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Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field

Stock, J. M. and Healy, J. H. and Hickman, S. H. and Zoback, M. D. (1985) Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field. Journal of Geophysical Research B, 90 (B10). pp. 8691-8706. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20140919-111922215

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Abstract

Hydraulic fracturing stress measurements and acoustic borehole televiewer logs were run in holes USW G-1 and USW G-2 at Yucca Mountain as part of the Nevada Nuclear Waste Storage Investigations for the U.S. Department of Energy. Eight tests in the saturated zone, at depths from 646 to 1288 m, yielded values of the least horizontal stress S_h that are considerably lower than the vertical principal stress S_v. In tests for which the greatest horizontal principal stress S_H could be determined, it was found to be less than S_v, indicating a normal faulting stress regime. The borehole televiewer logs showed the presence of long (in excess of 10 m), vertical, drilling-induced fractures in the first 300 m below the water table. These are believed to form by the propagation of small preexisting cracks under the excess downhole fluid pressures (up to 5.2 MPa) applied during drilling. The presence of these drilling-induced hydrofractures provides further confirmation of the low value of the least horizontal stresses. A least horizontal principal stress direction of N60°W–N65°W is indicated by the orientation of the drilling-induced hydrofractures (N25°E–N30°E), and the orientation of stress-induced well bore breakouts in the lower part of USW G-2 (N65°W). This direction is in good agreement with indicators of stress direction from elsewhere at the Nevada Test Site. The observed stress magnitudes and directions were examined for the possibility of slip on preexisting faults. Using these data, the Coulomb criterion for frictional sliding suggests that for coefficients of friction close to 0.6, movement on favorably oriented faults could be expected. For coefficients of friction of 1.0, preexisting faults of all orientations should be stable. Laboratory studies on the Yucca Mountain tuffs, reported elsewhere, yield coefficients of friction ranging from 0.6 to 0.9.


Item Type:Article
Related URLs:
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http://dx.doi.org/10.1029/JB090iB10p08691 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/JB090iB10p08691/abstractPublisherArticle
ORCID:
AuthorORCID
Stock, J. M.0000-0003-4816-7865
Additional Information:This paper is not subject to U.S. copyright. Published in 1985 by the American Geophysical Union. Paper number 4B5237. Received August 17, 1984; revised May 22, 1985; accepted May 24, 1985. We thank J. Svitek, D. Styles, J. Hennagan, and G. Zwart for invaluable help in the operation and maintenance of field equipment and Larry Mastin for discussions of breakout theory and observations. This work would not have been possible without the generous advice and assistance of Ray Escobedo, Wallace Hammer, and other personnel of Fenix and Scisson, Inc. Thoughtful reviews by A. McGarr, P. Segall, and W. F. Brace are greatly appreciated. J. M. Stock was partially supported by the Fannie and John Hertz Foundation. The work was performed in cooperation with the Nevada Operations Office of the U.S. Department of Energy under interagency agreement DE-AI08-78ET44802.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-AI08-78ET44802
Record Number:CaltechAUTHORS:20140919-111922215
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140919-111922215
Official Citation:Stock, J. M., J. H. Healy, S. H. Hickman, and M. D. Zoback (1985), Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field, J. Geophys. Res., 90(B10), 8691–8706, doi:10.1029/JB090iB10p08691
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49857
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Sep 2014 21:17
Last Modified:04 Dec 2015 20:41

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