Asphaltene Stability in Other Crude Oil Fractions

摘要

Changes in oil composition are unavoidable during production, transportation, and processing of crude oils. Questions about the effects of these changes on asphaltene stability have been addressed in this systematic study of different crude oils, asphaltene fractions, resins, and a range of hydrocarbon solvents and precipitants. The refractive index of onset mixtures is used to quantify asphaltene stability and the results are analyzed with an asphaltene solubility model. The results show that working with highly diluted oil samples or with isolated fractions of asphaltenes can lead to inaccurate predictions of the onset of asphaltene flocculation in their original crude oil. Toluene acts as an ideal solvent, but α-methylnaphthalene appears to interact with asphaltenes in solution. From a given crude oil, asphaltene fractions separated with higher molecular weight paraffins are more unstable than those separated by lower molecular weight precipitants. When resins are added, the changes in stability are continuous; there is no critical amount of resin that imparts stability. Instead, resins appear to be part of the continuum of species in which asphaltenes represent one end of the spectrum. Stability of asphaltenes in blended oils is intermediate between the two oils in the mixture.