A two-dimensional (2D) eXtended Finite Element Method (XFEM) simulation is presented for propagation of hydraulic fractures from wellbore that the minimum principal in-situ stress is in horizontal plane. One primary role of hydraulic fracturing is to provide a high conductivity pathway along which reservoir fluids can flow to the well. The prediction of crack initiation, fracture path in the near wellbore region and competition of multiple cracks, are very important for success in hydraulic fracturing process. So, we used enriched elements to predict the propagation of perforation crack without remeshing, however in traditional techniques (FEM), the fracture path should be predefine and need to remeshing and applying special elements for crack tip. On the other hand, analysis the crack propagation in FEM is more complexity than simulation with XFEM method. In this study, enriched pore pressure element has been applied with a maximum principal stress damage criterion, for initiation and evolution of crack in Abaqus6.12. The properties and input data for rock models were extracted experimentally from Ahwaz-Bangestan wellbore specimens. The specifications of crack initiation were studied by analyzing the rock model without any crack or flaw. In order to focus on propagation and competition of perforation crack, we designed two kinds of models with predefined perforation cracks and applied Haimson and Rummel in-situ stresses. For all cases, the victor crack in competition of multiple cracks, were the perforation cracks that were near to the direction of maximum compressive in-situ stress in horizontal plane and the crack initiated at this direction. For this case, our analysis demonstrates that the misalignment angle and the position of perforation cracks play an important role in near wellbore fracture path and pressure diagram. In addition to that, the predefined crack reoriented to the direction of maximum compressive in-situ stress (perpendicular to minimum in-situ stress) with smooth path, dependence on difference of maximum and minimum in-situ stresses in horizontal plane. Also, the stress intensity factor versus increasing the crack length were rather constantly, that based on using maximum principal stress damage criterion and fundamental of fracture mechanic, this procedure is reasonable. Our results show that the stress condition of borehole and pore pressure play primary role for specification of crack near wellbore, because by adding the pore pressure to rock models, the pressure of injection fluid decreased. These results are in close agreement with the experimental data and pervious researcher results, in spite of, our procedure is more efficiency, flexible and simple. key Words Hydraulic Fracturing, XFEM, Pore Pressure Element, Rock Mechanics, Crack Initiation, Perforation Crack Path, Abaqus6.12
