pressures for cleaner and more sustainable sources highlight the urgency of national energy diversification. One promising pathway is the repurposing of abandoned oil and gas wells for geothermal energy production, an approach that leverages existing subsurface infrastructure while significantly reducing the cost of new drilling. This opportunity could attract investment, enhance energy security, and reduce dependence on fossil fuels. Yet, the technical and economic viability of such systems in Nigeria remains largely underexplored, creating a critical knowledge gap this paper aims to address. This study develops a conceptual closed-loop geothermal system for abandoned Niger Delta wells. Wells were screened based on depth, temperature gradient, casing, and integrity; three representative cases were selected for thermo-economic modeling. A downhole U-tube heat exchanger with an insulated return leg was modeled, and multiple working fluids were evaluated for heat extraction efficiency, pumping requirements, and suitability for local geothermal conditions. The economic assessment considers well status (suspended, temporarily, or permanently plugged), including retrofitting costs, CAPEX, OPEX, surface facility costs, and levelized cost of energy (LCOE) for both direct-use and electricity generation applications. This approach enables a comparative assessment of technical and economic viability across case wells. Preliminary modeling indicates that the conceptual closed-loop geothermal system can deliver produced fluid temperatures of 131°F-167°F, sufficient for direct-use heating and low-temperature power generation. Economic analysis shows that retrofitting suspended or temporarily plugged wells is most cost-effective, with a modeled LCOE of 120-180 $/MWh and levelized cost of heat of 25-45 $/MWh. Overall, this study presents a pragmatic approach for turning decommissioning liabilities into useful energy assets while providing cleaner energy alternatives. However, widespread deployment will depend on supportive policies and integration into national renewable energy plans to enable commercial adoption.