Application of surfactants in enhancing oil recovery from tight carbonates: Physicochemical properties and core flooding experiments

Surfactant formulations are optimized according to reservoir conditions to ensure their efficiency in enhanced oil recovery (EOR).This experimental study aimed to examine the EOR performance of a group of novel Alfoterra surfactants, which are based on alcohol propoxy sulfates.The performance of the Alfoterra surfactants (anionic) was compared to that of sodium dodecyl sulfate (SDS, anionic), dodecyltrimethylammonium bromide (DTAB, cationic), cetyltrimethylammonium bromide (CTAB, cationic) and t-octylphenoxypolyethoxyethanol (Triton X-100, nonionic).First, surfactant formulations were optimized based on their critical micelle concentration as well as their aqueous stability at 55 • C under different salinities.Next, the effects of the stable surfactant formulations on the interfacial tension (IFT) and rock wettability were examined.It was shown that the presence of the surfactants and the increase in salinity both caused a significant reduction in the oil-water IFT.Additionally, all surfactant formulations altered the wettability of carbonate rock from intermediate-to water-wet conditions.Next, tests of surfactant adsorption onto a carbonate-rock adsorbent were performed, showing that the anionic surfactants tend to adsorb more onto carbonates compared to other surfactants.Finally, core flooding tests involving medium-viscosity oil recovery from tight carbonate cores showed an EOR of 25.7-39.4% of originaloil-in-place above that achieved using regular waterflooding.