Numerical simulation of pressure gradient of coalbed gas outburst and migration considering moving boundary

2nd International Symposium on Resource Exploration and Environmental Science

生态环境科学

Guan, Chi^1 ; Xie, Zhongkai^2 ; Xie, Haijian^3

School of Management Science and Engineering, Zhejiang Gongshang University, Hangzhou, China^1

Zhejiang Institute of Hydraulics and Estuary, Hangzhou, China^2

College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China^3

关键词: Comsol multiphysics;    Exposed surfaces;    Migration velocity;    Moving boundaries;    Physical coupling;    Pore characteristics;    Starting pressure;    Threshold pressure gradient;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/170/2/022022/pdf
DOI  :  10.1088/1755-1315/170/2/022022

学科分类：环境科学（综合）

来源: IOP

【 摘 要 】

The gas flow model is developed considering effects of gas convection, diffusion and slippage based on pore characteristics of medium and gas seepage theory in order to study the slippage effect and the effect of threshold pressure gradient on gas migration through the coal seam and determine the reasonable diameter of exposed surface. The numerical model was solved using the multiple physical coupling analysis software COMSOL Multiphysics, and good agreement was obtained by comparing the solution of numerical model with measured results. The speed of pressure change is larger when slippage effect is considered than the migration velocity of gas when slippage effect is not considered, and smaller of pressure decreases for the same cross-section. It is also concluded that the gas pressure changes faster in the coal seam, and the gas starting pressure gradient gets lower when the diameter of the exposed surface is larger. The model can be used to analyze the law of gas migration in coal seam and to determine the position of the cracking surface in coal seam effectively.