AbstractThe simplified version of the perturbed hard‐chain theory (SPHCT) developed by Kim et al. (1986) is modified by reformulating the attractive portion of the canonical partition function for mixtures, and replacing the repulsive portion by a simple simulated expression. The final equation of state developed is cubic in volume. The test results on pure fluids, binary/multi‐component mixtures and reservoir fluids indicate that the CSPHC EOS retains the advantages of the original PHCT, and significant improvements over the SPHCT in predicting the VLE of heavy hydrocarbon‐containing/CO2‐containing mixtures, and liquid phase density are o