Sources and magnitudes of gas pressure gradients during dynamic unsaturated flow in porous media

Abstract:

Because the viscosities of gases are typically two or more orders of magnitude lower than the viscosities of liquids, spatial gas pressure gradients are often considered to be negligible in the study of dynamic unsaturated flow in porous media. However, a wide range of systems exist where gas pressure gradients are not only substantial, but for which they can create the appearance of unexpected, anomalous phenomena. This work used a combination of experimental measurements and simulations to study the effects of gas pressure gradients and pressure drops during liquid drainage in porous media. Results suggest that system permeabilities in the phase boundaries strongly influence trends in gas pressure gradients, causing subtle differences in boundary properties to produce seemingly very different flow behaviors for the same material in different experiments. Methods for predicting the impacts of gas pressure gradients in existing systems are discussed.