Abstract:

Desorptivity of coalbed methane (CBM) is one of the key controls to CBM recovery ratio and production. Based on the
canister desorption experiments and relevant data of the 62 coal core samples from the Hancheng block, the correlation of the
desorptivity to the geological controls such as the coal rank, coal quality and maceral composition is discussed. Results showed
that the desorption ratios of all samples are higher than 80%, commonly from 90% to 95%. Adsorption time ranges from 0.03d
to 10d, in which the desorption ratios of the 82% samples are less than 6d. CBM desorbed with the stages, the reduction of the
desorption rate was resulted from the change of the average CBM content. Initial desorption rate and its attenuation are related
to the pore texture and connectivity in the samples. Desorption ratio has not a clear correlation with the coal rank but reduces
obviously with the increase of ash yield. Moreover, desorption ratio increases with increasing the vitrinite content and reduces with
decreasing the inertinite content. Adsorption time shortens discretely with the increase of the fixed carbon or moisture contents,
but has not a obvious correlation with the ash yield and maceral content.