Numerical Simulation Of Hydraulic Fracturing Based On Extended Finite Element Method

At present,most of the high permeability blocks in China are at the late stage of development and have low production capacity.The exploitation of low permeability oil and gas resources with huge reserves is expected to be the key supplement to the shortage of oil and gas resources.Hydraulic fracturing technology is the main method to improve the recovery efficiency of low permeability reservoir,so the study of hydraulic fracture propagation mechanism is of great practical significance.Based on fracture mechanics,rock mechanics theory and extended finite element method,this paper studies the fracture propagation mechanism of hydraulic fracturing,and the main work and results are as follows:Based on the XFEM method,the numerical model of hydraulic fracturing is established and improved,and the law of hydraulic fracture initiation and propagation under different in-situ stress and perforation angle is studied,the validity of the numerical model is verified.Based on the deficiency of Sneddon formula,the permeability Coefficient is introduced to study the effect of fluid permeability on the induced stress near the fracture,the distribution of induced stress of hydraulic fracture in rock with different permeability coefficient is numerically simulated.The induced stress around fracture and the net pressure in fracture are compared with the analytical solution,the accuracy of the model in the calculation of induced stress is verified.The numerical model of multi-fracture is established,and the INP file of ABAQUS software is edited to optimize the different analysis steps,and the simulation of multi-fracture and different fracture modes is realized,firstly,the influence of two hydraulic fractures on fracture propagation under different spacing and different in-situ stress difference is studied,the effects of different fracture spacing and fracturing methods on the propagation path,fracture width and pressure in three fractures in synchronous and stepwise fracturing are analyzed.Based on the theory of fracture mechanics and rock mechanics,the judging criterion of the intersection of hydraulic fracture and natural fracture is improved.The influence of parameters,such as intersection angle,in-situ stress difference and interface friction Coefficient of natural fractures on the interaction of two kinds of fractures is studied by the improved criterion.