Shaft bottom washing device for coal-bed gas well

The invention relates to a shaft bottom washing device for a coal-bed gas well. The shaft bottom washing device for the coal-bed gas well is composed of an outer oil tube, a diffusion tube, a connecting tube, a nozzle, a spray head and a mud dredger. The mud dredger is composed of mud loosening sheets, guide sheets and a cone-shaped body. The mud dredger is characterized in that the guide sheets are distributed around the cone-shaped body of the mud dredger; the mud loosening sheets are evenly installed on the cone-shaped body; in the process of placing down the oil tube through a wellhead workover rig, the guide sheets make contact with silt to make a rotary head rotate; in the process of going deep into a silt layer of the mud dredger, the mud loosening sheets are folded upwards under the resistance of the silt; in the process of lifting the oil tube through the wellhead workover rig, the bevel edges of the mud loosening sheets are unfolded naturally under the resistance of the silt layer, so that the effec