Simulation Of Hydraulic Fracturing By Extended Finite Element Method

Hydraulic fracturing technique is a widely used modern engineering technique for low permeability shale mining. The crack length and width in hydraulic fracturing process are important factors that influence the production of oil and gas, Therefore, Study of crack propagation in hydraulic fracturing has important practical significance. This paper reviewed some of the hydraulic fracturing research results, describe the development of fracture mechanics and crack propagation simulation methods, and make brief description of the basic principle of porous materials, fracture mechanics and the extended finite element methods. Using extended finite element method (XFEM) to simulate the hydraulic fracturing process of crack propagation. Building hydraulic fracturing model by ABAQUS, then simulating different pump time to analyze propagation of the crack and pore pressure of the model.Through the analysis, we get some features of the hydraulic fracturing process: Pore pressure gradient is an important factor that affect the process of crack growth, the size of the pore pressure will affect the final crack opening displacement and length of the crack, and the pore pressure will change the void ratio of the material itself, meanwhile, the crack shape is elliptic, pore pressure distribution on the interface of the crack is closely related to the crack shape; Geostress affected the crack length, different initial crack angle will produce a steering angle for the crack, when the angle is at 90°, the crack deflection does not occur; When injection flow is constant, the injection rate of fracturing fluid must be at a certain value, then we will get the maximum crack length and width; The fluids with higher viscosity will make larger maximum pore pressure in model, but will decrease the crack length; The model with larger permeability coefficient will make pore pressure smaller and crack length shorter; The initial pore pressure will affect the crack opening displacement, but the crack length would not change if the pump time was same; When two cracks fracture at the same time, the closer space between two cracks, the more serious interference between two cracks; In dealing with cracks that have close spacing, the hydraulic fracturing progress step by step will get better crack propagation result.This paper has a certain reference value for the improvement of hydraulic fracturing progress.