Geometric Considerations in Capillary Flow

FIGURE 6.8. In a foam system, differences in curvature along the hquid-gas interface due to distortion give rise to pressure differences and subsequent capillary flow. 

FIGURE 6.9. In the petroleum industry, crude oil is often recovered by the use of an aqueous plug in which a solution of surfactants, muds, polymers, and other compounds is forced into a reservoir to push the entrapped oil toward a central extraction well. If the proper solution balance and conditions of use are not employed, the crude oil may undergo surface yielding leading to the deposition of significant amounts of crude in the rock formation that cannot be recovered. 

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