Verification of Roof snap off as a foam-generation mechanism in porous media at steady state

An extensive microvisual analysis is reported of the hydrodynamics of simultaneous gas and water flow through homogeneous etched silicon micromodels. The object of this work is to prove, or to disprove, the relevance of Roof snap off during steady-state gas and water flow in homogeneous porous media. Significant evidence is found that repeated snap off of gas bubbles at pore throats is relevant to steady-state flow through porous media. Importantly, snap off is shown to be the dominant mechanism for generation of a discontinuous gas phase within this porous medium. Experiments are conducted under steady flow conditions in a relatively dry porous medium at significant capillary pressure. Smoothly constricted pores that exhibit small pore throat to pore body aspect ratios are found to be excellent sites for snap off even for low initial wetting liquid contents.