3D Reconstruction And Seepage Simulation Of Macropores Structure In Low Permeability Coal

The traditional coal pore and fracture observation can not accurately describe the flowing of CBM in the process.The 3D reconstruction and seepage simulation of micro-pore structure is an important way to reveal the macroscopic flow mechanism of CBM in complex low permeability coal,which can provide theoretical basis for its efficient development.The digital coal and equivalent pore network model is the basic platform for pore scale seepage simulation.In this paper,the 3~#coal seam of Yuwu coal mine in Lu'an mining area is taken as the research object,and the area of the coal pillar sample is scanned on the?CT225kVFCB test system.VCTiS4.2.1 for Reconstruction is used to reconstruct large cone angle of cone beam,and 2D CT slice is obtained;the median filter is used to smooth the noise in the slice,the pore distribution of DTM function combined with the measured porosity,the optimal threshold segmentation of CT slices was obtained by clamping force method,and the 3D visualization of coal was carried out.On this basis,Avizo is used to model the 3D pore structure(including digital coal and equivalent pore network model).The results show that the connected pores account for 92.3%of the total pore volume,and the micropores are in the form of small spherical and flaky form.The average coordination number of pore throat is 2.55,and the coordination number of 1~7accounted for more than 80%of the total pore pore,although the pore topology is complex,the connectivity is better.The single-phase flow stage simulation was carried out by COMSOL software,and the distribution of pressure field and velocity field was analyzed.The absolute permeability in the X,Y,and Z directions is calculated,and the feasibility of the docking technique between Avizo and COMSOL is verified by comparison with the measured results.The Poreflow.exe simulator was used to simulate the gas water two-phase flow,and the reliability of the simulation was verified by comparing with the measured results.The research results laid the foundation for the study of coal reservoir fine description and evaluation,accurate prediction of gas production in coalbed methane wells.