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In-situ stress and fracture permeability in a fault-hosted geothermal reservoir at Dixie Valley, Nevada

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Edited by:
Anon

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Abstract

As part of a study relating fractured rock hydrology to in-situ stress and recent deformation within the Dixie Valley Geothermal Field, borehole televiewer logging and hydraulic fracturing stress measurements were conducted in a 2.7-km-deep geothermal production well (73B-7) drilled into the Stillwater fault zone. Borehole televiewer logs from well 73B-7 show numerous drilling-induced tensile fractures, indicating that the direction of the minimum horizontal principal stress, Shmin, is S57 ??E. As the Stillwater fault at this location dips S50 ??E at approximately 3??, it is nearly at the optimal orientation for normal faulting in the current stress field. Analysis of the hydraulic fracturing data shows that the magnitude of Shmin is 24.1 and 25.9 MPa at 1.7 and 2.5 km, respectively. In addition, analysis of a hydraulic fracturing test from a shallow well 1.5 km northeast of 73B-7 indicates that the magnitude of Shmin is 5.6 MPa at 0.4 km depth. Coulomb failure analysis shows that the magnitude of Shmin in these wells is close to that predicted for incipient normal faulting on the Stillwater and subparallel faults, using coefficients of friction of 0.6-1.0 and estimates of the in-situ fluid pressure and overburden stress. Spinner flowmeter and temperature logs were also acquired in well 73B-7 and were used to identify hydraulically conductive fractures. Comparison of these stress and hydrologic data with fracture orientations from the televiewer log indicates that hydraulically conductive fractures within and adjacent to the Stillwater fault zone are critically stressed, potentially active normal faults in the current west-northwest extensional stress regime at Dixie Valley.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
In-situ stress and fracture permeability in a fault-hosted geothermal reservoir at Dixie Valley, Nevada
Volume
21
Year Published:
1997
Language:
English
Publisher:
Geothermal Resources Council
Publisher location:
Davis, CA, United States
First page:
181
Last page:
189
Number of Pages:
9
Conference Title:
Proceedings of the 1997 Annual Meeting of the Geothermal Resources Council
Conference Location:
Burlingame, CA, USA
Conference Date:
12 October 1997 through 15 October 1997