Simulation of Mineral Precipitation and Dissolution in the 5-km Deep Enhanced Geothermal Reservoir at Soultz-sous-ForÍts, France

Abstract

The long-term behaviour of the Soultz-sous-ForÍts enhanced geothermal reservoir has been investigated. Major processes susceptible to modify the properties of the reservoir were taken into account. Heat, fluid transport and geochemical reactions are coupled for modelling the reactive flow. As the fluid is a hot brine, a new code was built to simulate the Thermo-Hydraulic and Chemical effects (THC) within the fractures connecting the injection and production wells. The results revealed that re-injection of the formation brine after cooling changes the chemical equilibrium states between the formation fluid and different minerals present in the host rock. Due to their fast reaction rates, carbonate minerals are responsible for most of the reservoir evolution. Amounts of quartz and pyrite deposited are negligible during the period of simulation. In order to improve the hydraulic performance of the reservoir, the effects of acid addition and temporary reverse circulation of fluid were also investigated.