H2O - CO2 - NaCl phase calculations

Phase properties and an activity model for phase equilibria

Composition and physical properties of fluids and gases in the H2O-CO2-NaCl system:

  • CO2 solubility in water and brine
  • Viscosity of water and carbon dioxide
  • Density of water and carbon dioxide
  • Water content of gas phase

Fill the form below to run the program.

I want to carry out calculations with varying temperature, pressure, salinity.

How this works:

1. Select which of pressure, temperature or salinity will be allowed to vary

This program calculates the density and viscosity of water and carbon dioxide, and the composition of their mixture where the two phases are in equilibrium (between 10 and 380°C, 0.1 to ∼400 MPa and for NaCl concentrations up to 25 mol NaCl/kg H2O). It uses published thermodynamic and physical models. It has been formatted for iterative use and error propagation, where the thermodynamic model is the main source of uncertainties.

Phase diagram

Simplified phase diagram for CO2-H2O mixtures.
The solid black curve separates pressure-temperature domains where H2O and CO2 are fully miscible (``one-phase domain'' on the right-hand side) from domains where CO2-rich and water-rich phases may coexist. Note that pressure is on a logarithmic scale.
T&F 1963: measurements of Todheide and Franck (1963).
T&K 1964: measurements of Takenouchi and Kennedy (1964).
H&P 2003: model of Holland and Powell (2003), valid above 300°C and 300 MPa (open circles) but not below (small red circles).
The stability fields of high pressure - low temperature solid phases (ices and clathrates) are not represented.
Adapted from Dubacq et al. (2013).

In the figure above, the green field (``two-phase domain'') indicates pressure-temperature conditions for which the program is supposed to calculate the solubility of CO2 in water (or NaCl-brine) and that of H2O in the CO2-rich phase. The program estimates the density and viscosity of H2O and CO2 in both two-phase and one-phase domains (green and pale pink).
The thermodynamic model has not been parametrized above ∼400 MPa (i.e., in the white domain) as experimental results in this range are sparse.

2. Specify conditions and choose the output:

Indicate the number of points (up to 50) for the calculation, the range of the varying variable (minimum and maximum temperature, pressure or salinity) and constant values for the fixed variables. Choice is given between several outputs:

The solubility model is limited to the green field of the above figure.

3. Run the model

Press RUN.
You will be redirected to a page containing the results and a list of references, together with concise explanations about the results and the structure of the program.
Error propagation implies Monte-Carlo simulations and calculations may take up to 45 seconds. Note that your web browser must accept cookies (to pass user input to the program, not to collect any sort of personal information).

Feel free to contact the author, feedback is greatly valued.


Copyright 2015 Benoît Dubacq, CNRS.
The present program is distributed under the terms of the GNU General Public License.