Method for measuring pressure of gas in coal seam in fracture rock stratum

Abstract

The invention discloses a method for measuring pressure of gas in a coal seam in a fracture rock stratum. The method comprises the following steps of firstly, penetrating the seam, measuring the pressure, drilling and tapping to form an outer rock drill hole; after sleeving a borehole orifice-pipe, fixing the pipe and passing the pressure-tight test, continuously going deep into the drill hole to form an inner rock drill hole, then secondary grouting and solidifying the inner rock drill hole; sweeping the hole and drilling along the borehole orifice-pipe again, forming a coal drill hole after coal can be seen from the drill hole, inserting a pressure measuring pipe into the inner rock drill hole, and utilizing expanded synthetic resin to coordinate with a grout stop belt to block two ends of the inner rock drill hole of the drill hole to form a closed chamber; after grouting is performed for the third time in the closed chamber, mounting a pressure gage and observing for 20-30d and recording. Through drilling and grouting processes for multiple times, tight hole sealing and multilayer high-pressure grouting, as well as the functions of thoroughly blocking circumferential cracks of rocks, enhancing hole sealing quality and separating gas in the hole are realized. The method is strong in applicability, and can be adopted no matter how complex the geological conditions are.

Description

technical field [0001] The invention relates to the technical field of coal gas pressure measurement, in particular to a method for measuring coal gas pressure in a fractured rock formation. Background technique [0002] Coal seam gas pressure is an important index to evaluate whether a coal seam has outburst risk, but the coal seam gas pressure is affected by different measurement methods and different geological conditions, and the real coal seam gas pressure is difficult to be effectively measured. When measuring coal seam gas pressure by drilling through layers, if the formation fractures are developed or the hole sealing technology is backward, it is easy to cause a large amount of gas overflow in the drilling hole in actual measurement, which is the main reason for the distortion of the pressure display. [0003] Coal seam gas pressure measurement can be divided into active pressure measurement method and passive pressure measurement method according to differe...

AI Technical Summary

Problems solved by technology

Although this method can achieve a certain effect, the pressure bearing effect of the borehole is poor, which is not conducive to high-pressure grouting. It is easy to cause the solidified slurry to collide with the borehole wall due to the influence of coal, rock powder and other sundries in the borehole. Coupled with the influence of cracks in the rock wall, high-pressure gas still overflows from the borehole, so this method is not suitable for measuring in cracked rock formations.

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