Adaptation of the Bowers and Helgeson (1983) equation of state to the H2O-CO2-CH4-N-2-NaCl system

The equation of state developed by Bowers and Helgeson ([Bowers, T.S., Helg eson, H.C., 1983. Calculation of the thermodynamic and geochemical conseque nces of nonideal mixing in the system H2O-CO2-NaCl on phase relations in ge ological systems: equation of state for H2O-CO2-NaCl fluids at high pressur es and temperatures. Geochim. Cosmochim. Acta, 47, 1247-1275.] and [Bowers, T.S., Helgeson, H.C., 1985. Fortran programs for generating fluid inclusio n isochores and fugacity coefficients for the system H2O-CO2-NaCl at high p ressures and temperatures. Computers and Geosciences, 11, 203-213.]), which was originally designed for H2O-CO2-NaCl fluids, has been extended to CH4 and N-2 bearing fluids. Available experimental P-V-T-X data in the H2O-CO2- CH4-N-2-NaCl fluid system are accurately reproduced by this equation of sta te, and, therefore, isochores and fugacity coefficients can be accurately c alculated up to 1000 MPa and 1300 K. This equation of state cannot be used in and near immiscibility regions and critical points, like any modified Re dlich-Kwong equation of state. The empirical modifications allow isochore c onstruction for realistic geological fluid systems which are often found in fluid inclusions, and which involve several gases and salts. (C) 1999 Else vier Science B.V. All rights reserved.