With the further study of the extended finite element theory

the extended finite element method (XFEM) has been widely used to simulate hydraulic fracturing. In comparison with the conventional FEM

the XFEM method has substantial advantages

such as high precision and low computational complexity. However

there are still many difficult challenges including how to simulate the perforation and the interaction between fluid and rock and to analyze propagation law of hydraulic fracturing. In this paper

to study the propagation law of hydraulic fracturing

the stress equilibrium equation of rock porous medium

fluid continuity equation and boundary conditions are established. Through finite element discretization method

the coupling equation matrix is treated. The initial fracture (or propagation) is defined through enrichment functions

and the maximum principal stress and damage variable D are selected respectively as the criterion of fracture initiation and propagation. Hydraulic fracturing propagation process is simulated by using the level set method. Numerical results show that the increase of perforation azimuth

fracture fluid displacement and the reduction of the horizontal stress difference cause the increase of the fracture initiation pressure

and the viscosity has no obvious effect on the fracture initiation pressure. It helps to widen the fracture width by increasing the perforation azimuth

the fracturing fluid displacement

the fracturing fluid viscosity and decreasing the horizontal stress difference. Increasing the horizontal stress difference

fracturing fluid displacement and decreasing the perforation azimuth and the viscosity of fracturing fluid can help to increase the fracture length and vice versa. Different well types and parameters of reservoir and fracturing operation are analyzed by hydraulic fracture XFEM based on ABAQUS platform. The fracture shape is lifelike and the image of degree of concave-convex on the fracture surface is clear. In consequence the result is accurate. As a simple and effective research method for studying the criterion of hydraulic fracturing propagation

this study provides the reference for hydraulic fracturing design and operation in oil field.