Comparison of bio- and synthetic surfactants for EOR

In this work, the performance of three natural surfactants (one produced by a bacteria and two of vegetal origin) in comparison to synthetics surfactants (cationic, anionic, non-ionic and zwitterionic) for its potential use in enhanced oil recovery EOR application was compared. The basis of comparison was basically the surfactant's solutions surface tension (ST) at room temperature, in the presence and absence of brine (salinity of about 4.7%). These measurements were developed to estimate if surfactants will resist reservoir conditions such as 75 °C and high salinities (up to 5%), conditions prevailing in the oil-field of Chicontepec, Veracruz (Mexico). Results of the work showed that biosurfactants could have potential for EOR process. The rhamnolipid produced by Pseudomonas and guar gum natural surfactants developed characteristics as good or even better than the synthetic surfactants normally employed in this process. The rhamnolipid produced by Pseudomonas seems to be a natural surfactant with extremely interesting characteristics. Rhamnolipid solutions yielded quite low ST at low concentrations (i.e. < 30 mN/m), even in the presence of brine for concentrations below 0.08%. Heat treatment applied to rhamnolipid solutions change very slightly the ST values when solutions contained no salts and about of 30% oil when brine was present. Rhamnolipid solutions did not show the higher foam capabilities, but represented half the capability of Polafix CAPB surfactant in producing foam. Neither guar nor locust bean gums showed important diminutions of ST at different concentrations in the solution. Nevertheless, for certain gum concentrations and in the presence of brine, guar gum had a very good performance (0.02%). Neither guar nor locust bean gums produced foam.

Research highlights
► The Pseudomonas rhamnolipid is a natural surfactant with extremely interesting characteristics.
► For certain concentrations in the presence of brine, guar gum had a very good performance.
► Neither guar nor locust bean gums produced foam.