Microseismic Event Analysis in Conjunction with Stimulation Treatments at the Geothermal Research Well GtGrSk4/05 in Groß Schönebeck/Germany

Abstract

The technical feasibility of geothermal power production will be demonstrated in the geothermal research wells Groß Schönebeck using a borehole doublet. This task includes safeguarding the thermal fluid cycle and the optimisation of energy conversion technology at the surface. In order to complete the Enhanced Geothermal System, three massive hydraulic stimulations were performed injecting a total of 13000 m³ of water into the well Gt GrSk 4/05. To monitor injection-induced seismicity during the main injection a combined surface and downhole seismic network was deployed including a downhole seismic sensor at 3800 m depth at only 500 m distance to the injection point.

During the injection period of six days with injection rates of up to 150 l/s and maximum injection pressures of nearly 600 bar a total of 70 events were detected and located. Spectral parameters were calculated and magnitudes were found to cover the range -1.9<M<-1.1. The events show a strong spatial and temporal clustering with a maximum number of 22 events per day. The majority of events occurred towards the end of major stimulation phases indicating a similar behavior as observed at similar treatments in crystalline environments but at smaller level of seismic activity and at lowers magnitudes.