分子动力学模拟在三次采油中的应用

Application of molecular dynamics simulation in enhanced oil recovery

采用分子动力学模拟在微观尺度上解释三次采油领域的相关实验现象和过程机制,对后续提高原油采收率的现场应用有着重要的理论指导意义.本文综述了本课题组近年来利用分子动力学模拟针对三次采油中若干基本科学问题的研究,模拟表明表面活性剂的耐盐能力主要由极性头周围极化出的水化层的性质决定;泡沫的稳定性直接取决于假乳液膜和油桥结构的稳定性,两者分别受表面活性剂亲水基与水分子之间的结合能力以及疏水基与油相间的相互作用强弱影响;水通道的形成是影响固体表面的润湿翻转的重要因素;凝胶颗粒在纳米孔内的运移受孔径、表面结构等多种因素影响;稠油的高黏度主要来源于沥青质和胶质的堆积形成的网状结构,不同类型表面活性剂通过影响内部和界面结构起到降黏效果.同时应当指出,模拟结果受制于分子动力学方法中模型大小和模拟时间、力场的精确性等因素的影响,仍然需要结合实验方法进一步证实.

Enhanced oil recovery is an important technology to improve the oil recovery rate of oilfields.The understanding of the physical and chemical process mechanism in this field on the micro-scale is of important guiding significance for improving oil recovery efficiency.This article mainly reviews the recent research of basic scientific issues in the field of enhanced oil recovery through molecular dynamics simulation methods.The simulation shows that the salt tolerance of surfactants is mainly determined by the properties of the hydration layer polarized around the polar head;the stability of the foam directly depends on the stability of the pseudo-emulsion film and the oil bridge structure,which are affected by the binding ability between the head of surfactant and water and the strength of the interaction between the tail of surfactant and the oil phase;the formation of water channels is an important factor affecting the wettability alteration of solid surface;the transport of gel particles in the nanopores is affected by many factors such as pore size and surface structure;the high viscosity of heavy oil is mainly derived from the network structure formed by the accumulation of asphaltenes and resins.Different types of surfactants can reduce the viscosity by affecting the internal and interface structures.At the same time,it should be pointed out that the simulation results are subject to the influence of factors such as the model size,simulation time,and force field accuracy in molecular dynamics method.It still needs to be further confirmed with experimental methods.