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Geochemistry of Aluminum in High Temperature Brines

Description: The objective ofthis research is to provide quantitative data on the equilibrium and thermodynamic properties of aluminum minerals required to model changes in permeability and brine chemistry associated with fluid/rock interactions in the recharge, reservoir, and discharge zones of active geothermal systems. This requires a precise knowledge of the thermodynamics and speciation of aluminum in aqueous brines, spanning the temperature and fluid composition rangesencountered in active systems. The empirical and semi-empirical treatments of the solubility/hydrolysis experimental results on single aluminum mineral phases form the basis for the ultimate investigation of the behavior of complex aluminosilicate minerals. The principal objective in FY 1998 was to complete the solubility measurements on boehmite (AIOOH) inNaC1 media( 1 .O and 5.0 molal ionic strength, IOO-250°C). However, additional measurements were also made on boehmite solubility in pure NaOH solutions in order to bolster the database for fitting in-house isopiestic data on this system. Preliminary kinetic Measurements of the dissolution/precipitation of boehmite was also carried out, although these were also not planned in the earlier objective. The 1999 objectives are to incorporate these treatments into existing codes used by the geothermal industry to predict the chemistry ofthe reservoirs; these calculations will be tested for reliability against our laboratory results and field observations. Moreover, based on the success of the experimental methods developed in this program, we intend to use our unique high temperature pH easurement capabilities to make kinetic and equilibrium studies of pH-dependent aluminosilicate transformation reactions and other pH-dependent heterogeneous reactions.
Date: May 18, 1999
Creator: Benezeth, P.; Palmer, D. A. & Wesolowski, D. J.
Partner: UNT Libraries Government Documents Department