Effect of TiO2 Nanoparticles on Contact Angle and Oil Recovery during Low Salinity Waterflooding in Berea Sandstone

Abstract

Low salinity waterflooding is been investigated as an enhanced oil recovery (EOR) method because changes in crude oil–brine–rock interactions may alter wettability and promote residual oil displacement. This study investigates the effect of titanium dioxide (TiO₂) nanoparticles dispersed in NaCl brines of varying salinity on the wettability and oil recovery performance of Berea sandstone. Contact angle measurements are conducted using an optical tensiometer, while coreflooding experiments are performed using Berea sandstone and crude oil from an Indonesian oil field. Contact angle tests evaluate NaCl brine salinities of 500, 1000, 2000, 4000, and 8,000 ppm, each without nanoparticles and with 100 ppm TiO₂. Coreflooding experiments compare the corresponding formulations at 500 and 8,000 ppm NaCl. The addition of TiO₂ consistently reduces the measured contact angle, indicating a shift toward more water wet conditions. At 8,000 ppm NaCl, the recovery factor increases from 9.26% without nanoparticles to 30.42% with 100 ppm TiO₂. At 500 ppm NaCl, the recovery factor increases from 18.33% to 26.07% following the addition of 100 ppm TiO₂. These results suggest that wettability alteration may contribute to improved oil displacement but does not fully explain the observed core-scale recovery response. The underlying low salinity mechanism is inferred from the experimental trends rather than directly demonstrated. Further investigation of nanoparticle transport, retention, and dispersion stability is needed to clarify the processes controlling recovery under the tested conditions.