Effect of microwave electric field on asphaltene aggregation in a heavy oil system: MD and DFT investigation

An in-depth understanding of asphaltene aggregation is vital for the viscosity reduction of heavy oils, and essential for fully utilizing heavy oil resources. Therefore, the influence of microwave electric field on the aggregation of asphaltene in the heavy oil system was investigated via Molecular Dynamic simulation and Density Functional Theory calculation. The aggregation forms, interaction types and rheological behavior of asphaltene and other components were calculated by processing the trajectories. The results reveal that microwave electric fields play a significant role in the packing morphology of asphaltenes and other components at the micro-molecular level, leading to changes in the apparent viscosity of heavy oil system. It can be clearly manifested that under 5 V/nm of microwave electric field, asphaltenes primarily stack in TC -TC, connecting intimately with resin, constructing a stable colloidal structure of the system with high viscosity. Whereas, by enhancing the electric field, TC-TC stacking will gradually be destroyed, resulting in viscosity reduction. The T-shaped stacking of asphaltenes is favorable to form at 20 V/nm, inducing a stable network among the components, which is detrimental to the viscosity reduction. The achievements further confirm that an appropriate microwave electric field is the key to reducing the vis-cosity. In addition, considering the thermal and non-thermal effects of microwave, it is explored that microwave is more effective at low temperature. Therefore, the efficient combination of microwave power and treatment temperature is the critical factor to achieve better viscosity reduction effect.(c) 2023 Elsevier B.V. All rights reserved.