Equations of state should be tuned to reservoir conditions by PVT tests for phase behavior modeling. This tuning is achievable via an optimization method. In this work, simulated annealing algorithm is applied as a global optimization method to parameter optimization for PC-SAFT from the statistical associating fluid theory incorporating hard chain as reference fluid. The optimization parameters are determined by minimizing the calculated phase behavior of a synthetic petroleum mixture and real petroleum fluids from Iranian oil and gas reservoirs, based on their PVT-tests. We examined several tests, assumed to be representative of reservoir processes, such as differential liberation and constant composition expansion for oil samples and constant volume depletion for gas condensate sample. In petroleum systems, new petroleum fraction characterizing correlations were developed and validated according to PVT data and other equations of state. The results showed a high degree of accuracy for these newly developed correlations. It is observed that for the synthetic mixture and real reservoir fluids, considering the parameters obtained using the annealing technique, the solutions are theoretically justifiable. For real samples of petroleum fluid, the results are acceptables such results provide a measure of confidence that the annealing method does converge to the global minimum in the majority of the studied systems.
 Robinson D., The Characterization of Heptanes and Heavier fractions for The GPA Peng-Robinson Program, Ind. Eng. Chem. Fundam., pp. 59-64, 1978.
 Peng D., & Robinson D., A New Two Constant Equation of States, Ind. Eng. Chem. Fundam., 1976.
 Soave G., Equilibrium Constant from a Modified Redlich-Kwong Equation of State, Chemical Engineering Science, pp. 1197-1203, 1972.
 Praisnitz J., Lichtenthaler R., & de Azevedo R., Molecular Thermodynamics of Fluid Phase Equilibria, Prentice-Hall Inc, 1999.
 Chapman W., Gubbins K., Jackson G., & Radosz M., New reference equation of state for associating liquids, Industrial and Engineering Chemistry Research, pp. 1709-1721, 1990.
 Fu Y., & Sandler K., A simplified SAFT Equation of state for associating compounds and mixtures, Industrial and Engineering Chemistry Research, pp. 1897-1910, 1995.
 Huang S., & Radosz M., Equation of State for Small, Large, Polydisperse, and Associating Molecules: Extension to Fluid Mixtures, Industrial and Engineering Chemistry Research, 1994.
 Gross J., & Sadowski G., Perturbed-Chain SAFT: an equation of State Based on a Perturbation Theory for Chain Molecules, Industrial and Engineering Chemistry Research, pp. 1244-1260, 2001.
 Ahmed T., Hydrocarbon Phase Behavior, Gulf Publishing Co, 1990.
 Danesh A., PVT and Phase Behavior of Petroleum Reservoir Fluids, Elsevier, 1998.
 McCain Jr. W., The Properties of Petroleum Fluids, Pennwell Books, 1990.
 Kirkpatrick S., Optimization by Simulated Annealing. Science, pp. 671-680, 1983.
 Behzadi B.C. & Gulindo A., Application of the simplex simulated annealing technique to nonlinear parameter optimization for the SAFT-VR equation of state, Chemical Engineering Science, pp. 6607-6621, 2005.
 Michelsen M.L., Calculation of phase envelopes and critical points for multi-component mixtures, Fluid Phase Equilibria, pp. 1-10, 1980.
 Michelsen M., The Isothermal Flash Problem, Part I: Stability, Fluid Phase Equilibria, pp. 1-19, 1982.
 Li Y., Development of a General Phase Envelope Construction Algorithm for Reservoir Fluid Study, SPE, 11198, 1982.
 Herault L., Rescaled Simulated Annealing-Accelerating Convergence of Simulated Annealing by Rescaling the States Energies, Journal of Heuristics, pp. 215-252, 2000.
 Metropolis N., Equation of State Calculations by Fast Computing Machines, Journal of Chemical Physics, pp. 1087-1092, 1952.