A revised empirical model to calculate the dynamic viscosity of H2ONaCl fluids at elevated temperatures and pressures (≤1000 °C, ≤500 MPa, 0–100 wt % NaCl)

• We developed a revised model for viscosity of H2ONaCl at elevated PTx conditions.
• The revised model shows good correlation with experimental data.
• The revised model shows consistent and expected behavior at higher PTx conditions.

Examination of viscosities for fluids in the system H2ONaCl predicted by the commonly-used model of Palliser and McKibbin has identified regions of pressure-temperature-salinity (PTx) space in which the model delivers values that are inconsistent with some experimental data and exhibits discontinuities and trends that are unexpected. Here, we describe a revised empirical model to calculate viscosity of H2ONaCl fluids that shows good correlation with experimental values and shows trends that are consistent with known or expected behavior outside of the region where experimental data are available. The model described here is valid over the temperature range from the H2O solidus (∼0 °C) to ∼1000 °C, from ∼0.1 MPa to ≤500 MPa, and for salinities from 0 to 100 wt % NaCl.