Experiments on water flooding in fractured-vuggy cells in fractured-vuggy reservoirs

Based on the theory of scaling criteria, a physical experimental model of fractured-vuggy cell which meets the geometric similarity, kinematic similarity, dynamic similarity and characteristic parameters similarity was designed. The factors affecting fluid flow and water flooding characteristics, and the EOR features of different displacing modes were studied by experiments. The experimental results show that: Oil and water displacement effect caused by the density difference between oil and water is the main mechanism of water flooding; Injection rate has no effect on the remaining oil and water-cut; Fracture-vuggy connection is the dominant factor controlling water-free recovery, ultimate limit of remaining oil and water-cut variation in the fractured-vuggy cell; Oil-water viscosity ratio has an important effect on oil production rate, oil replacement ratio and economic limit remaining oil; When the filling degree is low, it has no effect on remaining oil, but when the filling degree is high, the remaining oil contains both “attic oil” and the oil existing in porous media; Foam flooding after water flooding enhances oil recovery by starting the attic oil at the top of vugs, and the remaining oil is in the center of the vugs after foam flooding; Polymer flooding after water flooding enhances the economic limit recovery by increasing the oil production rate and oil draining ratio, but it has no effect on the limit remaining oil of water flooding.