Method for modeling and simulating three-dimensional discrete element for shale pneumatic and hydraulic fracturing

Abstract

The invention provides a method for modeling and simulating a three-dimensional discrete element for shale pneumatic and hydraulic fracturing. The method includes the steps of (1) establishing a three-dimensional close packing model with specific elastic property and destructive property according to a conversion formula, and establishing an integrated isotropic random module through particle diameter normal distribution adjustment and random packing, (2) adjusting the diameter of particles according to given confining pressure, setting particle anisotropic ellipsoid parameters, moving the boundary of the models, adjusting the confining pressure to the given value, and finally connecting a particle solidification model to obtain an anisotropic shale model with specific confining pressure and mechanical property, (3) establishing a hydraulic pressure cavity model and a hydraulic pressure boundary model according to requirements, generating hydraulic pressure and stress waves through mutual extrusion of water particles, and simulating generation and development of hydraulic fractures. The method avoids human influences of a traditional method based on continuity mechanics, can simulate the processes of hydraulic pressure propagation and hydraulic fracturing more really, and achieves predication of shale pneumatic and hydraulic fracturing.

Description

technical field [0001] The invention relates to the technical field of shale gas hydraulic fracturing simulation, in particular to a three-dimensional discrete element modeling and simulation method for shale gas hydraulic fracturing. Background technique [0002] The hydraulic fracturing process is the main way to obtain shale gas. It is of great practical significance to determine the formation and development laws of hydraulic fractures under different lithology, stress, and fracture development conditions. However, the field measurement and indoor test of the hydraulic fracturing process have problems such as high cost and difficult detection. Studying the hydraulic fracturing process through computer numerical simulation and other technologies has the advantages of low cost, high efficiency, and repeatability. The current hydraulic fracturing simulation method is based on the continuum mechanical method (such as the finite element method), which requires additional hy...

AI Technical Summary

Problems solved by technology

However, the simulation of hydraulic fracturing involves complex factors such as rock anisotropy, stress conditions, primary fractures, and water-rock interaction, as well as multi-field coupling. The establishment of discrete element models is complex in theory and implementation. Failure to solve these problems affects the simulation and prediction of hydraulic fracturing processes under complex conditions

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