The film drainage, equilibria, and rupture characteristics

Abstract

Film/Foam stability is a key factor in the behavior of foam enhanced processes for the recovery of residual oil. In order to establish techniques for characterizing film stability, a thin film drainage experiment has been conducted to study film stability under controlled capillary pressure conditions. A computer operated microsyringe was used to control the drainage rate of the films and thus to change the film thickness. The corresponding film thickness and thickness profiles were calculated from the light intensities using the light interference method. The present study includes the characterization of film drainage behavior at surfactant concentrations above, near, and below the critical micelle concentration (CMC), and at three different solution ages for surfactant solutions containing sodium dodecyl sulfate. The effect of salt content and oleic contaminants were also studied. At concentrations below the CMC, film suction tests at controlled capillary pressure exhibited non-deterministic values of film rupture lifetimes. Such behavior suggests rupture by nucleation mechanisms of post-drainage stationary films. At concentrations near or above the CMC, slow suction experiments were used to investigate the nature of disjoining pressure isotherms and discontinuous film drainage behavior. The critical disjoining pressure(s) for film structure transitions and ultimate film rupture were determined. Modifications on light interference method were done to include the effects of distributed light wavelength and reflected background light to reflect actual experimental conditions. A correction coefficient should also be included in the calculation of film thickness to account for the reflected background light. Traditional DLVO theory was also modified. The modified DLVO theory and the simplified DLVO theory provide a better description in disjoining pressure isotherms when inequality effect takes place on ion concentrations. An experimental setup to observe the foam flow behavior in porous media was also built. This setup allowed the measurements of in-situ and effluent foam textures. Spatial gas and liquid phase saturation, pressure gradients, and capillary pressure distribution along the porous media were also measured. The deterministic factors of foam flow in porous media were therefore identified. Further study on the in-situ foam texture allows the characterization of foam texture on foam stability.