Pilgrim Hot Springs Geothermal Exploration
Pilgrim Hot Springs is the hottest resource in the state not directly associated with a volcanic system. It has a lengthy history of local use, and is currently listed on the national historic register. This project involves testing and verifying an innovative remote sensing technique developed by researchers at UAF’s Geophysical Institute. This technique, based on aerial infrared imaging, was originally used to map underground coal fires and subsurface movement of magma. However, by creating an accurate estimate of the natural heat flux at the surface from a geothermal resource, it also has the potential to significantly reduce the cost of geothermal exploration for low and moderate temperature geothermal sites, especially those located in inaccessible areas.
By testing and verifying this technique at the Pilgrim Hot Springs site and locating the source of the geothermal water, ACEP can assess the feasibility of various options for developing this site to benefit the region and its residents.
Pilgrim Hot Springs is located 60 miles northeast of Nome on the Seward Peninsula along the western coast of Alaska. The proximity of this geothermal resource to Nome as well as other communities and identified mineral resources in the region make this study of significant interest, as geothermal energy is one of the few renewable resources capable of providing reliable, baseload power comparable to diesel-based generation.
ACEP and its partners have successfully completed three seasons of fieldwork beginning with an airborne FLIR (forward looking infrared) survey conducted in 2010, and repeated in 2011. This was followed by ground-based and aerial geophysical surveys, as well as a drilling program which resulted in a total of 60+ shallow gradient holes of depths ranging from 80 to 500 ft, as well as 3 deeper confirmation holes that drilled to bedrock and were used to locate the source of the thermal fluids.
Through this exploration program, particularly the FLIR aspect, our team was able to expand the extent of the known thermal anomaly from the immediate area around the hot springs, to a much larger feature with surface expressions visible up to 2 miles from the main resource. Elevated subsurface temperatures have been recorded by a graphite mining core drilling program 18 miles west of Pilgrim Hot Springs, further supporting the idea that the deeper system may be much larger than previously estimated.
Today we know that the available heat from Pilgrim Hot Springs is approximately 20MW, with maximum downhole temperatures of 195°F, though the estimated reservoir temperature is considerably higher – likely approaching ~300 °F. This means the resource could be capable of sustaining approximately 2 MW of power generation, which could be used locally or delivered to Nome or a nearby mining operation via a transmission line.
Based on these results, ACEP recommended the drilling and testing of an additional, large-diameter well capable of producing up to 2000 gallons per minute (GPM) and sited near the upflow zone. During the 2013 field season, a 14 inch diameter hole and two smaller temperature gradient holes were drilled. Data from these holes will be used to further refine models to better isolate an upflow zone. The artesian flow from the 14” hole produced water with a volume and temperature capable of producing about 200 kW of power.
Additional temperature gradient holes will pinpoint the critical upflow zone of the deeper resource to determine if the well is capable of producing 2-5 MW of additional power.
ACEP determined that the resource should be capable of sustainably generating 2 MW of electric power, which could be used locally or delivered to Nome or other nearby loads via the construction of a power line. Based on the results of ACEP’s work, a power purchase agreement was signed between a private developer and the City of Nome as well as the landowner to develop a project. If the project is developed, it would be a milestone for Alaska as one of the first large-scale power projects developed in rural Alaska using largely private funding. At this time, the private developer and the landowners are actively pursuing the development of the project, and ACEP continues to support continued work at the site.