THERMODYNAMIC MODELING FOR PETROLEUM FLUIDS - I - EQUATION OF STATE AND GROUP-CONTRIBUTION FOR THE ESTIMATION OF THERMODYNAMIC PARAMETERS OF HEAVY HYDROCARBONS

A group contribution method is proposed for estimating the critical pr operties and acentric factors of paraffins, naphtenes and aromatics wi th emphasis on extrapolating to very heavy compounds. Group contributi ons for sulfurized compounds were added to improve further application s in petroleum engineering or in any other domain, From the experiment al normal boiling point, critical temperatures were correlated with a 0.6% average deviation on a set of 268 data and critical pressures wit h a 2.6% deviation on a 222 data set. The normal boiling points can be estimated without any experimental values, With this method, it was p ossible to correlate the normal boiling points of 641 hydrocarbons and sulfurized compounds with a deviation of less than 0.9%. From these e stimated values, a 1% deviation was obtained at the critical temperatu res and 2.8% at the critical pressures. The acentric factors of 160 co mpounds were correlated with a 6.5% deviation. With the proposed metho d, experimental vapor pressures were predicted using the Peng-Robinson equation of state for 125 compounds with a deviation of less than 5%, The results are compared with those obtained using other methods. (C) 1997 Elsevier Science B.V.