Application of Simulated Annealing Technique to Non-Linear Optimization of PC-SAFT for Petroleum Reservoir Fluids

Abstract

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.