Experimental study on coal seepage characteristics and stress sensitivity

Abstract

Taking No.3 coal seam of Daping Coal Mine in Lu’an Mining Area of Shanxi Province as the research object, the response law of coal permeability to pore pressure and surrounding pressure was systematically explored by using HB-2 type coal rock sample pore permeation adsorption measurement device, and the relationship between the permeability of loaded coal samples and pore pressure and surrounding pressure was quantitatively analyzed. The results show that: the permeability of coal samples under low pore pressure conditions decreases with the increase of pore pressure in accordance with the power function, and the permeability of coal samples is more sensitive when the pore pressure is below the critical value of 1.5 MPa; the permeability of coal samples under constant pore pressure conditions decreases with the increase of surrounding pressure in a power function, and the permeability decreases significantly, more than 85%; the change of stress in coal reservoir will produce more than 50% irreversible damage to coal permeability. The overall trend of the permeability decay rate during unloading of the coal body with the increase of the surrounding pressure is a downward decay law, and its local variation is characterized by fluctuations of more than one extreme value.

Keywords

• coal seepage characteristics
• pore pressure
• confining pressure
• effective confining pressure
• permeability
• stress sensitivity