Lessons Learned from Passive Seismic Monitoring of EGS Collab Experiment 1

Abstract

Experiment 1 of the EGS Collab project at the Sanford Underground Research Facility was monitored through a 3-D array of sensors deployed in six monitoring and two experimentation boreholes. In total we deployed 25 hydrophones in two borehole strings and one single sensor in the production borehole attached to a SIMFIP probe, 18 3-component accelerometers and about 700 m of fiber optic cables. We recorded data on a total of four digitizers operating in continuous mode: a 96-channel seismograph recording at 4 kHz, a 64-channel digitizer recording at 100 kHz, a 10 kHz digitizer used for the SIMFIP hydrophone and a DAS unit operating at 1 kHz or 10 kHz sampling frequencies. The 100 kHz system has been continuously operating since May 2018 monitoring stimulation periods and long-term flow tests. We achieved an uptime in critical phases of the experiment better than 95% and collected more than 700 TB of data which is being processed in near real-time. Here we report on lessons learned from implementing and operating this monitoring system.