分子动力学模拟表面活性剂驱油的研究进展与展望

Research progress and prospects of surfactant flooding in molecular dynamics simulation

表面活性剂在油田三次采油中具有广泛应用,从微观上对表面活性剂驱油的作用机理进行研究具有重要意义。近年来,分子动力学(Molecular Dynamics,MD)模拟已成为油气田开发研究的一种重要方法。运用MD模拟方法对表面活性剂进行研究已成为热点。通过MD模拟计算系统中所有运动粒子的牛顿方程数值解,分析原子位置随时间变化的规律。利用MD模拟研究表面活性剂分子的微观行为,从而探究表面活性剂分子的性能和微观驱油机理,MD模拟界面处表面活性剂的运动及聚集状态,分析界面处表面活性剂分子对界面体系的影响,对表面活性剂的现场应用具有一定的指导意义。为此,基于MD模拟的原理概述,首先对MD模拟中的力场、边界条件、系综类型和数值算法进行了总结;其次重点阐释了MD模拟表面活性剂驱油的微观机理,包括降低油水界面张力,改变表面润湿性,增加界面电荷及乳化作用等;介绍了MD模拟在表面活性剂驱油的应用实例;最后提出了MD模拟在表面活性剂驱油的发展方向,包括与生产相近的驱油环境、新型表面活性剂的设计、理论与实验的关系、分子力场和势能模型的优选、复合与多功能一体化表面活性剂的研发等。

Surfactants are widely used in the tertiary recovery of oilfields,and it is of great significance to study the mechanism of surfactant flooding from the microscopic point of view.In recent years,molecular dynamics(MD)simulation has become essential for oil and gas field development research.The use of MD simulation to study surfactants has become a hot spot.Through MD simulation,the numerical solutions of Newton’s equations are calculated for all the moving particles in the system,and the change in atomic positions with time is analyzed,from which some laws are found.MD simulation can be used to study the microscopic behavior of surfactant molecules to explore the properties of surfactant molecules and the microscopic flooding mechanism.MD simulation of the movement and aggregation state of surfactants at the interface and the analysis of the influence of surfactant molecules at the interface on the interfacial system are of some guiding significance for the field application of surfactants.To this end,based on the principle overview of MD simulation,firstly,the force field,boundary conditions,system types,and numerical algorithms in MD simulation are summarized;secondly,the microscopic mechanisms of MD simulation of surfactant flooding are highlighted,including the reduction of oil-water interfacial tension,the change in surface wettability,the increase in interfacial charge and emulsification,etc.;then,examples of the application of MD simulation in surfactant flooding are presented.Finally,the development directions of MD simulation technology in surfactant flooding are proposed,including the flooding environment similar to production,the design of new surfactants,the relationship between theory and experiment,the selection of molecular force field and potential energy model,and the research and development of composite and multifunctional integrated surfactants.