Permeability and volumetric changes in coal under different test environment
Permeability refers to the ability of coal to transmit gas when a pressure or concentration gradient exists across it. Permeability is considered by many researchers to have a significant impact on a coal seam's ability to produce gas). Permeability is closely related to the coal fabric (i.e. cleat spacing and aperture width) and varies significantly as fluid pressure changes during coal seam gas production. Permeability has a strong effect on the gas production profile and gas well performance and is dependent upon various factors, which include effective stress, gas pressure, water content, disturbance associated with drilling and matrix swelling/shrinkage due to adsorption/desorption.