油藏中分散非连续残余油膜的驱替机理分析

水驱后的残余油膜将贴于孔隙壁面，为壁面边界层流体，处于三相界面的包围和共同作用下。目前的调研结果显示，油膜的组成及力学特性沿孔壁方向上是变化的。在化学驱过程中油膜不仅受到驱油剂的驱替作用。还受驱油剂／油界面张力、油／固体界面张力及驱油剂／固体界面张力的阻碍作用。由于油膜组成、力学特性及相间作用的复杂性．以往对油膜驱替机理的研究都是从微观实验的角度对现象作观察和定性解释。本文根据水驱后残余油膜在油藏孔隙中存在的特点，提出了油膜驱替的简化模型。基于油膜驱替的微观实验，采用数值方法从定量的角度分别计算了不同黏弹性驱油剂在不同的驱油剂／原油界面张力作用下对残余油膜的驱替效率。考察了驱油剂的流变性、驱油剂／油界面张力、驱替速度等因素对驱替不同厚度油膜的影响规律。进一步探讨了驱油剂／原油界面特性和流变性在驱替残余油中的综合作用。研究结果表明，驱油剂对油膜的驱替始于驱油剂／油界面，要同时克服驱油剂／油界面约束力和油膜的屈服应力。降低界面张力、增强驱油剂的黏弹性、增加驱替速度，有利于提高驱替残余油膜的驱替效率。适当增加驱油刑的黏弹性可以放宽驱替薄油膜时对超低界面张力的要求。图13参9。

On the Displacement Mechanisms of Residual Oil Film

The residual oil film after water flooding is a near-wall fluid layer which is adhered to pore's wall and enclosed by three phase interfaces.The oil film is shown to be changeable in components and mechanical properties away from the pore's wall.In chemical flooding,the oil displacement agent is to mobilize the oil film,whereas the oil displacement agent/oil,oil/solid and oil displacement agent/solid interfacial tensions prevent the oil film from moving.Taking into consideration the complexity of composition and mechanical properties of the oil film and of the actions between phase interfaces,the previous investigations focused on the phenomena observation and the qualitative speculation of micro experiments of displacing oil film.In this study,a simplified pore model for displacing oil film is put forward according to the main feature of remained oil film after water flooding. Furthermore,based on the experimental results,the displacement efficiency for viscoelastic fluid is quantitatively calculated by a numerical method at different interfacial tensions.The effects of rheological properties of oil displacement agent,oil displacement agent/oil interfacial tension,and displacing velocity on oil film of different thickness are discussed.Synthetic effects of viscoelasticity and interfacial property on residual oil are further investigated.The results show that the displacement of an oil film starts from the oil displacement agent/oil interface,and the restriction of interface and the yield stress of the oil film are needed to overcome.Decreasing interfacial tension or enhancing the viscoelasticity or displacement velocity is favorable to increasing the displacement efficiency of oil film.With increasing viscoelasticity appropriately,the requirement to ultra-low interfacial tension can be loosened for a thin oil film to be displaced.