Effects of calcite reactions on aquifer permeability in high-temperature aquifer thermal energy storage

Abstract High-temperature aquifer thermal energy storage (HT-ATES) in deep aquifers has generated significant interest due to its high storage capacity, compatibility with various renewable energy sources, and utilization of surplus heat from industry. This study introduces a thermo-hydro-geochemical coupled model to address the challenges of aquifer clogging and other damage, subjected to fluid temperature changes. The model is applied to assess changes to aquifer permeability and pumping pressure during water injection at various temperatures and pH conditions. This study also investigates the effect of the heterogeneous permeability distribution on HT-ATES systems. Calcium carbonate precipitation occurs near the injection well. Simulations at different pH levels reveal that the association between changes in pumping pressure and pH follows a parabolic function. Conversely, at the cold well, calcite dissolution rates and pumping pressure changes were found to exhibit a linear correlation with the injection temperature. In heterogeneous aquifers, pumping pressure at the hot well gradually increases with successive cycles, and the magnitude of pumping pressure changes grows as the correlation length increases. The results can be used to estimate permeability and pumping pressure variations near the hot well at the altered pH of the injected fluid. The results also imply a low risk of aquifer damage at the cold well. The saturation isoline map and the correlation functions provided in this study may be useful for optimizing the operating temperatures and design of water treatment measures for improved HT-ATES performance.