An investigation of hydraulic fracture propagation in multi-layered formation via the phase field method

Fracture penetration or deflection may occur when the hydraulic fracture approaches weak interface in multilayered formation. However, the intrinsic mechanism of fracture propagation pattern remains unclear. A model was presented to investigate hydraulic fracture propagation in multi-layered formation via the phase field method. The interface is explicitly represented by a weak thin layer. Fluid flow in the fractured media was modeled by using the indicator function of phase field. The iterative algorithm was described and validated against the benchmark cases. Simulation results show that the evolution of injection pressure is more complex when the fracture deflects than that when the fracture penetrates the interface. The fracture is prone to penetrate the softer layer the perforated layer while deflects to the interface if the adjacent layer is stiffer. Decreasing the modulus ratio of interface to layers promotes the fracture deflecting to the interface, while increasing the stress ratio contributes to the fracture penetrating the interface. The stacking mode of layers greatly affects the fracture propagation morphology in three or more layered formations. Rock heterogeneity doesn't alter the fracture propagation pattern as a whole, but it affects the local fracture morphology. The results provide a cloud chart of the relationship between fracture propagation pattern and controlling factors for the potential of field application.