Coal mine underground coal seam long drill hole staged fracturing permeability increase and gas extraction method

Abstract

The invention discloses a coal mine underground coal seam long drill hole staged fracturing permeability increase and gas extraction method. The coal mine underground coal seam long drill hole stagedfracturing permeability increase and gas extraction method comprises the steps that a long drill hole with the length more than 100m are drilled into a coal seam using a underground tunnel drilling machine for a coal mine or a kilometer drilling machine; a rigid casing with an one-way valve is lowered into to protect the hole directly using the underground tunnel drilling machine or the kilometerdrilling machine, and casing centralizers are installed at regular intervals; after the casing is lowered, preset volumetric cement paste is injected into an annular space between the outer wall of the casing and a drill hole wall to carry out blocking and sealing; a rigid fracturing pipe with two or multiple packers is lowered into the casing to carry out coal seam staged fracturing step by stepor multistage staged fracturing; and the fracturing pipe and the packers are removed after staged fracturing permeability increase, the casing of coal seam long drill hole opening is accessed with a gas extraction pipeline after drainage finishes to carry out efficient extraction of gas. The engineering amount of a tunnel and hole-drilling can be greatly reduced, the coal seam gas extraction efficiency is improved, and the coal mine underground gas treatment cost is reduced.

Description

technical field [0001] The invention relates to a method for segmental fracturing and gas drainage of long boreholes in underground coal seams of coal mines, which is suitable for segmental fracturing and gas extraction of long boreholes in coal seams containing gas. Background technique [0002] With the increase of mining depth of coal resources, coal and gas outbursts, gas explosions and other disasters are becoming more and more serious, seriously restricting the safe and efficient production of coal mines, and the discharge of gas into the atmosphere will also cause air pollution. However, coal seam gas is also a valuable non-renewable energy source. Coal mine gas can be used as gas fuel and carbon black if it is properly pumped, collected, neutralized and treated. [0003] At present, increasing the permeability of high-gas coal seams, improving the permeability of coal seams and the efficiency of gas extraction is an important way to control gas disasters and develop ...

AI Technical Summary

Problems solved by technology

The above-mentioned technologies have achieved good pressure relief and anti-reflection effects, but they are restricted by many factors in the field application, and there are the following main problems: the high-energy medium used in some technologies directly acts on the gas coal seam, the construction safety cannot be guaranteed, and it is easy to Induce blowholes or even gas dynamic disasters; there are common problems such as large amount of tunneling and drilling, long construction period, low efficiency, and poor economic benefits, which seriously affect the efficient mining and production of coal mines; the common problems of coal seam anti-reflection range are small and regional anti-reflection effects are poor , Long gas extraction time and low efficiency

In underground coal seam fracturing and anti-permeability enhancement in coal mines, floor tunnel drilling or drilling along the coal seam is mainly used for fracturing, and the construction work of the roadway and drilling is large; One-time fracturing, the fracturing range is small, and the degree of pressure relief and permeability enhancement of the coal seam is low; since the fracturing is only carried out at the bottom of the borehole, the fracturing borehole has not been fully enhanced in the axial direction, and the utilization of the fracturing borehole The rate is very low; for the soft medium of coal seam, long boreholes are prone to hole collapse, and casings need to be used for hole protection

[0005] In recent years, in the field of oil and gas field development, surface horizontal drilling and multi-stage fracturing technology have been developed rapidly. However, the surface fracturing technology is complex, and the fracturing equipment is bulky, weighing hundreds of tons or even thousands of tons. Underground coal mines It cannot be used in a narrow space; in addition, ground fracturing methods and parameters do not consider the impact on coal mine mining operations and gas dynamic disasters

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