Deep Heat Mining Basel, Preliminary Results

Abstract

Geopower Basel-AG, a partnership of eleven public and private enterprises, endeavours to develop a geothermal cogeneration plant in Basel from an enhanced geothermal system. Basel, situated at the south-eastern margin of the Upper Rhinegraben has been selected as a suitable location for a pilot plant due to three favourable criteria: public and political willingness, favourable infrastructure (district heating grid, river cooling) and elevated heat flow. A refined microseismic monitoring system has been installed prior to drilling wells to a target depth of 5'000 metres, not only for visualizing microseismic acitivity during hydraulic stimulation, but also to observe the natural seismicity in this area of increased seismic hazard. The hydraulic stimulation process in well Basel-1 was stopped after six days when high seismic activity built up with magnitudes up to M 2.7. Four hours after shut in a seismic event of M 3.4 happened coinciding with the start of bleeding off to hydrostatic. Within 55 days after stimulation three after shocks with M >3 were recorded. The project has been suspended but not abandonned until further insight into the focal mechanisms is available and acceptable ways of reservoir enhancement become applicable.