Blue Mountain, Humboldt County, Nevada, U.S.A

Ted Fitzpatrick, Brian D. Fairbank

Nevada Geothermal Power (formerly Noramex Corp)

关键词: Quartz;    Fractures;    Fracturing;    Geothermal Fields;    Boreholes;   

DOI  :  10.2172/890022
RP-ID  :  GREDII - FTR
RP-ID  :  FC36-02AL68297
RP-ID  :  890022

美国|英语

来源: UNT Digital Library

【 摘 要 】

The report documents the drilling of well Deep Blue No.2, the second deep geothermal test hole at the Blue Mountain Geothermal Area, Humboldt County, Nevada. The well was drilled by Noramex Corp, a Nevada company, with funding support from the US Department of Energy, under the DOE’s GRED II Program. Deep Blue No.2 was drilled as a ‘step-out’ hole from Deep Blue No.1, to further evaluate the commercial potential of the geothermal resource. Deep Blue No.2 was designed as a vertical, slim observation test hole to a nominal target depth of 1000 meters (nominal 3400 feet). The well tests an area of projected high temperatures at depth, from temperature gradients measured in a group of shallow drill holes located approximately one kilometer to the northeast of observation hole Deep Blue No.1. The well is not intended for, or designed as, a commercial well or a production well. Deep Blue No.2 was spudded on March 25, 2004 and completed to a total depth of 1127.76m (3700 ft) on April 28, 2004. The well was drilled using conventional rotary drilling techniques to a depth of 201.17 m (660 ft), and continuously cored from 201.17m (660 ft) to 1127.76m (3700 ft). A brief rig-on flow-test was conducted at completion to determine basic reservoir parameters and obtain fluid samples. A permeable fracture zone with measured temperatures of 150 to 167°C (302 to 333°F) occurs between 500 to 750m (1640 to 2461ft). The well was left un-lined in anticipation of the Phase III - Flow and Injection Testing. A further Kuster temperature survey was attempted after the well had been shut in for almost 3 weeks. The well appears to have bridged off at 439m (1440ft) as the Kuster tool was unable to descend past this point. Several attempts to dislodge the obstruction using tube jars were unsuccessful. Deep Blue No.2 encountered variably fractured and veined, fine-grained rocks of the Singas Formation, and intruded by minor strongly altered fine-grained felsic dikes, and less altered fineto medium-grained felsic to intermediate dikes. Widespread open fractures and extensive of quartz veining in many intervals of the core indicate a high degree of fracturing and flow of silica-bearing fluids, almost certainly hotter than 200°C (392°F), at some time, but these fractures are now partially sealed. Intervals of soft shaly mudstone, common clay gouge, and rocks with generally low permeability (few veins and fractures) may also form a seal or ‘cap’ above the main high temperature reservoir at Blue Mountain. The encouraging results from Deep Blue No.2 support further drilling at Blue Mountain. Higher temperature fluids can be expected where fractures providing channels for the circulation of hot water from depth have not been sealed extensively by silica deposition.