Correlating Quartz Dissolution Kinetics in Pure Water from 25" to 625°c

During the past 50 years, quartz dissolution kinetics and solubility measurements have been the subject of numerous investigations. Researchers have been motivated either because of their interest in understanding important natural geologic processes in the earth or because of a need to quantify dissolution rates for chemical processes above ground or for geothermal heat extraction underground. Our motivation for carrying out experimental studies of quartz dissolution for the last 15 years was driven by engineering issues related to mineral transport in circulating hot dry rock (HDR) geothermal systems (Armstead and Tester, 1987; Grigsby et al., 1989; Charles et al., 1979; Tester et al., 1977). Of critical importance to HDR is the characterization of the rate of dissolution of host reservoir rock as a function of temperature, pressure and liquid phase composition. In general, quartz is a major mineral component in HDR reservoirs in low permeability crystalline rock. Furthermore, quartz is highly reactive relative to other constituent minerals in near neutral (non-acidiclnonbasic) aqueous environments at temperatures of interest to HDR geothermal energy extraction (150' to 300OC). Because of these two reasons, we were motivated to understand the quantitative aspects of quartz dissolution in pure water.