Foam volume ratio surfactants

Surfactant Oil phase Foam volume after x minutes, x = 30 min Foam volume ratio oil/no oil... 

The value of the 1.0X 1.5X brine foam volume ratio at 75 C may be taken as a measure of the sensitivity of surfactant foaming properties to aqueous phase salinity. Values of this ratio determined at 75 C in the presence of decane are summarized below ... 

Surfactant 30 min Foam Volume (cc) Foam Volume Ratio 30 min l min. 

Cf, C y, and Cq are the concentrations of the substance in question (which may be a colligend or a surfactant) in the feed stream, bottoms stream, and foamate (collapsed foam) respectively. G, F, and Q are the volumetric flow rates of gas, feed, and foamate respectively, is the surface excess in equilibrium with C y. S is the surface-to-volume ratio for a bubble. For a spherical bubble, S = 6/d, where d is the bubble diameter. For variation in bubble sizes, d should be taken as YLnid fLnidj, where n is the number of bubbles with diameter dj in a representative region of foam. 

The area of colloids, surfactants, and fluid interfaces is large in scope. It encompasses all fluid-fluid and fluid-solid systems in which interfacial properties play a dominant role in determining the behavior of the overall system. Such systems are often characterized by large surface-to-volume ratios (e.g., thin films, sols, and foams) and by the formation of macroscopic assembhes of molecules (e.g., colloids, micelles, vesicles, and Langmuir-Blodgett films). The peculiar properties of the interfaces in such media give rise to these otherwise unlikely (and often inherently unstable) structures. 

It should be noted that the formula about the modulus of bulk elasticity of a foam refers to deformation at both compression and expansion. At large deformations, however, their effects differ significantly. When the foam is compressed the gas volume can be reduced so that to become comparable to the liquid volume. The expansion of a foam cannot be unlimited depending on its initial expansion ratio, the volume of the foam can increase only until the border pressure reaches a critical value (see Section 6.5.2). The latter is related to foam dispersity and surfactant adsorption, and decreases with the increase in surface area. 

A positive influence of the internal collapse (internal dephlegmation) on the accumulation ratio (i.e. its increase) was observed only in the cases where a very small cl.o value lies in the range cm < c 0 < cr (cr, corresponds to the saturated adsorption layer). The reason is that desorption from film surfaces during foam collapse increases surfactant concentration in the foam liquid phase, and, as a consequence, the degree of adsorption increases to values that ensure the formation of a small volume of a stable foam. Therefore, it becomes possible to separate the foam from the original solution with Rf>. ... 

A high pressure windowed test cell was charged with a 0.5% solution of surfactant in l.OX brine. The cell was heated to 75 C and pressurized with COj to a pressure of 2500 psig (1.7237 X 10 Pa). A 1 1 volume ratio of liquid and COj was used. The charged cell was then agitated until its contents became thoroughly mixed. As soon as the fluids became static (ca 1 min), the foam height was measured. A second measurement was made 30 minutes later. 

Increasing the aqueous phase salinity appeared to increase foam sensitivity to the presence of a hydrocarbon phase. This behavior may be due to increased surfactant partitioning into the oil phase. This can be quantified by determining the ratio of foam volume in the presence of decane to that in the absence of an added hydrocarbon (Table II. Figure 3). With few exceptions, this ratio decreased with increasing aqueous phase salinity. The values of this ratio for AEGS surfactants declined less with increasing aqueous phase salinity than for other surfactants. 

For most of the AES surfactants studied, the ratio of foam volume in the presence of added decane to that in its absence was relatively constant over the 0.5X-1.5X salinity range but decreased significantly when the solvent was 2.OX brine. 

Procedures of these 40 C (104 F) experiments are described in the Experimental Section. Tests were performed at a representative west Texas formation temperature using a typical west Texas stock tank oil and a synthetic brine having a composition typical of west Texas injection waters. Results are summarized in Table III. The ratio of foam volume after 30 minutes at 40 C to that after 1 minute was used as an indication of foam stability. The surfactants which produced the greatest initial (1.0 minute) foam volumes also exhibited the greatest foam stability over the thirty minute test period. Because test temperature and salinity were different than used in earlier experiments, results in the presence of west Texas stock tank oil cannot be compared to results described above. However, trends in foam stability were consistent with those described above. Average stability of the foams produced by the AEGS and AES surfactant classes was greater than that of the AE foams. 

Owing to the foam s large surface area over liquid volume ratio, the liquid that results upon collapse of the foam is manifold enriched in the ion compared to the initial solution. The ion extraction and separation largely depends on the selectivity of the charged surfactant interface for the ion in the presence of competing counterions. 

We may extend this argument to mixtures of antifoam dispersions. Here we suppose, for example, that two different antifoams are separately dispersed in the same surfactant solution and the resultant dispersions are mixed in known ratios. Again we assume that the antifoam effects are caused by single entities and that therefore the effects are not cooperative. The argument is illustrated in terms of the ratio F but could of course be equally well illustrated using the relevant foam volumes since... 

The effect of asphaltene and resin on the surface tension of solvents has also been described by Poindexter and coworkers [20]. Here crude oil was simulated by mixtures of toluene and mineral oil. Volume ratios of mineral oil to toluene were 50 50, 60 40, and 70 30. In all cases, 1-3 wt.% asphaltene decreased the surface tension of the solvent, but by no more than 2 mN m. The decrease was more pronounced on increasing the proportion of mineral oil from 50 to 60 vol.%. In the case of both these 50 and 60 vol.% mineral oil solvents, the addition of asphaltenes increased both foamability by sparging and foam stability. Increasing the asphaltene concentration in both of these cases also reduced the surface tension until it became constant at a supposed critical nanoaggregate concentration, which Mullins [21] argues is analogous to the CMC of ordinary surfactant solutions. However, further increasing the proportion of mineral oil to 70 vol.% precipitated the asphaltene out of solution so that only a modest reduction in surface tension was observed, consistent with the concomitant reduction in activity. Unfortunately, Poindexter and coworkers [20] did not indicate whether their surface tension measurements were equilibrium values. 

The edges of this dodecahedron sized a - 8.5 cm. When the volume of the rubber balloon at inflation became bigger than the volume of the sphere inscribed in the dodecahedron, the balloon was deformed by the dedecahedron faces and took a shape close to the respective shape of a bubble in a monodisperse dodecahedral foam with a definite expansion ratio. The expansion ratio of the foam was determined by the volume of liquid (surfactant solution or black ink in the presence of sodium dodecylsulphate) poured into the dodecahedron. An electric bulb fixed in the centre of the balloon was used to take pictures of the model of the foam cell obtained. The film shape and the projection of the borders and vertexes on the dodecahedron face are clearly seen in Fig. 1.10. 

Achievement of low mobility ratios at the fronts between displacing and displaced fluids is of even greater concern in enhanced oil recovery than in waterflooding owing to the high costs and/or low viscosities of the injected fluids. One response to this concern has been the continuing effort to develop a fundamental understanding of so-called foam flow, which employs aqueous solutions of properly chosen surfactants at relatively low capillary numbers to reduce the effective mobility of low viscosity fluids (see 5,6 and papers on foam flow in this volume). 

Transient Displacement. Experimental displacement results for the simultaneous injection of aqueous surfactant solution and nitrogen into a core initially saturated with a surfactant solution are shown in Figures 12 and 13. Darcy velocities relative to the exit pressure of 4.8 MPa are 0.43 m/day (1.4 ft/day) for gas and 0.046 m/day (0.15 ft/day) for liquid yielding a gas fractional flow or foam quality of 90%. Figure 12 provides the transient liquid saturation profiles. Experimental data points are connected by dashed lines. Time is expressed nondimensionally in pore volumes, PV, which is the ratio of total volumetric flow rate (at exit pressure) multiplied by elapsed time and divided by the void volume of the core. 

Typically, the oil phase contained 78% monomer/co-monomer, 8% divinyl benzene (cross-linking agent), and 14% non-ionic surfactant Span 80 (Sorbitan monooleate), while the aqueous phase contained 1% potassium persulfate as the initiator. In most cases studied here, monomer is styrene and when elasticity of the polymer is required, 2-ethylhexyl acrylate (2EHA) was used (styrene/2EHA ratio is 1 4). Whenever additives/fillers are placed in the aqueous phase their amounts are stated as weight percent while the phase volume of the aqueous phase remains constant. In some cases, the aqueous phase contains 0.5% hydroxyapatite and 15% phosphoric acid which is used to dissolve the hydroxyapatite, or alternatively, the aqueous phase may contain varying amounts of water-soluble polymer, such as polyethylene glycol or polyethylene oxide. If the styrene-based PHP is to be sulfonated to obtain ionic-hydrophilic foam, the pre-dispersion of sulfuric acid within the pores is useful, if not essential, and in that case, acids (typically 10%) can be used as the internal phaseP . ... 

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