The European EGS project at Soultz-sous-Forêts: From extensive exploration to power production

The European EGS project of Soultz-sous-Forets (France) which was first investigated in 1987 is aimed at producing power by the extraction of the heat stored in deep, fractured crystalline rocks. Extensive research and development contributed to get a better understanding of the geothermal reservoir: large-scale hydrothermal circulation occurs within a network of large permeable faults developed within a Tertiary graben. 3 deep wells have been drilled down to 5 km depth, where a rock temperature of 200degC was reached. At the bottom depth, the horizontal distance between the producing wells is over 1.3 km length, knowing that the injection well is located in the middle. Several hydraulic and chemical stimulations were performed and combined in order to reactivate the system of fractures, which are often sealed by natural hydrothermal deposits. This led to improvement of injectivity and productivity of the wells. After a successful 5-months circulation test done in 2005, we are now building a pilot power plant. Two types of production pumps will be tested for this purpose and a first ORC conversion module of 1.5 MWe will be installed and tested in the beginning of 2008. If the results are promising, a second module should be later installed.