Asphaltenes Precipitation from Crude Oil and Hydrocarbon Media

摘要

The asphaltenes precipitation onset and the precipitation yield were determined for four different crude oil samples. The results confirm that crude oil samples presenting low precipitation onsets effectively present instability and depositional problems in field operations, whereas those with a high onset are stable and do not present separation or precipitation in production operations. It was also confirmed that, as reported in the literature, the onset increased and the amount of solids separated decreased with the molecular weight of the alkane used to induce the precipitation. The same methodology was extended to asphaltenes, resins, and asphaltenes/resins mixtures dissolved in toluene using n-heptane and the ethyl alcohol as nonsolvents to evaluate the influence of the resins fraction on asphaltenes stabilization. The results analyzed using the Hildebrand solubility parameter point out for asphaltenes and resins being a continuum or family of complex molecules with a variation in molecular weight and polarity rather than two fractions containing chemically different compounds. This observation seems to be corroborated by the FTIR results that show similar spectra for asphaltenes separated using different solvents and for the resins fraction.