Effect of kerosene aromaticity as a solvent on bulk and interfacial properties of Brazilian heavy crude oil with high asphaltene content

Abstract

This study investigated the effect of solvent aromaticity on asphaltene stability and interfacial behaviour using typical diluted heavy oils, which better represent the chemical diversity of petroleum components than previous studies that used simple solvent mixtures with low asphaltene concentrations. A Brazilian crude with high viscosity and asphaltene content was diluted with two kerosenes, one containing only saturated compounds (KeS), and the other a saturates/aromatics mixture (KeSA) to maintain total aromaticity in the oil mixture upon dilution. Viscosity, asphaltene stability, interfacial tension, and elasticity of the oil mixtures were measured, and correlated with emulsion stability, regarding the differences in solvent aromaticity and aromatics/saturates ratio. The results showed that the different kerosene compositions affected bulk viscosity and asphaltene flocculation, but had a lesser effect on oil/brine interfacial tension due to the high asphaltene content in the diluted oil. The elastic modulus decreased at higher dilutions with KeS, while it remained consistent for KeSA mixtures, which supported the differences obtained in emulsion stability, at solvent concentrations within the optimal aromaticity ratio reported for simple solvent mixtures. Interfacial segregation of the aromatics in KeSA was also observed, which has not been reported in previous studies using complex solvents. These findings suggest that the trends reported with model oils, such as heptol with added asphaltenes, can also be applied to more realistic complex oil mixtures with higher asphaltene concentrations. Nevertheless, it was suggested that maintaining the aromatic content may not be enough to prevent asphaltene flocculation upon dilution, due to the concurrent increase in saturates.

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“…However, at higher concentrations, asphaltenes can aggregate and form larger structures. These larger structures may not be as effective at reducing IFT. , Moreover, high-density and high-viscosity fluids typically have higher IFT because they have greater molecular complexity and are less mobile, making it more difficult for them to spread and mix with other fluids at the interface. , …”

“…These larger structures may not be as effective at reducing IFT. 85,86 Moreover, high-density and high-viscosity fluids typically have higher IFT because they have greater molecular complexity and are less mobile, making it more difficult for them to spread and mix with other fluids at the interface. 83,87 As can be seen, by increasing the salinity from DIW to 1.5 SW, the IFT consistently decreased.…”