Numerical modeling of a coaxial borehole heat exchanger to exploit geothermal energy from abandoned petroleum wells in Hinton, Alberta

Deep petroleum wells are often associated with high bottom-hole temperatures and can provide a cost-effective way to produce geothermal energy. The goal of this study is to develop a reliable simulation model to demonstrate the feasibility of extracting geothermal energy with deep coaxial borehole heat exchangers in abandoned petroleum wells in the Western Canadian Sedimentary Basin. Our simulation model was constructed with COMSOL Multiphysics and verified with analytical results. The temperature dependence of the working fluid's (water) and the reservoir rocks' thermodynamic properties were found to significantly affect the long-term performance of the heat exchanger. The production temperature and the geothermal well power stabilize at similar to 29 degrees C and 0.38 MW, respectively, during long-term running of the model. The performance of the heat exchanger can be controlled by varying the injection flow rate, the injection temperature, and the thermal conductivity of the insulating pipe. Heat exchanger performance is only marginally affected by a thermally insulated section at the top of the well casing. We conclude that abandoned petroleum wells in the Western Canadian Sedimentary Basin have a great potential for geothermal exploitation using coaxial borehole heat exchangers. (C) 2019 Elsevier Ltd. All rights reserved.