Identification of high angle structures controlling the geothermal system at Rye Patch, Nevada

Jump to: navigation, search


OpenEI Reference LibraryAdd to library

Conference Paper: Identification of high angle structures controlling the geothermal system at Rye Patch, Nevada

Abstract
The successful completion of a recent well in the Rye Patch Geothermal field, located in Pershing County, Nevada, supports the geologic and geophysical interpretation that high angle structures control this geothermal system. Although lower angle structures are present, hot water migrates up from deeper sources along high angle faults more efficiently than structures with a shallower dip. Earlier attempts to develop the resource focused on structures that dipped at an angle between 60 and 70 degrees from horizontal. Recently acquired geophysical data indicated that numerous high angle structures were present in the area, with dips between 80 and 90 degrees. Original drilling targets focused on the subsurface projection of a surface structure, mapped as the Rye Patch fault, with an erroneously low angle. These early attempts at drilling were discouraging and might have been more successful if additional geology and geophysics were used to evaluate the geothermal system and map the Rye Patch fault more accurately. The successful completion of the most recent well can be attributed to the incorporation of the geology of previous wells with additional geology and geophysics. Temperature gradient holes were used to confirm that the Rye Patch fault provided the primary plumbing for this geothermal system, and 3D seismic data indicated that most of the structures had dips between 80 and 90 degrees. Geothermometry at Rye Patch indicates that the resource has a relatively high quartz equilibrium temperature and it is speculated that the higher the angle of the structural control, the higher the resource temperature. The dip of Basin and Range normal faults varies considerably and the interpretation of these structures for geothermal, fossil geothermal mineral prospects, and or oil and gas prospects is important. At Rye Patch, the high angle structure feeds geothermal fluids into cavernous limestone beds, dipping to the west usually between 40 and 60 degrees, which is a shallower dip than the Rye Patch fault itself. Resistivity surveys at Rye Patch mapped the westward dipping anomalies, which correspond to the cavernous limestone porosity, and numerous vertical anomalies; which are attributable to the high angle normal faults. Time slices of interpreted 3D seismic data identified numerous high angle structures; however none of these seismic structures could be correlated with the Rye Patch fault. It is inferred that the Rye Patch Fault is the youngest fault in the system, having the only surface expression, and therefore the least amount of displacement, resulting in a difficult seismic target. The most recent well was targeted to intercept the Rye Patch fault at 4500' after evaluating the shallower intermediate depth limestone reservoir at about 2000'. Upon testing of the intermediate depth reservoir it was concluded that this zone was capable of commercial production and the well would be completed in this shallower interval

Author 
W.J. Ehni






Conference 
American Geophysical Union, 82(47) Fall Meeting; {{{ConferencePlace}}}"{{{ConferencePlace}}}" cannot be used as a page name in this wiki.;


Published 
American Geophysical Union, 2001





DOI 
Not Provided
Check for DOI availability: http://crossref.org


Online 
Internet link for Identification of high angle structures controlling the geothermal system at Rye Patch, Nevada

Citation

W.J. Ehni. 2001. Identification of high angle structures controlling the geothermal system at Rye Patch, Nevada. In: American Geophysical Union, 82(47) Fall Meeting; (!) ; (!) . (!) : American Geophysical Union; p. 1144