Abstract: In order to investigate the deformation characteristic and transport behavior of oil-water micro-interface and its evolution law under different wettability conditions in water flooding,a Hele-Shaw cylindrical model has been constructed based on the N-S equation.Phase field method has been employed to track the topological deformation characteristics of oil-water micro-interface in water flooding.The effect of wettability,oil-water viscosity ratio,and capillary number on the deformation characteristic and evolution process of oil-water micro-interfaces has been studied.The simulation results show that the dynamic evolution process of oil-water micro-interfaces observed from the model surface in water flooding can be divided into four stag-es,including breakthrough,fracture,three-phase contact line intersection,and micro-interface merging.The breakthrough and fracture phenomenon of oil-water micro-interfaces can be observed repeatedly in the displacement process,and is not affected by wettability and rock particle distribution.Three-phase contact line intersection and micro-interface merging phenomenon have the similar deformation characteristics and evolution law in the vertical profile of the model,which are mainly influenced by wet-tability and rock particle distribution.Three-phase contact line intersection phenomenon occurs more frequently under water-wet condition,while the micro-interface merging phenomenon occurs more frequently under oil-wet condition.The change amplitude of displacement front decreases and then increases in water flooding as wettability changes from strong water-wet to strong oil-wet,which exhibits the piston-like displacement under weak water-wet condition.The simulation results show that the highest oil displacement efficiency is observed under weak water-wet condition,while the lowest oil displacement efficiency(61.06%)is observed under strong oil-wet condition.Moreover,as the oil-water viscosity ratio increases from 20 to 100,the occurrence rate of three-phase contact line intersection phenomenon decreases,the micro oil displacement efficiency decreases by 8.56%,and the initial displacement pressure also increases under weak water-wet and the same injected pore volume multiple condition.As the capillary number increases from 0.66×10-3 to 2.0×10-3,the occurrence rate of three-phase contact line intersection phenomenon increases,the volumes of residual oil decreases,the micro oil displacement efficiency increases by 9.36%,and the displacement pressure also decreases under weak water-wet and the same injected pore volume multiple condition.This reveals that the micro oil displacement efficiency can be significantly improved by increasing the occurrence rate of three-phase contact line intersection phenomenon under water-wet condition.The research results can enrich the micro flow mechanism in water flooding,and provide a theoretical basis for further explore and utilize the residual oil.

Key words: water flooding, micro-interface deformation characteristics, wettability, oil-water viscosity ratio, capillary number

摘要： 为探究水驱过程中不同润湿性条件下油水微界面的运移特征及其演变规律,基于N-S方程建立Hele-Shaw圆柱式模型,采用相场法界面追踪驱替过程中油水微界面的拓扑变形特征,研究润湿性、油水粘度比及毛细管数对油水微界面形变的影响.结果表明,水驱过程中油水微界面的动态演变过程可以分为 4 个阶段,即突破、分裂、三相接触线交汇及微界面融合.微界面的突破和分裂在驱替周期内重复发生,且不受润湿性和岩石颗粒分布的影响;三相接触线交汇和微界面融合具有相近的形变特征,主要受润湿性和岩石颗粒分布的影响.三相接触线交汇现象主要出现在亲水条件,而微界面融合现象则出现在亲油条件.润湿性由强亲水转变为强亲油时,水驱前缘变化幅度先降低后升高,在弱亲水条件时,呈现"活塞式"驱替模式.模拟发现在弱亲水条件下的驱油效率最高,而强亲油条件下的驱油效率最低(61.06%).在弱亲水和相同注入孔隙体积倍数条件下,随着油水粘度比从 20 增加到 100 时,三相接触线交汇现象的发生率逐渐降低,微观驱油效率降幅为8.56%,且驱替启动压力也随之降低;毛细管数从 0.66×10-3 增加至 2.0×10-3 时,三相接触线交汇的发生率增加,模型内的剩余油体积减小,驱油效率提高 9.36%.这表明在亲水条件下,增加三相接触线交汇现象的发生率能够显著提高驱油效率.研究结果能够丰富水驱微观渗流机理,为深度挖潜水驱剩余油提供理论依据.

关键词: 水驱, 微界面运移特征, 润湿性, 油水粘度比, 毛细管数

CLC Number: 

• TE341 TE312