Extension calculation of vertical fracture considering fracture tip plasticity

Based on the fracture mechanics and elastic-plastic mechanics,the plastic area in vicinity of the fracture tip in hydraulic fracture extension is studied.The dimension of the plastic area around the fracture tip is quantitatively presented,the fracture height equation considering the fracture tip plasticity is derived,and 3D extension model is established with respect to the plastic yielding.Then the effect of the plastic yielding on the hydraulic facture extension is simulated and analyzed.The study results demonstrate that, extension of fracture length increases a little,and the vertical extension of fractures is restrained apparently under the influence of fracture tip plasticity.Moreover,the fracture tip plasticity results in the increase of operation pressure,at the same time the increase of operation pressure causes the increase of fracture width.The more adjacent to the fracture tip,the more sensitive for the influence of fracture tip plasticity on the operation pressure and fracture width is observed.