离子匹配精细水驱提高采收率机理研究

水驱是油田开发的主要技术，但常规水驱只是通过向地层补充能量的方式提高采收率，而离子匹配水驱技术则是基于油藏介质中固-液微界面作用强的特点，通过对注入水离子类型和强度的精确离子匹配实现剥离残余油膜提高驱油效率。以西峰油田为例，结合室内驱油实验、Zeta电位测量、原子力显微分析和界面作用力数值计算等方法，系统研究了离子匹配精细水驱技术提高低渗油藏采收率的主控因素。结果表明，随着注入水离子类型的调整和离子浓度的改变，在二次采油和在三次采油模式下，离子匹配精细水驱分别比模拟地层水驱提高采出程度15.6和9.8个百分点。其中，界面的Zeta电位和分离压的大小与离子匹配精细水的离子类型关系密切。相同离子浓度情况下，数值计算与原子力显微分析实验所得结果均表明，Na⁺比Ca²⁺和Mg²⁺的分离压高，从而表现出了更有利于从岩石表面剥离油膜的能力；同时，随着注入水离子浓度的降低，盐水-原油-岩石界面的Zeta电位负值和分离压均呈增大的趋势，油和岩石表面之间的斥力增大，致使残余油更容易从岩石表面剥落，离子匹配精细水驱有助于提高水驱油藏的开发效果。

A Study on Mechanism of EOR by Ion Matching Water Injection

Water flooding is the main technology of oilfield development, with conventional mechanism of supplementing energy to the formation. However, ion matching water injection technology enhance the oil recovery through reservoir oil-water-rock interaction. Taking advantage of strong solid-liquid micro interface in the reservoir media, injection with ion matched water could improve oil displacement efficiency by matching the type and strength of ions in injected water with that in reservoir to peel off the residual oil film. Taking Xifeng Oilfield as an example, laboratory core flooding experiment, Zeta-potential measurements, Atomic force microscopy(AFM) force-distance measurement and direct numerical simulation of interfacial force are used to analyze the influencing factors of disjoining pressure as well as Zeta-potential at the oil-brine-rock interfaces, so as to explain the EOR mechanism of ions tuning water(ITW) flooding from microscale. Core flooding experiments show that both in secondary and tertiary modes, ITW can enhance oil recovery by 15.6 and 9.8 percentage point compared with coventional water flooding; Zeta-potential and AFM force-distance measurements show that Zeta-potential and disjoining pressure are influenced by the concentration and ionic type of the brine, which determine the detachment of the residual oil from rock. At the same ion concentration, the results of numerical calculation and atomic force microscopy analysis show that the disjoining pressure of Na⁺ is higher than that of Ca²⁺ and Mg²⁺, which shows the stronger ability to peel oil film from rock surface. Moreover, with the decrease of ion concentration of injected water, the negative value of Zeta-potential and disjoining pressure at the interface of brine-crude oil-rock are increasing, and the repulsion force between oil and rock is increasing, which makes the residual oil easier to peel off from the rock. ITW is helpful to improve the development effect of water flooding reservoir.