Abstract
Realistic modelling of heat transport in low-enthalpy geothermal reservoirs is essential for optimizing energy extraction and ensuring long-term system efficiency. This study investigates the impact of sedimentary heterogeneity and model resolution on fluid flow and heat transport within a geothermal doublet system. Geocellular models representing a sand-prone meander-belt succession were developed that incorporate multiple scales of geological heterogeneity. Reservoir simulations were conducted using MODFLOW-2005 and MT3D-USGS to evaluate how grid resolution and hierarchies of sedimentary heterogeneity influence hydraulic head evolution (reservoir pressure distribution), and thermal breakthrough. Results indicate that, although grid resolution does not show a clear correlation with temporal hydraulic head changes, higher-resolution grids tend to generate greater absolute head differences over time, likely due to their ability to capture localized variations in hydraulic conductivity and flow resistance. Additionally, the study reveals that increased geological heterogeneity leads to enhanced pressure buildup at injection wells, irrespective of well orientation. Regarding doublet performance, no systematic correlation is observed between grid resolution and fluid-temperature changes, whose prediction is, however, impacted by the hierarchy of depositional units incorporated in the static models. These findings emphasize that, although increased resolution improves flow behaviour representation, geological heterogeneity plays a more critical role in shaping pressure and temperature evolution in geothermal-doublet systems.