Changing Law of Permeability of Coal Reservoirs under Variable Pressure Conditions and Its Influence on Extraction Efficiency of Coalbed Methane

Coal permeability data are critical in the prevention and control of coal gas outbursts mines an important reservoir parameter for development coalbed methane. The mechanism by which is affected pressure complex. We used a self-developed true triaxial seepage experimental device that collects lignite anthracite samples, sets fixed axial confining pressure, changes changing orientation seam to study influence on under conditions different types bedding orientations. decreased rapidly then slowly tended be stable with increase pressure. This conformed power exponential fitting relationship, degree reached more than 99%. comparison two samples showed sample’s plane vertical direction was significantly lower parallel direction, indicating seeped easily along bedding. sensitivity coefficient change calculated. analysis sensitive during low-pressure stage. When greater 0.8 MPa, reduced, may have been related slow amount absorbed high-pressure A theoretical calculation model considering adsorption/desorption effects proposed verified results showing better reflected characteristics predicted its permeability. Using finite element simulation software COMSOL, extraction efficiency simulated. In stage, reduction evident