Experiments of Gas-water Cooperative Flooding in Fracture Network System

Fractures are the main seepage channels and the critical oil storage space in fracture-vuggy reservoirs. In this paper, the staggered fracture system was abstracted into an orthogonal fracture network. A physical experimental model was made with a laser-etched acrylic plate. The physical experiments of water flooding, gas flooding, water-alternating-gas, and simultaneous-water-and-gas were carried out using the physical experiment model of the fracture network. The results show that gas is more accessible to break through in gas flooding than water in water flooding, resulting in a lower recovery factor. Water-alternating-gas and simultaneous-water-and-gas can effectively improve oil displacement efficiency through the action of gravity difference and the interaction mechanism of gas and water. Increasing the injection rate properly, increasing slug size properly before water and gas breakthrough during water-alternating-gas simultaneous-water-and-gas, and decreasing the gas-water ratio properly during simultaneous-water-and-gas simultaneous-water-and-gas can effectively expand the sweep scope and improve recovery. The experiment provides a basis for efficient water and gas injection development in fracture-vuggy reservoirs.