3D VSP Experiment Design Study of the Raft River Geothermal Field

Abstract

Geothermal systems are, in many cases, characterized by complex geological structures with discernible anomalous zones, related to the presence of geothermal fluids. Development of geothermal energy production increasing requires more accurate information on fault distributions, and paths of or barriers to fluid flow within the reservoir. Toward this purpose, we have embarked upon a survey design study using vertical seismic profiling (VSP) measurements for imaging seismic attributes within the Narrows Zone, a striking geological feature, which strongly controls permeability and fluid flow within the Raft River geothermal reservoir. The geothermal field is located in Cassia County in southwestern Idaho and is the site of a Department of Energy Enhanced Geothermal System (EGS) project. Motivating this study is our plans to acquire VSP data later this this year at Raft River. Full waveform inversion (FWI) of simulated data with frequency content between 5 through 15 Hz has been analyzed and is presented. The data arise from a 3D elastic model of the Narrows Zone, developed by Hi-Q and the University of Utah. Our goal is to determine acceptable survey design parameters needed for 3D imaging of elastic attributes within anticipated survey cost.