Effect of Capillary Pressure on Wetting Film Imbibition Ahead of Main Liquid-Gas Displacement Front in Porous Media

The effect of capillary pressure on wetting film imbibition along the edges of pores in porous media is investigated experimentally. It is found that the capillary pressure at the main liquid-gas front (the main displacement front) plays a major role, among other factors, in determining the imbibition rate of a wetting liquid along pore edges. The measured velocities of the wetting film in a two-dimensional consolidated glass bead model and the imbibed volumes of the wetting liquid into the mode ahead of the main front are found to be proportional to 1/P1/2C and 1/P5/2C, respectively, where PC is the capillary pressure at the main liquid-gas front. The effect of capillary pressure on wetting film imbibition along the edges of pores is also illustrated by the experiments in a periodically constricted capillary where different film imbibition rates were obtained when the main liquid-gas meniscus is kept at a throat and a pore. Both theoretical analysis and experimental results show that the length of the wetting film ahead of the main meniscus increases greatly as the injection rate is decreased.