Multiangle Perforation Effects on Fracture Propagation and Inter-Fracture Interference in Shale via XFEM

Shale reservoirs feature extremely low permeability, necessitating hydraulic fracturing to establish complex fracture networks for efficient hydrocarbon extraction. This study aims to clarify the influence of multiangle perforation on fracture propagation and interaction in shale horizontal wells, addressing the limitations of previous works that mainly considered single-angle perforations. An extended finite element method (XFEM) model was established in ABAQUS to simulate multiangle perforation fracturing in shale horizontal wells under realistic in situ stress conditions. The model was validated through triaxial fracturing experiments and theoretical analysis, ensuring its reliability. Subsequently, it was employed to investigate the effects of different perforation azimuths (0, 15, 30, 45, 60, and 75°) on fracture initiation pressure, propagation behavior, and interference characteristics. The XFEM simulations show that, except for 0°, fractures align with the maximum principal stress, with the greatest deflection at 60°. As perforation azimuth increases, fracture initiation and propagation pressures rise from 41.2 to 51.5 MPa and from 14.8 to 18.2 MPa, respectively. The fracture width first decreases and then increases, while the half-length decreases by 31.22%. Interference mainly occurs near crack tips, causing later fractures to deflect and weaken. The findings offer theoretical guidance for optimizing perforation design, enhancing fracturing efficiency, and improving oil and gas recovery in low-permeability shale reservoirs.