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Title: Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir

Abstract

We present a three-dimensional thermohydromechanical numerical study of the evolution and distribution of the stress tensor within the northwest part of The Geysers geothermal reservoir (in California), including a detailed study of the region around one injection well from 2003 to 2012. Initially, after imposing a normal faulting stress regime, we calculated local changes in the stress regime around injection wells. Our results were compared with previously published studies in which the stress state was inferred from inverting the focal plane mechanism of seismic events. Our main finding is that changes in stress tensor orientation are caused by injection-induced progressive cooling of the reservoir, as well as by the seasonal variations in injection rate. Because of the gravity flow and cooling around a liquid zone formed by the injection, the vertical stress reduction is larger and propagates far below the injection well. At the same time, the horizontal stress increases, mostly because of stress redistribution below and above the cooling area. These two phenomena cause the rotation of the stress tensor and the appearance of a strike-slip regime above, inside, and below the cooling area. The cooling and the associated rotation of the stress regime can play a significant rolemore » in the observed long-term deepening of the microseismicity below active injection wells.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Calpine Corp., Middletown, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G)
OSTI Identifier:
1410323
Alternate Identifier(s):
OSTI ID: 1402223
Grant/Contract Number:  
AC02-05CH11231; DE‐AC02‐05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 120; Journal Issue: 12; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; enhanced geothermal system; stress state rotation; microseismicity; thermohydromechanical simulation

Citation Formats

Jeanne, Pierre, Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Walters, Mark, Hartline, Craig, and Borgia, Andrea. Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir. United States: N. p., 2015. Web. doi:10.1002/2015JB012414.
Jeanne, Pierre, Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Walters, Mark, Hartline, Craig, & Borgia, Andrea. Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir. United States. doi:10.1002/2015JB012414.
Jeanne, Pierre, Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Walters, Mark, Hartline, Craig, and Borgia, Andrea. Thu . "Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir". United States. doi:10.1002/2015JB012414. https://www.osti.gov/servlets/purl/1410323.
@article{osti_1410323,
title = {Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir},
author = {Jeanne, Pierre and Rutqvist, Jonny and Dobson, Patrick F. and Garcia, Julio and Walters, Mark and Hartline, Craig and Borgia, Andrea},
abstractNote = {We present a three-dimensional thermohydromechanical numerical study of the evolution and distribution of the stress tensor within the northwest part of The Geysers geothermal reservoir (in California), including a detailed study of the region around one injection well from 2003 to 2012. Initially, after imposing a normal faulting stress regime, we calculated local changes in the stress regime around injection wells. Our results were compared with previously published studies in which the stress state was inferred from inverting the focal plane mechanism of seismic events. Our main finding is that changes in stress tensor orientation are caused by injection-induced progressive cooling of the reservoir, as well as by the seasonal variations in injection rate. Because of the gravity flow and cooling around a liquid zone formed by the injection, the vertical stress reduction is larger and propagates far below the injection well. At the same time, the horizontal stress increases, mostly because of stress redistribution below and above the cooling area. These two phenomena cause the rotation of the stress tensor and the appearance of a strike-slip regime above, inside, and below the cooling area. The cooling and the associated rotation of the stress regime can play a significant role in the observed long-term deepening of the microseismicity below active injection wells.},
doi = {10.1002/2015JB012414},
journal = {Journal of Geophysical Research. Solid Earth},
number = 12,
volume = 120,
place = {United States},
year = {2015},
month = {11}
}

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Cited by: 11 works
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