Advanced geothermal energy storage systems by repurposing existing oil and gas wells: A full-scale experimental and numerical investigation

Advanced Geothermal Energy Storage systems provides an innovative approach that can help supply energy demand at-large scales. They operate by injection of heat collected from various sources into an existing well in low temperature subsurface to create an artificial and sustainable geothermal reservoir to enable electricity generation. Very few studies investigated this approach, but those relied on hypothetical scenarios. Therefore, this study focuses on the field-scale investigation of an Advanced Geothermal Energy Storage in the low-temperature Illinois basin. A systematic preliminary data analysis was conducted to probe thermal energy storage properties of the subsurface. A full-scale field test was performed to delineate the subsurface thermal processes. Results from the field test were used to calibrate a two-dimensional axisymmetric numerical model for a single push/pull well. Various operational schemes were simulated for using the validated numerical model. The results indicated that the energy storage efficiency might reach up to 82% and the extracted fluids could generate an electrical power of 5.74 MW in five years for a simultaneous monthly injection and production scheme with an initial 90 days charging period. The proposed system which benefits from existing infrastructure, offers an economical and environmental approach for thermal storage with high storage efficiency.