Geothermal represents a promising energy source to satisfy the growing energy needs with only minimal environmental impacts. To develop and test new technologies for energy production and storage in geothermal reservoirs, deep understanding of heat transport in fractured media is critically needed. The THERM project focuses on the investigation of heat transport and associated thermo-hydro-mechanical (THM) processes occurring during the lifetime of a geothermal reservoir. Fractured reservoirs, such as those found in enhanced geothermal systems, are characterized by a strong hydraulic and transport complexity coming from the fractures’ surface roughness, from their arrangement in networks, and from the interaction of the fractures with the surrounding rocks. As a result, the characteristics of the hydro-thermal flow which occurs when a cold fluid is injected into a hot fractured rock mass are controlled by fracture network discontinuities and properties of fracture surfaces themselves. While progresses have been made in characterizing and modeling subsurface heterogeneity in flow and solute transport processes, the effects of multi-scale subsurface heterogeneities on heat transport remains an open question. I propose new 3D fully coupled physical-based numerical models at different scales associated to state-of-the-art field experiments to develop a quantitative understanding of complex coupled processes occurring along fluid-rock interfaces during fluid circulation in geothermal systems. The main objectives are (i) to characterize the combined effect of fracture-scale and network-scale heterogeneity on flow and heat transport phenomena, and (ii) to design new field experiment to jointly measure the integrated THM behavior of fractures. Thanks to THERM, the ER will receive a unique multidisciplinary scientific training by Rennes 1 University that will reinforce significantly her expertise for future research activities and open new perspectives for career.