Basic Research Needs for Geosciences - Energetics Meetings and ...

GRAND CHALLENGE: COMPUTATIONAL THERMODYNAMICS OF COMPLEX FLUIDS AND SOLIDSCourtesy of J. WeareFigure 27. Solubility of carbonate minerals as a function of temperature and pCO 2 . Triangles, squares and circlesrepresent experimental data; lines represent EOS predictions (Moller et al. 2005).The principal limitation to the development of accurate EOS models of the fluids encountered inthe application of energy strategies is the lack of understanding of the speciation (e.g., thestructure and dynamics of polyions and colloids) present in the liquid phase. For example, evenfor the Al system, one of the most common elements in the Earth’s crust, we have a veryincomplete understanding of the speciation in solution.EOS models for mixtures of aqueous electrolytes and nonaqueous mixtures also have importantapplications to CO 2 sequestration in salt formations. Recently there has been progress in thedevelopment of Mixed-Solvent Electrolyte (MSE) models that have been shown to accuratelypredict the thermodynamics of electrolyte solutions extending to the fused salt limit and over abroad range of temperatures in aqueous-solvent mixtures. The development and application ofsuch new approaches to chemical systems involving salt brines-CO 2 mixtures could greatlyenhance our ability to predict the chemical changes in deep geologic systems of importance inCO 2 disposal. As in other areas, there is an important need for the development of more firstprinciples-basedEOS methods in this area. EOS based on a fundamental understanding of thespecies present in the phases are important to reduce the dependence on data and extend theextrapolation of the EOS region of reliability outside the range of the data.EOS for solids, solid solutions and absorbed phases. Current EOS for mineral systems areessentially empirical. For pure minerals this is not a problem as long as data exist to parameterizethe temperature-pressure dependence. On the other hand, even commonly encountered solidphases such as dolomite can be very complex solid solutions, with like-like and like-unlike76 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems