A stochastic trapping model for non-wetting phase ganglias in two phase flow through porous media

Residual trapping is one of the CO2 retention mechanism during CO2 storage in saline aquifers. In a region where the CO2 saturation falls below the residual saturation, isolated ganglias of CO2 are formed which can become immobile (trapped). In this paper, we propose a stochastic model for trapping and release of non-wetting phase ganglias. Opposed to traditional trapping models, which only take into account of the mean quantities, the proposed stochastic model contains additional statistical informations, e.g., correlation time. By selecting appropriate model parameters, both drainage and imbibition can be described without a priori knowledge of the displacement direction.