Perpustakaan Digital ITB

This study investigates the synergistic performance of alkaline–surfactant flooding by systematically evaluating how ion composition influences interfacial tension (IFT) reduction of Field T light crude oil using Sulfonated di-Alkyl Ester (SAE-2) surfactant. Chemical formulations combining different alkaline agents with controlled monovalent and divalent cation additions were assessed through aqueous stability testing, phase behavior characterization, and dynamic IFT measurements at 60 °C. Results demonstrate that the optimal formulation comprises synthetic reservoir brine with 1.5 %wt Na2CO3 and 100 ppm CaCl2, achieving a low IFT of 2.19 × 10?2 mN/m at 31,175 ppm total dissolved solids (TDS). This low IFT corresponds to Winsor Type III microemulsion formation, which maximizes thermodynamic stability for residual oil mobilization. Spontaneous imbibition testing on Berea Sandstone core plugs using this optimized formulation yielded a 57.6% increase in recovery factor compared to base brine, substantially exceeding conventional waterflooding performance and validating laboratory-scale observations at the core scale. Meticulous control of divalent cation concentrations within the optimum salinity window (29,000– 32,000 ppm TDS) maximizes synergistic interactions among in-situ generated soap, synthetic surfactant, and reservoir rock properties, thereby enhancing the system's ultimate hydrocarbon recovery capacity.