TiO₂ Nanoparticles in Low-Salinity Waterflooding: An Experimental Study on Wettability Alteration and Oil Recovery

Abstract

Low-salinity waterflooding combined with titanium dioxide (TiO₂) nanoparticles can improve microscopic oil displacement by modifying oil–brine and rock–fluid interactions. This study presents a preliminary experimental evaluation of TiO₂-assisted low-salinity waterflooding using Berea sandstone and crude oil from a mature oil field in Indonesia. Synthetic NaCl brines with salinities of 500–32,000 ppm were prepared, while TiO₂ concentrations of 100, 250, and 500 ppm were evaluated. Interfacial tension (IFT) was measured using a spinning-drop tensiometer, wettability was assessed through contact-angle measurements, and selected formulations were subsequently evaluated by coreflooding at 68°C. The measured IFT values ranged approximately from 1.4 to 7.5 mN/m, with 100 ppm TiO₂ producing the lowest IFT under most tested salinity conditions. Contact-angle measurements also shifted toward more water-wet conditions, with the largest decrease from approximately 29.5° to 14.5° after adding 100 ppm TiO₂. Coreflooding at 8,000 ppm brine showed that 100 ppm TiO₂ increased the recovery factor from 9.26% to 30.42% ROIP, corresponding to an incremental recovery of 21.16 percentage points. These preliminary results identify 100 ppm TiO₂ as the most favorable tested concentration. Nevertheless, the optimum formulation remains specific to the investigated rock–brine–oil system because nanoparticle stability, retention, and surface charge were not independently measured.