Monitoring of Reservoir Behavior at Soultz HDR Field by Super-Resolution Microseismic Mapping

The second hydraulic stimulation at a depth around 4500m to 5000m was carried out at Soultz HDR site, Alsace, France in 2003 to create a deep reservoir for a pilot plant. Around 38,000 m3 of heavy brine and water was injected in the 5005m borehole GPK-3 (which was drilled in 2002), and the other deep well GPK-2. The induced microseismic events were detected by a seismic network consisting of three downhole 4 component accelerometers and two 3component geophones. The authors picked onsets of events using automatic picking software and located the events onsite. The number of triggered events during the stimulation was approximately 87,000, and we picked approximately 8,100 high quality events. The authors manually re-picked the events, which are automatically picked on-site, and located them by JHD (joint hypocenter determination) and the coherence-collapsing methods. The relocated seismic cloud extends mainly NS direction around GPK-3 and N 45˚W around GPK-2.