A comprehensive numerical model for the thermodynamic and transport properties of H2O-NaCl fluids

Abstract

Saline fluids are common to a variety of geologic settings in Earth's crust and upper mantle. The binary system H2O-NaCl is commonly used to interpret data obtained from fluid inclusions, and for geochemical modeling of mass and energy transport and fluid-rock interaction. Modeling of fluid properties in this binary system has generally relied on piecemeal compilations from available models specific to certain properties, whereas a standalone, comprehensive tool has been lacking. Here, we present a new computer package, entitled ProBrine (Properties of Brine) to evaluate the thermodynamic and transport properties of H2O-NaCl fluids over the range of temperatures from 0 to 1000 °C, pressure from 1 to 5000 bar, and salinity from 0 to 100 wt% NaCl. ProBrine is designed to calculate a wide range of thermodynamic and transport properties, including (but not limited to): phase equilibria (liquid, vapor, and halite); molar volume, density, specific enthalpy, and viscosity. The program is also equipped to calculate derived properties such as: 1) the coefficient of isobaric thermal expansion; 2) the coefficient of isothermal compressibility; 3) the reduced susceptibility; 4) the isobaric specific heat capacity, and the fluxibility. In addition, the model will calculate solubility of the following six minerals: fluorapatite, calcite, corundum, fluorite, rutile, and quartz, as well as the respective temperature and pressure derivatives, which can be used to predict mineral dissolution and precipitation along a flow path. Moreover, the program is equipped to interpret fluid-inclusion data. The program is written in Visual Basic (VBA) in Microsoft Excel and is released open-source, allowing a user full scope to review, copy, modify and expand the program code.