This paper examines the factors which influence the permeability of coals with particular reference to coal stresses and mechanical properties including cleat spacing, Young's Modulus, Poisson's ratio and the effects of shrinkage caused by the loss of gas and water. This paper updates the work of the author in published in1983 (SPE 12514). The approach presented is mathematically based with reference to field examples and laboratory work. These include measurements of stress and permeability. The application of the work is in establishing how the permeability of a coal seam will vary during production.

The prime contribution is a theoretically sound, experimentally based, unified approach to determine the effective stress path and hence gain an indication of permeability changes through production.

Keywords:
initial stress, permeability, spe 135814, variation, stress measurement, stress change, fluid pressure, coal seam, flow in porous media, fluid dynamics
Subjects:
Reservoir Characterization, Reservoir Fluid Dynamics, Flow in porous media
Copyright 2010, Society of Petroleum Engineers
You can access this article if you purchase or spend a download.