Three-phase foams

Three phase foam stability, as has been discussed by numerous authors is of great practical significanct (1-14). However, despite the recognized significance, the mechanisms by which oil affects foam stability are still under investigation. 

Our objective in this study is to elucidate the complex phenomena occurring during the process of three phase foam thinning, to identify the interaction mechanisms between the oil droplets, the thinning foam film and the Plateau-Gibbs borders and the role of surface and interfacial tension gradients in foam stability, and to examine the implications upon crude oil displacement by foam in pourous media. 

During the process of three phase foam thinning, three distinct films may occur foam films (water film between air bubbles), emulsion films (water between oil droplets) and pseudoemulsion films (water film between air and oil droplets) (Figure 1). To study the behavior of these films and particularly the oil droplet-droplet, oil droplet-air bubble and oil droplet-foam frame interactions it is necessary to utilize numerous microscopic techniques, including transmitted light, microinterferometric, differential interferometric and cinemicrographic microscopy. 

Macroscopic Observations of Three Phase Foam Structure. In Figures 2 and 3 are shown foam drainage results in the presence of Salem crude oil with the surfactants C. OS and C..AOS at 1 wt% NaCl. obtained from the transmitted light microscope. Surfactant chain length is clearly seen to be a significant factor (compare Figure 2 with Figure 3). 

Macroscopic three phase foam observations therefore reveal that C-. AOS produces a more stable foam in the presence of oil than C 2 AoS. 

Microscopic Observations of Three Phase Foam Structure. We will now discuss observations of the microscopic oil droplet-foam interactions, and observations regarding the attachment of oil droplets to the air-water surface. 

The study of the behavior of this pseudoemulsion film with curvature is essential for understanding the role of spreading phenomena in three phase foam stability. 

To establish a correlation between the interracial tension gradient measurements given above with three phase foam stability we used the qualitative Barch method for determining foam stability, due to the physicochemical difficulties in providing an accurate measure of three phase foam stability. 

In a 25 ml cylinder, 10 ml aqueous surfactant solution was preequilibrated with 2 ml oil phase for one week. Strong agitation produced a three phase foam, which was then observed from the moment of formation to collapse. 

These high stability foams correlate directly with the results based upon interfacial tension gradient measurements, confirming the significance of Marangoni phenomena (31) in three phase foam stability. 

Similar three phase foam stability tests have been performed for presence of Salem (light oil) and... 

Of course the Marangoni effect is not the only stabilizing factor in the three phase foam. Another critical factor is droplet size. Smaller droplet size is accomplished by lower interfacial tension, wherefore it is found that C AOS yields more stable foam... 

Figure 12. Three phase foam structure as a function of time.

There appear then three primary mechanisms for stabilizing (or destabilizing) a three phase foam. The first derives from the micelle structuring in the film and depends directly upon surfactant concentration and electrolyte concentration. The second is a surface tension gradient (Marangoni) mechanism which relates to the short range intermolecular interactions and the rate of surface expansion. And the third is an oil droplet size effect which depends upon the magnitude of the dynamic interfacial tension. 

The interactions between an oil phase and foam lamellae are extremely complex. Foam destabilization in the presence of oil may not be a simple matter of oil droplets spreading upon foam film surfaces but may often involve the migration of emulsified oil droplets from the foam film lamellae into the Plateau borders where critical factors, such as the magnitude of the Marangoni effect in the pseudoemulsion film, the pseudoemulsion film tension, the droplet size and number of droplets may all contribute to destabilizing or stabilizing the three phase foam structure. 

The stability of emulsion and foam films have also been found dependent upon the micellar microstructure within the film. Electrolyte concentration, and surfactant type and concentration have been shown to directly influence this microstructure stabilizing mechanism. The effect of oil solubilization has also been discussed. The preceding stabilizing/destabilizing mechanisms for three phase foam systems have been shown to predict the effectiveness of aqueous foam systems for displacing oil in enhanced oil recovery experiments in Berea Sandstone cores. 

Finally we should comment that it is necessary to employ in the calculation of the spreading coefficient (which is often used as a stability criterion) accurately measured values of the various tensions operative in the pseudoemulsion film to determine whether oil is spreading or nonspreading in the three phase foam structure. 

Schramm and Novosad (76), Manlowe and Radke (77), and Hanssen and Dalland (80) also concluded that the pseudoemulsion film stability is a controlling factor in the stability of three-phase foams within porous media. 

Influence of Unstable Pseudoemulsion Film Antifoaming and Defoaming Action. When the pseudoemulsion films are unstable in the three-phase foam, the oil generally destabilizes the foam. Destabilizing of foam has important applications as antifoaming or defoaming in several industrial processes (83, 84). Foam inhibitors are also used in the petroleum industry, such as in gas—oil separation, in natural gas processing, and in distillation processes (85). 

Influence of Emulsion Film Stability. The stability of the emulsion drops inside three-phase foam systems has an influence on the foam stability. When the oil drops collect (flocculate) in the Plateau borders, the drops are compressed and give rise to the formation of emulsion films (Figures 1 and 2). If the emulsion films are stable, drops do not coalesce, and the foam stability is not affected. However, if these emulsion films are unstable, the oil drops coalesce in the Plateau borders and then, on further foam drainage, the large drops relocate, under the action... 

Gel foam combines the advantages of gel and three-phase foam, and overcomes their shortcomings, its character mainly contains ... 

Xie Zhenhua, Li Xiaochao. Application of Three-phase Foam Technology for Spontaneous Combustion Prevention in Ixtngdong Coal Mine. Procedia Engineering, 2011, 26 63-69. 

Chen Zuzhang Zhao Qingming. Application of Three-phase Foam in Mine Fire Prevention[J], Coal Mine Modernization, 2010, 3 26-28. 

Lin Yihua. Application of Three-phase Foam Fire Extinguishing Technology in Dazhuang mine[J]. Zhongzhou... 

Fire prevention mechanism of three-phase foam... 

First point three-phase foam preparation... 

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