关键词: 中高阶煤, 孔隙特征, 分形维数, 瓦斯吸附

Abstract: In order to investigate the influence of fractal features on coalbed methane adsorption in middle-high rank coal samples (Vdaf < 25%), methane adsorption capacities of 6 coal samples from different mining areas were tested using high-pressure volumetric method. Langmuir equation was used to fit the experimental data and two parameters, Langmuir volume (VL) and Lanmuir pressure (PL), were obtained to characterize the adsorption capacity. Meanwhile, on the basis of scanning electron microscopy (SEM), the pore characterization on coal surface was analyzed. The fractal dimension of pore distribution (D) was calculated according to the Kolomogrov capacity dimension theory, and the effect of fractal dimension on methane adsorption was also analyzed. The results show that the pore structure significantly varies between coal samples, suggesting that the pore distribution on coal surface has obvious heterogeneity and fractal features. The fractal dimension (D) is greatly affected by metamorphism, and coalification makes pore structure complex. D values have different effects on VL and PL. VL has a linear increase with increasing D values. While, the relationship between PL and D values is characterized as a quadratic curve. The increase of complexity on coal surface benefits the methane adsorption.