1. A method for characterizing one or more properties of a geological formation including brine, the method comprising: (a) inputting at least one first property of the geological formation into an equation of state (EOS) model, the EOS model accounting for a high temperature effect on the brine; (b) solving the EOS model to determine at least one second property of the geological formation; and (c) outputting the at least one second property to a display device.