Microseismic Monitoring for Observation of Reservoir Processes – A Case study of the EGS Project Basel

Development of the EGS reservoir in Basel was monitored by an array of six downhole geophone. An additional geophone was installed at 4422 m.b.s.l. depth for the initial phase of the stimulation. The calibration of the required velocity model was a crucial task prior to localization of events. The velocity model was derived directly from the microseismic data set. During a ten-days stimulation period, approximately 13’500 events were recorded, of which about 3’000 could be located in real-time with great spatial precision, allowing for a detailed study of the evolving reservoir. The event rate decreased within few months reaching a recent rate of approximately one event every two weeks. The monitoring network is still working with 4 stations.