Polymer/micellar flooding

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). 

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. 

The pilot area used for this test was relatively small, 0.71 acres. However, the test was a technical success, recovering 68% of the water-flood residual oil. The pilot began in 1982 and ended in November 1983. Since that time, Exxon has initiated two other micellar-polymer floods in the Loudon field, one a 40-acre pilot and the other an 80-acre pilot. 

Many of the basic concepts of micellar-polymer flooding apply to alkaline flooding. However, alkaline flooding is fundamentally different because a surfactant is created in the reservoir from the reaction of hydroxide with acidic components in crude oil. This reaction means that the amount of petroleum soap will vary locally as the water-to-oil ratio varies. The amount of petroleum soap has a large effect on phase behavior in crude-oil-alkali-surfactant systems. 

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... 

Micellar-polymer flooding and alkali-surfactant-polymer flooding both rely on the injection into a crude-oil reservoir of surfactants or surfactantforming materials. Emulsions may be injected into the reservoir, or they may be formed in the reservoir, but their properties will change as they travel through the reservoir to eventually flow from a producing well after weeks or months. 

Micellar-polymer flooding is a technically well-developed process. Phase compositional aspects of microemulsion design are relatively well understood, and several technically successful field trials have been carried out. Micellar-polymer floods can be designed and carried out with a good chance of success. However, the process is too expensive. This high cost is due primarily to the high concentrations of synthetic surfactants required. The problem is further compounded because these synthetic surfactants are made from petrochemicals, a fact that ties their price to the price of crude oil. 

Micellar/polymer flooding 4807 m (equivalent to 0.33 PV), 5% YPS-3A (local snrfactant) + 3% n-bntanol (cosolvent) + 0.4% K2CO3 that is followed... 

This subsection presents the alkaline preflush and micellar-polymer flooding in this pilot test. The economic data is also presented. 

Camilleri, D., 1983. Micellar/Polymer Flooding Experiments and Comparison with an Improved 1-D Simulator. M.S. thesis. University of Texas at Austin, May. 

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. 

Holm, L.W., Robertson, S.D., 1981. Improved micellar/polymer flooding with high-pH chemicals. JPT 33 (1), 161-172. 

Pope, G.A., Wang, B., Tsaur, K., 1979. A sensitivity study of micellar/polymer flooding. JPT (December), 357-368. 

Wang, D.-C., Yang, T.-R., Du, T.-R, Fang, B.-F., Yang, C.-Z., 1999a. Micellar/polymer flooding pilot test in the HI84 well pattern in the Laojunmiao field. Petroleum Exploration and Development 26 (1), 47-49. 

The enhanced oil recovery using solutions of surfactants or their mixtures has attained relatively little application. This is, first of all, due to the fact that surfactants adsorb from the solution on porous media of the reservoir, the specific surface of which may range from 150 to 3000 cmVcm, therefore, the use of emulsions, microemulsions and the so-called micellar-polymer flooding turned out to be more effective. In all of these processes, the flow... 

Several micellar-polymer flooding models as applied to the EOR are discussed in [237]. It is noted that the co-solvent ordinarily used in this process considerably influences not only the microemulsion stabilisation, but also the removal of impurities in the pores of the medium. The idea of using an alkali in micellar-polymer flooding is discussed in [238] in detail. The alkali effect on the main oil components was studied aromatic hydrocarbons, saturated and unsaturated compounds, light and heavy resin compounds and asphaltenes. It is demonstrated that at pH 12 surfactants formed from resins allow to achieve an interfacial tension value close to zero. For asphaltenes, such results are achieved at pH 14. In the system alkali solution (concentration between 1300 to 9000 ppm)/crude oil at 1 1 volume ratio a zone of spontaneous emulsification appears, which is only possible at ultra-low interfacial tensions. 

Work by Holm (14, 15) has established the benefit of using alkaline chemicals as a preflush agent for micellar/polymer floods. A field trial of this process using an orthosilicate preflush has been carried out at Gary Energy s Bell Creek Field... 

Thomas, S. and Farouq Ali, S.M., Micellar-polymer flooding status and recent advances. J. Can. Petrol. TechnoL, 31, 53-60, 1992. 

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