HR: 0800h
AN: NS31B-0386    [Abstracts]
TI: Geothermal Reservoir Boundary Characterization Using Detailed Shallow Geophysical Methods at the Redfield Campus in Steamboat Hills, NV.
AU: * Huebner, L E
EM: lehuebner@gmail.com
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Oppliger, G
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Van Gundy, T
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Mankhemthong, N
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: McDonald, J
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Robertson, W
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Shoffner, J
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Johnson, G
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AU: Murtagh, A
AF: The University of Nevada, Reno, Mackay School of Earth sciences and Engineering/MS 172, Reno, NV 89557, United States
AB: The University of Nevada, Reno's new Redfield campus in south Reno, Nevada directly overlies the Northwestern edge of the Steamboat Hills geothermal reservoir. Ormat Technologies currently generates over 90 MW of electric power from this significant geothermal complex. Although the geothermal field has been the subject of numerous geophysical studies (gravity, 3-D seismic, airborne magnetics and electromagnetics) over the past 70 years, the work has typically been conducted at large station spacing's, providing a only low resolution picture of the reservoir's bounding structures. Largely spaced drill hole isotherm data and InSAR observations of subsidence from reservoir cooling provide strong evidence for a sharp N60E, linear control on the Northwestern reservoir boundary, which projects through the campus. The proximity of the underlying geothermal resource and the prospect of future geothermal space heating at the campus motivated a program of integrated shallow geophysical surveys to investigate the subsurface and characterize the reservoir boundary under the campus. Completed surveys include closely spaced gravity measurements, ground magnetics, and electric resistivity. The reduced geophysical data have been integrated with surface geology and surface heat flow in a geographic information system. Interpretive results to date include a gravity defined fault running approximately N60E across the campus with ~50 meters of basement offset with the down block to the northwest, this fault correlates with a zone of low magnetic susceptibility, which is consistent with hydrothermal alteration. Resistivity data shows conductivities indicative of clay or hydrothermal fluids more than 80 meters thick extending within 10 to 20 meters of the surface, although no clear resistivity offset was apparent across the gravity and magnetically defined structure. A seismic reflection line is also being collected across the possible fault to constrain its spatial attributes. Although this group of shallow surveys examine only the Redfield campus, an area of approximately 500 by 430 m, covering a small fraction of the larger Steamboat Hills Geothermal field (approximately 3.2 by 2.8 km) the insights grained are proving useful in understanding the nature of the northwestern boundary and other parts of the geothermal field.
DE: 0920 Gravity methods (1219)
DE: 0925 Magnetic and electrical methods (5109)
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting