Polymers flooding

Chemical techniques change the physical properties of either the displacing fluid, or of the oil, and comprise of polymer flooding and surfactant flooding. 

Polymer flooding alms at reducing the amount of by-passed oil by increasing the viscosity of the displacing fluid, say water, and thereby improving the mobility ratio (M). 

Thermal Recovery Polymer Flooding Infill Wells... 

D. O. Shah and R. S. Schechter, eds.. Improved OilRecovery by Suf actant and Polymer Flooding, Academic Press, New York, 1977. 

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. 

Polymer Flooding. Even in the absence of fractures and thief 2ones, the volumetric sweep efficiency of injected fluids can be quite low. The poor volumetric sweep efficiency exhibited in waterfloods is related to the mobiUty ratio, Af, the mobiUty of the injected water in the highly flooded (low oil saturation) rock, divided by the mobiUty of the oil in oil-bearing portions of the reservoir, (72,73). The mobiUty ratio is related to the rock permeabihty to oil, and injected water, and to the viscosity of these fluids by the following equation ... 

Eig. 3. This polymer flooding method requites a preflush to condition the reservoir, the injection of a polymer solution for mobihty control to niinimi2e... 

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). 

A second field evaluation of the ASP process has been initiated in Wyoming. Additionally, an ASP field project has been designed for the Peoples Repubhc of China. The appHcability of the ASP process to a variety of reservoirs has yet to be fully determined. AppHcation of alkali and alkali polymer flooding has been limited to cmde oils having discernible acid numbers, wherein the alkali produced cmde oil soaps which in combination with alkali resulted in providing low interfacial tensions. The ASP process appears to be suitable for cmde oils with nil acid numbers (177), and hence should have broad apphcabdity. 

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. 

J. C. Mack and M. L. Duvall, "Performance and Economics of Minnelusa Polymer Floods," paper presented at the 1984 Mountain Regional Meeting of S ociety of Petroleum Engineers, Casper, Wyo., May 21—23,1984. 

Chemical EOR methods are based on the injection of chemicals to develop fluid or interfacial properties that favor oil production. The three most common of these methods are polymer flooding, alkaline flooding, and surfactant flooding. 

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]. 

The low-tension polymer flood technique consists of combining low levels of polymer-compatible surfactants and a polymer with a waterflood. This affects mobility control and reduces front-end and total costs. [929]. 

Alkali/polymer flooding Alkali/surfactant/polymer flooding Alkaline-assisted thermal oil recovery Alkaline steamflooding Polymer-assisted surfactant flooding Water-alternating gas technology... 

Second-order Godunov-type finite difference for 2-dimensional, 3-component incompressible polymer floods [845]... 

S. S. Ashrawi. Hot water, surfactant, and polymer flooding process for heavy oil. Patent US 5083612,1992. 

T. Austad, K. Veggeland, I. Fjelde, and K. Taugbol. Physicochemical principles of low tension polymer flood. In Proceedings Volume, volume 1, pages 208-219.7th Eapg Impr Oil Recovery Europe Symp (Moscow, Russia, 10/27-10/29), 1993. 

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

B. Kalpakci, T. G. Arf, D. M. Grist, S. B. Hyde, O. Vikane, and S. Es-pedal. A preliminary evaluation of an LTPF (low tension polymer flood) process for Stat ord Field, Norway. In Proceedings Volume,... 

I. Lakatos and S. J. Lakatosne. Dynamical characteristics of the polymer flooding Pt 2 (a polimeres elarasztas kinamikus jellemzoi 2. resz). Koolaj Foldgaz, 24(6) 170-178, June 1991. 

W. Littmann. Polymer flooding, volume 24 of Developments in Petroleum Science. Elsevier Science Publishing Co Inc, New York, 1988. 

G. Ma. Laboratory study on polymer flooding in oil reservoir with high salinity. Oil Gas Recovery Technol, 3(2) I,1, 33,1996. 

W. T. Osterloh and M. J. Jante, Jr. Surfactant-polymer flooding with anionic PO/EO surfactant microemulsions containing polyethylene glycol additives. In Proceedings Volume, volume 1, pages 485 94. 8th SPE/DOE Enhanced Oil Recovery Symp (Tulsa, OK, 4/22-4/24), 1992. 

K. Taugbol, H. H. Zhou, and T. Austad. Low tension polymer flood the influence of surfactant-polymer interaction. In Proceedings Volume, pages 281-294. Rec Adv Oilfield Chem, 5th Royal Soc Chem Int Symp (Ambleside, England, 4/13-4/15), 1994. 

Careful sizing of the treatment and choice of injection rates is required to prevent inadvertent overtreatment i.e., excessive treatment of oil-containing rock. The post-treatment fluid injection rate is usually significantly less than that prior to treatment. While successful applications of this technology in waterfloods and in surfactant polymer floods have been reported, temperature and pH stability limitations of the polymer and the crosslinking chemistry result in few if any applications in steam and CO2 injection wells. 

Surfactant and Polymer Flooding, Academic Press, New York, 1977. 

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