Parametric study on near-wellbore fracture geometry for wellbore strengthening in anisotropic formation

Wellbore strengthening technique is one of the most commonly used treatment to prevent leakage into natural or induced fractures. The accurate prediction of fracture geometry is essential for the particle size distribution (PSD) optimization of wellbore strengthening material (WSM). Due to the existence of weak planes, the rock has the anisotropic characteristic, which results in fracture distortion. Thus, a fully coupled poro-elastic model is solved with Abaqus by using the extended finite element method (XFEM) - based cohesive zone method (CZM) to investigate the geometry of near-wellbore fracture. The fracture trajectory and opening are captured before and after bridging by coupling the rock deformation, seepage flow of pore fluid, fluid flow in fracture and leak-off of drilling fluid. The sensitive analysis results illustrate that the fracture tends to propagate along the principal material direction with the effect of anisotropy. The larger ratio of Young's modulus aggravates fracture distortion in the near-wellbore area. The increase of ratio of horizontal in-situ stress weakens the effect of anisotropy. The anisotropic permeability has minor effects on fracture geometry with the combined influence of anisotropic mechanical properties and horizontal stress. The lower injection rate decreases fracture width after bridging and makes the fracture propagation process more controllable through the influence of filtration. The increase of viscosity widens the fracture aperture and increases cuttings transport capacity of drilling fluid.