Dissolution, Transport and Precipitation of Silica in Geothermal System

Abstract

Dissolution and precipitation of silica polymorphs (amorphous silica, cristobalite and quartz) were incorporated into a geothermal reservoir simulator based on reaction kinetics. We simplified the reaction kinetics as silica minerals being always precipitated from or dissolved into the neutral dilute solution without a direct solid phase transition among them. Based on this assumption and published experimental data of rate constants and solubilities of silica minerals, three dimensional numerical simulations of geothermal system development were performed. Alteration zoning of silica minerals was reproduced in the simulations as observed in natural geothermal systems, and we examined the relation of the silica alteration zoning to the thermal and hydrological structure of the geothermal system.