Investigation Of The Impact Of Micro-fracture Morphology On The Fluid Flow By Lattice-Boltzmann Method

The study of seepage characteristics of micro-fractures in the rock(ie,the same or slightly higher scale-micrometer or millimeter)is an important direction for the study of micro-oil and gas seepage in reservoirs.Including the physical rock experimental analysis and numerical simulation and other research methods,which numerical simulation method is economical,fast,and can be some of the micro-phenomena in the fluid flow to give a better explanation and phenomenon to reproduce,so it has a broad application prospects.This paper mainly uses the LBM method for numerical simulation and correlation analysis.LBM is a numerical simulation method developed in recent years.It is a kind of method between macroscopic and microscopic.The method has the advantages of micro method and macroscopic method,and has reliable calculation precision.In the solution of practical problem In the easy parallel,easy programming,the theory is clear and easy to understand,and easy to deal with the advantages of boundary conditions.In this paper,the LBM method is applied to the simulation of micro-fractures,and the calculation method of effective opening degree of fractures is studied.The work of this paper is divided into three aspects:Firstly,two works are done at the LBM theoretical level: 1.Based on the two-dimensional dynamic boundary conditions,I deduce the dynamic boundary conditions under three-dimensional conditions;2.I deduce the unit conversion in lattice units and physical units for calculating the permeability.Secondly,LBM is used to simulate the seepage process of single-phase flow in microfractures,including two-dimensional fractures and three-dimensional fractures.The LBM method was successfully applied to simulate microfract seepage and the corresponding fracture permeability was calculated.Finally,study the fracture morphology(mainly effective fracture opening)quantization method.We propose two new methods to calculate the effective opening degree by finding the effective opening degree of the wall surface and calculating the effective opening degree by using the average number other than the arithmetic mean.By comparing the calculated effective opening degree with the classical cube law and the fracture permeability simulated by the LBM,the relationship between the fracture morphology and the permeability is estimated,and the two effective degrees The calculation method is superior to the method of calculating the effective opening degree directly using the arithmetic mean.