A capillary network model for gas migration in low-permeability media

A two-dimensional capillary network model for gas migration through a water-saturated medium is presented. The model is an extension of previously developed capillary bundle models and provides a discrete alternative to classical continuum Darcy models. The need for such an alternative has become apparent from recent experimental results that suggest gas migrates through low-permeability water-saturated media via a small number of preferential pathways. The capillary network model directly simulates this mode of gas migration, including the dynamics of gas/water interface motion, and as a consequence exhibits time-dependent behavior, such as intermittency of output gas flux and hysteresis effects, that has been observed in experiments but are not reproduced in continuum Darcy models.