Interfacial tension behavior

The dynamic interfacial tension behavior of reacting acidic oil-alkaline solutions has been studied for both an artificially acidified synthetic oil and a real crude oil at various concentrations [131,132] with either a drop volume tensiometer or a spinning drop tensiometer. 

S. D. Ball, V. Homof, and G. H. Neale. Transient interfacial tension behavior between acidic oils and alkaline solutions. Chem Eng Com-mun, 147 145-156, May 1996. 

The interfacial tension behavior between a crude oil (as opposed to pure hydrocarbon) and an aqueous surfactant phase as a function of temperature has not been extensively studied. Burkowsky and Marx T181 observed interfacial tension minima at temperatures between 50 and 80°C for crude oils with some surfactant formulations, whereas interfacial tensions for other formulations were not affected by temperature changes. Handy et al. [191 observed little or no temperature dependence (25-180°C) for interfacial tensions between California crude and aqueous petroleum sulfonate surfactants at various NaCI concentrations. In contrast, for a pure hydrocarbon or mineral oil and the same surfactant systems, an abrupt decrease in interfacial tension was observed at temperatures in excess of 120°C 1 20]. Non ionic surfactants showed sharp minima of interfacial tension for crude... 

Isaacs and Smolek [211 observed that low tensions obtained for an Athabasca bitumen/brine-suIfonate surfactant system were likely associated with the formation of a surfactant-rich film lying between the oil and water, which can be hindered by an increase in temperature. Babu et al. [221 obtained little effect of temperature on interfacial tensions however, values of about 0.02 mN/m were obtained for a light crude (39°API), and were about an order of magnitude lower than those observed for a heavy crude (14°API) with the same aqueous surfactant formulations. For pure hydrocarbon phases and ambient conditions, it is well established that the interfacial tension behavior is dependent on the oleic phase [15.231 In general, interfacial tension values of crude oiI-containing systems are considerably higher than the equivalent values observed with pure hydrocarbons. 

Effect of Temperature. In the absence of surfactant, interfacial tensions of the Athabasca 1 211. Karamay 1 51, and other heavy oils 1 321 show little or no dependence on temperature. For surfactant-containing systems, Figure 6 shows an example of the effect of temperature (50-200°C) on interfacial tensions for the Athabasca, Clearwater and Peace River bitumens in Sun Tech IV solutions containing 0 and 10 g/L NaCI. The interfacial tension behavior for the three bitumens was very similar. At a given temperature, the presence of brine caused a reduction in interfacial tension by one to two orders of magnitude. The tensions were seen to increase substantially with temperature. For the case of no added NaCI, the values approached those observed T211 in the absence of surfactant. 

For results where comparisons could be made, the interfacial tension behavior was practically independent of the type of heavy oil used. Interfacial tensions strongly depended on the surfactant type, temperature, and NaCI and CaCI2 concentrations. Changes in the structure of the amphiphile at the oil/water interface is affected by these variables and accounted for some of the experimental observations. 

ARNEODO ET AL. Interfacial Tension Behavior of Citrus Oils... 

Figure 5. Microemulsion phase and interfacial tension behavior in a salinity scan.

IFT against that reference surfactant. The EACN thus allows predictions to be made about the interfacial tension behavior of a crude oil in the presence of surfactant. See references 8 and 9. 

Sharma, M.M., Jang, L.K., Yen, T.R, 1989. Transient interfacial tension behavior of crude-oil/ caustic interfaces. SPERE (May), 228-236. 

Clearly, this particular selection of surfactants divides, in their interfacial tension behavior against crude oils, along the lines which were predicted by considering their alkane preferences. This provides support for the idea that estimation of alkane preference by consideration of hydrophobic/interfering group balance (16) can be used as a screening test for deciding whether a surfactant has potential for use in oil recovery. Obviously, the evidence is still limited. In particular, the surfactants compared in the present study have very similar structures and we cannot be... 

Interfacial Tension Behavior. Reduction in the residual oil saturation over and above that obtained by steam injection is desirable and, in many heavy oil reservoirs, essential to ensure efficient foam formation during application of steam-foam processes (13). The extent of heavy oil desaturation is, however, dependent on the reduction in interfacial tension between oil and water. Thus, foam-forming surfactants can improve their own cause by reducing interfacial tensions at steam temperature. 

M Bourrel, C Koukounis, RS Schechter, WH Wade. Phase and interfacial tension behavior of nonionic surfactants. J Dispers SciTechnol 1 13—35, 1980. 

MM Sharma, LK Jang, TF Yen. Transient interfacial tension behavior of crude-oU/caustic interfaces. SPE Reservoir Eng (May) 228, 1989. 

In conjunction with the above studies of the time-dependent interfacial tension behavior and the coalescence properties of water-in-Leduc crude oil emulsions, the electrokinetic behavior of oil droplets in aqueous media (reverse emulsion) was also studied in the presence of Duomeen C and Aerosol OT. It was hoped that this will provide additional information on the adsorption of material at the oil/water interface. 

In general, their work indicates that the surfactant partition coefficient between the oil phase and the excess brine phase is unity at the optimal parameter value. Their work indicates that there is a strong similarity between the interfacial tension behavior of low concentration systems and those of high concentration systems. Bansal and Shah (104) also showed that the salt tolerance of surfactant systems can be extended to rather high salt concentrations by mixing ethoxylated sulfonates with the usual petroleum sulfonate materials. An optimal salinity as high as 32% sodium chloride was observed in one of the mixed systems which was also characterized by very low oil-water interfacial tensions. 

The adsorption from microemulsion of two petroleum sulfonates, PDM-334 and TRS 10-410, on Berea sand/montmorillonite clay adsorbents has been studied to determine 1) the effect of microemulsion composition, specifically its relative oil and brine content, on sulfonate adsorption 2) the effect of adsorption on the microemulsion composition and interfacial tension behavior. Whereas the degree of sulfonate adsorption can be determined by conventional methods (e.g. UV spectroscopy), one must utilize a microemulsion property which is a sensitive function of the relative oil and brine content of the microemulsion in order to determine the adsorption-induced changes in the microemulsion composition. This can be accomplished by the use of the microemulsion specific refraction. 

Table 2 also shows that the specific refraction of each microemulsion increases as a consequence of adsorption. This result indicates that all post-adsorption microemulsions have higher oil to brine ratios than the corresponding pre-adsorption microemulsions. The effect of these compositional changes is reflected in the interfacial tension behavior of the microemulsions (Figure 3). The microemulsion-oil and microemulsion-brine interfacial tensions both before and after adsorption exhibit the familiar correlation with r (8) however, all values are decreased and all values are increased as a consequence of adsorption. The minimum in the controlling interfacial tension (yc)xnin also increased from 0.0070 dyne/cm to 0.0077 dyne/cm. It is interesting to note that the values for the n-butanol microemulsion both before and after adsorption lie considerably above the y curves. The microemulsion at r = 0.288 cm /g was not part of the adsorption... 

Equivalent Alkane Carbon Number. (EACN) Each surfactant, or surfactant mixture, in a reference series will produce a minimum inter-facial tension (IFT) when measured against a different n-alkane. For any crude oil or oil component, a minimum IFT will be observed against one of the reference surfactants. The EACN for the crude oil refers to the n-alkane that would yield minimum IFT against that reference surfactant. The EACN thus allows predictions to be made about the interfacial tension behavior of a crude oil in the presence of surfactant. See references [JJ, 12]... 

An important point here is that according to the theory of critical phenomena, the critical exponents take universal values essentially independent of the microscopic details of the system. The natural question then is whether the exponents characterizing the curve, the radiation scattering intensity, the correlation length, and the interfacial tension behavior in polymer-polymer-solvent systems are the same as for ternary mixtures of small molecules. It is also essential to study how the critical amplitudes depend on the molecular weight of chains. 

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