Surfactant mixing rules

Because the value of the parameter k in Eqs. (3.24) and (3.25) depends on the polar group, it has been found convenient to compare surfactants according to their characteristic 

When two ethoxylated non-ionic surfactants with same hydrophobic groups are mixed, the linear mixing rule on parameter [3 becomes a linear mixing rule on the degree of ethoxylation EON and may be written as 

---

Practical Surfactant Mixing Rules Based on the Attainment of Microemulsion-Oil-Water Three-Phase Behavior Systems... 

Micellar-polymer flooding and alkali-surfactant-polymer (ASP) flooding are discussed in terms of emulsion behavior and interfacial properties. Oil entrapment mechanisms are reviewed, followed by the role of capillary number in oil mobilization. Principles of micellar-polymer flooding such as phase behavior, solubilization parameter, salinity requirement diagrams, and process design are used to introduce the ASP process. The improvements in ""classicaV alkaline flooding that have resulted in the ASP process are discussed. The ASP process is then further examined by discussion of surfactant mixing rules, phase behavior, and dynamic interfacial tension. 

Surfactant Mixing Rules. The petroleum soaps produced in alkaline flooding have an extremely low optimal salinity. For instance, most acidic crude oils will have optimal phase behavior at a sodium hydroxide concentration of approximately 0.05 wt% in distilled water. At that concentration (about pH 12) essentially all of the acidic components in the oil have reacted, and type HI phase behavior occurs. An increase in sodium hydroxide concentration increases the ionic strength and is equivalent to an increase in salinity because more petroleum soap is not produced. As salinity increases, the petroleum soaps become much less soluble in the aqueous phase than in the oil phase, and a shift to over-optimum or type H(+) behavior occurs. The water in most oil reservoirs contains significant quantities of dissolved solids, resulting in increased IFT. Interfacial tension is also increased because high concentrations of alkali are required to counter the effect of losses due to alkali-rock interactions. 

The mixing of a synthetic surfactant and a petroleum soap can be explained in terms of surfactant mixing rules proposed by Wade et al. in 1977 (53). These rules are based on previous studies (54) of the equivalent alkane carbon number (EACN) concept, which show that hydrocarbon behavior toward surfactants is additive and weighted by mole fraction according to the formula ... 

Phase Behavior. The use of phase-behavior diagrams in surfactant-enhanced alkaline flooding is more complicated than in micellar-polymer flooding for several reasons. One reason is that phase behavior is very sensitive to the water-to-oil ratio employed. From surfactant mixing rules, varying the amount of oil present will vary the amount of petroleum soap... 

---