Influence of coal adsorption deformation on permeability evolution of three kinds of gas

Abstract

In order to deeply understand the control mechanism of gas adsorption on coal permeability, based on the seepage experiment, the variation of coal permeability of helium, nitrogen and carbon dioxide under different pressures and effective stress was studied by using triaxial percolation apparatus. The conclusions are follows: under the same conditions, the permeability of the three gases is helium>nitrogen>carbon dioxide, and the permeability of carbon dioxide is most significantly affected by adsorption deformation. The relationship between gas adsorption and effective stress is competitive on coal permeability under the constant external stress. The gas adsorption is stronger than the effective stress in low pressure stage, but on the contrary in high pressure stage, the coal permeability firstly decreases and then increases. When the pressure is constant, the permeability of three kinds of gas decreases with the increase of effective stress. Under the same effective stress, the permeability damage rates of nitrogen and carbon dioxide are higher than that of helium. At the same time, the decline of permeability at 2 MPa can reach up to 30.98% than that at 1 MPa, and the average compressibility is about 15%.

Keywords

• gas adsorption
• permeability
• effective stress
• coal seam
• adsorption deformation of coal