Enhanced Microseismicity During Production Pumping Cessation at the San Emidio Geothermal Field (Nevada, USA) in December 2016
[1];
[1];
[2];
[3];
[1];
[1];
[5];
[1]
- Department of Geoscience University of Wisconsin‐Madison Madison WI USA
- National Renewable Energy Laboratory Golden CO USA, Now at Zanskar Geothermal &, Minerals, Inc. Salt Lake City UT USA
- Department of Geoscience University of Wisconsin‐Madison Madison WI USA, Now at National Tsunami Warning Center Palmer AK USA
- Ormat Technologies, Inc. Reno NV USA, Now at Geologica Geothermal Group, Inc. Reno NV USA
- Ormat Technologies, Inc. Reno NV USA
Abstract Tectonic activity, geothermal fluids, and microseismic events (MSEs) tend to occur in similar locations as a result of spatiotemporal changes in the subsurface stress state. To quantify this association, we analyze data from a dense seismic array deployed at the San Emidio geothermal field, Nevada for 1 week in December 2016 to coincide with a 19.45‐hr shutdown of all injection and production pumping operations. 123 MSEs were detected, of which 101 occurred during the shutdown. The spatial association of the MSEs with the production wells suggests a causal relationship between the production cessation and the MSEs. Here we performed a detailed analysis to investigate reservoir material properties, distribution of seismically activated faults, and local stress state. We determined the hypocenters, magnitudes, and focal mechanisms for the MSEs, P‐wave tomographic velocity model, and local stress tensor. The results show that most MSEs occurred near the production wells. Magnitudes fall between −2.2 and 0.0 with larger events located closer to the production wells. Most MSEs occurred within a westward‐dipping normal fault zone in the reservoir associated with anomalously low P‐wave velocity values. The focal mechanism and stress inversion results show predominantly normal faulting with the maximum horizontal stress oriented north‐south. We suggest that the MSEs during shutdown were triggered on pre‐existing, small‐scale, critically stressed fault patches in the reservoir as the pore pressure increased around the production wells when the production pumping ceased. We interpret the larger MSE magnitudes closer to the production wells as a result of higher pore pressure increase.
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- EE0007698; EE0009032
- OSTI ID:
- 2205394
- Alternate ID(s):
- OSTI ID: 2205396; OSTI ID: 2229746
- Journal Information:
- Journal of Geophysical Research. Solid Earth, Journal Name: Journal of Geophysical Research. Solid Earth Journal Issue: 11 Vol. 128; ISSN 2169-9313
- Publisher:
- American Geophysical Union (AGU)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
WHOLESCALE: Mass Flux Rates for Wells at San Emidio in December 2016
WHOLESCALE: Seismic Survey Data from San Emidio Nevada 2021