加热温度对含蜡原油胶凝过程微观机理的影响

Effect of heating temperature on the microscopic mechanism of gelat in process of waxy crude oil

加热温度是含蜡原油胶凝程度的主要影响因素。基于油品实验基本物性数据,选取与实验原油实际分子结构较接近的蜡晶、胶质和沥青质分子模型构建含蜡原油体系,应用Materials Studio软件进行分子动力学模拟,研究加热温度对含蜡原油胶凝过程微观机理的影响。结果表明:含蜡原油凝点温度可由密度—温度曲线和自扩散系数—温度曲线综合判断;加热温度降低时,含蜡原油体系分子链由直链转变为卷曲状态且在凝点时发生明显变化;蜡晶同种分子间的聚集是含蜡原油胶凝的主要影响因素。蜡晶分子间的径向分布函数(RDF)存在峰值且集中,使凝点恶化的加热温度RDF峰值明显升高。该结果从分子间作用机理上为含蜡原油胶凝体系流变特性的影响规律研究提供依据。

Heating temperature is the main factor affecting the gelling degree of waxy crude oil.According to the physical property data of oil products measured in the macro experiment,the wax crystal,colloid and asphaltene molecular models closest to the actual molecular structure of the experimental crude oil are selected to construct the waxy crude oil system.The molecular dynamics simulation is carried out with Materials Studio software to explore the influence of heating temperature on the micro mechanism of the gelation process of waxy crude oil.The results show that the condensation point of waxy crude oil can be determined by the curves of density-temperature and self-diffusion coefficient-temperature.When the temperature decreases,the molecular chain of waxy crude oil system changes from straight chain to curl state,and changes significantly at the condensation point temperature.The aggregation among the same molecules of wax crystal is the main factor of the gelation of waxy crude oil.The radial distribution function(RDF)between wax molecules has a peak value and concentration,which significantly increases the RDF peak value of the heating temperature at which the solidification point deteriorates.The results provide a basis for the study of the rheological properties of waxy crude oil gelling system from the perspective of intermolecular interaction mechanism.