Prediction of Asphaltene Precipitation by Using an Association Equation of State

In this work, a new and efficient algorithm for asphaltene deposition modeling through application of an association thermodynamic model is introduced. It is assumed that pure asphaltene component only participates in the deposition phase. For characterization of asphaltenes, a two-phase flash calculation and cubic equation of state (Peng-Robinson equation of state) were used to describe asphaltene-toluene mixture (non-association mixture) and vapor-liquid equilibria, in which the critical properties of pure asphaltene component for the initial guess are adjusted with experimental data. Some of the association equation of state (AEOS) are selected for asphaltene modeling in a crude oil system as association mixture, which gives accurate results for water. To extend the model to crude oil mixtures, AEOS and vapor-liquid-deposition phase three-phase flash calculation are used to obtain the amount of asphaltene deposition and association model parameters. The authors' experimental data from the Iranian crude oil reservoir, in this study, were used to examine the proposed asphaltene association model. It has been shown that the calculated results are in good agreement with the experimental data.