Estimating the Density and Compressibility of Natural Hypersaline Brines Using the Pitzer Ionic Interaction Model

Measurements of density and compressibility of naturally occurring hypersaline brines (Red Sea, Dead Sea, Orca Basin, and Mono Lake) have been analyzed using Pitzer’s ionic interaction model. Pitzer’s volume and compressibility equations for the major components of brines have been used to estimate the densities and compressibilities as a function of temperature and salinity. The estimates at 25 °C were in reasonable agreement with the measured values (0.008 ± 0.127 × 10⁻³ g cm⁻³). At higher and lower temperatures (0–40 °C), estimates are less reliable (0.229 ± 0.246 × 10⁻³ g cm⁻³). This is largely due to the lack of Pitzer parameters for all the salts at high concentration as a function of temperature. The compressibility estimates at 25 °C are in reasonable agreement with measured values (0.184 ± 0.261 × 10⁻⁶ bar⁻¹), but the estimates from 15 to 35 °C are less reliable (0.204 ± 0.726 × 10⁻⁶ × bar⁻¹), especially at high salinities. This is largely due to the limited compressibility data as a function of temperature for the major components of brines. These results demonstrate the utility of the Pitzer ionic interaction model to obtain reasonable estimates of density and compressibility of natural brines of known composition.