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Desert Peak (updated 2008)

The Desert Peak geothermal prospect is located in the northern part of the Hot Springs Mountains about 6.4 km southeast of Bradys Hot Springs, and is named for a prominent peak 3-5 km northwest of the area of the steam wells. A thermal area centered on Secs. 21,29, T22N, R27E (map) was discovered by Phillips Petroleum Co. after drilling about 50 temperature gradient holes up to 153 m in depth. This drilling began to the north at the Bradys geothermal area (Benoit and Butler, 1983).

There are no surface thermal indications at the area, other than a few small occurrences of opal-cemented sand and travertine, probably from springs that are now inactive. The geology of the rocks exposed at the surface has not been helpful in predicting the subsurface geology. The three geothermal wells drilled in the 1974-1976 period encountered Mesozoic metavolcanic and metasedimentary rocks at depths of 915 to 1,372 m, below a sequence of Miocene volcanic rocks (cross section). Wells 21-1 and 21-2 produce a mixture of steam and water from fractured meta-andesite. It has been suggested that the Tertiary volcanic rocks may act as a seal for the reservoir. The reservoir is believed to have a temperature of 208°C, and the fluid produced is a sodium chloride type containing about 7,500 ppm total dissolved solids.

Following exploration drilling in the 1970s and early 1980s, the Western States Geothermal Co. Desert Peak double flash power plant came on line in 1985, producing 9.9 MW from a 205°C resource. The two production wells are located east-northeast of the power plant. Tertiary volcanic and sedimentary rocks are present to depths of about 1,000 m (Benoit and others, 1982; Faulder and Johnson, 1987), and they overlie a basement of Mesozoic metavolcanic, metasedimentary, and plutonic rocks whose complex relationships are poorly understood. The reservoir is at a depth of 900-1,000 m; fracturing, particularly in greenstones, is believed to be a major control on porosity and permeability (Faulder and Johnson, 1987). The plant was purchased by ORMAT Nevada, Inc. in July 2001. An area to the east of the present plant and production wells is being evaluated for the feasibility of creating an artificial geothermal reservoir development as an Enhanced Geothermal System (Carlson and others, 2004; Robertson-Tait and Morris, 2003; Robertson-Tait and Lovekin, 2000; Robertson-Tait and Johnson, 2005).

As of 2006, Ormat Nevada, Inc. has constructed a new 23-MW binary power plant near the old 9.9-MW dual flash geothermal power plant at Desert Peak. The original geothermal power plant at Desert Peak came online in 1985 and was decommissioned in May 2006. Power generated from this project will be sold to Nevada Power Co.

Desert Peak Map