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Method for extracting gas in low air permeability coal layer by pulse fracture anti-reflection

A gas drainage and gas permeability technology, which is applied in the direction of gas discharge, mining fluid, mining equipment, etc., can solve the problems of small effective drilling range, uncontrollable fracturing direction, and difficult regional overall pressure relief, etc., to achieve improvement Gas flow state, wide applicability, and the effect of improving air permeability

Active Publication Date: 2013-05-22
CHINA UNIV OF MINING & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Deep hole loosening blasting, water jet slotting technology, and hydraulic punching technology have problems such as small effective drilling range, heavy workload, complex construction technology, and low drainage efficiency.
Conventional downhole hydraulic fracturing technology can achieve large-scale coal seam pressure relief relatively. Due to the use of high-flow high-pressure water injection, high-pressure water will flow in the direction of the coal seam's main fractures in the coal body, and the fracturing direction cannot be controlled. It leads to partial pressure relief and partial stress concentration, and it is easy to produce high stress concentration areas during pressure relief. The concentrated stress can reach about 3 to 4 times the original stress, and it is difficult to form a regional overall pressure relief and antireflection

Method used

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  • Method for extracting gas in low air permeability coal layer by pulse fracture anti-reflection
  • Method for extracting gas in low air permeability coal layer by pulse fracture anti-reflection
  • Method for extracting gas in low air permeability coal layer by pulse fracture anti-reflection

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Effect test

Embodiment 1

[0023] like figure 1 , figure 2 As shown in the figure, it is the drilling of high-pressure pulse hydraulic fracturing along the coal seam 3 to enhance the drainage of gas. Firstly, the fracturing units are implemented in groups along the coal seam 3 along the coal seam 3 in the air inlet lane or return air lane 4. 1. Then construct a pilot hole 2 on both sides of the center position L 10-20m away from the fracturing hole 1, and three drilling holes form a fracturing unit; the depth of the drilling hole in the coal seam 3 is 50-120m, Same as the prior art, the helical drill rod, circular drill rod or triangular drill rod can be selected as required. After the drilling construction is completed, insert a high-pressure resistant seamless steel pipe with several holes evenly distributed on the front pipe wall into the fracturing hole 1. The length of the front pipe wall is 0.5~1.5m. Seal the gap between the high-pressure seamless steel pipe and the fracturing hole 1 with a ho...

Embodiment 2

[0025] like image 3 , Figure 4 As shown, the high-level roadway 6 penetrates the layer and goes down the hole, and the high-pressure pulse hydraulic fracturing enhances the drainage of gas, which is basically the same as the first embodiment. The different parts are mainly to implement fracturing units sequentially in groups from the high-level roadway through the bed to the fracturing target area of ​​the lower coal seam 3. Firstly, the fracturing hole 1 is constructed, and then the center position L of the fracturing hole 1 is located on both sides. A pilot hole 2 is constructed respectively, and three drill holes form a fracturing unit; the depth of the drill holes penetrates the coal seam 3 . The remaining parts are all the same as in Embodiment 1, and the same parts are omitted.

Embodiment 3

[0027] like Figure 5 , Figure 6 As shown, the low-level roadway 7 penetrates the layer and goes up the hole for high-pressure pulse hydraulic fracturing to enhance the drainage of gas, which is basically the same as that of the first embodiment. The different parts are mainly to carry out fracturing units sequentially in groups from the lower roadway 7 to the upper coal seam 3 to the fracturing target area. A pilot hole 2 is constructed on each side, and three drill holes form a fracturing unit; the depth of the drill holes should penetrate the coal seam 3 . The remaining parts are all the same as in Embodiment 1, and the same parts are omitted.

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Abstract

The invention relates to a method for extracting gas in low air permeability coal layer by pulse fracture anti-reflection, comprising the following steps: firstly using the blast-proof pulse-type coal layer high pressure water injector with adjustable frequency and pressure from the coal layer, high tunnel or low tunnel; using the pulse water effect generated by the periodical change of high pressure pulse water inside the drill hole of coal body, wherein the maximum pulse pressure is 35 MPa, the flow is about 300 L / min, and the pulse frequency is 0-1460 times / min; forcing the macroscopic fracture in the coal layer to be expanded and communicated; promoting the micro-pore fracture to be formed and extended; forming a new regeneration fracture net; providing a permeable channel of water inthe coal layer so as to achieve the effects of improving the mechanical property of the coal body, reducing the stress of the coal body in front of the working face and improving the discharge rate of the gas. Through the method, the pressure releasing range of the coal layer is enlarged, the whole pressure is adequately released, the radius of influence range of fracture can reach 10-40 m, and the air permeability of the coal body can be improved by 100-1000 times; and the method is simple, easy to operate and good in effect.

Description

technical field [0001] The invention relates to a gas drainage method, in particular to a gas drainage method suitable for pulse fracturing of high-gas and low-permeability coal seams. technical background [0002] my country's coal seam gas has the characteristics of microporosity, low permeability, and high adsorption. More than 80% of coal seams are high gas and low permeability coal seams. The mining of high-gassy and low-permeability coal seams is often accompanied by a large amount of gas emission, especially with the efficient intensification of coal production and the increase of mining depth, the amount of gas emission is increasing, and the threat of gas explosion and gas outburst is increasing. It's getting serious. The main measure to solve the gas problem in the mining process of high-gassy and low-permeability coal seams is to implement coal seam gas drainage in advance. Conventional gas drainage methods have a small effective range of influence, and the amoun...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): E21F7/00E21B43/26
Inventor 翟成林柏泉李贤忠李全贵张萌博杨威张超
Owner CHINA UNIV OF MINING & TECH
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