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Title: Characterization of Fracture Patterns in the Geysers Geothermal Reservoir by Shear-wave Splitting

Abstract

The authors have analyzed the splitting of shear waves from microearthquakes recorded by a 16-station three-component seismic network at the Northwest Geysers geothermal field, Geysers, California, to determine the preferred orientation of subsurface fractures and cracks. Average polarization crack directions with standard deviation were computed for each station. Also, graphical fracture characterizations in the form of equal-area projections and rose diagrams were created to depict the results. The main crack orientations within the steam field are predominantly in the N10{degree}E to N50{degree}E direction, consistent with expected fracture directions in a pull-apart basin created by sub-parallel right-lateral strike-slip faults related to the San Andreas fault system. Time delays range from 15--60 ms, similar to the time delays from previous studies at geothermal reservoirs. They have detected a significant increase in time delays between 1988 and 1994, which they attribute to widening of the cracks or filling of the cracks with fluid. Increase in production activities during this time also could have influenced this widening.

Authors:
;
Publication Date:
Research Org.:
USDOE Idaho Operations Office, Idaho Falls, ID; University of North Carolina, Chapel Hill, NC (US)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EE) (US)
OSTI Identifier:
758724
Report Number(s):
DOE/ID/13468
TRN: AH200028%%91
DOE Contract Number:  
FG07-96ID13468
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 15 Sep 1999
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOLOGIC FRACTURES; GEYSERS GEOTHERMAL FIELD; MICROEARTHQUAKES; NATURAL STEAM; SEISMIC SURVEYS; SEISMIC S WAVES; Geothermal Legacy; SHEAR WAVES; NORTHWEST GEYSERS; SUBSURFACE FRACTURES; POLARIZATION; CRACK ORIENTATION; TIME DELAYS; GEOTHERMAL RESERVOIRS

Citation Formats

D. Erten, and J. A. Rial. Characterization of Fracture Patterns in the Geysers Geothermal Reservoir by Shear-wave Splitting. United States: N. p., 1999. Web. doi:10.2172/758724.
D. Erten, & J. A. Rial. Characterization of Fracture Patterns in the Geysers Geothermal Reservoir by Shear-wave Splitting. United States. doi:10.2172/758724.
D. Erten, and J. A. Rial. Wed . "Characterization of Fracture Patterns in the Geysers Geothermal Reservoir by Shear-wave Splitting". United States. doi:10.2172/758724. https://www.osti.gov/servlets/purl/758724.
@article{osti_758724,
title = {Characterization of Fracture Patterns in the Geysers Geothermal Reservoir by Shear-wave Splitting},
author = {D. Erten and J. A. Rial},
abstractNote = {The authors have analyzed the splitting of shear waves from microearthquakes recorded by a 16-station three-component seismic network at the Northwest Geysers geothermal field, Geysers, California, to determine the preferred orientation of subsurface fractures and cracks. Average polarization crack directions with standard deviation were computed for each station. Also, graphical fracture characterizations in the form of equal-area projections and rose diagrams were created to depict the results. The main crack orientations within the steam field are predominantly in the N10{degree}E to N50{degree}E direction, consistent with expected fracture directions in a pull-apart basin created by sub-parallel right-lateral strike-slip faults related to the San Andreas fault system. Time delays range from 15--60 ms, similar to the time delays from previous studies at geothermal reservoirs. They have detected a significant increase in time delays between 1988 and 1994, which they attribute to widening of the cracks or filling of the cracks with fluid. Increase in production activities during this time also could have influenced this widening.},
doi = {10.2172/758724},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {9}
}