Visualization experiments and numerical simulation on the growth of fracture height in bedding-rich reservoirs

The development of shale bedding and differences in properties have significant effects on the growth of the fracture height. To investigate the impact mechanism of bedding on the fracture growth height, the visualization fracturing experiments based on polymethylmethacrylate (PMMA) samples were performed to investigate the impact of the injection rates, viscosity and temporary plugging parameters on the growth pattern of hydraulic fractures. Furthermore, the solid–fluid-damage fracturing coupled model considering the vertical distribution of bedding was constructed by the continuous-discontinuous element method, and the impact of key formation parameters and treatment parameters were investigated. The results show that the height growth pattern of PMMA samples was affected by the flow rate and fluid viscosity. The fracture can cross the bedding at high-viscosity fluid. But in low-viscosity fluid the fracture tends to be arrested by the bedding. And the fracture cannot cross the bedding again after In-fracture temporary plugging. The fractures vertical growth pattern mainly includes three types at various stratigraphic parameters and treatment parameters, “工” type fracture, “丰” type fracture, and “I” type fracture, respectively. For vertical stress differentials below 3 MPa or Young's modulus below 20 GPa or injection rates below 1.8 m3/min or the fluid viscosity below 5 mPa·s, the fracture will be limited within the bedding.