文献类型：期刊文献

中文题名：多孔介质非均质性对水油非混相驱替的影响及机理分析

英文题名：Influence of porous media heterogeneity on water-oil immiscible displacement and mechanism analysis

作者：郭曜豪[1,2];蔡诗妤[3];李大军[4];张磊[2];孙海[2];杨永飞[2];朱光普[2];徐至[1];鲍博[1]

机构：[1]华东理工大学化工学院,上海200237;[2]中国石油大学(华东)石油工程学院,青岛266580;[3]中国石油大学(华东)化学工程学院,青岛266580;[4]中国石油化工股份有限公司胜利油田分公司滨南采油厂,滨州256600

年份：2022

卷号：52

期号：5

起止页码：807

中文期刊名：中国科学：技术科学

外文期刊名：Scientia Sinica(Technologica)

收录：CSTPCD;;EI(收录号：20222112135919);Scopus;北大核心:【北大核心2020】；CSCD:【CSCD2021_2022】；

基金：国家自然科学基金(批准号:21808056,51674280);中国石油科技创新基金(编号:2019D-5007-0208);山东省自然科学杰出青年基金(编号:ZR2019JQ21)资助项目。

语种：中文

中文关键词：N-S方程;孔隙尺度;非混相驱替;非均质性;采收率

外文关键词：N-S equation;pore scale;immiscible displacement;heterogeneity;oil recovery

摘要：深入理解水油两相在多孔介质内的非混相驱替过程对于水驱油藏开发具有至关重要的意义.为摸清水油两相流动模式,本研究基于Navier-Stokes(N-S)方程模拟水油两相在微观多孔介质中的非混相驱替过程,采用相场方法实时描述两相界面变化.并对比了均质多孔介质模型与非均质多孔介质模型内的水驱油过程,研究了多孔介质非均质性对于水油非混相驱替模式、驱替效率及出口端见水时间的影响.两相流体的非混相驱替模式通常可分为三种类型:毛管指进、稳定驱替、黏性指进.其流动模式通常取决于两个无量纲数,毛管数和黏度比.本研究结果表明,多孔介质非均质性会增强水油两相驱替过程界面的不稳定性,使得非均质模型内的非混相驱替更易向黏性指进发展,降低黏性指进产生的临界毛管数;非均质模型的无水采收率较均质模型低,多孔介质无水采收率并不随毛管数的增大而增大,当驱替模式由毛管指进向黏性指进转变时,无水采收率随毛管数的增大而减小;相同毛管数条件下,非均质模型出口端的见水时间比均质模型早,黏性指进的形成会减小均质与非均质模型见水时间差异.该研究初步揭示了多孔介质非均质性对于水油非混相驱的影响,为深入理解油气储层中水油两相流动规律提供了理论支持.
Water is usually injected into the reservoirs during the development of oil and gas resources to improve oil recovery due to its effectiveness and economic feasibility.Predicting the remaining oil distributions,fluid flow pathways,and oil recovery require a solid understanding of the water-oil immiscible displacement process at the pore scale.Previous researchers have divided immiscible fluids displacement patterns into three types,namely capillary fingering,stable displacement,and viscous fingering.These patterns are strongly influenced by two dimensionless numbers,fluid viscosity ratio(M)and capillary number(Ca).Then,some phase diagrams based on viscosity ratio and capillary number can be established to describe the parameter region for different displacement patterns.However,several recent studies have shown that the heterogeneity of porous media has a significant effect on immiscible displacement.At the same time,heterogeneity is also a major characteristic of oil reservoirs.In this study,the Navier-Stokes(N-S)equation is employed to simulate the water-oil immiscible displacement in two micro models,one with a homogeneous porous medium and another with a heterogeneous one.The dynamic change of the two-phase interface is tracked by the phase-field method.The porous medium was initially saturated with oil as the wetting fluid and water were injected.A series of displacement experiments were performed for six different capillary numbers,ranging from log Ca=-3.48 to-2.63,with a fixed oil-water viscosity ratio of 30.The effects of capillary number and heterogeneity on the flow patterns were analyzed,and the displacement efficiency and breakthrough time of injected water were also investigated.The unstable displacement caused by capillary fingering occurred at low capillary numbers,and the viscous force gradually dominated the displacement process with the increase of injection rate.Nevertheless,the flow pattern did not change from capillary fingering to stable displacement but directly to viscous fingering.The latter was associated with the high oil-water viscosity ratio in our experiments.Under the same displacement conditions,the fluid dynamics at moderate capillary numbers for homogeneous and heterogeneous models were different.More specifically,heterogeneous porous media enhanced the displacement instability and promoted immiscible drainage to viscous fingering.The latter resulted in reducing the critical capillary number of viscous fingering.The primary reason was that the heterogeneity resulted in a decrease in the sweep efficiency and an increase in the flow rate of injected water in pore throats.In order to quantify the impact of heterogeneity on displacement efficiency,we also compared the oil recovery of different porous media when the injected water broke through at the outlet.The oil recovery generally increased with the capillary number prior to the flow pattern changing to viscous fingering.However,there was a slight drop in oil recovery when log Ca increased to-2.78 and-2.93 for homogeneous and heterogeneous models,respectively.The drop was related to the transition from capillary to viscous fingering in porous media.At the same time,the oil recovery in the homogeneous model was higher.The difference in flow patterns resulted in an early breakthrough for the heterogeneous model.And the formation of viscous fingering would reduce the difference in water breakthrough time.This study revealed the influence of porous media heterogeneity on immiscible displacement and provided the theoretical background for a fundamental understanding of the water-oil flow in oil reservoirs.