Study on Injection Mechanism of Fracturing-Flooding Technology in Low Permeability Reservoir

In order to reveal the injection mechanism of fracturing-flooding and deepen the understanding of the initiation and propagation of cracks during fracturing-flooding, the formation breakdown pressure, the characteristics of fracture distribution and propagation under different conditions were studied based on physical simulation device for fracturing-flooding, tri-axial stress fluid-structure coupling experimental device, micro-CT and scanning electron microscopy. The experiment results show that the formation breakdown pressure and crack morphology are affected by injected fluid viscosity and injection displacement. The lower injection speed and viscosity of the injected fluid, the more favorable to form the complex fracture network. The morphology of fracture network is determined by the principal fracture and the micro-cracks. The micro-crack is attached to the principal fracture, the principal fracture controls the direction of fracture development, and the micro-fracture determines the spatial distribution of the fracture network. After fracturing-flooding, the permeability of core increases by 10–100 times, and the permeability change area accounts for more than 30% of the plat model.