Influence of Meander-Belt Sedimentary Architecture on Performance of Low-Enthalpy Geothermal Doublet: Insights From High-Resolution Heat-Transport Simulations

This work is a study on the impact of sedimentary heterogeneity on groundwater flow and heat transport with a focus on meander-belt fluvial successions acting as low-enthalpy geothermal reservoirs. Geocellular models were generated to represent three types of meander belts produced by rivers that were ca. 12 m deep and include km-scale long and wide point-bar elements. Well doublets of typical spacing were placed on individual point-bar elements. Groundwater-flow and heat transport models were developed using MODFLOW 2005 and MT3D-USGS, respectively. The results suggest a relationship between the shape of the thermal plume and aspects of sedimentary heterogeneity. Mud plugs are a significant cause of asymmetry on thermal plume propagation, whereas discontinuous mud drapes have limited impact. The presence of openwork gravels, which act as thief zones, does not necessarily cause a reduction in thermal breakthrough time, although their impact is dependent on their orientation relative to the well doublet. The results of this study can assist the optimization of well-doublet planning based on knowledge of the subsurface. Yet, the impact of sedimentary heterogeneity in the successions of meandering rivers warrants further investigation, to be undertaken considering a wider natural variability of meander-belt sizes, architecture and styles of facies heterogeneity.