Analysis of Injection Capacity of Aquifer Thermal Energy Storage System

Aquifer thermal energy storage (ATES) is a technique to conserve thermal energy while reducing carbon dioxide (CO2) emissions. ATES system utilizes heat by injecting hot or cold water into subsurface aquifers and recovering it when there is a heating or cooling need. In recent years, the interest in ATES systems has been gradually increasing in North America, and the technique is becoming an important part of the energy transition process. However, there lacks enough research on ATES in North America, especially its impact on the subsurface environment and the necessary regulations. This research aims to analyze one of the seldom investigated but important limiting factors of the ATES operation, the injection pressure. With an undesired injection pressure, the well operations could trigger fractures near the injection zone and create pathways for the injected fluid, causing cross-contamination or surface flooding. This research simulates long-term ATES operations in COMSOL. The numerical simulation results are benchmarked with several analytical results under simplified aquifer and operational conditions. The upper limit of injection pressure is quantified while maintaining an appropriate energy storage efficiency and avoiding negative environmental effects. Alternative solutions such as substituting conventional vertical to horizontal wells to reduce fracturing possibilities are proposed and compared.