Peng-Robinson predictions for hydrocarbons, CO2, N2, and H2 S with pure water and NaCI brine

Abstract

Søreide, I. and Whitson, C.H., 1992. Peng-Robinson predictions for hydrocarbons, CO2, N2 and H2S with pure water and NaCI brine. id Phase Equilibria 77: 217-240. Attempts at predicting mutual solubilities with a conventional cubic equation of state (EOS) including the effect of salts in the aqueous phase have so far been limited. The main purpose of this work is to provide a simple and novel approach for predicting mutual solubilities of brine/hydrocarbon mixtures with an EOS at high pressures and temperatures, including the effect of salinity in the aqueous phase. The Peng-Robinson EOS 2 has been applied in this study with two modifications: (1) an α-term in the EOS constant a has been developed specifically for the water/brine component as a function of sodium chloride (NaCl) brine salinity and pure water reduced temperature, TI, and (2) two sets of binary interaction parameters (BIP) in the classical mixing rule for mixture EOS constant a have been determined as a function of acentric factor, temperature, and salinity. Experimental data of vapor pressures and mutual solubilities provide the basis for the proposed methods. Applications of the methods described include phase behavior prediction of reservoir gas-oil/brine systems at high pressures, including (1) gas solubility in water/brine and (2) water solubility in hydrocarbon reservoir fluids.