Depressurized extraction method for cutting through roof or floor of coal seam by abrasive water jet

Abstract

The invention discloses a depressurized extraction method for cutting through a roof or a floor of a coal seam by an abrasive water jet, which comprises the following steps: a. drilling a bedding drill hole to set depth on the roof or the floor of a coal-rock mass or a hard layer by using a drilling machine through a drill stem and a slotting drill bit; b. delivering a high-pressure abrasive water jet of which the pressure is 25-30MPa to the slotting drill bit through the drill stem, wherein the drill stem rotates in situ; forming a radial slit on the hole wall of the bedding drill hole, wherein the slit penetrates the roof or the floor of the coal-rock mass or the hard layer and a soft layer; c. enabling the drill stem to rapidly retreat for 1.5-3m so as to form a new slit; d. repeating the step c until a plurality of radial slits are formed on the bedding drill hole, and moreover, reserving a safety rock pillar of at least 5m at the slit located at the position of the orifice of the bedding drill hole at a certain distance from the orifice; e. retreating the drill stem and the slotting drill bit and sealing the hole; and f. extracting gas by a gas extraction system. The depressurized extraction method for cutting through the roof or the floor of the coal seam by the abrasive water jet has the beneficial effects that the drill hole does not have potential safety hazards and is easy to form; a hole sealing effect is good; the time of reaching the standards of extraction is short; the production efficiency is high; and the extraction is safe.

Description

technical field [0001] The invention relates to the technical field of coal seam gas drainage, in particular to a pressure relief drainage method in which an abrasive jet cuts through a coal seam roof or bottom. Background technique [0002] Coal seam gas is a kind of clean energy, but it is also a source of disaster for coal mine production. The geological conditions of coal occurrence in my country are complex, mainly relying on underground mining. With the increase of mining depth, the gas content of coal seams gradually increases, the pressure of coal seam gas increases, the risk of outburst increases, and the difficulty of outburst prevention becomes more and more difficult. Most of the domestic coal and outbursts occur in the coal roadway excavation face, accounting for 66.2% of all outburst times, and the average outburst intensity is 66.9 t / time. . Roadway excavation is the first step in all coal mining work. How to realize roadway excavation, especially the pre-pu...

AI Technical Summary

Problems solved by technology

The method is to drill a hole in the coal seam on the roof of the coal seam. Although the safety of drilling the hole in the seam is higher than that in the coal seam, there are still potential safety hazards caused by gas leakage in the coal seam when drilling; at the same time , it is necessary to set non-metallic casing in the well of the coal seam, which not only affects the drilling efficiency, but also causes waste of materials

[0004] Chinese Patent Announcement No. CN 101718191A, announcement date June 2, 2010, invention name "method for exploiting coalbed methane with hydraulic jet drilling pressure relief", the method discloses a drilling and slotting method using a slotted drill bit Integrated operation method, although this method needs to set non-metallic casing in the well of the coal seam, which improves the efficiency of drilling and slotting; but this method does not reveal how to ensure the safety of drainage

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