A method of improving the wetted radius of high pressure water injection of lowly permeable coal seams through sublevel presplitting

摘要

#$%^&*AU2016231635A120170504.pdf#####ABSTRACT The present invention provides a method of improving the wetted radius of high pressure water injection of lowly permeable coal seams through sublevel presplitting, which comprises the following steps: the presplitting boreholes with a depth equal to that of the high pressure water injection boreholes are bored with drill rigs at both sides of every existing high pressure water injection borehole at the pre-mined coal seam of the gate entry, and one high pressure water injection borehole and the presplitting boreholes at its both sides form a unit for coal seam weakening and permeability improvement; firstly, one unit for coal seam weakening and permeability improvement is weakened and improved in permeability, then the presplitting device is removed after such weakening and permeability improvement of the said unit and the next unit for coal seam weakening and permeability improvement is weakened and improved in permeability. The carbon dioxide phase transition fracturing technique is utilized, ensuring the uniformity of fissure development, significantly improving the wetted radius of high pressure water injection of the coal seams in China that are difficult to be injected with water, thus changing the properties of the coal seams, minimizing the dust generated from the working face and the risks of the coal and gas outbursts, rockbursts and other disasters. FIG 21 2 1 FIG. 1 3 4 5 6 FIG. 2