Freezing fracturing and hydraulic punching type permeability improving and drainage promoting method for low-permeability coal seam

Abstract

The invention provides a freezing fracturing and hydraulic punching type permeability improving and drainage promoting method for a low-permeability coal seam. The method comprises the following stepsthat cross-layer drilling is conducted on a coal body in a bottom plate rock roadway, the final hole points of all drilled holes are arranged in a grid array mode, and every two adjacent drilled holes are named as a liquid injection hole and a drainage hole correspondingly; drainage pipes are arranged in the drill holes for hole sealing, and an underground drainage system is connected for gas drainage; high-pressure water is injected into the liquid injection holes; special hole sealing devices are fed into the drainage pipes in the liquid injection holes and perform hole sealing; liquid nitrogen is injected into the liquid injection holes through the special hole sealing devices to freeze the coal body around the liquid injection holes; the liquid nitrogen is slowly sublimated into nitrogen under the action of the ground temperature, and the nitrogen effectively replaces and displaces gas in the coal body; and the drainage pipes in the liquid injection holes are connected with the drainage system for gas drainage work. The principle is scientific, design is ingenious, hole sealing is tight, the method can be widely applied to rock cross-cut coal uncovering, fault crossing, anti-reflection and drainage promoting of an excavation working face and other work, the anti-reflection and drainage promoting effects are good, and the application prospects are wide.

Description

technical field [0001] The invention belongs to the technical field of coal mine safety production, and in particular relates to a method for freezing and fracturing in conjunction with hydraulic punching to increase permeability and promote pumping for low-permeability coal seams. Background technique [0002] Most coal seams in my country have the characteristics of "three lows and one high" (low permeability, low saturation, low reservoir pressure, and high degree of metamorphism). The low permeability of the coal seam makes it difficult to extract gas, resulting in the imbalance of "pumping-excavation-mining" in the mine, forming a major safety hazard, and laying hidden dangers for the occurrence of coal mine gas accidents. Therefore, scholars at home and abroad have proposed hydraulic cutting, protective layer mining, deep hole blasting, CO 2 Phase change fracturing and other technical measures to increase permeability of coal seam and promote drainage. However, due t...

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Problems solved by technology

[0008] In order to solve the deficiencies in the prior art, the present invention provides a freezing fracturing collaborative hydraulic punching anti-reflection and pumping promotion method for low-permeability coal seams to solve the problems of conventional hole sealing devices and sealing methods in freezing fracturing. In the process of coal and gas drainage, the sealing effect is poor, which leads to poor drainage effects, etc., so as to improve the degree of freezing and fracturing of coal, reduce the amount of punching engineering, and improve the effect of coal seam gas drainage

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