Comparative Simulation of Homogeneous and Heterogeneous ATES Systems Scenarios in the Permo-Triassic Sherwood Sandstone Group

Summary The Permo-Triassic Sherwood Sandstone Group (SSG) is an important formation for geothermal energy across UK basins. The UK Government, including its devolved government in Northern Ireland, has identified geothermal energy as a viable source of green energy. Although the SSG is a viable formation for aquifer thermal energy storage (ATES) systems in the UK, numerical modelling for predicting ATES system performance usually assumes homogeneity despite geological heterogeneity, which significantly contributes to hydraulic and thermal properties. This study compares the thermal recovery efficiency of ATES systems for the SSG in Northern Ireland using numerical modelling under homogeneous and heterogeneous scenarios, building on previous field studies that determined the hydrogeological and thermal properties of the SSG in three boreholes. 2D and 3D numerical models were developed in FEFLOW to evaluate the thermal storage and extraction potential of the boreholes over a ten-year operational period. The results of the numerical modelling showed a significant difference in thermal recovery efficiency, with the homogeneous model having an efficiency of over 60% and the heterogeneous model having a lower efficiency. This underscores the need for accurate site-specific characterisation and high-resolution hydrogeological data to optimise ATES performance in complex formations such as SSG.