Measuring method for coal seam gas permeability coefficient

Abstract

The invention discloses a measuring method for a coal seam gas permeability coefficient, which comprises the following steps: constructing two drill holes, with the same depth, perpendicular to a coal seam at a certain interval, and recording the distance d between the two drill holes; obtaining coal seam absolute gas pressure p; injecting tracer gas into one drill hole, wherein an air compressor is connected with the drill hole so as to provide certain pressure for the drill hole, and connecting the other drill hole with a gas extraction system pipeline in a sealing manner; detecting the tracer gas, and determining the time t from the time when the drill hole is connected to the gas extraction system pipeline to the time when the tracer gas is detected; substituting the measuring result into a computational formula of the coal seam gas permeability coefficient to obtain the coal seam gas permeability coefficient. The computational process is simple; through the certain gas injection pressure provided by the compressor, and the connection between the other drill hole and the gas extraction system pipeline, orifices are kept under negative pressure. Therefore, the tracer gas can be measured quickly, the measuring period is short, and the general applicability is strong.

Description

technical field [0001] The invention relates to the technical field of coal mine gas control, in particular to a method for testing the air permeability coefficient of coal seams. Background technique [0002] my country is not only the world's largest coal producer, but also the largest coal consumer. For a long time, coal has accounted for more than two-thirds of China's primary energy production and consumption structure. With the increase of mine mining depth and the increase of ground stress, the risk of coal seam outburst is increasing day by day. my country has become the country with the most serious coal and gas outburst accidents in the world, and the number and intensity of coal and gas outbursts have also reached best in the world. Gas drainage is a key technical means to effectively control gas accidents and solve the problem of safety production in coal mines in my country. The coal seam air permeability coefficient is a sign of the difficulty of coal seam gas...

AI Technical Summary

Problems solved by technology

However, when this test method calculates the air permeability coefficient, it needs to go through several trials in a set of formulas to find a suitable calculation formula, which brings inconvenience to the calculation.

At the same time, the theoretical analysis also shows that the existing calculation methods still have problems such as being unable to find a suitable calculation formula or having two conflicting calculation results.

Moreover, the borehole radial flow method first needs to accurately measure the original gas pressure of the coal seam, and then test the borehole gas flow rate at each time; the test period is longer, and for coal seams with lower coal seam gas pressure, the coal seam gas pressure and borehole gas flow rate are often It is difficult to measure accurately, so its applicability is also limited

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