PERFORMANCE EVALUATION OF MODIFIED RHAMNOLIPID SURFACTANT FOR ENHANCED OIL RECOVERY (EOR)

ABSTRACT Enhanced oil recovery (EOR) techniques extend the productive life of oil wells by overcoming the physical and chemical mechanisms that trap oil in reservoir rocks, thereby increasing the amount of recoverable oil. Conventional chemical EOR methods employ synthetic surfactants that, despite their effectiveness, raise environmental concerns due to their toxicity and poor biodegradability. This study evaluates the application of rhamnolipid biosurfactant produced by Pseudomonas putida, a less commonly used gram-negative bacterium isolated from soil, and its modification with low-salinity brine for enhanced oil recovery in sandstone reservoirs. The biosurfactant, a biodegradable surface-active compound, offers a sustainable alternative to conventional synthetic surfactants. The biosurfactant exhibited FTIR absorption bands corresponding to hydroxyl, ester, and glycosidic functional groups, consistent with the expected molecular structure of rhamnolipids. To evaluate its performance, core flooding experiments were performed on a sandstone core plug with a porosity of 20.8% at room temperature. Both unmodified and low-salinity brine-modified forms of rhamnolipid were tested. The modified rhamnolipid yielded incremental oil recoveries ranging from 21.90% to 30.00%, outperforming the unmodified biosurfactant, which achieved 18.33% to 27.27%. The highest total recovery factor observed was 87.50%, obtained using the low-salinity brine- modified rhamnolipid at full concentration. The improved oil recovery is attributed to reduced interfacial tension and enhanced rock-fluid interactions facilitated by the biosurfactant. These findings confirm the potential of rhamnolipid biosurfactants as environmentally friendly and effective agents for enhanced oil recovery.