Coal body desorption
characteristics are one of the key factors
that influence the development of coalbed methane (CBM). In this study,
91 coal core samples from 11 CBM wells in the Fukang mining area were
collected from Xinjiang, China, and the coal quality, high-pressure
mercury compression, gas content, and natural desorption characteristics
measurements were launched. With the detailed analyses of the differences
in cumulative desorption volume, desorption ratio, and on-site average
desorption rate for the coal samples with different body structures
and macrolithotypes, the influence of the maximum reflectance of vitrinite,
microscopic coal rock composition, and coal quality and pore characteristics
on CBM desorption characteristics were discussed. The results showed
that the cumulative desorption volume, desorption ratio, and desorption
rate of cataclastic structure-bright coal are higher than those of
primary structure-semibright coal. With the increase of R
O,max and vitrinite content, the adsorption capacity of
coal increases, and the increased methane concentration difference
during desorption leads to an increase in cumulative desorption volume
and on-site average desorption rate. The higher contents of moisture
and ash yield would occupy the adsorption sites and hinder gas diffusion,
which would decrease the desorption of coalbed methane. The greater
porosity/pore volume ratio of medium and large pores can enhance the
connectivity of pores, which increases the desorption ratio and the
average desorption rate, while the higher micropore porosity/pore
volume ratio can increase the gas adsorption space and the cumulative
desorption volume. The pore characteristics have the most significant
effect on the cumulative desorption volume and desorption ratio. The
results of the study can help guide coal mine gas management and CBM
development from middle-and low-rank coal reservoirs in Xinjiang.