Influence Factors Analysis of Coal Seam Drainage Effect and Its Technical Countermeasures

According to gas drainage theory and field practice, the unsteady gas flow filed, low permeability, sealing tightness, drilling hole collapse, gas flow state in the borehole and borehole layout parameters in coal seam were considered to be the main factors influencing the drilling of gas drainage. Based on the above factors, the paper summarizes the methods to increase the borehole gas drainage: coal seam mining and pressure relief, coal seam fracturing and permeability increase of coal seam （including pre-splitting blasting, CO₂ blasting, hydraulic fracturing）, expanding the influence radius of drilling （increasing the hole diameter, hydraulic slotting, hydraulic reaming, hydraulic punching, etc.）, using new sealing process, improving gas flow in borehole （reasonable negative pressure distribution, inserting screen, etc.） and the optimization of drilling layout parameters.