Technical Assistance from Lawrence Berkeley National Laboratory and National Energy Technology Laboratory to Elko Heat Company and the City of Wells, Nevada

Abstract

Warm waters in several domestic and municipal water wells in and around the City of Wells, Nevada, along with several hot springs a few kilometers away, suggest economical geothermal resources that could meet residential and commercial space heating demands, perhaps even geothermal electricity generation. To date, only a few low-temperature, single-user space heating applications have been developed. Under the U.S. Department of Energy’s Small Business Vouchers Pilot (SBV) Program, research teams from Lawrence Berkeley National Laboratory (LBNL) and the National Energy Technology Laboratory (NETL), in collaboration with the University of Nevada, Reno (UNR), Better Cities, and Lumos & Associates, advised the Elko Heat Company and the City of Wells in their recent drilling of a shallow geothermal gradient well, based on new field work along with a compilation and review of existing geologic, geochemical, geothermal, and geophysical data for this area. New field data include ground temperature measurements with shallow 2-meter probes and with Geoprobe holes penetrating to depths of 5 to 9 meters, new geochemical analysis of springs and wells, revision of geologic maps through geologic and structural mapping, and shallow direct current resistivity and electromagnetic induction surveys. All 51 datasets collected and created throughout the project were cataloged and categorized according to their metadata and attributes, and compiled into a data catalog and ESRI ArcGIS geodatabase and map package, all of which are available as shared, public resources through NETL’s Energy Data eXchange (EDX)1. Once assembled, 11 surface- and subsurface- spatial-datasets were incorporated into NETL’s Cumulative Spatial Impact Layers (CSIL) tool, and imported into EarthVision, a 3-dimensional visualization software, to demonstrate regions of high-data density, construct an interpolated temperature model, and identify favorable locations to drill a geothermal exploration well. Anomalously high temperatures (≥43°C) at shallow depths (5 to 9 m) were found along the north floodplain margin of the Humboldt River, northwest of the City of Wells and coinciding with the possible intersection of N-S and E-W faults. While no subsurface waters have been analyzed in this anomaly, water samples from springs and wells to the east and west of this zone were found to display differing chemical and isotopic characteristics, suggesting two different deep circulations on either side of the shallow anomaly that could provide shallow hydrothermal flow: outflow from the hot spring system northwest of the City, and outflow from a blind system further east following the regional hydraulic gradient. Maximum temperatures at depth for the two fluid types as estimated by multicomponent geothermometry are ~180°C for the hot spring system and ~150°C east of the shallow temperature anomaly. The drilling of four temperature gradient wells (GEO#1 -- GEO#4) within and near the shallow temperature anomaly failed to encounter a useful resource, but other shallow prospects and deeper resource prospects remain untested.