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 <i>Candida bombicola</i> 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.