Lithium de France is the first independent French operator that aims to extract heat and geothermal lithium. Their project consists in producing hot and Li-rich fluid naturally circulating inside a fracture network in the Upper Rhine Graben. Nonetheless, previous geothermal projects have highlighted the highly seismogenic nature of the faults system in this region. Therefore, mitigating the seismic risk related to deep geothermal exploitation and anticipating reservoir development is essential for the project of Lithium de France. Using the subsurface knowledge acquired during geophysical exploration campaigns, a thermo-hydro-geomechanical model has been built with the 2D finite element code DISROC. The fault zones have been divided into a discrete core zone, and an inner and an outer damage zone, represented as equivalent continuous formations. Cold fluid is injected inside the outer damage zone of a major fault zone, near 2000 meters depth. The open-hole section of the production well is located 1.2km away from the injection point at a similar depth within the fault damage zone (FDZ). In order to evaluate the reservoir storage capacity and the risks of fault reactivation, 2 ranges of permeability for the fault zones have been compared: a large permeability case and a low permeability case. The case with the largest permeability shows small fluid pressure variations (less than 20 bars after 20 years of fluid circulation), with productivity and injectivity indexes observed in similar geothermal projects such as the neighbor project of Rittershoffen. In the low permeability case, induced seismicity is expected at a similar flowrate after a few years, as observed in such geothermal projects. Therefore, a permeability anisotropy must be considered in fault zones, to account for both the storage and the geomechanical aspects of the geothermal fault reservoir.

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