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

Abstract

ABSTRACT 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.