NUMERICAL SIMULATION OF HYDRAULIC FRACTURE PROPAGATION BEHAVIORS IN BEDDING SHALE

To gain an in-depth understanding of hydraulic fracture propagation in bedded shale,this study systematically investigated the effects of bedding density,fracture inclination,and stress difference on fracture propagation paths and initiation pressure using a numerical model of shale with randomly distributed bedding. The results indicate that bedding plays a dominant role in the complexity of fracture networks due to its weak interfacial properties. Moderate bedding density promotes hydraulic fracture bifurcation,resulting in complex propagation paths,while highly dense bedding tends to guide fractures along a single dominant pathway. At a fracture inclination of 45°,the interaction between hydraulic fractures and bedding planes is most conducive to forming complex fracture patterns. High stress difference suppresses bedding activation,leading to the formation of dominant longitudinal fractures. Under moderate stress difference,fractures propagate alternately along the maximum principal stress direction and bedding planes,resulting in densely branched fracture paths. The bonding strength of bedding interfaces governs the hydraulic fracture propagation mode,which manifests in three distinct patterns: direct penetration through bedding under high bonding strength; a composite path with main fracture penetration and secondary fractures extending along bedding under medium bonding strength; and confinement to the bedding plane under low bonding strength. Fracture initiation pressure is synergistically controlled by multiple factors. Bedding weakening and high stress difference significantly reduce initiation pressure. When the fracture inclination is 45°,the tensile stress around the wellbore is minimized due to optimal geometric configuration,resulting in the lowest initiation pressure. These findings provide valuable insights into the mechanisms underlying complex fracture network formation during volumetric fracturing in bedded shale reservoirs.