Surfactant flooding micellar

The structure and thermodynamics of formation of mixed micelles is of great theoretical interest. Micelles are also present and often integrally involved in practical processes. For example, in a small pore volume surfactant flooding process (sometimes called micellar flooding), the solution injected into an oil field generally contains 5-12 weight X surfactant (i) and the surfactant is predominately in micellar form in the reservoir water. In detergency, solubilization can be... 

In water floods, and to prevent viscous fingering In surfactant, or micellar, floods. If one attempts to drive surfactant or banked oil with water, which is of lower viscosity than the driven banks, an unstable front develops, and eventually water breaks through prematurely to the production well. A path of low resistance to flow between injection and production wells is established, and much of the oil and expensive chemicals are thus not forced toward the production well. Raising viscosity of the drive water, and perhaps of the surfactant bank, by polymer addition tends to counteract this difficulty. 

Adsorption isotherms from surfactant solutions have been reported to often exhibit maximum and sometimes even minimum in the region around critical micelle concentration (1-4). The phenomenon of maximum and minimum is of such theoretical interest as well as practical importance in such areas as enhanced oil recovery using surfactant flooding. The presence of maximum has been attributed in the past to mechanisms involving micellar exclusion from interfacial region due to electrostatic repulsion or structural incompatibility, presence of impurities, surfactant composition, adsorbent morphology, etc. (1,2). None of these mechanisms is, however, fully substantiated to be considered as a confirmed mechanism for surfactant adsorption from concentrated solutions particularly due to serious possibilities for experimental arti-... 

Cmc values are important in virtually all of the petroleum industry surfactant applications. For example, a number of improved or enhanced oil recovery processes involve the use of surfactants including micellar, alkali/surfactant/polymer (A/S/P) and gas (hydrocarbon, N2, CO2 or steam) flooding. In these processes, surfactant must usually be present at a concentration higher than the cmc because the greatest effect of the surfactant, whether in interfacial tension lowering [30] or in promoting foam stability [3J], is achieved when a significant concentration of micelles is present. The cmc is also of interest because at concentrations... 

Fred Wassmuth graduated from the University of Calgary with a Ph.D. in physical chemistry in 1990. Fred s work on chemically improved oil recovery processes started in 1991 at the Petroleum Recovery Institute, now a legacy company of the Alberta Research Council. He has been involved with traditional chemical flooding methods such as polymer, alkah/surfactant/ polymer and micellar surfactant floods for recovering conventional oils. This research led to several field projects which demonstrated the commercial apphcation of polymer flooding to improve the recovery of heavy oils in Western Canada. 

An alternative to this process is low (<10 N/m (10 dynes /cm)) tension polymer flooding where lower concentrations of surfactant are used compared to micellar polymer flooding. Chemical adsorption is reduced compared to micellar polymer flooding. Increases in oil production compared to waterflooding have been observed in laboratory tests. The physical chemistry of this process has been reviewed (247). Among the surfactants used in this process are alcohol propoxyethoxy sulfonates, the stmcture of which can be adjusted to the salinity of the injection water (248). 

Micellar flooding is a promising tertiary oil-recovery method, perhaps the only method that has been shown to be successful in the field for depleted light oil reservoirs. As a tertiary recovery method, the micellar flooding process has desirable features of several chemical methods (e.g., miscible-type displacement) and is less susceptible to some of the drawbacks of chemical methods, such as adsorption. It has been shown that a suitable preflush can considerably curtail the surfactant loss to the rock matrix. In addition, the use of multiple micellar solutions, selected on the basis of phase behavior, can increase oil recovery with respect to the amount of surfactant, in comparison with a single solution. Laboratory tests showed that oil recovery-to-slug volume ratios as high as 15 can be achieved [439]. 

Recent research and field tests have focused on the use of relatively low concentrations or volumes of chemicals as additives to other oil recovery processes. Of particular interest is the use of surfactants as CO (184) and steam mobility control agents (foam). Also combinations of older EOR processes such as surfactant enhanced alkaline flooding and alkaline-surfactant-polymer flooding have been the subjects of recent interest. Older technologies polymer flooding (185,186) and micellar flooding (187-189) have been the subject of recent reviews. In 1988 84 commercial products polymers, surfactants, and other additives, were listed as being marketed by 19 companies for various enhanced oil recovery applications (190). 

A micellar flood was then started with the injection of the micellar slug, polymer buffer, and the drive water in succession, at a rate of 1.3 m/day. Two types of polymers - polyacrylamide polymer (Dow Pusher 700) and Xanthan Gum polymer (Kelzan XC) - were used as the polymer buffers. Sodium chloride brine (1%) was used as the drive water. Effluent was collected and analyzed for surfactant content using the IR and UV techniques. 

Ethylene Oxide Addition. Anionic and nonionic alkylaryl compounds containing amound of thylene oxide were used in this study. Addition of ethylene oxide groups is known to impart salt tolerance to the surfactant and therefore these compounds are of particular interest for micellar flooding purposes. 

In the water-flooding process, mixed emulsifiers are used. Soluble oils are used in various oil-well-treating processes, such as the treatment of water injection wells to improve water injectivity and to remove water blockage in producing wells. The same method is useful in different cleaning processes with oil wells. This is known to be effective since water-in-oil microemulsions are found in these mixtures, and with high viscosity. The micellar solution is composed essentially of hydrocarbon, aqueous phase, and surfactant sufficient to impart micellar solution characteristics to the emulsion. The hydrocarbon is crude oil or gasoline. Surfactants are alkyl aryl... 

Microemulsion, or micellar/emulsion, flooding an augmented waterflooding technique in which a surfactant system is injected in order to enhance oil displacement toward producing wells. 

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. 

Early researchers sought to choose appropriate surfactants for mobility control from the hundreds or thousands that might be used, but very little of the technology base that they needed had yet been created. Since then, work on micellar/polymer flooding has established several phase properties that must be met by almost any EOR surfactant, regardless of the application. This list of properties includes a Krafft temperature that is below the reservoir temperature, even if the connate brine contains a high concentration of divalent ions (i.e., hardness tolerance), and a lower consolute solution temperature (cloud point) that is above the reservoir temperature. 

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. 

Micellar-polymer flooding relies on the injection of a surfactant solution to lower interfacial tension to ultralow levels, on the order of 10 mN/m. The resulting increase in capillary number allows the recovery of residual oil from porous media. The term micellar is used because the concentrations of injected surfactant solutions are always above their critical micelle concentration. That is, they are always above the concentration at which micelles form. 

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