Analysis of the impact of confining layers on aquifer thermal energy storage (ATES) systems with a horizontal well doublet

Aquifer thermal energy storage (ATES) utilizes groundwater aquifers to store excess heat and conserve energy. The system is gaining popularity due to its potential in the energy transition as a renewable energy source. To better design the ATES system, it is critical to understand and model the heat transport process in the domain. Current studies applying numerical and analytical solutions to simulate ATES systems often simplify the model by ignoring the confining layers. Additionally, some studies fail to consider both transverse and longitudinal heat conductivity in this mode. This study presents a novel approach to modeling the ATES system by incorporating upper and lower confining layers with different geological materials. The thermal anisotropy of confining materials is incorporated into the model to evaluate the influence of transverse and longitudinal heat transport processes on thermal energy loss in the aquifer. More importantly, the model is tested with horizontal well doublets, which have not been discussed before. The results indicate that the horizontal well is as compatible as conventional vertical wells under the parameters used in this study. Ignoring confining layers, however, will overestimate the system’s recovery efficiency. With relatively large injection and extraction rates, the anisotropy of the confining materials has a minimal impact on the system. Overall, considering the existence of confining layers is critical for accurate ATES system modeling, and more accurate analytical or numerical models are still needed to better constrain the relative importance of each thermal parameter.