Comparisons of Geothermal Systems in Central Nevada: Evidence for Deep Regional Geothermal Potential Based on Heat Flow, Geology, and Fluid Chemistry

摘要

Central Nevada may have significant untapped deep geothermal potential. Existing geologic and heat flow data indicate the potential for carbonate aquifers at temperatures greater than 180°C at depths below 3 kilometers. Compiled fluid chemistry from producing geothermal fields at Tuscarora and Beowawe, produced water from the Blackburn oil field, and thermal springs and wells (with temperatures greater than 30°C) all have unique and remarkably consistent major ion chemistry. Nearly all compiled samples are Na-HCO_3 type water with generally low total dissolved solids and high concentrations of dissolved silica. These chemistries may result from equilibrium in warm carbonate aquifers and ion exchange and mineral precipitation as thermal fluids move toward the surface. Similarities in chemistry may result from similar thermal reservoir conditions beneath large areas of central Nevada. Simple geothermometry yields the highest temperatures for samples from the Beowawe geothermal field. Other areas with elevated geothermometry and Na-HCO_3 waters include the Tuscarora geothermal field, the Mary's River area, and Ruby Valley. Samples from the Blackburn oilfield are similar to other thermal samples except for higher Na, Cl, and HCO_3 which may result from active petroleum generation in this system. Limited stable isotope data indicate a significant geothermal signal for several samples with lower geothermometry. Similarities in heat flow and geology between central Nevada and Utah may allow for analogous geothermal conditions to exist in adjoining parts of western Utah.