Exploration of the Fundamental Factor for the Synergistic Modification of Model Waxy Oil by Eva and Asphaltene: An Experiment and Simulation Study

It has been well documented that the synergistic effect of polymer pour point depressant (PPD) and asphaltenes improves the low-temperature rheology of waxy oil. However, the fundamental factor of this synergistic effect has been little studied. In this paper, we innovatively combine macroscopic rheology experiment, mesoscopic particle size test and microscopic molecular dynamics simulation, supplemented by crystallization exotherm test and wax crystal morphology observation, to investigate the effect of solvent composition on the synergistic modification ability between ethylene-vinyl acetate (EVA) PPD and asphaltene, and then reveal the fundamental factor of this synergistic effect. The results showed that the EVA's adsorption on the asphaltene surface is the key element influencing their synergistic effects. With the deterioration of asphaltene dispersion in the solvent, the ability of asphaltene and EVA to synergistically improve the low-temperature rheology of model waxy oil increases and then decreases. When the aromatic component in the solvent was too high, a large number of aromatic solvent molecules were distributed around the asphaltene molecules through 7C-7C conjugation, which interfered with the adsorption of EVA on asphaltene due to the existence of spatial site resistance. When the content of saturated hydrocarbon component in the solvent was too high, the self-aggregation tendency of asphaltenes led to a decrease in the number of adsorption sites on their surfaces, resulting in the decline of the adsorption efficiency of EVA on the asphaltene surface, and the synergistic modification effect between them was reduced. This work offers fresh ideas for the design of waxy crude oil PPD, which is crucial for the efficient pipeline transmission of waxy crude oil.