An alternate characterization procedure of crude oils and modeling of asphaltene precipitation using PC-SAFT equation of state: estimation of asphaltene-rich phase maximum

In the present work, we propose an alternate characterization procedure to represent asphaltene precipitation using the Perturbed Chain-Statistical Associating Fluid Theory (PC-SAFT) equation of state (EOS) for modeling the behavior of various crude oils. The association term was omitted. The Saturates, Aromatics, Resins, and Asphaltenes (SARA) analysis, and recombined oil sample compositional analysis are used to perform the characterization of crude oil. The phase behavior optimization task is conducted and performed sequentially. First, the three-phase vapor pressure, and stock tank oil molecular weight and density are fitted with the molecular weight of saturates and aromatics, and the binary interaction parameter of saturates. Second, the asphaltene onset pressure and precipitated amount are adjusted with asphaltene aromaticity and binary interaction parameters. The calculations are conducted using an improved vapor-liquid-liquid equilibrium (VLLE) flash calculation algorithm. The phase behavior and the amount of precipitated phase are presented for nine crude oils. Component behavior in the three-phase region at the asphaltene-rich phase maximum is predicted. The results of the bubble point and asphaltene onset precipitation curves obtained using the proposed characterization method closely match the experimental data with or without gas injection. A linear model correlation of asphaltene-rich phase maximum is proposed.

Automated summary

In this study, an alternate characterization procedure using the PC-SAFT equation of state (EOS) is proposed to represent asphaltene precipitation in various crude oils. The SARA analysis and recombined oil sample compositional analysis are used for crude oil characterization. A phased behavior optimization task is conducted, adjusting the molecular weight and binary interaction parameters to fit various properties. The proposed method closely matches the experimental data, and a linear model correlation of asphaltene-rich phase maximum is proposed.