Propagation of hydraulic fractures in bedded shale based on phase-field method

Accurate prediction of the propagation path of hydraulic fractures in shale plays an important role in optimizing fracturing schemes and evaluating fracturing effects. Based on the theory of poroelasticity and the energy minimization principle, a hydro-mechanical coupling phase-field model is established. The segregated coupling method based on the staggered scheme is adopted to solve it numerically. The reliability of the model is verified by the existing experimental results. The simulation analysis of 3D hydraulic fracturing confirms the feasibility of the proposed method in capturing the propagation path of hydraulic fractures under different in-situ stress configurations. Based on the model, the mechanical and seepage parameters of bedding planes and matrix are characterized by the interpolation function. The interactions among hydraulic fractures, natural fractures and bedding planes are investigated under different bedding angles and in-situ stress configurations. The results show that the bedding planes of shale alter the expected propagation path of hydraulic fractures, which depends on the bedding angle. With the increase of in-situ stress difference, the propagation path of hydraulic fractures and the interaction mode are gradually controlled by the in-situ stress difference. Compared with other numerical methods, the phase-field method has a significant advantage in simulating complex crack propagation and interaction in coupled multiphysics environment.