Mineral precipitation in geothermal reservoir : the study case of calcite in the Soultz-sous-Forêts enhanced geothermal system

Abstract : The results of a calcimetry performed on cuttings from the 3 wells of the Enhanced Geothermal System of Soultz-sous-Forêts (France) are compared to other available data (petrography, mineralogy, fracture zones, flow pathways, etc...). The relationship between flow ranking and calcite content for the fracture zones of GPK3 and GPK4 is opposite to the one of GPK2 (the better the fluid flow, the lower the calcite content). This suggests that the fracture zones of GPK2 are different from those of GPK3 and GPK4, and that the connectivity to the fracture network may be different too. The results of this study provide also some explanation for the effects of the chemical stimulations performed in the 3 wells, as well as some information for future chemical stimulations that could be aimed to improve the connectivity between the wells and the fracture network.