A micromodel investigation on the flooding of glycolipid biosurfactants for enhanced oil recovery

Biosurfactants can enhance oil recovery by decreasing the interfacial tension between water and oil, and altering the rock's wettability. In this study, the effect of two low molecular-weight glycolipid biosurfactants (rhamnolipid and sophorolipid) on enhancing oil recovery was investigated. The biosurfactants were economically produced from waste sunflower oil. The qualitative oil dispersion experiments were used to evaluate the biosurfactants' ability to separate oil, Surface tension and interfacial tension tests were carried out at various salinity rates. The potential of rhamnolipid and sophorolipid solutions to alter carbonate rock from an oil-wet state to a water-wet state was studied using the wettability test by measuring the contact angle. Moreover, the effect of rhamnolipid and sophorolipid biosurfactants on breaking the emulsion and improving the sweeping efficiency in porous media was investigated and compared using the micromodel test. Then three distinct homogeneous, heterogeneous, and layered patterns were created and tested in order to completely investigate the difference in oil displacement mechanism in three micromodels, and the impacts of the biosurfactant injection zone's permeability on oil recovery to design injection well patterns. The test results showed that these two biosurfactants were effective at separating crude oil from water. It was further observed that the rhamnolipid solution at 1000 ppm concentration and 60,000 ppm salinity reduced the interfacial tension to 5.42 mN/m, and the sophorolipid solution at 5000 ppm concentration and 80,000 ppm salinity reduced it to 7.93 mN/m. The rhamnolipid solution increased the contact angle between the oil drop and the carbonate rock from 41.42 degrees to 109.26 degrees, and the sophorolipid solution increased it from 32.16 degrees to 104.12 degrees. Also, the micromodel flooding test confirmed that in the case of rhamnolipid solution at the optimal concentration and salinity, the amount of oil recovery was measured as 80, 70, and 74% in the homogeneous, heterogeneous, and layered micromodels, respectively, while for the sophorolipid solution at the optimal concentration and salinity, it was recorded as 71, 61, and 69%, respectively. The micromodel results did not prove the fingering phenomenon under injection of either rhamnolipid or sophorolipid. Furthermore, proper distribution and breaking of the emulsion into micron size were confirmed. Accordingly, one can conclude that both surfactants (rhamnolipid and sophorolipid) have the potential to be utilized in oil field operations.