Least-Squares Reverse-Time Migration of Walkaway VSP Data from the Raft River Geothermal Field

摘要

The U.S. Department of Energy selected the Raft River geothermal field as an enhanced geothermal system demonstration project in 2010. Reliable geothermal reservoir characterization requires high-resolution subsurface imaging. We carried out a vertical seismic profile (VSP) survey in 2016 along five walkaway lines around the stimulation well, RRG-9 ST1. We construct a high-resolution velocity model using first-arrival traveltime tomography of the downgoing VSP data and elastic-waveform inversion of the VSP waveform data. We then use the inverted P- and S-velocity models and our newly developed least-squares reverse-time migration to obtain high-resolution P- and S-images of the Raft River geothermal reservoir. Our inversion version clearly reveals the low-velocity Narrows zone, which is the stimulation zone to enhance geothermal production.