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重质油组分分子的聚集是重质油最显著的特征之一,重质油的高粘特性和相态稳定性均与此聚集行为有紧密的联系。为克服实验研究获得重质油微观聚集结构的困难,本文采用Zhang等人针对重质油体系改进的耗散粒子动力学(DPD)方法,研究重质油的分子聚集结构及其对重质油稳定性的影响。根据重质油组分的结构特征,可将重质油表达为其他轻组分、饱和分、芳香分、胶质和沥青质五种DPD模型分子的混合物。模拟结果表明,本文采取的重质油模拟体系和参数是合理的,很好地反映了重质油中的分子聚集结构。重质油具有胶体多分散体系的特征。其中,芳香度最高的沥青质分子对聚集结构的有序性有显著影响,重质油中的胶质具有胶溶作用,能抑制因沥青质分子聚集导致的相分离和聚沉,芳香分与饱和分和其他轻组分将构成胶体的连续相。本文对重质油稳定性的预测获得了与实验研究一致的结果。对于一定的沥青质与芳香分质量比m_(Asph)/m_(Arom),在沥青质与胶质质量比m_(Asph)/m_(Resin)较小的情况下,重质油都将保持稳定。沥青质与胶质的质量比m_(Asph)/m_(Resin)存在一个极限,当大于这个极限时,重质油将出现聚沉。沥青质与芳香分质量比m_(Asph)/m_(Arom)的降低将使重质油的稳定域出现扩张。
The aggregation of heavy oil molecules is one of the most prominent features of heavy oil. The high viscosity and phase stability of heavy oil are closely related to this aggregation behavior. In order to overcome the difficulty of obtaining microscopic aggregates of heavy oil in experimental studies, this paper adopts the improved dissipative particle dynamics (DPD) method developed by Zhang et al. To study the molecular aggregation structure of heavy oil and its effect on heavy oil The impact of stability. Depending on the structural characteristics of the heavy oil components, the heavy oil can be expressed as a mixture of other light, saturated, aromatic, glial and asphaltene five DPD model molecules. The simulation results show that the simulation system and parameters of heavy oil adopted in this paper are reasonable and well reflect the molecular aggregation structure in heavy oil. Heavy oils have the characteristics of a colloidal, polydispersed system. Among them, asphaltene molecules with the highest degree of aroma have a significant influence on the orderliness of the aggregated structure, and the gums in the heavy oil have a peptizing effect, which can inhibit the phase separation and coagulation caused by the aggregation of asphaltene molecules, the aromatic fraction Saturated and other light components will form a colloidal continuous phase. The prediction of the stability of heavy oil obtained in this paper is consistent with the experimental results. For a certain Asphaltene to Asphaltene / As (Arom) ratio, the heavy oil will remain stable with a small Asphaltene / Asph / Resin ratio . Asphaltene and colloidal mass ratio m_ (Asph) / m_ (Resin) there is a limit, when greater than this limit, the heavy oil will appear to sink. Asphaltene to aromatic fractional mass ratio m_ (Asph) / m_ (Arom) reduction will make heavy oil stable domain expansion.