Pressure alternate gas exhausting method by slotting and fracturing coal seams

Abstract

A pressure alternate gas exhausting method by slotting and fracturing coal seams is applicable to the gas control of complex coal seams in a high-gas-content high-ground-stress area, aims to improve the air permeability of coal bodies and the capacity of drilling gas exhausting, and realizes continuous and efficient drilling gas exhausting of the complex coal seams. According to the pressure alternate gas exhausting method, drill holes to-be-slotted and drill holes to-be-fractured are formed by drilling coal seams to a coal floor; pressure-relief annular slots are formed in the bottom area of a coal seam section by virtue of the rotation of high pressure water jets in the drill holes; ground stress around the drill holes is manually discharged, and internal energy of coal seam gas is released; drilling pressure alternate gas exhausting is performed through designed drilling gas exhausting pipes which can shift the functions of gas exhausting and water injection fracturing; the water injection fracturing of the slotted drill holes and the gas exhausting of the fractured drill holes are performed simultaneously (or the water injection fracturing of the fractured drill holes and the gas exhausting of the slotted drill holes are performed simultaneously). Through alternate and repeated operations, the capacity of continuous and efficient drilling gas exhausting is increased; the effective influence range of drilling gas exhausting is increased by 2-4 times; the air permeability coefficient of coal bodies around the drill holes is increased by 200-500 times; the quantity of exhausted gas of drill holes with lengths of 100 m is increased by 2-5 times, so that the pressure alternate gas exhausting method has higher field application value and social benefits.

Description

technical field [0001] The invention relates to a coal seam slit fracturing and pressure pumping alternate gas extraction method, which is especially suitable for the bottom pumping roadway of high gas and low permeability coal seam to cover the tunneling of coal roadway by drilling through layers, improving the gas drainage efficiency and efficiency of a single borehole. The total amount of gas extraction. Background technique [0002] With the increase of coal mining depth, many coal mines are facing the problem of difficult pre-extraction of coal seam gas with high gas and low permeability, which seriously restricts the safe production of coal mines. The main measure to solve the problem of gas gushing in the process of mining high gas and low permeability coal seam and to prevent it is gas drainage. However, due to the low permeability of high-gassy and low-permeability coal seams, conventional drainage is difficult and the effect is poor, so technical measures for pres...

AI Technical Summary

Problems solved by technology

When mining a single coal seam, the currently adopted high-gassy and low-permeability coal seam pressure relief and anti-reflection technical measures mainly include deep hole loosening blasting, hydraulic punching, hydraulic slotting, coal seam water injection, and hydraulic fracturing to relieve pressure and increase the permeability of the seam. However, these methods have certain problems

In the initial stage of taking these measures, due to the increase of coal seam fissures, the concentration of gas drainage was high, but with the redistribution of stress, the fissures tended to close gradually, and the negative pressure generated by the gas pump was continuous and unidirectional, which also led to The fractures tend to shrink, so the concentration of gas drainage decreases rapidly, which affects the application of these methods in gas drainage

When hydraulic slits are applied in soft coal seams, the coal seam collapse around the annular slit will reduce the permeability of the coal seam and affect its effect.

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