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Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada

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We deployed a dense seismic array to image the shallow structure in the injection area of the Brady Hot Springs geothermal site in Nevada. The array was composed of 238 5 Hz, three-component nodal instruments and 8,700 m of distributed acoustic sensing (DAS) fiber-optic cable installed in surface trenches plus 400 m installed in a borehole. The geophone array had about 60 m instrument spacing in the target zone, whereas DAS channel separations were about 1 m. The acquisition systems provided 15 days of continuous records including active source and ambient noise signals. A large vibroseis truck (T-Rex) was operated at 196 locations exciting a swept-frequency signal from 5 to 80 Hz over 20 seconds using three vibration modes. Sweeps were repeated up to four times during different modes of geothermal plant operation: normal operation, shutdown, high and oscillatory injection and production, and normal operation again. The cross- correlation method was utilized to remove the sweep signal from the geophone records. The first P arrivals were automatically picked from the cross-correlation functions using a combination of methods, and the travel times were used to invert for the 3D P-wave velocity structure.

Models with 50 m horizontal node spacing were obtained, with vertical node spacing of 10 to 50 m. The travel time data were fit to about 30 ms, close to our estimated picking uncertainty. Boundaries between high and low velocity zones agree with previous surveys of local faults and low velocity zones near the surface correspond to fumarole locations. A rapid increase in velocity at about 50 m depth fits with borehole data on the depth of the Quaternary sediments. There is some evidence for changes in the P-wave velocity during the experiment with slower travel times at the beginning of the experiment.

Citation Formats

TY - DATA AB - We deployed a dense seismic array to image the shallow structure in the injection area of the Brady Hot Springs geothermal site in Nevada. The array was composed of 238 5 Hz, three-component nodal instruments and 8,700 m of distributed acoustic sensing (DAS) fiber-optic cable installed in surface trenches plus 400 m installed in a borehole. The geophone array had about 60 m instrument spacing in the target zone, whereas DAS channel separations were about 1 m. The acquisition systems provided 15 days of continuous records including active source and ambient noise signals. A large vibroseis truck (T-Rex) was operated at 196 locations exciting a swept-frequency signal from 5 to 80 Hz over 20 seconds using three vibration modes. Sweeps were repeated up to four times during different modes of geothermal plant operation: normal operation, shutdown, high and oscillatory injection and production, and normal operation again. The cross- correlation method was utilized to remove the sweep signal from the geophone records. The first P arrivals were automatically picked from the cross-correlation functions using a combination of methods, and the travel times were used to invert for the 3D P-wave velocity structure. Models with 50 m horizontal node spacing were obtained, with vertical node spacing of 10 to 50 m. The travel time data were fit to about 30 ms, close to our estimated picking uncertainty. Boundaries between high and low velocity zones agree with previous surveys of local faults and low velocity zones near the surface correspond to fumarole locations. A rapid increase in velocity at about 50 m depth fits with borehole data on the depth of the Quaternary sediments. There is some evidence for changes in the P-wave velocity during the experiment with slower travel times at the beginning of the experiment. AU - Parker, Lesley M. DB - Open Energy Data Initiative (OEDI) DP - Open EI | National Renewable Energy Laboratory DO - KW - geothermal KW - Brady Hot Springs KW - Nevada KW - seismic tomography KW - active source KW - PoroTomo KW - brady geothermal field KW - bradys KW - shallow KW - seismic imaging KW - poroelastic tomography LA - English DA - 2017/08/09 PY - 2017 PB - University of Wisconsin T1 - Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada UR - https://data.openei.org/submissions/7223 ER -
Export Citation to RIS
Parker, Lesley M.. Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada. University of Wisconsin, 9 August, 2017, GDR. https://gdr.openei.org/submissions/1070.
Parker, L. (2017). Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada. [Data set]. GDR. University of Wisconsin. https://gdr.openei.org/submissions/1070
Parker, Lesley M.. Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada. University of Wisconsin, August, 9, 2017. Distributed by GDR. https://gdr.openei.org/submissions/1070
@misc{OEDI_Dataset_7223, title = {Active Source 3D Seismic Tomography of Brady Hot Springs Geothermal Field, Nevada}, author = {Parker, Lesley M.}, abstractNote = {We deployed a dense seismic array to image the shallow structure in the injection area of the Brady Hot Springs geothermal site in Nevada. The array was composed of 238 5 Hz, three-component nodal instruments and 8,700 m of distributed acoustic sensing (DAS) fiber-optic cable installed in surface trenches plus 400 m installed in a borehole. The geophone array had about 60 m instrument spacing in the target zone, whereas DAS channel separations were about 1 m. The acquisition systems provided 15 days of continuous records including active source and ambient noise signals. A large vibroseis truck (T-Rex) was operated at 196 locations exciting a swept-frequency signal from 5 to 80 Hz over 20 seconds using three vibration modes. Sweeps were repeated up to four times during different modes of geothermal plant operation: normal operation, shutdown, high and oscillatory injection and production, and normal operation again. The cross- correlation method was utilized to remove the sweep signal from the geophone records. The first P arrivals were automatically picked from the cross-correlation functions using a combination of methods, and the travel times were used to invert for the 3D P-wave velocity structure.

Models with 50 m horizontal node spacing were obtained, with vertical node spacing of 10 to 50 m. The travel time data were fit to about 30 ms, close to our estimated picking uncertainty. Boundaries between high and low velocity zones agree with previous surveys of local faults and low velocity zones near the surface correspond to fumarole locations. A rapid increase in velocity at about 50 m depth fits with borehole data on the depth of the Quaternary sediments. There is some evidence for changes in the P-wave velocity during the experiment with slower travel times at the beginning of the experiment.}, url = {https://gdr.openei.org/submissions/1070}, year = {2017}, howpublished = {GDR, University of Wisconsin, https://gdr.openei.org/submissions/1070}, note = {Accessed: 2025-05-03} }

Details

Data from Aug 9, 2017

Last updated Jun 12, 2018

Submitted Jun 7, 2018

Organization

University of Wisconsin

Contact

Kurt Feigl

Authors

Lesley M. Parker

University of Wisconsin

Research Areas

DOE Project Details

Project Name PoroTomo Project

Project Lead Elisabet Metcalfe

Project Number EE0006760

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