Investigating the impact of wellbore lateral heat transfer on the performance of high-temperature aquifer thermal energy storage system by the coupling of wellbore and reservoir simulators

Abstract

This study investigates the often-overlooked impact of wellbore lateral heat transfer on high-temperature aquifer thermal energy storage (HT-ATES) systems, focusing on the Swiss Bern project. We coupled our in-house wellbore simulator (Moskito) with the reservoir simulator (PorousFlow) under the MOOSE framework to analyze wellbore heat loss. Utilizing both numerical and analytical approaches, we reveal how wellbore heat loss affects HT-ATES performance compared to previous studies that ignored it. Our sensitivity analysis examines various wellbore configurations and operational parameters, evaluating performance indicators including extracted energy, wellbore lateral heat loss fraction, and reservoir heat loss fraction. Key findings include: a more than 10 % difference between the analytical and numerical calculations of wellbore lateral heat loss. Smaller wellbore diameters, such as 6.75 inches, enhance energy recovery efficiency by enabling larger fluid extraction volumes. Low thermal conductivity wellbore casing materials (e.g., 0.045 W m⁻¹∙K⁻¹) could reduce wellbore lateral heat loss by 51.4 %. Although energy recovery efficiency declines with more supporting wells during the initial storage cycle, three supporting wells yield the best performance in later cycles due to larger extracted fluid volumes. High flow rates (e.g., 25 L s⁻¹) enhance energy recovery efficiency by decreasing heat losses through faster fluid movement, which reduces residence time and thermal diffusion. While high fluid injection temperatures (e.g., 210 °C) increase heat losses, overall heat loss fractions decrease due to significant injected energy. This study highlights the critical role of wellbore lateral heat loss in evaluating the performance of the HT-ATES system, providing insights on how to design and optimize these systems.