Synthesis of silica nanoparticles with different morphologies and their effects on enhanced oil recovery

Silica nanoparticles (NPs) have been synthesized by titration of potassium silicate with hydrochloric acid, characterized and the effects of process parameters on size and morphology have been investigated. The size of the NPs decreased with increasing temperature and potassium silicate concentration. Central composite design (CCD) was applied to systematically determine the most significant factors affecting the particle size and optimize the experimental conditions to achieve minimum particle size. The optimal experimental conditions were obtained at hydrochloric acid concentration of 0.6 M, potassium silicate concentration of 11.85 wt% and temperature of 63.3 degrees C. SEM images proved that the pH and temperature shifted the NPs to non-spherical morphologies. To identify the effect of NPs morphology on oil recovery, some micromodel tests were conducted using the synthesized NPs with different shapes (0.1 wt%). The results showed that spherical NPs with high uniformity were the most effective in interfacial tension (IFT) reduction (3.66 mN/m) and wettability alteration to more water wet state (47.1% reduction of contact angle) compared to other applied NPs, resulted in highest oil recovery (32%). This was attributed to more homogeneity and better dispersion of spherical NPs compared to others.