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 prev iously developed capillary bundle models and provides a discrete alter native to classical continuum Darcy models. The need for such an alter native has become apparent from recent experimental results that sugge st gas migrates through low-permeability water-saturated media via a s mall number of preferential pathways. The capillary network model dire ctly simulates this mode of gas migration, including the dynamics of g as/water interface motion, and as a consequence exhibits time-dependen t behavior, such as intermittency of output gas flux and hysteresis ef fects, that has been observed in experiments but are not reproduced in continuum Darcy models.