Method for simulating fracture toughness of layered rock based on extended finite elements

Abstract

The invention discloses a method for simulating the fracture toughness of a layered rock based on an extended finite element. The method comprises the following steps: establishing a Brazilian disc numerical model for simulating the fracture toughness based on the extended finite element; simulating and calculating crack initiation and propagation of cracks; defining a transverse isotropic material to describe bedding distribution characteristics in the rock mass, and promoting an isotropic molar-coulomb criterion to the anisotropic layered rock mass; taking an initial critical damage criterion of rock crack simulation as a maximum principal stress criterion, determining damage evolution and damage stability viscosity parameters based on an energy damage evolution type, specifying a contact effect of rock bedding, a matrix and cracks, and finally applying boundary conditions; extracting an analysis and calculation result, calculating the fracture toughness of Brazilian disc numerical simulation, comparing the fracture toughness value of the Brazilian disc in an indoor test, and for crack propagation of the Brazilian disc, comparing an analysis numerical value with a crack propagation condition in an actual test; and finally, achieving accurate simulation of a crack propagation path and a fracture toughness value.

Description

technical field [0001] The invention relates to the technical field of petroleum exploitation, in particular to a method for simulating the fracture toughness of layered rocks based on extended finite elements. Background technique [0002] Reservoirs such as shale oil and gas and tight oil and gas are different from conventional gas reservoirs and have the characteristics of self-generation and self-storage. At the same time, their reservoir characteristics are characterized by extremely low porosity and low permeability. Therefore, complex fracture networks must be formed through volume fracturing technology. for efficient development. Fracture toughness of rock is a key parameter in hydraulic fracturing design. The correct prediction of fracture toughness can quantitatively evaluate the compressibility of reservoirs and provide reference for fracture network morphology during fracturing. [0003] Fracture toughness, also known as the critical stress intensity factor, can...

AI Technical Summary

Problems solved by technology

At present, there are many numerical methods for the fracture toughness of layered rocks, but the existing methods perform high-density meshing in areas of high stress and deformation concentration, such as the crack tip, and need to re-mesh in the process of fracture initiation and propagation to It is difficult to accurately capture the real fracture propagation process due to the huge amount of calculation to adapt to the fracture steering

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