Three-dimensional numerical investigation of the interaction between multiple hydraulic fractures in horizontal wells

Complex, non-planar fracture geometry is often observed in multi-stage hydraulic fracturing. The opening of hydraulic fractures results in a disturbance of local stress, which in turn affects the propagation of the adjacent fractures (stress shadow effect). The interaction between multiple fractures is of major importance in the design of fracturing treatments. In this study, a fully-coupled three-dimensional lattice-spring code is utilized to study the interference among multiple fractures. The results indicate that simultaneous propagating fractures can move towards or away from each other, resulting in complicated non-planar geometry and branching of hydraulic fractures. In an isotropic stress field, continued fracture propagation involves reorientation into a direction normal to the initial fracture plane, leading to an S-shaped fracture geometry. Higher Young's modulus values amplify the interaction of multiple fractures, resulting in more secondary fractures normal to the initial fracture plane and the greater dimension of fracture. Treatments assuming a higher magnitude of fluid viscosity /injection rate induce more branches at the tips of the primary fracture. An adjacent layer with a low modulus restricts the height growth of fractures, whereas the lateral growth and the stress interference will be in contrast relatively enhanced. This study provides further insight into the design and optimization of multiple-stage hydraulic fracturing in horizontal wells.