A Numerical Method for Predicting Thermophysical Properties of Complex Chloride-Dominated Brines

Abstract

Complex aqueous solutions containing high concentrations of chloride ions are found throughout nature. Examples include seawater and geothermal brines. Accurate models of the thermophysical properties of such solutions are needed for numerous scientific and engineering disciplines; in particular, applications associated with geothermal energy and the oil and gas industry. Often however, it is either impossible or overly computationally taxing to determine the properties of such complex aqueous solutions from first principles considerations.
Instead, numerous tables and functions exist to empirically determine the properties of single-salt solutions or predefined mixtures. In general, such properties are expressed as a function of solute mass fraction. However, more descriptive models are needed that are capable of determining the thermophysical properties of fluids of arbitrary chemical composition.
Ideally, the model should be able to calculate the properties of aqueous solutions based on a consideration of the contributions of key aqueous components; it should contain fitting parameters that are easy to solve for new aqueous species; and the model should be easy to implement and extrapolate well. In this paper, we discuss a model that achieves these goals by deriving physical properties based on correlations at the ionic level, and accounting for the chloride-dominated nature of the brine.