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Stress tensor changes related to fluid injection at The Geysers geothermal field, California
Author(s) -
MartínezGarzón Patricia,
Bohnhoff Marco,
Kwiatek Grzegorz,
Dresen Georg
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50438
Subject(s) - geothermal gradient , geology , cauchy stress tensor , induced seismicity , stress field , principal stress , seismology , stress (linguistics) , focal mechanism , orientation (vector space) , geophysics , petrology , viscous stress tensor , geometry , shear (geology) , mathematics , physics , finite element method , linguistics , philosophy , thermodynamics , mathematical analysis
Studying variations of the stress field in reservoirs caused by massive fluid injection is important toward an improved understanding of geomechanical processes involved. We report on spatio‐temporal variations of the local stress tensor orientation at The Geysers geothermal field, California. We apply two stress inversion methods with detailed uncertainty assessments using a selection of events recorded between 2007 and 2012. Our results clearly indicate variations in the orientation of the principal stress axes for the reservoir as a whole showing a normal faulting regime at the reservoir depth between 2 and 3.7 km bounded by a strike‐slip regime above and below. Analyzing the temporal evolution of the stress tensor orientation for a prominent seismicity cluster we observe a clear correlation of changes in orientation for σ 1–3 with the highest injection rates. These results suggest that temporal changes in the stress tensor orientation could contribute to characterize reservoirs during stimulation.