Studies On The Effect Of Asphaltene On The High Viscosity Characteristics Of Heavy Oil

The conventional crude oil resources all over the world reduced year by year, accounting for a growing proportion of heavy oil. However, by contrasting with conventional crude oil, the high viscosity characteristic of heavy oil is a major bottleneck for the development and utilization of heavy oil. Heavy oil is a kind of complex colloidal system, both temperature and the own nature of heavy oil are important factors which related with its viscosity. In this paper, effects of asphaltenes on the high viscosity characteristic were mainly studied. It has important realistic significance to enhance heavy oil recovery and improve the technology for gathering and processing heavy oil.In this paper, six kinds of xinjiang heavy oil were used as the main research object. First, the basic composition and properties of the heavy oil were determined. Its functional structure was characterized by FTIR spectroscopy, and the basic structural parameters of asphaltene were determined by 1H-NMR, while viscosity-temperature characteristic of the heavy oil were studied; Second, the different contents of asphaltenes for homologous and heterologous heavy oil were preparaed, and the influence of content and nature of asphaltene on viscosity were investigated by viscosity method; Finally, the average size of asphaltenes of heavy oil were characterized by small-angle X-ray scattering(SAXS), the morphology of S,N,O elements of asphaltenes were measured with the X-ray photoelectron spectroscopy(XPS), and the dipole moment of asphaltenes were also measured.The results showed that, the light fraction(<180℃) in heavy oil was little, but vacuum residue(>500℃) were high, including high resins and asphaltenes contents. To different heavy oil,the higher contents of resins and asphaltenes, the larger viscosity of heavy oil; the viscosity of heavy oil was closely related to the size of the chemical structure of asphaltenes, it became larger with the lower ratio of hydrogen to carbon atoms and the bigger aromatic carbon ratio and condensation index; except for its structural properties, temperature is an important external factor affecting the viscosity of heavy oil.The homologous and heterologous heavy oil suggested that, with the increase of asphaltene content, the viscosity of heavy oil were showed a trend of increase, and the viscosity mutation point appeared when the asphaltene content reached a certain value which was coincide with the abrupt change point of the asphaltene average size. That is to say the viscosity would increase suddenly when association occurred between one asphaltene particle and another, indicating that in addition to the asphaltene content, association was also an important factor influencing the viscosity of heavy oil; The polarity of asphaltene was closely related with its hetero atom number and morphology in it. The greater the polarity of the asphaltene, associating activities were stronger, its microscopic performance was that the asphaltene average particle size were increased, and macroeconomic performance was the increase of the viscosity of heavy oil.