A high-efficiency anti-permeability coal method using liquid nitrogen-hot gas cooling and heating cycles

Abstract

The invention discloses a high-efficiency anti-permeability coal body method using liquid nitrogen-hot gas cold and hot cycle impact. Liquid nitrogen is injected and gasified to absorb heat so that the temperature of the coal body is rapidly reduced, and the moisture in the coal body freezes and expands to exert pressure on the coal body. The freezing expansion force causes cracking; at the same time, the rapid expansion of the gasified nitrogen volume exerts gas expansion force cracking on the coal body, the air pressure in the drill hole increases rapidly, and the nitrogen gas is discharged through the exhaust pipe; then stop the injection of liquid nitrogen, the liquid nitrogen Nitrogen continues to gasify and expand in the borehole through the bed, exerting gas expansion force on the coal body to cause cracking, and the gasified nitrogen gas is refluxed and recovered; it is convenient for subsequent reuse; hot steam is injected to exert gas impact force on the coal body Cracking, at the same time, the temperature of the coal body is raised rapidly and the coal body is cracked by using the temperature difference; then the hot steam is discharged from the drill hole through the layer, thereby reducing the pressure in the drill hole through the layer so that the hot steam can be continuously injected; so repeated cycle, cooling and heating Alternately impact the coal body; thus effectively shorten the anti-reflection time and ensure the anti-reflection effect.

Description

technical field [0001] The invention relates to a coal seam anti-permeability method, in particular to a high-efficiency anti-permeability method for coal by using liquid nitrogen-hot air cold and heat cycle impact. Background technique [0002] High-gas coal seams account for 50% to 70% of my country's coal mines. With the continuous increase of mining depth, the pressure of coal seams and gas pressure are constantly increasing, and the gas problem is becoming more and more serious. Gas explosion and gas outburst have become problems that need to be solved urgently in mine safety production. . Most of the coal seams in our country are high-gas and low-permeability coal seams. Existing methods such as hydraulic fracturing, hydraulic slotting and pre-splitting blasting are not enough to overcome the problems of high adsorption and low permeability of coal seam gas. Low, small drainage volume, unsatisfactory drainage effect. At present, the way of liquid nitrogen injection in...

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Problems solved by technology

However, in the actual test, it was found that the existing liquid nitrogen injection methods and patents have the following significant problems: due to the severe gasification problem in the liquid nitrogen injection process, the gasification and expansion of liquid nitrogen into pure nitrogen at 21 °C will make it The volume has an expansion rate of 696 times, which means that at the initial stage of liquid nitrogen injection, the borehole has been filled with heated and gasified nitrogen before the liquid nitrogen has flowed to the coal body, and the pressure in the borehole is very high. It quickly reached tens of MPa, and the poor stability of liquid nitrogen led to the low effective pressure and flow rate that the well injection pump could provide, which was more than 10 times different from the expansion pressure of the gas generated in the borehole, which eventually led to Liquid nitrogen cannot be injected into boreholes in large quantities quickly, and liquid nitrogen can only be injected into boreholes with a very small flow rate, but in this way, the advantages of liquid nitrogen anti-reflection cannot be exerted (that is, the impact force of volume expansion during gasification of liquid nitrogen and the impact of liquid nitrogen Low temperature superimposes the freezing effect of coal, and once the liquid nitrogen is injected with a small flow rate, it will lose the impact force generated by rapid expansion); at the same time, it will greatly increase the time required for coal seam anti-reflection and cannot guarantee the effect of anti-reflection

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