Current Status of the EGS Soultz Geothermal Project (France)

Over two decades of research and development of the EGS Soultz reservoir carried out with French, German and Swiss governmental and European funding, a pilot geothermal power plant have been built by a French-German industrial consortium. The drilling of three boreholes to 5 km, the deepest penetration of crystalline rock in France, has yielded fundamental insights into the geology, nature of fracturing, fluid geochemistry, temperature and hydraulic properties of deep crystalline rock masses. On surface, the binary power plant is based on an ORC system (Organic Rankine Cycle). The organic working fluid is isobutane and the pilot plant has a net capacity of 1,5MWe. The three deep deviated wells were drilled from the same platform and are cased from the surface to 4.5 km depth. After the drilling operations, all the wells were hydraulically stimulated as well as chemically stimulated. Several circulation tests were done and shown encouraging results. A fourth geothermal well corresponding to a former exploration well drilled to 3.6 km depth could be used as an additional re-injection well if needed. The geothermal fluid which is a natural brine (100g/L) is pumped from the 2 deep production wells equipped with down-hole pumps. After giving its energy to the isobutane, the cooled brine is fully re-injected. Surface equipments (turbine, air cooling system, heat exchanger) as well as two different types of down-hole pumps (Line Shaft Pump, Electro Submersible Pump) were installed respectively on surface and in the production wells. Reservoir evolution is monitored from surface measurements in terms of hydraulics and temperature evolution. In the meantime, microseismicity is also monitored continuously during the circulation. On surface, corrosion-scaling studies are carried out based on on-site testing facilities by using various steels belonging to the geothermal components of the power plant. An innovative corrosion pilot was set up in the re-injection part of the geothermal loop (70°C, 20 bars).