Sophorolipid-Based Biosurfactant Application for Carbonated Water Flooding: An Experimental Approach for Enhanced Oil Recovery.

Enhanced oil recovery (EOR) technologies are facing growing pressure to strike a balance between production efficiency and environmental sustainability. This study investigated sophorolipid (SL) biosurfactants produced by Candida bombicola as environmentally compatible alternatives to synthetic surfactants in carbonated water flooding applications. Comprehensive characterization using Fourier transform infrared (FTIR) and NMR spectroscopy confirmed a glycolipid structure with hydrophilic sophorose disaccharide heads and hydrophobic fatty acid tails. The biosurfactant demonstrated exceptional surface activity with a critical micelle concentration of 250 ppm, reducing the surface tension from 72 to 31 mN/m and achieving an ultralow interfacial tension of 2.2 mN/m, representing an 85% reduction from baseline conditions. The wettability modification experiments showed a systematic transition from oil-wet (106°) to water-wet (48°) conditions, facilitating enhanced oil mobilization. Synergistic effects were observed when 250 ppm of sophrolipid was combined with 1500 ppm of polyacrylamide (PAM), producing optimal shear-thinning rheology and a remarkable CO2 absorption capacity (2.82 mol/kg), 77% higher than that of water alone. High-pressure interfacial tension measurements confirmed the stability under CO2-enriched conditions (2.18 mN/m). These results establish SL-based biosurfactants as viable game changers for next-generation sustainable EOR operations, offering superior biodegradability, reduced toxicity, and the dual benefits of enhanced oil recovery with a CO2 sequestration potential.