Study on Permeability Improvement Technology by Injecting Air into the Gas Drainage Borehole in Low-Permeability Coal Seam

Table 1

Parameters for coal and gas in need.

Parameter	Value
Density of coal body,	1.38 × 10^3 kg·m^−3
Porosity of coal body,	0.0320
Permeability of coal body,	1.35 × 10^−17 m^2
Density of CH4 in the standard condition,	0.717 kg·m^−3
Dynamic viscosity coefficient of CH4,	1.03 × 10^−5 Pa·s
Ultimate adsorption capacity of CH4
In coal seam adsorption alone,	0.03832 m^3·kg^−1
Adsorption equilibrium constant of CH4,	0.51 MPa^−1
Density of N2 in standard condition,	1.25 kg·m^−3
Dynamic viscosity coefficient of N2,	1.69 × 10^−5 Pa·s
Ultimate adsorption capacity of N2
In coal seam adsorption alone,	0.01658 m^3·kg^−1
Adsorption equilibrium constant of N2,	0.46 MPa^−1
Pressure of gas in standard condition,	0.101325 MPa