Three-dimensional network gel structure and viscosity reduction mechanism of heavy oil

Abstract

The internal structure of heavy oil plays an important role in the research of the viscosity reduction mechanism of heavy oil. On the one hand, the influence of heavy oil composition on the viscosity of heavy oil is discussed. The results show that the influence rate of composition on viscosity is Asphaltenes (0.11377) > resins (0.07566) > saturated hydrocarbon (−0.06027) > aromatics (−0.07536), and the influence range of composition on viscosity is Asphaltenes (3.5348%) > resins (2.828%) > saturated hydrocarbon (0.861%) > aromatics (0.167%). On the other hand, the structural changes of heavy oil before and after viscosity reduction were studied by elemental analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Based on Yen's heavy oil colloid model, the hypothesis of the three-dimensional network gel structure model is put forward. The possible reason for forming the gel structure is that the system contains a large number of gel factors, which can spontaneously aggregate and assemble into ordered structures in the solvent. What's more, the hypothesis of heavy oil gel structure was verified by rheological experiments. Rheological tests showed that resins and Asphaltenes were packed together by hydrogen bonds and π-π bonds, forming a tight gel network structure. Saturates and aromatics were dispersed in heavy oil as solvents. The essence of heavy oil viscosity reduction is that the π-π bonds and hydrogen bonds are destroyed, disintegrating the heavy oil gel structure, which is transformed into a sol structure model.