Nonlinear relationship between heavy oil viscosity and asphaltene dispersion: A molecular dynamics simulation study

Theoretically clarifying the sources of viscosity of heavy oil is an essential premise for achieving effective exploitation and viscosity reduction. However, the complicated dispersion behavior of asphaltenes hinders the elucidation of the underlying viscosity mechanisms. Therefore, we investigated the relationship between heavy oil viscosity and asphaltene dispersion, identifying an unconventional nonlinear V-shaped trend. A generalized physical model is then proposed to elucidate the determining sources of heavy oil viscosity. This viscosity model emphasizes the dynamic balance role of external molecular friction and internal structural deformation of asphaltene aggregates in their contribution to viscosity, deepening the understanding of the nature of high viscosity in heavy oil. These results provide valuable theoretical support to enhance our understanding of the microscopic molecular mechanisms underlying heavy oil viscosity, which is expected to contribute to a better comprehension of the intricate viscosity phenomena and the development of more effective viscosity reducers.