Deflected crack trajectories are detected in hydraulic fracturing. There are numerous physical quantities impacting the deflection of a fluid-driven crack. A 2D model of the elasto-hydrodynamics system is established to predict the crack trajectory and to investigate the coupling effects of anisotropic in-situ stress, fluid viscosity, fluid injection rate and crack inclination on the crack deflection. The displacement discontinuity method (DDM) and the finite difference method (FDM) are used to solve the nonlinear problem. The concept of deflection region is defined to quantify the crack deflection. Results show that the size of the deflection region is dominated by the inclination angle. Increase of the magnitude and the difference of in-situ stresses promotes crack deflection. The combined effects of fluid viscosity and fluid injection rate are divided into three stages: significant prevention stage, significant promotion stage and insignificant prevention stage. This study provides the method for crack trajectory prediction and crack deflection control.

No abstract