The Desert Peak Reservoir

In this report the term reservoir is considered to be that volume of rock above a depth of 10,000 feet which gives an isothermal temperature profile with a temperature near 400 F. Wells deeper than 10,000 feet in this area are unlikely to be profitable at the present time. The isothermal profile is assumed to be the result of geothermal fluids convecting in fractures. Of course, large fractures, which are referred to as producing zones within the reservoir, must be intersected if a well is to...

History

Due to the desolate nature of the Hot Springs Mountains, the history of the area has been dominated by a series of people passing through, or by people searching for and attempting to produce a wide variety of mineral resources. Although there is a lack of known archaeological sites and artifacts in the Hot Springs Mountains, Indians probably visited nearby Brady's Hot Springs regularly. Early explorers visited Brady's Hot Springs but rapidly moved on in search of more productive land. The...

Shallow Temperaturegradient Holes

After a seven-year hiatus, geothermal exploration in the Brady's area resumed in 1973. The U. S. Geological Survey and the U. S. Bureau of Reclamation drilled 21 FIGURE 6. Three of Brady's geothermal wells flowing photo from Garside, 1974 . shallow test holes to determine shallow subsurface temperatures and temperature gradients and to evaluate the movement of ground water Olmsted and others, 1975 . Most of these drill holes hereafter referred to as holes are located within 1 mile of Brady's...

Geologic Structure And The Geothermal Reservoir

Silo Field Fault Map

Post-discovery geologic mapping in the northern part of the Hot Springs Mountains shows that the area underlain by the Desert Peak geothermal field is structurally higher than other parts of the northern Hot Springs Mountains. Most of the surface in this area is covered by alluvium, but where bedrock is exposed it consists mostly of rocks of the lower Chloropagus Formation or of units of the unnamed rhyolite sequence. The subsurface temperature distribution is areally nonlinear based on present...

Magnetotelluric Survey

Magnetotelluric MT surveys are unique among electrical surveys since they can provide resistivity data from depths up to several tens of miles. Consequently, numerous magnetotelluric surveys have been run in geothermal exploration and research. The method is expensive and data handling and interpretation are complex. If additional information is desired on the magnetotelluric method the reader is referred to Pdlmason 1975 for a brief description and to Vozoff 1972 for a more thorough treatment....

Stratigraphic Test No

Strat. test no. 1 is located near shallow temperature-gradient hole no. 37 principally because hole no. 37 had such a high bottom-hole temperature and thermal gradient. Hopefully, the 64 F 100 foot gradient would continue to a depth of 500 or 600 feet and possibly would give the base temperature of the geothermal system. There was also some meager geological and geophysical evidence ground magnetics, gravity, and heat flow that a northwest-southeast trending structure was located near strat....

Roving Dipole Electrical Resistivity Survey

During the latter stages of the shallow temperature-gradient program a roving dipole resistivity reconnaissance survey was run over the entire thermal anomaly by an independent contractor. In addition, ten depth soundings were made to provide more detailed information on lateral and vertical resistivity variations. Two plates from this survey are included as plates 4 and 5, an apparent resistivity anomaly map and a total-field apparent conductance map. There were six dipole source locations...

Truckee Formation

The Truckee Formation is composed of fluvial and lacustrine sediments and associated volcanic rocks. It is well exposed on the northern and western margins of the Hot Springs Mountains but is absent in the interior portions due to erosion. Axelrod 1956 divided the formation into three members. The lower member consists of basaltic tuff palagonite tuff gray, mollusc-rich, sandy coquina limestone water-laid ash tuff breccia sandstone diatomaceous shale and basalt. The middle member is...