Low permeability coal bed liquid nitrogen freeze thawing cracking permeability increasing method

A freeze-thaw, coal seam technology, applied in earth-moving drilling, gas discharge, mining fluids, etc., can solve the problems of high technical cost, difficult drug delivery, difficult pipe down, high coal seam stress, high gas and low permeability, etc. The effect of large humidity range and expansion of freeze-thaw cracking range

Active Publication Date: 2015-10-07
CCTEG CHINA COAL RES INST
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AI Technical Summary

Problems solved by technology

Among them, the hydraulic anti-reflection technology has the advantages of simple process operation and low technical cost, but it usually requires the conditions to protect the coal and rock pillars on site, and it is easy to induce injection holes to cause the gas in the roadway to exceed the limit, which affects the safety of construction operations
Due to the complex technical process and high technical cost of high-energy gas permeability enhancement, it is difficult to feed and lower the tube during the construction of low-permeability broken soft coal seams, and due to the anisotropy of the coal body and the limitation of the amount of charge, the blasting range is small and cracks Expansion directionality is poor. At the same time, due to the existence of gas in the coal seam, the risk of gas explosion and outburst in the hole is increased during the blasting process. Therefore, the application of this anti-reflection technology is severely limited
Directional long-hole drilling technology has the advantages of large drilling length and directional drilling, but it is difficult to take advantage of the drainage effect in low-permeability broken soft coal seams
[0004] As coal enters deep mining, the characteristics of high stress, high gas and low permeability of coal seams become more and more significant, and the existing anti-reflection technology of coal seams is increasingly unable to meet the safety production requirements of mines

Method used

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  • Low permeability coal bed liquid nitrogen freeze thawing cracking permeability increasing method

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Experimental program
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Effect test

Embodiment 1

[0031] The low-permeability coal seam liquid nitrogen freeze-thaw cracking anti-permeability method comprises the following steps:

[0032] a) Drilling a freeze-thaw borehole 2 and a monitoring borehole 3 to the low-permeability coal seam 1 in the underground roadway, the diameter of the freeze-thaw borehole 2 is 80mm, and the depth of the hole is 26m. The minimum distance to monitor the inner wall of borehole 3 is 5m;

[0033] b) arrange the first pipeline 4, extend one end of the first pipeline 4 into the freeze-thaw borehole 2, and seal the freeze-thaw borehole 2 with the sealing device 5 at the same time, and place the first pipeline The other end of the road 4 is connected to a nitrogen generating separation device 6, which is used to produce liquid nitrogen, and the nitrogen generating separation device 6 is connected to a liquid nitrogen injection pump 7;

[0034] c) Install a temperature monitoring device 8 in the monitoring borehole 3, after the temperature monitored...

Embodiment 2

[0040] Compared with Embodiment 1, in this embodiment, after step b) and before step c), step c1) is also implemented: arranging the first pipeline branch 9, connecting one end of the first pipeline branch 9 with The first pipeline 4 communicates, and the other end is connected with the water tank 10, and the water tank 10 is connected with the water injection pump 11, and the first pipeline 4 and the first pipeline branch 9 are respectively installed with first The control valve 12 and the second control valve 13 are used to switch between injecting liquid nitrogen and injecting water into the freeze-thaw borehole 2 .

[0041]After step c1) and before step d), step d1) is also included: closing the first control valve 12, opening the second control valve 13, starting the water injection pump 11, and starting to pass through the first pipeline The branch 9 injects water into the freeze-thaw borehole 2, and monitors in real time whether there is water seepage in the monitoring ...

Embodiment 3

[0047] Compared with Embodiment 1, this embodiment also implements step c2) after step b) and before step c): arranging the second pipeline 14, and extending one end of the second pipeline 14 into the freeze-thaw In the borehole 2, the other end is connected with the water tank 10, the water tank 10 is connected with the water injection pump 11, and a third control valve 15 is installed in the second pipeline 14 for feeding the freeze-thaw drill. Well 2 is switched between liquid nitrogen injection and water injection. After step c2), before step d), step d2) is also implemented: close the first control valve 12, open the third control valve 15, start the water injection pump 11, and start to pass through the second The pipeline 14 injects water into the freeze-thaw borehole 2, and monitors in real time whether there is water seepage in the monitoring borehole 3. After confirming that there is water seepage, continue to inject water for 50 minutes, then stop the water injectio...

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Abstract

The invention provides a low permeability coal bed liquid nitrogen freeze thawing cracking permeability increasing method. The low permeability coal bed liquid nitrogen freeze thawing cracking permeability increasing method comprises the following steps that a, a freeze thawing drill hole and a monitoring drill hole are drilled; b, a first pipeline is arranged, one end of the first pipeline extends into the freeze thawing drill hole, the other end of the first pipeline is connected with a nitrogen generation separating device, and the nitrogen generation separating device is connected with a liquid nitrogen injection pump; c, a temperature monitoring device is installed in the monitoring drill hole, after the temperature monitored by the temperature monitoring device is stable, the temperature at the moment is determined to service as the initial temperature T0; d, the liquid nitrogen injection pump is started, the nitrogen generation separating device is driven to inject liquid nitrogen into the freeze thawing drill hole, and the temperature of the freeze thawing drill hole is monitored in real time; e, when the temperature T in the monitored drill hole is reduced by 50%-80% compared with the T0, the liquid nitrogen is stopped from being injected, and the temperature in the drill hole is monitored continuously; f, when the temperature T in the monitored drill hole is increased to the condition when |T-T0| / T0<5%, the step d and the step e are repeated; g, the step f is repeated for 3-5 times. By means of the low permeability coal bed liquid nitrogen freeze thawing cracking permeability increasing method, the pore structure of an original coal body is modified, the problem that the permeability effect of a low permeability coal bed is poor, and the permeability increasing efficiency of the low permeability coal bed is effectively improved.

Description

technical field [0001] The invention relates to a coal seam permeability enhancement method, in particular to a low permeability coal seam liquid nitrogen freeze-thaw cracking enhancement method. Background technique [0002] Draining coalbed methane can not only develop and utilize coalbed methane resources, but more importantly, it can guarantee the production safety of coalbed mining. However, due to the insufficient development of coal seam cracks and bedding in low-permeability coal seams, the permeability of coal bed methane is extremely low, which is not only unfavorable to the development and utilization of coal bed methane, but also unfavorable to the production safety of coal seam mining. How to exploit low-permeability coal seam coalbed methane efficiently has become a technical topic of widespread concern to domestic and foreign researchers and engineers, and many scientific research results have been obtained. [0003] At present, the method to increase the rec...

Claims

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Application Information

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IPC IPC(8): E21B43/26E21F7/00
Inventor 沈春明张浪汪东舒龙勇郭建行高旭张慧杰齐庆新
Owner CCTEG CHINA COAL RES INST
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