A molecular dynamics approach to revealing effect mechanism of asphaltene on wax deposition behavior

Abstract

The complex structure of asphaltene itself leads to obvious precipitation and aggregation characteristics, and it interacts with wax molecules, thereby affecting the wax precipitation characteristics of waxy crude oil. To clarify the effect of asphaltene on wax deposition behavior, molecular dynamics simulations were conducted to analyze the aggregation behavior of wax molecules in waxy crude oil systems and the effect of asphaltene on wax deposition. Subsequently, dynamic wax deposition experiments were used to validate the simulation results, and the influence of asphaltene on wax deposition behavior was further discussed in conjunction with the simulation results. The results show that the lower the temperature of the crude oil system, the lower the cooling rate, and the higher the aggregation degree of wax molecules; As the concentration of asphaltene increases, the existence state of asphaltene will undergo a transition, with a concentration of 0.2 wt% asphaltene as the transition boundary. The aggregation of asphaltene molecules is mainly in the form of F-type stacking, and the presence of asphaltene weakens the structural strength of the wax deposition layer. On the other hand, the aggregated asphaltene hinders the growth of wax crystal clusters due to spatial hindrance; Increase the concentration of asphaltene in the model oil, when the asphaltene concentration is 0.2 wt%, the wax deposition rate reaches its maximum, which means that the asphaltene concentration will affect its existence state in the waxy crude oil system, thereby affecting the wax deposition behavior. And analyzed the effects of temperature and moisture content on wax deposition.