A multiple front propagation model for gas migration through clay

A model for the migration of gas through clay is described, in which gas pr opagates as a set of independent paths. The paths are constructed stochasti cally from sections of capillary-like tubes which inflate when the gas pres sure exceeds a threshold value. The paths partially deflate when they break through the clay, but their inflation is still sufficient to significantly increase the resultant slow flow of gas. The model also includes gas flows for path content and gas puss at breakthrough, and describes expelled wate r in a simple manner. (C) 1999 Elsevier Science B.V. All rights reserved.