Geochemical Modeling of a Hydrothermal System of the Pauzhetka Geothermal Production Field

Abstract

The Pauzhetka geothermal production field in the southern part of the Kamchatka peninsula (Russia) supports an existing geothermal power plant. This geothermal field is a high-temperature, retrograde, low-sulfidation magmatic-hydrothermal system in an active island-arc volcanic setting. We present here a geochemical model for the magmatic-hydrothermal system, involving the following six main regions of the system: primary deep sodium-chloride waters, convective fissure, two-phase geothermal reservoir, aquifers, vadose zone, and surface. Moreover, the model takes fluxes between these regions and also mixing of cool underground water with geothermal fluid and condensed steam into account. The model has been verified using some analytical data of geothermal waters form a drill hole within the Pauzhetka geothermal field. Thermodynamic modeling using a Selektor-C program based upon the Gibbs free energy minimization provides the following results for the system: mineral composition, aqueous spiecies, Eh, pe, pH etc. In this study, quantity of aqueous species of the system under investigation at various temperatures and pressures and also in the presence/absence of atmospheric air has been estimated, implying that chemical analysis of samples from various drill depth is performed under the conditions of an analytical laboratory.