Geochemical Feed Zone Analysis Based on the Mineral–Solution Equilibrium Hypothesis

In this work we propose a method of geochemical feed zone (FZ) analysis based on the assumption of thermochemical equilibrium between geothermal fluids and hydrothermal minerals, for each FZ contributing to well discharge. Using our method, it is possible to calculate the mass fraction and the chemistry of each FZ fluid, namely (1) the pH and the concentrations of SiO2, CO2, Na, K, Ca, Mg, HCO3, SO4, F, and Cl of FZ liquids, and (2) the concentrations of SiO2 and CO2 of FZ vapors. The method can be applied to wells with two single-phase FZs and to wells with either three single-phase FZs or two FZs, one single-phase and the other two-phase, with different temperature and fluid chemistry.