Study and application on pressure releasing and permeability improved technology with digging and reaming out borehole

摘要

To improve the gas drainage effect in low permeability coal, we introduced the pressure releasing and permeability improved technology with digging and reaming out the borehole in seam segment, combined with numerical simulation and field practice, study its mechanism of permeability and fluidity improvement.The results show that massive coal fragments were ejected after dig and ream out the borehole in seam segment, coal seam would expand deformed around the borehole, the crustal stress relieved, the quantity of fracture increased, and a substantial increase in permeability.The influence radius of gas drainage increased can be increased by 34.2 ％ ,the drainage gas concentration would be increased to 2 times, and the flow rate can be increased 4～6 times.