Study on the Mechanism and Simulation of the Hydraulic Fracture Propagation in the Argillaceous Unconsolidated Sandstone

It is an urgent task to explore the development of argillaceous unconsolidated sandstone reservoir by hydraulic fracturing. Based on the physical parameters of the core, a physical simulation method is established and the fracturing test of argillaceous unconsolidated sandstone is carried out. Based on the analysis of the structure and physical properties of the argillaceous unconsolidated sandstone reservoir, the imitation method was established. With the increase of clay content, the hydraulic fracture was changed from the straight fracture to the fishbone seams which are in twists and turns with a seepage zone being tested. Based on the PFC discrete element method, the model of the argillaceous unconsolidated sandstone was established and the microscopic parameters were obtained. The fluid solid coupling was established. The simulation shows that the natural fractures are formed by the communication of the fracturing fluid, but the main fracture of the hydraulic fracturing was still extended along the direction of perpendicular to minimum principal stress. The smaller the difference between maximum principal stress and minimum principal stress was, the fracture was more Chaos. Through stress chain analysis, it was found that the stress direction is obvious, but the distribution of stress is very uneven. This phenomenon leads to shear stress in the process of crack propagation, which makes the hydraulic fracture more easily to divert branch fractures and produces broken zones.