Multi-level Mechanism Of SARA Components Contribution To Heavy Oil Viscosity

The high viscosity of heavy oil seriously restricts the exploitation and transportation of heavy oil,so many scholars have done a lot of work on the viscosity reduction technology of heavy oil.However,there is still a lack of clear understanding of the hierarchical structure and viscosity in heavy crude oil.Therefore,we should further study the molecular aggregation of SARA components,the formation process of aggregation,and the relationship between macroscopic size and viscosity at the molecular level,which is of great significance to the exploitation and transportation of heavy oil.Micro Visc has high accuracy for viscosity measurement of petroleum system,especially for exploring the law of low viscosity varying with concentration.In this thesis,the vacuum residue was separated into SARA by total solvent extraction.The results show that theη_r-c curves show a good linear relationship,which meets the Einstein law.The solvation ability of molecules K and molecular size can be obtained by the intrinsic viscosity.The results show that the K values of the SARA components are all more than 1,so the SARA components have solvation effect in solvent and form the size of adsorption-solvation layer.The molecular structure model was constructed by ¹H-NMR data to obtain the average structure equivalent diameter.The comparison between the diameter shows that the viscosity equivalent diameters of SARA components are some what higher than the average structure equivalent diameters.When the concentration is in the range of 2-12g/L,there is a weak interaction force between the components and solvent molecules and there is obvious nano-aggregate characteristics in asphaltenes.The viscosity mixing rule is generally applicable in the petroleum system,from which the viscosity mixing rule and viscosity-temperature mixing rule of saturates,aromatics and resins of Liaohe heavy oil residue suitable for high concentration system are selected.The viscosity-temperature properties of saturates,aromatics and resins can be accurately described by Walther viscosity-temperature equation.The relationship between viscosity and weight concentration of SARA components conforms to the modified Chirinos model.Through the Chirinos model,the m number is defined to describe the contribution of component to the viscosity of the system,and the m value is the slope of the linear relationship between loglog（0.7+η）and weight concentration.The results show that the more the m value,the more the viscosity growth rate of the component system;m value is not only related to the structure of component molecules,but also related to the aggregation of components in solution.By analogy with the intrinsic viscosity,the slope of the relative viscosity-concentration in the Einstein formula is the intrinsic viscosity[η],which unit is cm³/g.In high asphaltene concentration system,[η]_asp is defined as the equivalent viscosity of asphaltene at different concentrations,and the slope[η]_asp is used to describe the hierarchical relationship of asphaltene aggregates.This hierarchical relationship conforms to the Yen model.