Reassessment of coal permeability evolution using steady-state flow methods: The role of flow regime transition

Steady-state flow methods are widely applied in the laboratory where permeability evolution is typically evaluated assuming a uniform pressure gradient along the sample. The accuracy of this approach is questionable for tight geomaterials when gas is used as the injecting fluid, due to: (i) the nonlinear distribution of pore pressure and gradient along the sample, suggesting that (ii) both slip and viscous flow may occur concurrently within...