Multi-azimuth minimal radius punching technology for strata-penetrating borehole of underground coal mine

Abstract

The broken and soft coal seam has high gas content and poor permeability. The single hole drainage radius is small when the conventional through-bed drilling is used for gas drainage, and the drilling engineering volume is large. To this end, a gas extraction technology of crushed soft coal is proposed by radial punching and burrowing. The idea of gas drainage technology by punching holes with multi-direction and minimum radius through-bed drilling is proposed, a punching drilling tool capable of bending in a fixed direction with a minimum radius is designed, through the push of the orifice drilling tool and the resistance exerted on the jet nozzle from the bottom of the hole, the fixed direction bending punching of the drilling tool is realized, and the bending direction is controlled by rotating and fixing the drilling tool held by the power head. In this way, multi-azimuth and multi-branch hole with minimum radius can be formed. The relationship between bending angle, length and radius of curvature of drill tool is analyzed, which provides theoretical support for tool design; the tensile strength and pressure resistance parameters of the tool are obtained through testing; the feasibility of multi-direction punching is theoretically analyzed, and the technological process is designed; the simulation test was conducted on the ground with the trial produced drilling tools, the test results show that the one-way bending drilling tool combined with the hydraulic oscillating impactor can realize the punching of four branch holes in one main hole, the hole depth of the branch hole is 6-8 m. The experiment proves the feasibility of the technical assumption and the rationality of the drilling tool structure design.

Keywords

• through-bed hole
• multi-azimuth
• minimal radius
• hydraulic punching hole formation
• gas extraction