The EGS pilot plant is located in deep sedimentary structures which consists of two deep wells (4 300 m and 4 400 m) with an injection well (GrSk3/90) and a production well (GrSk4/05). The doublet system was established in 2007 and tested in the subsequent years. Downhole measurements and logging, well testing and reservoir stimulation tests, surface geophysical monitoring, reservoir simulation as well as cross-well measurements can be performed at this research platform. Reservoir stimulation and short-time testing were undertaken, but the long-term performance proved not to be sustainable due to chemical precipitation. The concept of circulation was based on a matrix dominated flow through the permeable sandstones between the doublets. Finally, no sustainable and sufficient flow rate could be achieved and it is assumed that the transmissibility between the wells is lower than expected from the previous testing.
It is planned to drill a third well, proposed to be funded by the German Government, which passes the vicinity of the other wells in two different depth sections and using a new exploitation strategy. This strategy is fracture dominated and considers the connection between the wells with intersecting fracture networks. The new well path is planned to be deviated up to 50° at the reservoir depth at 4 000 m and connects the GrSk4/05 well in the sandstone section and the GrSk3/90 well in the volcanic rock section at a distance of a few hundred meters. Connection is then established via hydraulic stimulation treatments. Start of the drilling is scheduled to be in 2017 or 2018 and stimulation is expected to take place subsequently. The site will serve as a fall back option in this demonstration project in unforeseen developments at the regular proposed sites.