In micellar flooding

Phase Behavior. Nelson and co-workers (23-25) and Healy et al. (26) have written extensively on phase behavior in micellar flooding. In Nelson s methodology, three different phase-behavior environments occur... 

Cation Exchange, Surfactant Precipitation, and Adsorption in Micellar Flooding... 

The large supply of tall oils and the well-known surface properties of many of the components have led to several suggestions to use them or their derivatives in micellar flooding (X58.5 9.). However, there are, so far as we know, no extensive laboratory investigations underway nor plans to test these possibilities in the field. In view of the contribution tall oils might make to enhanced recovery if they could be used, a survey of interfacial tension properties of aqueous/hydrocarbon systems, similar to those which have become common with the petroleum sulfonate and other surfactants under consideration for micellar floods, seemed worthwhile. 

Entrapment and mobilization mechanisms at low flow rates and low interfacial tension can also control the recovery obtained by tertiary methods. In micellar flooding, for example, high ratios of viscous to capillary forces arise at field flow rates when interfacial tensions are very low. Development of a continuous oil bank having significant mobility requires that discontinuous oil be mobilized to form a continuous bank which gathers more residual oil as it advances. Interfacial tensions may exist or develop between the micellar bank and the oil, or between the micellar fluid and the aqueous polymer bank used to push the micellar fluid. Entrapment of oil by the micellar bank, or of micellar fluid by the polymer bank would eventually cause the process to fail. 

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]. 

The state of the art in chemical oil recovery has been reviewed [1732]. More than two thirds of the original oil remains unrecovered in an oil reservoir after primary and secondary recovery methods have been exhausted. Many chemically based oil-recovery methods have been proposed and tested in the laboratory and field. Indeed, chemical oil-recovery methods offer a real challenge in view of their success in the laboratory and lack of success in the field. The problem lies in the inadequacy of laboratory experiments and the limited knowledge of reservoir characteristics. Field test performances of polymer, alkaline, and micellar flooding methods have been examined for nearly 50 field tests. The oil-recovery performance of micellar floods is the highest, followed by polymer floods. Alkaline floods have been largely unsuccessful. The reasons underlying success or failure are examined in the literature [1732]. 

R. Daharu, S. Thomas, and Ali. S. M. Farouq. Micellar flooding for tertiary recovery Recent advances and potential. In Proceedings Volume, pages 414-428. 10th SPE Trinidad Tobago Sect Tech Conf (Port of Spain, Trinidad, 6/26-6/28), 1991. 

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). 

The works of various investigators such as Gogarty and Tosch (1), Healy and Reed (2), and Davis and Jones (2), have shown that the micellar flooding process can be used effectively to mobilize residual oil in watered-out light oil reservoirs. Many field tests conducted in the U.S. have further proved its effectiveness. However, the economics of the process remain unattractive for implementing the process for tertiary oil recovery. 

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. 

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... 

The micelles present also help to solubilize the released oil droplets hence, this process is sometimes referred to as micellar flooding. The emulsions can be formulated to have moderately high viscosities that help to achieve a more uniform displacement front in the reservoir this uniform front gives improved sweep efficiency. Thus, a number of factors can be adjusted when using a microemulsion system for enhanced oil recovery. These are discussed in detail in Chapter 7. 

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... 

Camilleri, D., Fil, A., Pope, G.A., Rouse, B.A., Sepehrnoori, K., 1987. Improvements in physical-property models used in micellar/polymer flooding. SPERE (November), 433-440. 

Trushenski, S.P., 1977. Micellar flooding sulfonate-polymer interaction. In Shah, D.O., Schechter, R.S. (Eds.), Improved Oil Recovery by Surfactant and Polymer Flooding. Academic Press, pp. 555-575. 

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. 

Large quantities would be used in a micellar flood program. 

If appreciable precipitation occurs, however, it leads to erroneous adsorption data—as we have noted in several cases. The problem is obviously more serious with the higher equivalent weight surfactants (Eq. wt. > 400) and these are the surfactants of greatest interest for improved oil recovery by micellar flooding. 

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