Numerical Simulation of Fracture Propagation in Bedded Shale Based on Cohesive Zone Model

based on the global embedded cohesive zone model, the finite element model of complex hydraulic fracture (HF) propagation in layered shale is established in this paper. Considering the effects of fluid flow/geological stress coupling, pore elastic deformation and back stress, the effects of stratification approach angle, horizontal stress difference, displacement and fracturing fluid viscosity on the morphology of complex HF were studied based on the model. The results show that when the bedding approach angle is greater than 45°, it is more likely to form complex fractures through the bedding, and when the bedding approach angle is less than 45°, it is more likely to form simple fractures along the bedding direction. When the approach angle is 45°, HF tend to form simple fractures captured by bedding under low stress difference, and simple fractures that extend along bedding after passing through partial bedding under high stress difference. In the case of moderate stress difference, it is more likely to form complex cracks that extend through and along the bedding. The increase in the flow rate and the viscosity of the fracturing fluid can lead to the formation of more fractures across the bedding, higher fracture complexity and greater maximum fracture opening.