The effect of bitumen molecular fractions on diffusivity and rheology of bitumen under high-temperature conditions: Molecular dynamics (MD) simulation study

Heavy oil and bitumen play an incredible role in Canada's energy resources. The main processes that have already been applied to produce heavy oil and bitumen are in-situ thermal methods. The primary mechanism of production in these reservoirs is a reduction in heavy oil and bitumen viscosities via heat transfer. Having deep knowledge about the rheological behaviour of heavy oil and bitumen is crucial to designing a more accurate and efficient in-situ thermal recovery method. In this work, molecular dynamics (MD) simulation was used to model the rheological behaviour of bitumen under different temperatures. According to MD outputs, the highest diffusion coefficient between bitumen fractions belongs to saturate fractions. On the other hand, the lowest diffusion coefficient belongs to asphaltene fractions. The size of asphaltene, its polarity, and the polarity of a resin fraction affect the diffusion coefficient of asphaltene in a bitumen sample and its rheological behaviour. The MD simulation aims to provide molecular insights and essential information about the rheological trend of bitumen under different thermodynamic conditions. The results of the current work provide essential information about the effect of bitumen fractions on its rheological behaviour.