Numerical investigation on the influence of micropore structure characteristics on gas seepage in coal with lattice Boltzmann method

The micropore structure of coal has a significant impact on gas seepage in a coal reservoir. In this study, the micropore structure of coal was reconstructed and then quantitatively analysed using independently developed image analysis software. The lattice Boltzmann method (LBM) at representative elementary volume (REV) scale was used on the reconstructed pore structure to simulate gas seepage and obtain the gas velocity distribution. The effects of porosity and pore structure on gas seepage were studied. The results indicated that gas seepage velocity and apparent permeability increase with porosity. The average gas seepage velocity in the pore structure with >25% porosity was more than two-fold that in the pore structure with <25% porosity, and apparent permeability increased by at least three orders of magnitude. The gas seepage velocity in open-pore areas was higher than that in closed-pore areas and highest in through holes, followed by semi-through holes and closed pores. The gas seepage velocity was higher in long and narrow pore structures and reached a maximum along the centre line of the pore throat. The non-main flow areas of gas appeared in through holes that had noticeable shrinkage, expansion, and high tortuosity, causing gas accumulation in the coal body. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The micropore structure of coal was reconstructed and quantitatively analysed to study its impact on gas seepage in a coal reservoir. It was found that porosity and pore structure had significant effects on gas seepage velocity and apparent permeability. The study revealed that gas seepage velocity increased with porosity, with different pore structures exhibiting varied gas seepage characteristics.