A liquid nitrogen circulation cold shock anti-reflection method based on multi-parameter monitoring

Abstract

The invention discloses a liquid nitrogen cycle cold shock anti-reflection method based on multi-parameter monitoring. The video monitoring lens shoots in real time to monitor the size of the bubbles and the flow rate of the bubbles generated inside the liquid nitrogen in the drilled hole, and feeds back to the monitoring control center for storage. ; The quality sensor monitors the mass loss rate of liquid nitrogen in the drilled hole in real time and feeds back to the monitoring and control center for storage; the gas monitoring device detects the gas pressure, gas flow and gas temperature in the pressure relief pipe in real time and feeds back to the monitoring and control center for storage; completed After one fracturing, then SF 6 The gas detector, the acoustic wave transmitter and the acoustic wave receiver detect the anti-reflection cracking effect, that is, the sound wave velocity can detect the number of cracks generated after the anti-reflection is generated, and the SF 6 Gas detection can detect the connectivity between created fractures. Through the monitoring data, the cold shock of liquid nitrogen, the expansion pressure of phase change gas and the frost heave pressure of water in the crack can be used to crack the coal body, and the anti-permeability effect can be effectively monitored.

Description

technical field [0001] The invention relates to a coal seam anti-permeability method, in particular to a liquid nitrogen circulation cold shock anti-permeability method based on multi-parameter monitoring. 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 into wells h...

AI Technical Summary

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 this will not be able to take advantage of the advantages of liquid nitrogen anti-reflection (that is, the impact force of volume expansion and liquid nitrogen gasification when liquid nitrogen is vaporized). 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 caused by rapid expansion; at the same time, it will greatly increase the time required for the coal seam to increase the permeability and cannot guarantee the effect of the enhancement

Images