Location and Size
The Silver Peak project is located in Esmeralda County, Nevada, 240 km (150 miles) northwest from Las Vegas and spans 32 km2 (7873 acres). There are two 55 kV transmission lines and a substation within SGP's lease boundaries.
Exploration Activities
Silver Peak was first explored for geothermal potential in the 1980s by Phillips Petroleum Company who drilled six temperature gradient wells in the area. Exploration resumed in 2005 with two more gradient holes drilled by the property vendor. Many geothermal features are visible on the property including geothermal vents, travertine-manganese silica sinter deposits, fossilized algae mats and complex faulting. Also present are shallow wells with temperatures of up to 75°C (167°F) at depths less than 21 meters (70 feet). Chemical geothermometry analysis indicates reservoir temperatures up to 227° C (441°F) at depth.In April 2008, SGP obtained a positive environmental assessment decision from the Bureau of Land Management (BLM) (a "Finding of No Significant Impact") on its proposed exploration and drilling plan.
In October 2009, SGP was awarded a US$5 million grant on the Silver Peak project by the US Department of Energy as part of the American Reinvestment and Recovery Act. The funds are to be used for drilling and exploration activities on the project, on a 50:50 cost share basis.
In November 2009, SGP’s exploration drilling consisted of ten shallow temperature gradient holes with a total of 1,522 meters, including 238 meters of core. Core samples allow a greater insight into the geological composition and nature of structural controls of the subsurface and complement the data provided by the analysis of drill cuttings. The maximum temperature recorded from these ten holes was 88° Celsius at a depth of 140 meters. The maximum temperature gradient recorded from the 10 wells exceeded 500° Celsius per kilometer. The results of this drilling showed that the minimum size of the thermal anomaly is significantly larger and is hotter than previous measurements had indicated.
SGP also completed detailed ground-based magnetotelluric (MT) surveys and airborne Z-tipper Electromagnetic (ZTEM) surveys at Silver Peak. Preliminary analysis of the MT datasets reveals the extent and thickness of overlying layers of conductive sediments as well as the inferred locations of zones of potential permeability. A radiometric survey was recently completed at Silver Peak. Data processing and interpretation of all data sets into 3D subsurface models is ongoing.
Within the next 12 months SGP intends to complete power purchase agreements and related transmission studies, as well as geophysical and production well drilling activities. SGP proposed drilling program consists of drilling temperature gradient wells (300 meter deep holes to measure subsurface temperature gradients throughout the lease), core holes (core data between 1-2 kilometers depth for resource modeling), slim wells (6 inch diameter rotary holes to measure temperature and flow rates to depths of 1-2 kilometers) and production assessment wells (13 inch diameter wells to depths of 1-2 kilometers) in order to move what are now “probability resource estimates” to the “economically proven resource” category.
SGP is also planning additional exploration work, shallow temperature probe measurements and an airborne thermal infrared remote-sensing survey at Silver Peak. Further drilling is planned at both Silver Peak in January 2010.
Resource Estimate
In Setptember 2006, an independent assessment conducted by GeothermEx has estimated a 90% probability (confidence level) that the project could generate 15 MW and a 50% probability of 42 MW. A 15 MW geothermal power plant can supply enough electricity for 12,000 homes.