A New Method of Evaluation of Chemical Geothermometers for Calculating Reservoir Temperatures from Thermal Springs in Nevada

Abstract

Early work by Edmiston and Benoit (1984) found that the Na-K-Ca geothermometer tended to overestimate reservoir temperatures of geothermal systems in the Basin and Range. The purpose of this paper is to determine if a new method based on theoretical mixing calculations can better predict reservoir temperatures for Nevada/Great Basin geothermal systems than other traditional geothermometer calculations. The geothermometers that are compared in this work are the Quartz, no steam loss (Fournier 1977; Fournier, 1981) and the Na-K-Ca, Mg-corrected (Fournier and Potter, 1979). Several examples suggest that this new mixing method can predict realistic reservoir temperatures under suitable conditions. Preliminary analysis suggests that the method tends to work better when the Na-K-Ca geothermometer is greater than the SiO2 geothermometer for an area. It also appears to work better when the temperature difference between the two thermal waters being mixed is >25°C and when the two geothermometers for the mixed fluids differ by >10°C for either the Na-K-Ca or SiO2 when compared between the two fluids (e.g., SiO2 geothermometer of fluid 1 is 10°C greater than SiO2 geothermometer of fluid 2).