The Quartz -and Na/k Geothermometers. I. New Thermodynamic Calibration

Abstract

Quartz equilibrium temperatures can be assessed with confidence for liquid enthalpy wet-steam wells by assuming boiling to be adiabatic. On the other hand, an uncertainty is involved with respect to "excess" enthalpy wells because the boiling processes leading to the "excess" enthalpy cannot be rigorously constrained. It appears that an open system model generally gives the most reliable results. Mixing of equilibrated geothermal waters of different temperatures leads to discrepancy between quartz and Na/K geothermometry temperatures, the discrepancy increasing with increasing temperature difference between the end member components in the mixture. Time variations in quartz and Na/K temperatures for producing wells and discrepancy between the two geothermometers provide useful information on the response of exploited geothermal reservoirs to the production load, such as cold water recharge and partial re-equilibration in the depressurization zone around the producing wells.