Gas Drainage Based on Screen Pipe Placing in Borehole Technology Without Drilling Rod Lifting in Soft Seam

According to gas drainage channel jammed problem caused by a borehole wall easily collapsed after borehole drilled in a soft seam, the paper analyzed the insufficient the available borehole wall protection methods. The paper provided a screen pipe placing in the borehole technology without drilling rod lifting applied to the borehole wall protection for the gas drainage in the soft seam. Related drilling bit, drilling rod, borehole bottom suspended device and other equipment were researc hed and developed. An optimized design was conducted on the pore structure of PVC screen pipe. An industrial trial in the underground showed that an advancement a nd relability of the screen pipe placing in the borehole technology without drilling rod lifting was verified in the application of the borehole wall protection to the gas drai nage borehole in the soft seam. In comparison with the screen pipe placing in an open borehole after the drilling rod lifted, the technology could reduce screen pipe pla cing time 4 ~ 5 h in the borehole and could improve the screen pipe placing rate 28% ~ 38% and gas drainage scalar 50%.