Retrofitting abandoned petroleum wells as doublet deep borehole heat exchangers for geothermal energy production—a numerical investigation

Abstract

This study aims to develop a simulation model to investigate the feasibility of extracting geothermal energy from abandoned petroleum wells using doublet deep borehole heat exchangers (DBHEs) in the Western Canadian Sedimentary Basin near Hinton. A three-dimensional simulation model that simplifies heat convection to one dimension was built and verified with a conjugate heat transfer model. The simulation results show that doublet DBHEs perform better than single-well DBHEs in extracting geothermal energy from abandoned wells. The lateral branch contributed much greater to the performance than other sections in the doublet DBHE: the average temperature increase rates per unit length of different sections were 1.59, 3.53, and 1.17 °C/km after 25 years in the injection well, the lateral branch, and the production well, respectively. Employing multilateral branches can significantly improve the performance of doublet DBHEs. Besides, the outlet of the doublet DBHE had a higher static pressure than the inlet due to the thermosiphon effect. A higher production temperature led to a lower static pressure difference between the inlet and outlet of the doublet DBHE. Using doublet DBHEs, abandoned wells in the Western Canadian Sedimentary Basin near Hinton can work as a heat source either for direct use or power generation.