Stillwater geothermal field is located near the small community of Stillwater, Nevada, approximately 20 km east of Fallon and just south of the Stillwater National Wildlife Refuge. The community of Stillwater is near the center of a thermal groundwater anomaly covering 52-65 km2 .
The Stillwater area, like Desert Peak and Soda Lake, is a "hidden" geothermal area, its presence being discovered while exploring for other resources. In 1919, Charles Kent hit hot water in a shallow well and shortly thereafter, W. W. Wheeler and a man named Freeman struck hot water in a well drilled for oil. Geysers erupted from the well about once a minute, shooting water into the air to a height of over 9 m, until the well was capped some time later. This well was the first of many hot artesian wells in the area. Water from the well at Greenwood's store in Stillwater was used to heat the store in 1947; the well is 70 m deep and has a temperature of 87.7 C. A geothermally heated greenhouse operated in the community of Stillwater in the early 1980s, illustrating the continuing utilization of the resource.
The Stillwater geothermal area appears to be in a portion of the Carson Sink that has had recurrent faulting and to lie along the extension of a fault bordering the west side of Rainbow Mountain a few kilometers to the south. One hypothesis suggests that the upflow velocity of the thermal water is sufficient to maintain the water temperature near that of the deep source, which was inferred to be close to 160C on the basis of geochemical data. The source of the thermal water probably lies at a depth of several kilometers.
Several geothermal wells have been drilled in the Stillwater area, but the only data available from older wells is from the O'Neill Geothermal Inc. (Oliphant) Reynolds No. 1 well, which was drilled to a depth of 1,292 m in 1964. The maximum temperature recorded was 136C. Three other wells were drilled to about 1,220 m in 1976 and 1977 by Union Oil Co. in several sections about 1.6 km north of Stillwater.
Currently, one binary power plant at Stillwater produces from the 158C reservoir. The plant came on line in 1989 and produces 13 MW of electricity. Thermal production originates from poorly consolidated and fractured rock units. Geothermal flow is thought to have moved from north to south before production; to the north, higher subsurface temperatures could be related to hot fluid movement upward from considerable depth along a northerly striking fault. To the north of the Stillwater plant, a somewhat higher temperature geothermal resource is located about 3 km to the north, where temperatures as high as 182C have been recorded from 700-1,350 m drill holes. Stillwater Geothermal Company sold the plant to Geothermal Management Services in April 2002, and AMP Resources LLC purchased the Stillwater Power Plant and associated geothermal resources from Stillwater Holdings LLC in 2004.
None at this time.