The main objective of the HDR/EGS project at Soultz is the installation of a geothermal pilot plant for power production in 2008. The system consists of a triplet with two production wells (GPK2 and GPK4) and a central injection well (GPK3), all drilled down to 5000 m into a crystalline formation with temperature of 200°C.
The after-drilling hydraulic tests, performed to determine the natural performance of the wells, showed a very low productivity of the production wells. Each well was therefore stimulated by massive water injection with volumes up to 30000 m³ and typical flow rates of 30 - 50 l/s. The productivity of the wells could be enhanced by a factor of up to 20 after hydraulic stimulation operations. The results of stimulation operations were evaluated using short-term hydraulic tests, conventional pressure transient analysis, interference pressure data, microseismic monitoring, as well as temperature and flow logs. This combination of evaluation techniques helped in getting insight into the origin of the productivity enhancement.
The poster presents a general overview of the Soultz project and illustrates, on the example of the stimulation of GPK2, the reservoir development with the hydraulic and microseismic observations. The current reservoir, after completing all hydraulic stimulations, covers a volume of 2.5 km in N-S-direction, 1.5 km in E-W-direction and roughly 1 km height. With the current performance of the wells, the geothermal fluid can be produced at a flow rate of 30 – 35 l/s from one of the two production wells, with a production temperature of 175 °C. This configuration allows, in a first step, the construction of a 1.5 MWel power production unit in 2008. Later on, the power plant can be upgraded by including GPK4, the second production well, into the geothermal circuit and by installing a second power unit.

Vilnius, Lithuania