Methodology for the characterization and modeling of asphaltene precipitation from heavy oils diluted with n-alkanes

A regular solution model, previously used to model asphaltene precipitation from Western Canadian bitumens, was tested on four international heavy oil and bitumen samples. The input parameters for the model are the mole fraction, the molar volume, and the solubility parameter for each component. Heavy oils and bitumens were divided into four main pseudo-components, corresponding to the SARA fractions (saturates, aromatics, resins, and asphaltenes). Asphaltenes were divided into fractions of different molar mass, based on a gamma molar mass distribution. The molar volumes and solubility parameters of the pseudo-components were calculated using solubility, density, and molar mass measurements and previously developed correlations. Model predictions were compared with the measured onset and the amount of asphaltene precipitation for solutions of asphaltenes in toluene and n-heptane and for heavy oils diluted with n-alkanes, all under ambient conditions. The overall average absolute deviations (AAD) of the predicted fractional precipitation or yields were <0.031 for the asphaltene solutions and <0.008 for the diluted heavy oils. A methodology for characterizing heavy oils and modeling asphaltene precipitation from n-alkane-diluted heavy oils is proposed.