During the development of deep coalbed methane (CBM),
the production
of coal fines is common and suppresses the yield of CBM. This work
takes the deep CBM wells in the Qinshui Basin as a case study, and
the output, composition, morphology, and sources of coal fines were
investigated through scanning electron microscopy, X-ray diffraction,
proximate analysis, and particle size measurement including image
analysis, laser diffraction, and dynamic light scattering. The results
indicate that, in comparison with shallow CBM wells, deep wells produce
a greater quantity of coal fines which are darker in color and have
smaller particle sizes, with the majority being less than 10 μm.
The coal fines exist predominantly as aggregates that contained the
iron-bearing and clay minerals. Based on the Liddinger particle settling
model, the water production volume required for the coal fines to
return to the surface in the Wuxiang block was calculated to be 8.55
m3/d. This work can provide a scientific basis for the
prevention and control of coal fines in deep CBM wells.