纳米孔道中重质油缔合结构及传质特性的模拟研究

In depth understanding of the mass transfer characteristics of heavy crude oil in nanochannels is of great significance for the efficient catalytic conversion of heavy crude oil. The current understanding on the hindered mass transfer mechnism of heavy crude oil is still based on the Renkin equation or the power law, ignoring the impacts of the complexity in oil composition and its easily aggregation characteristics. Moreover, the wall effect which is more prominent in nanoscale is neglected in the existing models. How to summarize the above factors and quantitative reveal the impacts of aggregation structure and wall effect on the hindered mass transfer of heavy crude oil is still the key problem to be solved. Starting from the typical molecular structures of heavy crude oil, this project plans to develop the coupled MD and DPD multi-scale simulation method to study the variation of aggregation structure and mass transfer process of heavy crude oil in nanochannels, and figure out the synergistic effects of the molecular steric effect, the wall adsorption effect, the external fields and the heavy crude oil composition. Combined with theoretical analysis, the quantitive association between structure and mass transfer characteristics will be established, and a new theoretical model for hindered mass transfer of heavy crude oil will be constructed with the key control factors determined, which is expected to provide theoretical basis to the optimization design for the utilization of heavy crude oil.

深入认识纳米孔道中重质油的限域传质机制对重质油的高效催化转化具有重要意义。目前对重质油受限传质的认识仍基于Renkin方程或幂率定律，忽略了重质油组成复杂及易于缔合等特征的影响，此外，纳米尺度更加突出的壁面作用在已有的模型中并没有体现，如何综合上述因素，定量揭示重质油缔合结构及壁面作用对重质油受限传质的影响规律仍是亟待解决的关键问题。本项目拟从重质油特征分子结构出发，发展分子动力学、耗散粒子动力学耦合的多尺度模拟方法，深入研究纳米孔道中重质油缔合结构的变化规律，分析纳米孔道中重质油的传质过程，阐明分子排体积效应、壁面吸附效应、外场作用及重质油组成等因素的协同作用机制，结合理论分析，建立缔合结构-传质特性之间的定量关联，构建重质油受限传质新理论模型，确定关键控制因素，以期所得到的规律可以为重质油加工过程的优化设计提供理论基础。

深入认识纳通道中重质油的限域传质机制对重质油的高效催化转化具有重要意义，如何定量揭示重质油缔合结构及壁面作用对重质油受限传质的影响规律仍是亟待解决的关键问题。本项目以实验获得的不同地区重质油的组成为基础，构建了四种重质油的模型化合物，分析了分子构象以及分子缔合对不同地区重质油流变和粘温性的影响，明确了构象及缔合结构在不同地区重质油中的致粘机理。基于重质油组成，深入分析了重质油乳化液界面组成和含水量对乳化液稳定性的影响，基于Ostwald熟化速率模型获得了重质油聚集体的动态演化规律，揭示了重质油乳化液乳化稳定性转变机制。模拟了纳米狭缝中受限条件对自扩散的影响以及压力驱动流特征，厘清了界面作用、沥青质构型及缔合结构对沥青质分子受限扩散系数的影响规律及调控机制，明确了界面作用及流变性在不同孔径中重质油传递通量的主导作用机理。理论研究了油藏内重质油渗流规律，通过渗流实验得到流度与剪切梯度之间的关系。建立了适用于多通道体系中非牛顿流体的通量模型，得到了最小启动推动力、拟启动推动力和临界启动推动力之间的关系，并通过渗流实验验证了上述理论模型的可靠性。上述研究为重质油开采、储运和加工过程设计与优化提供了理论指导。