Published online by Cambridge University Press: 22 May 2007
This paper presents some simple analytical and numerical models which describe the dynamics of gas flowing from a multilayered low-permeability porous rock into a fracture. The models account for the vertical flow between relatively high- and low-permeability layers. The motion of gas in a permeable rock is governed by a nonlinear diffusion equation for the gas pressure. We analyse the gas flow described by this equation in both bounded and unbounded domains. In both cases simple scalings laws are developed to determine the fluxes and the dimensions of the regions within the rock which may be depleted over a given time scale. These are compared with the results of a full numerical model.