Effect of pulverized coal dispersant on coal in the CBM well-washing technology

In order to screen synthetically the dispersants of pulverized coal in CBM well-washing technology,the ex- periments of the dispersion stability of pulverized coal,the wetting characteristics and the coal reservoir damage evalua- tion have been carried out by using the No. 11 coal of Taiyuan formation in Hancheng mining area and different anion- ic dispersants,based on the influences of dispersant solution on pulverized coal,coal surface properties and coal reser- voir. The effects of different dispersants on coal rock have been investigated. The results show that the pulverized coal with a particle size of less than 300 μm has a poor dispersion stability in water. Adding a dispersant can help to im- prove the dispersion stability of the pulverized coal. Combined the surface tension of the different dispersant solutions, the contact angle,spreading coefficient and the adhesion work,different pispersants have different wetting degrees to pulverized coal,the best one is the 2 g / L SDS solution. The coal permeability varies due to the invasion of dispersant solution and the effect of water lock of coal. The damage degree of permeability shows a relationship of SDS>CMN> SN. And with the changes of capillary force,the permeability damage rate by the invasion of dispersant solution increa- ses. For the Hancheng block,the SDS dispersant can make the pulverized coal easier to disperse,and it can cause some damage to coal permeability. Therefore,in the well-washing process,the bottom-hole flowing pressure should be kept stable and the dispersant solution should be avoided entering into the coal reservoir in the near-well bore region.