Creation and Mapping of 5000 m deep HDR/HFR Reservoir to Produce Electricity

The current phase of the European Hot Dry Rock Project at Soultz-sous-Forets requires the drilling of two additional deep wells to 5000 m depth into the crystalline basement, to form a module consisting of a central injector and two producers. The first well GPK-2 was drilled to 5000 m in 1999 and stimulated in 2000. The well GPK-3 (the injector) was drilled in 2002 and targeted using microseismic and other data. The bottom hole temperature was 200.6 oC and separation between the two wells at the bottom is around 600 m. GPK3 was then stimulated to enhance the permeability between the wells. A number of stimulation techniques were tried including “focused” stimulation, a novel method of injecting simultaneously in two wells. Microseismic monitoring, flow logging and other diagnostic methods were used during these injections. The “sparse” microseismic network at the Soultz site consists of a number of seismic sensors deployed in wells between 1500 m and 3600 m deep with bottom hole temperatures of 130-160 oC. A 48 channel, 22 bit data digitizing unit was used for data acquisition in conjunction with proprietary software to carry out automatic timing and location in real time. This gave a real time decision-making possibility and control of the reservoir. This was the first time that such an interactive method had been carried out at this site.