A Drainage Method for Enhanced Permeability of Gas Explosion Coal Seam in Boreholes in Late Induction Drainage

Abstract

Provided is a gas explosion coal seam permeability increasing extraction method in a borehole in the later period of induction extraction. The method comprises: inserting a gas extraction pipe (7) into a borehole; a down-hole negative pressure extraction main pipeline (1) and the pipeline of a three-way ball valve (5) being provided with a gas density monitoring device (2), a carbon monoxide monitoring device (3), and a temperature monitoring device (4), a gas extraction pipe being provided with a spark generator (6), when the gas density monitoring device monitors that gas density in the gas extraction pipe is in the range of 9%-10%, the spark generator switching on to make gas in the borehole blast; extracting gas in the borehole; when carbon monoxide density in the extracted gas is monitored to exceed a warming value or the temperature of the extracted gas exceeds the warming value, injecting water into the borehole to prevent coal spontaneous combustion. The method uses the natural attenuation characteristics of the density of a gas extraction borehole to induce repeated detonation, cracks of coal mass on the periphery of a hole wall are developed, and coal seam gas permeability is improved continuously. The method is suitable to be used for a high-gas low permeability coal seam.

Description

technical field [0001] The invention relates to a coal seam anti-permeability drainage method, in particular to a gas detonation coal seam anti-permeability extraction method in a bore hole in the later stage of induced drainage, and belongs to the technical field of gas anti-permeability extraction. Background technique [0002] The gas permeability of my country's coal seams is 2-3 orders of magnitude lower than that of the United States and Australia, and coal seam permeability enhancement is the main way to increase gas extraction. At present, the main anti-permeability measures for a single coal seam in coal mines include two measures: hydraulic anti-permeability and blasting. However, these two anti-permeability measures have certain limitations: hydraulic anti-permeability measures such as hydraulic fracturing, hydraulic slotting and Hydraulic punching in soft and low-permeability coal seams can easily induce accidents in holes such as collapse holes and injection hol...

AI Technical Summary

Problems solved by technology

At present, the main anti-permeability measures for a single coal seam in coal mines include two measures: hydraulic anti-permeability and blasting. However, these two anti-permeability measures have certain limitations: hydraulic anti-permeability measures such as hydraulic fracturing, hydraulic slotting and Hydraulic punching in soft and low-permeability coal seams can easily induce accidents in holes such as collapsed holes and spray holes, blocking gas flow channels, and limited by the surface tension of water, the penetration range is limited

A Chinese Invention Patent published on January 28, 2015 has a publication number of CN104314605A "A Method for Intensified Drainage of Coal by Gas Explosion Fracture in Boreholes" and a Chinese Invention Patent published on December 24, 2014. No. CN104234739A "a kind of in-drilling gas explosion fracturing coal enhanced drainage method" all proposes a kind of active injection of air to the drilling, so that the gas concentration in the hole is reduced to the optimum explosion concentration range, and then detonates the gas in the hole. The method of gas fracturing, the above method relies on active gas injection to dilute the gas, which has the problem of uneven distribution of gas concentration in the hole, and the distribution area of ​​detonable gas concentration in the hole is uneven and discontinuous, which will easily lead to ignition failure and internal combustion in the hole The explosion range is limited, and it does not involve the safety protection problem of coal spontaneous combustion in the hole after the explosion

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