Hydro-Mechanical Coupled FDEM Modeling of Multi-Cluster Hydraulic Fracture Propagation and Interaction in Shale Reservoirs

Competition among hydraulic fractures can redistribute growth between clusters without producing a comparable increase in total fracture length. We examine this distinction using a two-dimensional hydro-mechanical finite–discrete element method (FDEM) formulation and the available three-cluster results. The formulation accounts for poroelastic deformation, matrix and fracture flow, cohesive damage and post-failure contact. At five reported times, fracture half-length and maximum aperture agree with the tabulated KGD benchmark within 3%, with mean absolute percentage errors of 1.91% and 2.00%, respectively. Increasing cluster spacing from 5 to 20 m increases middle-fracture length from 18.5 to 39.8 m and its share of the three-fracture total from 11.87% to 24.43%. In contrast, total length increases by only 4.6%. A dimensionless length uniformity index rises from 0.828 to 0.965, demonstrating that the principal spacing response is a redistribution of growth. Increasing the reported injection rate from 6 to 12 m3/min increases maximum aperture from 1.4 to 3.2 mm. Stress-difference and viscosity cases provide additional qualitative evidence of changes in fracture morphology. The results support comparative parameter screening, while the limited benchmark, unresolved implementation details and absence of discretization studies preclude a field-optimum or mesh-independent branching claim.