Interfacial tension between oil and

Fig. III-9. Representative plots of surface tension versus composition, (a) Isooctane-n-dodecane at 30°C 1 linear, 2 ideal, with a = 48.6. Isooctane-benzene at 30°C 3 ideal, with a = 35.4, 4 ideal-like with empirical a of 112, 5 unsymmetrical, with ai = 136 and U2 = 45. Isooctane-

Surfactants have been widely used to reduce the interfacial tension between oil and soil, thus enhancing the efficiency of rinsing oil from soil. Numerous environmentally safe and relatively inexpensive surfactants are commercially available. Table 18.6 lists some surfactants and their chemical properties.74 The data in Table 18.6 are based on laboratory experimentation therefore, before selection, further field testing on their performance is recommended. The Texas Research Institute75 demonstrated that a mixture of anionic and nonionic surfactants resulted in contaminant recovery of up to 40%. A laboratory study showed that crude oil recovery was increased from less than 1% to 86%, and PCB recovery was increased from less than 1% to 68% when soil columns were flushed with an aqueous surfactant solution.74-76... 

The use of surfactants to achieve low (<10 mN/m) interfacial tensions between oil and water as a means of enhancing recovery from partially depleted conventional reservoirs is well recognized I ll. In steam injection processes... 

The interfacial tension between oil and distilled water provides an indication of compounds in the oil that have an affinity for water. The measurement of... 

Figure 1.5. Influence of temperature on the interfacial tension between oil and water in the presence of a polyethoxylated surfactant.

The influence of the oil type and quality on oil absorption and residues absorbed by fried foods is widely documented (e.g., Blumenthal, 1991 Blumenthal and Stier, 1991 Krokida et al., 2000 Nonaka et al, 1977 Pokomy, 1980). No relationship has been found between oil type and oil absorption however, it has been shown that an increase in the initial interfacial tension between oil and restructured potato products decreases oil absorption (Pinthus and Saguy, 1994). Further, as mentioned earlier, oil degradation produces surfactants that act as wetting agents, which also increase the absorption (Blumenthal, 1991). 

Go and n being the interfacial tension between oil and water, and the surface pressure due to the adsorption of proteins and emulsifier, respectively. Combining equations 1-4, we obtain. 

Another way of looking at this mechanism is to consider the polarity difference between oil and aqueous phases in absence of surfactant. Generally, the more hydrophobic is one phase and the more hydrophilic the other phase, the more stable are the emulsions [110]. Thus, the greater the interfacial tension between oil and water phases, in absence of surfactant, the greater the stability of the HIPE. 

Fig. 16-24. Interfacial tension between oil and water. (Hocott, Trans., AIME 132, 184. Copyright 1939 SPE-AIME.)...

Most single-chain surfactants do not sufficiently lower the oil-water interfacial tension to form MEs, nor are they of the right molecular structure (i.e., HLB) to act as cosolvents. To overcome such a barrier, cosurfactant/cosolvent molecules are added to further lower the interfacial tension between oil and water, fluidize the hydrocarbon region of the interfacial film, and influence the curvature of the film. Typically small molecules (C3-C8) with a polar head (hydroxyl or amine) group that can diffuse between the bulk oil and water phase and the interfacial film are suitable candidates [11],... 

Enhanced oil recovery (EOR) is a collective term for various methods of increasing oil recoveries that have been developed since about 1970. Up until about 1980, the use of surfactants in EOR was more or less synonymous with "micellar/polymer" flooding, in which surfactants are used to decrease the interfacial tension between "oil" and "water" from 10 dyne/cm to < 0.01 dyne/cm. 

Phospholipids, monacyloglycerol, and diacylglycerol can reduce the interfacial tension between oil and air. This increases the amount of contact between the oil and oxygen in frying, promoting autoxidation... 

Crude oil becomes trapped in porous media as a result of capillary forces. The reduction of these forces is required for the recovery of residual oil, and this is the basis of enhanced oil recovery. In practice capillary forces are reduced primarily by lowering interfacial tension between oil and water phases, although increasing the viscosity of the water is also important. Lowering interfacial tension leads to the formation of emulsions and microemulsions, which are of great importance in enhanced oil recovery techniques. 

In processing petroleum emulsions, chemical treating compounds may be added to a crude-oil emulsion to produce desirable oil quality and remove water or inorganic solids. The most common types of treating compounds are referred to as emulsion breakers. Various mechanisms are postulated as to how emulsion breakers function, but it is clear that an emulsion breaker must reach the interface of an emulsified droplet and the surrounding liquid. At that point, an emulsion breaker disrupts the interfacial tensions between oil and water and allows the droplets to coalesce and settle by gravity. 

Certain compounds, because of their chemical structure, have a tendency to accumulate at the boundary between two phases. Such compounds are termed amphiphiles, surface-active agents, or surfactants. The adsorption at the various interfaces between solids, liquids and gases results in changes in the nature of the interface which are of considerable importance in pharmacy. For example, the lowering of the interfacial tension between oil and water phases facilitates emulsion formation the adsorption of surfactants on the insoluble particles enables these particles to be dispersed in the form of a suspension and the incorporation of insoluble compounds within micelles of the surfactant can lead to the production of clear solutions. 

The capillary pressures are determined by the hydrocarbon-water interfacial tension, y, and the diameters of the interconnected pore throats of the carrier rock. The interfacial tension between oil and water increases a little with depth it varies between 25 x 10 Nm and 35 x 10" Nm (Berg, 1975). The gas-water interfacial tension decreases with depth from 75 x 10 Nm" at ground surface conditions to 35 x lO Nm at depths of > 2 km (Berg, 1975). At depths of more than 2 km, the gas-water interfacial tension is similar to the oil-water interfacial tension (Berg, 1975 England et al., 1987). The size of the pore throats is determined by the physical properties of the carrier rock. 

The formation of a surfactant film around droplets facilitates the emulsification process and also tends to minimize the coalescence of droplets. Macroemulsion stability in terms of short and long range interactions has been discussed. For surfactant stabilized macroemulsions, the energy barrier obtained experimentally is very high, which prevents the occurrence of flocculation in primary minimum. Several mechanisms of microemulsion formation have been described. Based on thermodynamic approach to these systems, it has been shown that interfacial tension between oil and water of the order of 10- dynes/cm is needed for spontaneous formation of microemulsions. The distinction between the cosolubilized and microemulsion systems has been emphasized. 

Oil spreads horizontally over the water surface even in the complete absence of wind and water currents. This spreading is caused by the force of gravity and the interfacial tension between oil and water. The viscosity of the oil opposes these forces. As time passes, the effect of gravity on the oil diminishes, but the force of the interfacial tension continues to spread the oil. The transition between these forces takes place in the first few hours after the spill occurs. 

It is also seen that there are great differences between systems, both in the preexponential factor—which primarily affects the overall level of the nucleation rate—and in the exponential factor—which primarily determines the steepness of the curve with respect to temperature. The difference Teq — Thom roughly equals 40 K for ice, 28 K for sucrose, and 26 K for tristearate in paraffin oil. In natural fats, where triglycerides crystallize from a triglyceride oil, the temperature difference is only about 20 K, presumably because the interfacial tension between oil and crystal is far smaller (about 4 rather than lOmN-m-1). 

It is commonly known that the constituents of a micellar slug may interact in several ways with both the rock and the formation fluids when injected into a reservoir, and a considerable body of literature exists (1-8). In spite of this knowledge, however, it is not yet possible to design a micellar slug for tertiary oil recovery from basic principles because of the complexity of the phenomena and inadequate understanding of the processes involved. The primary objectives of this paper are to present the results of some experiments on the structure and mineralogy of selected rock and reservoir core samples, on the interactions within surfactant solutions and between surfactant solutions and rock, and to attempt to draw from these observations some conclusions as to the phenomena and mechanisms involved-especially surfactant loss processes-as these can affect the maintenance of low interfacial tension between oil and water. 

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. 

For our laboratory work with aqueous foams, oil was generally present at SQIV/. This value was chosen because it can be achieved in a reproducible manner. Oil saturation is largely unaffected by foam generation, because most foamers do not reduce the interfacial tension between oil and water, irreducible water, to capture any sensitivity to water (which, until now, has not been observed) as well as to maintain the porous medium in contact with its preferred wetting liquid. 

In most of the emulsions, surfactants alone are not able to sufficiently reduce the interfacial tension between oil and water. Cosurfactants further reduce the interfacial tension and increase the fluidity of the interfacial film. The use of cosurfactants imparts sufficient flexibility to the interfacial film to take up different curvatures, which may be required to form microemulsion over a wide range of proportions of the components. The main role of cosurfactant is to destroy liquid crystalline or gel structures that form in place of a microemulsion phase. Typically used cosurfactants are short chain alcohols (C3-C8), glycols such as propylene glycol, medium chain alcohols, amines, or acids. - Cosurfactants are mainly used in microemulsion formulation for the following reasons ... 

Microemulsions can be prepared by controlled addition of lower alkanols (butanol, pentanol, and hexanol) to milky emulsions to produce transparent solutions comprising dispersions of either water-in-oil (w/o) or oil-in-water (o/w) in nanometer or colloidal dispersions (-100 nm). The alkanols (called cosurfactants) lower the interfacial tension between oil and water sufficiently for almost spontaneous formation. The miscibility of oU, water, and amphiphile (surfactant plus cosurfactant) depends on the overall composition, which is systan specific. Phase inversion method is further divided into two types ... 

The formation of microcapsules is greatly affected by the surfactant, which influences not only the mean diameter but also the stability of the dispersion. The surfactants used in the system have two roles, the first one to reduce the interfacial tension between oil and aqueous phases allowing formation of smaller microcapsules and the other one to prevent coalescence by its adsorption on the oil-water interface and therefore by forming a layer around the oil droplets. The synthesis of a core/ shell particle or other possible morphologies is mainly governed by the kinetic factors and thermodynamic factors. 

The largest interfacial tension in the Winsor III systems (bicontinuous microemulsions in equilibrium with both excess oil and water) is also equal to the interfacial tension between oil and water in the presence of a saturated surfactant monolayer, i.e.. 

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