Cross-Layer Propagation Behavior of Multi-Cluster Hydraulic Fractures in Inclined Bedded Reservoirs

Abstract

Bedding planes widely exist in stratified reservoirs and strongly restrict the vertical cross-layer growth of hydraulic fractures. Traditional displacement discontinuity method (DDM) tends to produce spurious negative apertures for compressed weak bedding interfaces and neglects multi-cluster stress superposition in inclined formations. This work proposes an improved DDM incorporating bedding-plane normal-tangential support-stiffness contact constraints together with Mohr–Coulomb-based opening-slip-closure discrimination, which removes non-physical negative-aperture artifacts of closed weak interfaces. The proposed numerical framework is adopted to model fracture initiation, propagation and bedding-interface penetration under multi-fracture interference. Key coupled influences of net pressure, bedding-plane dip angle and fracture-cluster number are quantitatively investigated. Numerical simulations reveal that higher net pressure enhances the lasting cross-layer propagation capacity of hydraulic fractures. Among the examined cases, a bedding dip angle of 60° facilitates fracture penetration through interfaces. Bedding features amplify inter-cluster mechanical interference and lead to asymmetric fracture evolution, tip arrest and interface-parallel fracture propagation, which becomes more pronounced as the number of fracture clusters increases. This study provides theoretical references for multi-cluster fracturing design in low-permeability layered reservoirs.