Clathrates: Computer programs to calculate fluid inclusion V- X properties using clathrate melting temperatures

Abstract

Knowledge of final clathrate melting temperatures is essential for estimates of salinity, bulk composition and density in H 2O-gas-rich fluid inclusions by nondestructive methods. The salinities calculated strongly depend on the thermodynamic model used, which involves many independent intensive properties and related parameters, such as osmotic coefficients, fugacity coefficients, gas solubilities. Four programs have been developed ( DENSITY, ICE, Q2 , and NOSALT ) using Turbo C++ version 3.0 to handle clathrate melting temperatures with several initiation procedures. These programs allow the calculation of bulk densities and compositions ( V- X properties) for H 2O-CO 2-CH 4-N 2-NaCl-KCl-CaCl 2-rich fluid inclusions using the clathrate melting temperature in combnation with liquidvapour equilibria, data from Raman spectroscopic analysis of the nonaqueous phases, and volume fraction estimates of the phases present. Calculations are restricted to fluid compositions less than eutectic salinities. If volume estimates are not provided, the programs calculate only the properties of the individual phases present in fluid inclusions during clathrate melting, including the salinity. Errors in measured parameters and in volume fraction estimates, which may be relatively large, are also handled by the programs.