Insights, Trends and Challenges Associated with Measuring Coal Relative Permeability

Abstract

Due to the poroelasticity of coal, both porosity and permeability change over the life of the field as pore pressure decreases and effective stress increases. The relative permeability also changes as the effective stress regime shifts from one state to another. This paper examines coal relative permeability trends for changes in effective stress. The unsteady-state technique was used to determine experimental relativepermeability curves, which were then corrected for capillary-end effect through history matching. A modified Brooks-Corey correlation was sufficient for generating relative permeability curves and was successfully used to history match the laboratory data. Analysis of the corrected curves indicate that as effective stress increases, gas relative permeability increases, irreducible water saturation increases and the relative permeability cross-point shifts to the right.

Dewatering Optimization of Coal Seam Gas Production Wells: A Review and Future Perspectives

“…Mazumder et al.,146 Nicot et al,147 and Shen et al148 P c = P e (S e ) −1/ λ are the fitting factors, P e the entry pressure, J the shape factor and can be obtained by regressing the capillary pressure curves, S e the normalized water saturation, S w the water saturation, S wr is the residual water saturation, S gr is the residual gas saturation, p cmax the maximum capillary pressure, η the tortuosity parameter, λ the cleat size distribution index, ω the cleat geometry factor, and n wr the residual saturation fitting factor.…”