A Simulation Approach on the Techno-economic Feasibility of Wells in Depleted Oil Reservoirs for Geothermal Well Systems in the Niger Delta

Majority of matured and abandoned wells in depleted oil reservoirs in the Niger Delta are becoming economically unviable. Recently, application of geothermal well system has gained acceptance in the re-use of wells in depleted oil reservoirs. Unfortunately, there are limited studies in the conversion of matured and abandoned wells into geothermal well system in the Niger Delta. Therefore, this study evaluates the techno-economic feasibility of applying geothermal well systems (GWS) in wells in depleted oil reservoirs in the Niger Delta. In this study, characterization and screening of the gathered data from wells in depleted oil reservoirs were performed for GWS application, considering a reservoir temperature above 80°C (176°F) and a water cut of more than 85%. The screened well data were modelled using petroleum production software, PROSPER™, to evaluate their performances and estimate geothermal gradients. A model was developed from a simple regression technique in Microsoft Excel software to predict fluid flowing temperature gradient, using the simulated geothermal data. From the result, the temperature gradient varies by 0.011°F/ft. Estimation of overall heat recovery was then calculated with a simplified heat model, considering an open loop vertical coaxial single geothermal well system. The estimated overall heat recovery ranged from 0.1 MW to 8 MW, for the wells under study. Sensitivity analyses were also conducted to assess the impact of various operating parameters on the overall heat recovery. Finally, economic analyses were performed to evaluate the economic viability of converting matured and abandoned oil wells into geothermal well systems; the simplified economic analyses, considering net present value (NPV), showed geothermal well system with heat capacity above 5 MW to be economically viable. The study demonstrates that wells in depleted oil reservoirs in the Niger Delta can be effectively repurposed for geothermal electricity generation.