| Title | Using Gravity and Magnetics to Delineate Structural Controls on Geothermal Fluids, Northern Cache Valley, Idaho |
|---|---|
| Authors | Wade WORTHING, Tom WOOD, Jonathan GLEN, Travis MCLING, Pat DOBSON, Brent RITZINGER, Ghanashyam NEUPANE, Michael THORNE |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | gravity, magnetics, geothermal, faults, geophysics, potential fields, idaho |
| Abstract | The Northern Cache Valley (NCV) of southeastern Idaho is a north-south trending Basin and Range graben that is receiving renewed interest for its geothermal potential. In the 1970s and 80s, geophysical and hydrological studies were undertaken, motivated by the presence of thermal wells and springs in the area. Geothermal exploration in this era culminated with the drilling of geothermal exploration wells by Sunedco Energy Development in 1979 and 1980. The test borehole temperatures were deemed too low ( less than 120o C) for power production using technology available at the time. In January of 2014, a water well drilled to 79 meters, encountered Na-Cl-HCO3 water with a measured bottom hole temperature of 104o C. Traditional magnesium corrected Na-K-Ca geothermometry of water from that well estimated the temperature of the thermal reservoir to be 204° C. Due to this revived interest, new studies utilizing updated geochemical and geophysical techniques were undertaken. Present understanding of the NCV geothermal system suggests that fluid flow is associated with a fault(s) adjacent to Clifton Hill (aka Little Mountain) – a secondary horst complex rising from the floor of the Cache Valley graben. The existing data from the area is relatively sparse and is not suitable for pinpointing the location of faults thought to be acting as conduits for thermal water to travel from depth to the shallow subsurface. To investigate the locations of these faults and accurately characterize the plumbing of the geothermal system, high resolution potential field (gravity and magnetic) data was collected along lines made across the suspected location of the Clifton Hill bounding faults. Geophysical models of the subsurface using these data in conjunction with existing hydrogeological and geochemical data have aided in better determining fault locations. Future work proposed to better characterize the geothermal system includes groundwater level and aquifer temperature mapping to explore the behavior of the shallow ground water aquifer in response to the discharge of thermal water through the system’s faults. As funding allows, thermal imaging, utilizing an unmanned aerial vehicle (UAV), will be used to detect elevated ground surface temperatures thought to exist based on preferential melting of snow that has been reported to occur in this area. |