In the early 1990s, groundwater as hot as 88°C was found in gold exploration drill holes in the Blue Mountain area 35 km west of Winnemucca (Parr and Percival, 1991). Later temperature logging of drill holes found temperatures up to 81°C in a 108-m drill hole (Fairbank and Ross, 1999) No hot springs or spring deposits were known in the area, which is mostly covered by Quaternary alluvium. The thermal anomaly of over 12 km2 is centered on Sec. 14, T36N, R34E (Fairbank and Niggemann, 2004). The hot fluids probably circulate along numerous north-striking normal faults in Triassic metasedimentary rocks present in the subsurface along the west flank of Blue Mountain, which is controlled by a northeast-striking range fault in this area. A 650-m exploration core hole drilled at this site, Deep Blue No. 1, recorded 144.7ºC at 644.5 m (Fairbank and Niggemann, 2004). The U.S. Department of Energy agreed to provide funding ($657,000 over 3 years) to Noramax Corporation to study and help define the resource. Drilling of an exploration core hole commenced in April 2002. Samples from this new drill hole were collected in summer 2002. (www.eere.energy.gov)
Noramax began drilling Deep Blue No.2 (DB-2) on March 25, 2004, which was successfully completed to a vertical depth of 1128 meters (3700 feet) on April 28, 2004 (see also GeothermEx, 2004). Costs for the operations were shared between Noramex Corp. (NGP wholly-owned subsidiary) and the U.S. Department of Energy. The maximum recorded temperature was 167°C (330°F) at 585 meters (1920 feet). Temperatures of 150-160ºC were recorded in the 200-585 m interval in November, five months after drilling (Nevada Geothermal Power press release, 12/20/2004). A potential geothermal production zone between 515 and 760 m is characterized by >150°C temperatures, multiple crystal-lined, open fractures and vuggy quartz veins, and lost circulation zones. A temperature reversal was observed in the well below 585 m. Geothermometry suggests a higher temperature reservoir at greater depth (Niggemann and others, 2005).
A full-diameter production well, 26A-14, was completed to 858 m in September 2006. A 60 hr flow test reported unassisted flow of over 650,000 lbs/hr of fluid. For a complete report see: www.nevadageothermal.com/s/Home.asp. A bottom-hole temperature of 183°C was reported following drilling. Nevada Geothermal Power has announced a Power Purchase Agreement with Nevada Power Co. for geothermal power to be produced from the site (Nevada Geothermal Power Co. press release, 2006). Another production well, 23-14, completed to 1,041 m in September 2007, has a maximum downhole temperature of 190ºC and flowed 118L/sec (Nevada Geothermal Power press release, September 19, 2007).
The current drilling program is aimed at developing a 30-MW power plant. If a suitable geothermal resource is identified in the deep well, the production potential for this site could be as high as 100 MW. Nevada Geothermal Power has increased its leased ground to approximately 9,600 acres (Nevada Geothermal Power Co. press release, May 2006).
Photos
Map showing drill holes and projected isotemperature contours at 500 m depth for the Blue Mountain geothermal area. From Fairbank and Ross (1999). As of 2006, Nevada Geothermal Power Inc. has started its initial production well drilling program aimed at developing a 30 MW power plant in the Blue Mountain area.
Temperature gradient profiles in shallow wells at the Blue Mountain geothermal area. From Fairbank and Ross (1999). As of 2006, Nevada Geothermal Power Inc. has started its initial production well drilling program aimed at developing a 30 MW power plant in the Blue Mountain area.