Advanced seismic imaging for geothermal development
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In the geothermal fields of the Great Basin physiographic province of western North America, drilling success or failure often depends on hitting fault or fracture zones. Advanced seismic reflection imaging has proven to be the only effective geophysical means of accurately targeting geothermal drilling. At target depths of 1 to 2 kilometers, the pay zones are often less than 0.1 km wide. Surface geological and “integral” (e.g., potential-field, electrical, magnetotelluric, seismic-refraction) geophysical studies have often proven successful at locating new geothermal fields for development. However, surface and integral methods cannot direct exploration or development within a field, and geothermal exploration drilling in the region has had a success rate as small as 10%. Such high risk for costly drilling has long held back the development of the region’s full geothermal-power potential. The development of advanced seismic imaging techniques has led to drilling success rates of 80% at some prospects. Advanced seismic imaging, as a “differential” method, is able to focus direct images of steeply dipping faults as seismic reflectors, allowing accurate planning of geothermal drill targets. The technology achieves the focusing and accurate location of structure and stratigraphy through thick piles of heterogeneous Tertiary volcanics, below complex surficial basin structure. This capability has allowed researchers to use these seismic images to carry out advanced seismic attribute analyses, model testing, and verification of tectonic hypotheses. We are collaborating on research to further refine these imaging methodologies.