Abstract: Surfactant flooding is an important means to improve the recovery of residual oil. It is of great significance to enhanced oil recovery (EOR)through clarifying the micro mechanism of oil film detachment from surfactant solution and optimizing the injection parameters. Using the molecular simulation technology, this paper investigates the dynamic detachment process and micro detachment mechanism of alkanes, polar components, asphaltene and the simulated crude oil composed of the aforesaid three components in pure water and surfactant systems under reservoir temperature and pressure, and further analyzes the sensitivity of different components to detachment speed, reservoir temperature and pressure, and surfactant concentration. The results show that the detachment process can be divided into detachment starting stage, parallel dislocation stage and subsequent detachment stage under reservoir temperature and pressure conditions. The detachment efficiency of alkanes failed to keep increasing, but experienced a significant fall in a specific stage, and that promoted by water flooding and surfactant flooding experienced such a fall in the subsequent detachment stage and the parallel dislocation stage, respectively; in general, low speed is favorable for the detachment of alkanes and asphaltenes by surfactant flooding; the detachment efficiency of alkanes is less sensitive to reservoir temperature, while that of polar components increases first and then decreases with the increasing of reservoir temperature, and high temperature is beneficial to the detachment of asphaltenes; alkanes and asphaltenes in middle-shallow reservoirs and polar components in deep reservoirs are easier to be detached; the optimal surfactant concentration for detachment of polar components is roughly twice that for alkanes, and the starting concentration of surfactant is high for asphaltene detachment.

Key words: surfactant, residual oil, molecular simulation, nonequilibrium dynamics, sensitivity analysis

摘要： 表 面活性剂驱是提高残余油采收率的重要手段,厘清表面活性剂溶液剥离油膜微观机制进而优化注入参数对提高采收率具有重要意义。利用分子模拟技术研究了纯水和表面活性剂体系在储层温压条件下对原油中的烷烃、极性组分、沥青质以及三者组成的模拟原油的动态剥离过程及微观机制,分析了原油组分剥离效率对剥离速度、油藏温度、压力和表面活性剂浓度的敏感性。研究结果表明:在地层温度和压力条件下,工作液体系剥离原油组分可分为剥离启动阶段、平行错位阶段、后续剥离阶段。对于烷烃组分,剥离效率并不会持续升高,而是在特定阶段出现明显的"回落"现象,水驱和表面活性剂驱剥离效率"回落"现象分别出现在后续剥离阶段和平行错位阶段;总体上,低速有利于表面活性剂剥离烷烃和沥青质;烷烃剥离效率对油藏温度敏感性较低,极性组分剥离效率随油藏温度升高先增大后减小,高温有利于沥青质的剥离;中—浅层油藏有利于烷烃和沥青质的剥离,而深层油藏极性组分更容易剥离;剥离极性组分的最优表面活性剂浓度约为烷烃的2倍,表面活性剂剥离沥青质存在较高的"启动"浓度。

关键词: 表面活性剂, 残余油, 分子模拟, 非平衡动力学, 敏感性分析