Geology, Geophysics and Geochemistry in the Upper Rhine Graben - the frame for geothermal energy use

Abstract

Deep geothermal energy, namely EGS (Enhanced Geothermal System), has been successfully developed in the Upper Rhine Graben (URG) based on a full geological, geochemical and geophysical characterization of deep fractured reservoirs. Over the last 30 years, many geothermal sites have been developed for electricity generation via binary system (Soultz-sous-Forêts, Bruchsal, Insheim, Landau) to fully thermal project operating at high temperature (Rittershoffen). A series of new geothermal projects for heat and/or power generation in the URG is targeted (Illkirch, Reichstett, Wissembourg, …) which demonstrated the impact of the lessons learnt on the pilot Soultz research project. Based on various geoscientific deep drilling data collected between 2.5 and 5 km depth, it has been shown that geothermal resource corresponding to very saline fluids is trapped into the natural fracture network at the sediments-basement interface.