Enhanced Oil Recovery in High-Temperature, High-Salinity Offshore Reservoirs: Performance Analysis of Di-Alkyl Sulfosuccinate and Carboxy-Betaine Surfactant Systems
摘要
Surfactant flooding in high-temperature, high-salinity offshore reservoirs requires formulations that remain chemically stable and capable of generating ultra-low interfacial tension at low concentration. Three surfactant blends were developed and evaluated under representative offshore conditions of 90 °C and 34 g/L salinity using sandstone cores matching target reservoir properties, with porosity ranging from 17 to 19% and permeability between 66 and 185 mD. Among the tested formulations, the di-alkyl sulfosuccinate–based surfactant (Comp-S) demonstrated the strongest overall performance. The experimental program included surface and interfacial tension measurements, contact angle analysis, static and dynamic adsorption quantified by high-performance liquid chromatography, and core flooding tests. Comp-S exhibited a critical micelle concentration of 0.025%, at which the interfacial tension decreased to 5 × 10−2 mN/m. Surface tension declined from 61 to 33 mN/m at 0.075%, after which further increases showed minimal change, indicating saturation of interfacial adsorption sites. Wettability alteration occurred rapidly, with the contact angle decreasing from 94° to 21° upon exposure and reaching complete spreading within 5–10 s. Static adsorption after five days was 4.0 mg/g, while dynamic adsorption under flow conditions was 3.5 mg/g. In core flooding experiments, a 0.3% Comp-S solution yielded an incremental oil recovery of 10.87% under standard injection, increasing to 12.84% with a 48-h soaking period. The combination of ultra-low interfacial tension, rapid wettability modification, and thermal stability at 90 °C demonstrates that Comp-S is a technically reliable and operationally efficient surfactant for offshore enhanced oil recovery under high-temperature, high-salinity conditions.