Reinjection of reservoir fluids as part of deep geothermal energy production can lead to both, precipitation and dissolution of minerals in the local fracture network. Thereby, the hydraulic and mechanical rock properties will change. Within the framework of the joint project ReSalt, funded by the BMWi, the work of the engineering geology sections focuses on the characterization of reservoir analogs with respect to the geometry of the fracture network, the determination of the rock mechanical properties of the rocks and fractures, as well as the upscaling from the laboratory to the reservoir scale. The geological survey and sampling of two quarries, which serve as outcrop analogs, is performed using terrestrial laser scanning (see figure on the right) and drill cores, respectively. The mechanical properties of the rocks and fracture surfaces are determined by uniaxial and triaxial tests as well as direct shear tests in the laboratory.