Equation of state (EOS) calculations

DiadFit includes the CO2 equation of state of Sterner and Pitzer (1994) and Span and Wagner (1996), as well as the mixed H2O-CO2 EOS of Duan and Zhang (2006). These EOS can be used for a variety of different calculations, described below:

Example 5a - Different EOS functions

Example 5a shows how to perform different CO2 EOS calculations in DiadFit:

Calc 1: Calculating P for a given T and CO2 density.
Calc 2: Calculating CO2 density for a given T and P
Calc 3: Calculating T for a given P and CO2 density.
Calc 4: Calculating co-existing liquid and vapour densities
Calc 5: Converting homogenization temperatures from microthermometry into CO2 densities, and propagating errors.

Example 5b - Visualizing how CO$_2$ density relates to P and T

Example 5b shows how to perform EOS calculations of CO2 density for an array of pressures at different temperatures. The resulting plots in pressure-density space with lines for different temperatures are very helpful to demonstrate that the CO2 EOS isn’t that sensitive to temperature.

Example 5c - Calculating fluid inclusion entrapment pressures and depths in La Palma

Example 5c uses CO2 densities from Dayton et al. (2022, Science Advances) to calculate entrapment pressures, and then a 2 step density profile to calculate storage depths

Example 5d - Calculating fluid inclusion entrapment pressures and depths for different density profiles

Example 5d shows how to convert CO2 density to depth, and then calculate storage depths using a variety of crustal density profiles (2, 3 step, etc).

Example 5e - Propagating uncertainties in fluid inclusion barometry

Example 5e shows how to propagate uncertainties in temperature, CO2 density, XH2O and crustal density using Monte Carlo methods.

Example 5f - Calculations using CO$_2$-H$_2$O EOS

Example 5f shows how to perform calculations using CO2-H2O EOs, and how to integrate XH2O measurements from melt inclusions into this correction.