Polymer flooding polymers used

Zerpa, L.E., Queipoa, N.V., Pintosa, T.S., Salagerb, J.L., 2005. An optimization methodology of alkaUne-surfactant-polymer flooding processes using field scale numerical simulation and multiple surrogates. J. Pet. Sci. Eng. 47, 197-208. 

Water- and polymer flood predictions using the vertical well injectors are shown in Figure 6. The cumulative oil recovery of the polymer flood does not outperform the waterflood until the year 2020. However, the polymer flood produces approximately half the water compared to the waterflood. The main reason for the water and polymer injection rates to be abnormally high for this pattern is Aat the passive horizontal wellbore buried in the reservoir allows for the distribution of the injected water or polymer along its trajectory. 

When simulating the waterflood, the line drive configuration with vertical wells provided the quickest oil recovery and the best sweep efficiency, since the complete pattern was swept even at the edges. For a polymer flood, the use of three parallel, horizontal wells with a central injector provided the optimum configuration since the fastest oil recovery was achieved in comparison to the other configurations, as shown in Figure 11. By the year 2020, polymer flood with the horizontal well configuration recovered... 

Liu, S., Zhao, X., Dong, X., Miao, B., and Du, W. 2005. Treatment of Produced Water From Polymer Flooding Process Using a New Type of Air Sparged Hydrocyclone. Paper SPE 95343 presented at the SPE Asia Pacific Health, Safety and Environment Conference and Exhibition, Kuala Lumpur, 19-21 September. DPI 10.2118/95343-MS. 

Clemens, T., Abdev, J., and Thiele, M. 2010. Improved Polymer-Flood Management Using Streamlines Paper SPE 132774 presented at the SPE Annual Technical Conference and Exhibition, Florence, Italy, 19-22 September. DPI 10.2118/132774-MS. 

The focus of more recent work has been the use of relatively low concentrations of additives in other oil recovery processes. Of particular interest is the use of surfactants (qv) as CO2 (4) and steam mobiUty control agents (foam). Combinations of older EOR processes such as surfactant-enhanced alkaline flooding and alkaline—surfactant—polymer flooding show promise of improved cost effectiveness. 

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). 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

A clear solution of aluminum citrate neutralized to pH 7 is used for in situ gelling of polymers in polymer flooding and well stimulation in enhanced oil recovery techniques (128—132). The citrate chelate maintains aluminum ion solubiUty and controls the rate of release of the aluminum cross-linker. 

H. Dakhlia. A simulation study of polymer flooding and surfactant flooding using horizontal wells. PhD thesis, Texas Univ, Austin, 1995. 

Both nonionic and anionic surfactants have been evaluated in this application (488,489) including internal olefin sulfonates (487, 490), linear alkylxylene sulfonates (490), petroleum sulfonates (491), alcohol ethoxysulfates (487,489,492). Ethoxylated alcohols have been added to some anionic surfactant formulations to improve interfacial properties (486). The use of water thickening polymers, either xanthan or polyacrylamide to reduce injected fluid mobility mobility has been proposed for both alkaline flooding (493) and surfactant enhanced alkaline flooding (492). Crosslinked polymers have been used to increase volumetric sweep efficiency of surfactant - polymer - alkaline agent formulations (493). 

The usefulness of xanthan in polymer flooding for enhanced oil recovery is based on its ability to yield large increase in viscosity at low polymer concentrations under high-temperature and high salinity conditions. This important property of xanthan is determined both by its molecular weight and by the conformation adopted in solution (1). 

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. 

The use of chemicals to coax more oil out of the ground has been investigated for many years. Chemically enhanced methods are of three major types (1) polymer flooding (2) surfactant flooding and (3) alkaline flooding. 

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. 

---