Seismic imaging through the volcanic rocks of the Snake River Plain: insights from Project Hotspot

Abstract

A B S T R A C THotspot: The Snake River Geothermal Drilling Project was undertaken to better understand geothermal systems across the Snake River Plain volcanic province. A series of surface and borehole seismic profiles were obtained to provide insights into volcanic stratigraphy and test the capabilities of engineering-scale seismic imaging in such terranes. The Kimberly site drilled through 1.9 km of mostly rhyolite, with thin sedimentary interbeds in the upper part of the section. The Kimama site drilled through 1.9 km of mostly basalt with sedimentary interbeds at ß200 m depth and 1700 m depth. The Mountain Home site contained numerous sediment and volcanic rock layers. Downhole and surface vibroseis seismic results suggest sedimentary interbeds at depth correspond with low-velocity, high-temperature zones that relate to reflections on seismic profiles. Our results suggest that eruption flow volumes can be estimated and flow boundaries can be imaged with surface seismic methods using relatively high-fold and wide-angle coverage. High-frequency attenuation is observed at all sites, and this deficit may be countered by acquisition design and a focus on signal processing steps. Separation of surface and body waves was obtained by muting, and the potential for large static effects was identified and addressed in processing. An accurate velocity model and lithology contacts derived from borehole information improved the confidence of our seismic interpretations.resources are located at depth with little to no surface expression, Project Hotspot has utilized geophysical, geological, and geochemical techniques to better understand the heat distribution and to identify pathways for fluid flow. Here, we discuss surface and borehole seismic data that were acquired to identify key lithologic and hydrogeologic boundaries that are relevant to geothermal exploration in this volcanic province. We focus our study on geothermal resources located in the upper 2 km. To date, seismic imaging within such complex geological environments has been limited, in part, by the large seismic velocity and density contrasts between volcanic rocks and the often thin sediment interbeds, and the large lateral variations in volcanic flow boundaries. These

Geothermal Play Fairway Analysis of the Snake River Plain, Idaho

“…They also collected hundreds of rock-property measurements on outcrops and samples (including magnetic susceptibility, density, and magnetic remanence) to constrain potential field modeling and integrated ground water well logs into our analyses. These data have been used, along with previously acquired data from Project Hotspot (e.g., Shervais et al, 2013;Shervais, 2014;Liberty et al, 2015;Kessler et al, 2017) to define basement structures (faults and lineaments) and to create detailed crustal density models. The MT survey was carried out in three study areas: 33 stations were acquired around the two deep drill holes (MH-1 and MH-2) on Mountain Home Air Force Base ( Figure 2).…”