作　　者： (朱光普）; (姚军）; (张磊）; (孙海）; (李爱芬）; (张凯）;

机构地区： 中国石油大学华东石油工程学院,青岛266580

出　　处： 《科学通报》 2017年第22期2553-2563,共11页

摘　　要： 目前我国东部老油区普遍进入特高含水阶段,水驱开发效果变差,采收率明显下降,有效挖掘剩余油潜力是当前开发的重点所在.特高含水期油相主要以非连续状态存在于孔隙空间内,基于宏观认识的达西定律很难准确描述地下剩余油的真实流动状态.为摸清特高含水期剩余油分布状况,研究剩余油形成机理并挖掘剩余油潜力,基于N-S方程模拟油水两相在微尺度多孔介质内流动,运用相场方法实时追踪驱替过程中的两相界面,建立微观流动模型.研究特高含水期剩余油分布,并从力学角度分析残余油形成机理.结果表明特高含水期多孔介质内剩余油主要可以分为5种类型:孤立油滴、孔喉残余油、簇状非均质残余油、油膜、盲端残余油.毛管力,孔隙结构以及壁面润湿性是影响特高含水期剩余油的分布与类型的主要因素.孔隙尺度流动模拟得到的水驱曲线与矿场规律基本一致.特高含水期增注与注入表面活性剂均是通过驱替出簇状非均质剩余油,孔喉残余油以及孤立油滴达到提高剩余油采收程度的目的.簇状非均质剩余油的减少是采收程度提高的主要原因.矿场增注时机对经济开发有重要影响.该研究初步揭示了特高含水期剩余油分布及形成机理,为水驱油藏的后期开发提供有效指导. Water flooding has been widely applied in the oilfield development as a secondary recovery method due to its effectiveness and economic feasibility. After several decades of production, numerous oil fields are normally entering into the extra-high water-cut stage （water cut higher than 90%）. The extra-high water-cut stage takes an extremely important role in the whole development process since a large amount of residual oil remains trapped in reservoirs （approximately 50% to 60% of initial oil in place） at this stage. The extensively continuous distribution of subsurface oil at the low water-cut stage has changed greatly after the water cut of mature oilfields becomes over 90%. The residual oil distributes mainly in a scattered state at the extra-high water-cut stage, while water flows in a continuous state. Oilfields with high water cut are normally suffering from poor flooding efficiency, to improve water flooding efficiency, it is necessary to understand distributions and formation mechanisms of residual oil at the extra-high water-cut stage. In this study, a pore-scale simulation model is developed to exploit the potential of residual oil in a porous media. A direct numerical simulation method is employed to simulate fluid flow in a porous media, the position of interface between water and oil is determined by the phase field method. The capacity and accuracy of the model is validated by a classical benchmark： a layered two-phase flow with a variable viscosity ratio. The formation processes of residual oil and mechanisms behind this are investigated in terms of mechanics. The results show that the residual oil in porous media at the extra-high water-cut stage can be classified as five types, namely, isolated oil droplet, residual oil in pore throats, cluster residual oil, oil film and residual oil in dead end. Rock configuration, wettability and capillary pressure play important roles in the formation of residual oil. The formation of isolated oil droplet is dominated by rock configuration, capillar

关 键 词： 特高含水期 方程 相场 微观流动 剩余油