Study on migration characteristics of oil gas water three-phase interface and distribution law of remaining oil in gas cap edge water reservoir

Reservoirs with gas cap and edge water grow rapidly in the early stage of development, the oil well has no water, the recovery period is short, the three phases of oil, gas, and water are easy to cross each other, the production decreases rapidly, and the development is difficult. Therefore, it is necessary to clarify the migration law of oil, gas, and water three-phase interface, find out the distribution law of remaining oil, and put forward the direction of EOR. In order to study the migration law of oil, gas, and water three-phase interface in the development of this kind of reservoir, taking JZ25-1S gas cap edge water reservoir as an example, a three-dimensional physical model is established based on the similarity criterion. The characteristics of fluid interface migration and the distribution of remaining oil under depletion development and barrier waterflood development are studied through experiments. The research results show that gas channeling occurs after 30 minutes of depletion development, and the migration speed of the oil-gas interface is faster than that of the oil-water interface, and the migration speed of the high-permeability layer is faster. The remaining oil in the low-permeability layer is mainly distributed on both sides of the oil and gas and oil-water channels, and the remaining oil in the high-permeability layer is mainly composed of rock particles, pore walls, and surfaces of interstitial materials. The ultimate recovery rate of depletion development is 25%. At the barrier waterflooding development for 60 minutes, gas began to appear, the migration rate of oil-gas and oil-water interface was stable, and the shape of fluid interface was gentle. A small amount of remaining oil in each permeability layer is distributed in the oil ring and gas cap area, and the distribution of remaining oil is mainly affected by injection timing and injection-production ratio. The final recovery rate of barrier waterflooding development is 51%, which is 26% higher than that of depletion development. The findings of this study can help for better understanding of great significance to the formulation of production parameters for depleted development of gas cap and edge water reservoirs and the implementation of later production stimulation measures.带气顶与边水的油藏在开发初期产量增长迅猛，油井初期无出水现象，开发周期较短，油气水三相极易发生窜流，产量快速递减，开发难度较大。因此，亟需明确油气水三相界面的运移规律，厘清剩余油分布特征，并提出提高采收率（Enhanced Oil Recovery, EOR）的技术方向。为研究此类油藏开发过程中油气水三相界面的运移规律，本研究以JZ25-1S气顶边水油藏为研究对象，基于相似准则建立三维物理模型。通过物理模拟实验，分析了衰竭式开发与阻隔式注水开发条件下的流体界面运移特征及剩余油分布规律。研究结果表明：衰竭式开发30分钟后即发生气窜现象，油气界面运移速度快于油水界面，且高渗透层内界面运移速度更快。低渗透层内剩余油主要分布于油气通道与油水通道两侧；高渗透层内剩余油则主要附着于岩石颗粒、孔隙壁面及胶结物表面。衰竭式开发的最终采收率为25%。阻隔式注水开发60分钟后开始出现气窜，油气与油水界面运移速率趋于稳定，流体界面形态趋于平缓。各渗透层内均仅有少量剩余油分布于油环与气顶区域，剩余油分布主要受注入时机与注采比影响。阻隔式注水开发的最终采收率可达51%，较衰竭式开发提升26%。本研究成果对气顶边水油藏衰竭开发的生产参数制定及后期增产措施的实施具有重要指导意义，有助于深化对相关开发规律的认知。