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Method for preventing drilling collapse of downhole coal bed

A coal seam and drill pipe technology, applied in drilling equipment and methods, drilling equipment, earthwork drilling, etc., can solve problems such as collapse and collapse of high-gas soft coal seams, achieve large gas drainage flow, and reduce the possibility of hole collapse , the effect of wide practicability

Active Publication Date: 2013-07-10
CHINA UNIV OF MINING & TECH
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AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to provide a method for preventing the collapse of boreholes in underground coal seams, and to solve the problem of collapse after drilling holes in high-gas soft coal seams
It can not only solve the problem of coal seam collapse after drilling, but also ensure efficient gas extraction

Method used

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  • Method for preventing drilling collapse of downhole coal bed
  • Method for preventing drilling collapse of downhole coal bed
  • Method for preventing drilling collapse of downhole coal bed

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Embodiment 1

[0023] Embodiment 1: the method for preventing borehole from collapsing, the steps are as follows:

[0024] a. Use the drilling device to construct gas drainage drilling holes in the underground coal wall, and stop drilling when the drill bit reaches the final hole position. Generally, the drilling depth is 80-100m, and the length of each drill pipe is 0.8-1.0m;

[0025] b. Withdraw 3~4 drill pipes, connect the compressed air to the porous material conveying device, and convey the porous material in the porous material conveying device to the inner hole of the drill pipe, so that the porous material enters through the inner hole of the drill pipe The reserved drilling space in front of the drill bit will stop the air supply until it is filled with more than 2 / 3 of its volume capacity;

[0026] d. Repeat step b until there are only 10 to 20 drill pipes left in the hole, stop conveying the porous material, and withdraw all the remaining drill pipes in the hole;

[0027] e. The ...

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Abstract

The invention discloses a method for preventing drilling collapse of a downhole coal bed and belongs to a method for preventing drilling collapse. During constructing a gas extraction hole of the coal bed, a drill bit retreats a certain distance after arriving a finished hole position, porous materials in a porous material conveying device are conveyed to a reserved filling section of the front end of the drill bit through an inner hole of a drill rod by the aid of the compressed air. Then the porous materials are conveyed once when the drill bit retreats a certain distance each time until the drill bit retreats to a preset sealed hole position. Porous materials reserved in holes can support hole walls to prevent collapse, and meanwhile, gaps between the holes and the porous materials provide good passages for gas suction and flowing, gas of the coal bed can be guaranteed to leak from the drilled holes to some extent even if the drilled holes collapse. The method for preventing drilling collapse of the downhole coal bed has the advantages that system and process are unique, drilling gas extraction is high in flow and concentration, the method has widely practicality and is particularly applicable to drilling of the coal bed with firmness coefficient f smaller than 0.5.

Description

technical field [0001] The invention relates to a method for preventing borehole collapse, in particular to a method for preventing underground coal seam borehole collapse. Background technique [0002] At present, the main means of gas control in my country's coal mines is to conduct underground drilling to pre-drain high-gas coal seams in advance. This method has the advantages of convenient construction, relatively small engineering volume, and high gas extraction efficiency. It is the most widely used technology in coal mines in my country. measure. However, soft coal seams account for a relatively large proportion of the coal seams mined in my country, and the main coal seams in Pingdingshan, Huainan, Huaibei, Guizhou, Sichuan and other mining areas are soft and high-gas coal seams. Affected by factors such as in-situ stress, coal seam gas content, gas pressure, and coal strength, gas drainage boreholes in soft coal seams are prone to shrinkage and local collapse after ...

Claims

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Application Information

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IPC IPC(8): E21F7/00E21B7/00
Inventor 周福宝高峰刘应科刘春肖翔杨磊
Owner CHINA UNIV OF MINING & TECH
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