Static settlement of different types of pulverized coal in CBM wells

In order to study the particle size of the pulverized coal that bring trouble to pump and reduce pump accident.The size analysis of drilling cuttings finds that the fines less than 0.0374 mm and more than 3.8 mm are the main particle for stuck pump, plug pump or plug shaft.Further study narrows the size range by means of LPSA (Laser Particle Size Analyzer) .In the static settling velocities experiment, it is found that when the concentration of fines is very low, settlement velocity decreases with the increase of concentration. When the concentration is increased, coal settlement rate will no longer change and tend to a constant value.It is also found that the lower of concentration of fines, the higher of coal suspension rate.In the wetting experiments of different pulverized coal samples, it is found that the wettability of fine sample of the drilling cuttings is poorer than that of sample of output of drainage, but the wetting modification effect of fine sample of the drilling cuttings is better.According to the experimental results, the basic physical characteristics of fines are summarized in order to guide the production of fines in the coalbed methane well.