Imaging Fracture Zones Using Continuous Active Source Seismic Monitoring for the EGS Collab Project: A Synthetic Study

Abstract

The EGS Collab project of the U.S. Department of Energy is conducting a field experiment at the Stanford Underground Research Facility (SURF) site to study subsurface fracture creation and appropriate tools for characterization and monitoring. The SURF site is located in Lead, South Dakota, at the site of the former Homestake Gold Mine. The EGS Collab project is conducting the experiment from a drift located approximately 1.5 km beneath the surface. A multi-level continuous active source seismic monitoring (ML-CASSM) system designed by Lawrence Berkeley National Laboratory will be used to monitor fracture creation, coupled to extensive passive (microseismic) monitoring. Four fracture-parallel boreholes and two orthogonal boreholes will be used to acquire active and passive seismic data during the experiment. We use the same borehole configuration and geophone distribution to conduct a numerical study in order to evaluate the potential to image the created fracture. We perform anisotropic elastic full-waveform inversion of synthetic transmission and reflection data to image the fracture. To alleviate artifacts caused by sparse seismic data, we employ high-order compressive sensing in our anisotropic elastic full-waveform inversion. Our results demonstrate that it is possible to use the ML-CASSM system to image the fracture created during the EGS Collab experiment.