Fracture-matrix heat exchange quantification in thermal reservoirs: A coupled numerical and experimental study – FraMatEx

The project FraMatEx aims to improve the understanding of fracture and matrix heat exchange, resulting in enhanced efficiency of heat extraction in low-enthalpy geothermal energy production. Considering that the direct measurement of fracture-matrix heat exchange rate is difficult, indirect methods like electrical geophysics provide valuable insights. Electrical resistivity tomography have shown promising results in identification of active fractures. Here we propose the use of complex resistivity measurement by applying induced polarization (IP) method to measure heat loss plume and heat exchange between fractures and adjacent porous matrix. Nevertheless, the IP results need to be quantified using advanced numerical techniques to be clarified and exempt from ambiguous interpretation. To these ends, the project is structured into three work packages (WP). WP1 involves experimental work using IP to measure thermal exchanges in fractured sandstone samples. Various fracture configurations and thermo-hydrodynamic conditions will be tested to produce data for later numerical analysis. WP2 focuses on developing advanced numerical models using machine learning, particularly physics-informed neural networks, to quantify exchange rates and improve existing semi-empirical models. Data from WP1 will be used to refine these models, which will be integrated into simulators for fractured porous media. WP3 consists of a mini-field scale study to validate findings from WP1 and WP2 in a controlled field environment. This involves real-time complex electrical resistivity monitoring and heat transfer measurements in an artificial platform, with dimensions of few tens of meters in horizontal plane and few meters in depth (i.e., PEGGHY). The coordinator, Behshad Koohbor is an associate professor of hydrogeology in the University of Lorraine working in GeoRessources laboratory. The funding is asked for hiring two post-doctoral researchers for an overall period of 36 months.