The role of surfactants in enhanced oil recovery

A number of reviews appeared on the use of surfactants and their mixtures, as well as surfactant-polymer mixtures in EOR during the sixties to eighties [219 -223]. Schramm published monographs on the use of emulsions [37] and foams [224] in oil recovery processes. In Russia, a small guidebook on agents used in the petroleum industry was issued 15 years ago [225]. All this facilitates the discussion of this problem in the present chapter where we make efforts to demonstrate the main results obtained earlier and to attract attention to new work. 

These experiments show that it is possible to achieve positive results using EOR after a thorough investigation of the nature of mineral rock constituents of the oil reservoir and the choice of the surfactant delivery method. The dynamic interfacial tension is crucial in EOR. Using a model acidic oil, alkali solutions and surfactants at an optimum ratio, ionised water and surfactant adsorb simultaneous onto the interface, resulting in low dynamic interfacial tension [229]. Combined adsorption of surfactant (alkyl propoxyethoxy sulphate) and polymer (xanthan) was studied in [230]. 

Positive results for high-temperature oil deposits are obtained when using a complex mixture consisting of surfactants, metal salts and carbamide. This composition was used in Noyabrsk field trials [232]. Water composition and injection rate also substantially influence the EOR efficiency [233]. At low flow rates, surfactant-containing connate water injected into the reservoir substantially enhances the oil recovery, while at high flow rates it has practically no effect on the efficiency. 

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