experimental investigation of silica nanoparticle size effect on oil recovery in carbonate reservoirs

Rock wettability is one of the main factors which plays a vital role in oil recovery. in this study, the effect of silica nanofluid concentration and nanoparticle size on the wettability of carbonate reservoir rocks was investigated. oil-aged thin sections were soaked in different nanofluid samples with different concentrations and nanoaparticle size at 80°c. the effect of nanofluid on wettability alteration was studied by measuring the contact angle. results showed that wettability altered from oil-wet to water-wet after adsorption of nanofluid on the rock surface. by reducing nanoparticle size from 154.9 nm to 2 nm, contact angle reduces about 37%. in addition, the presence of nacl plays a positive role until a specific concentration (20000 ppm). the optimum concentration obtained was 0.02 wt. % that changed contact angle from 140.2° to 35.86° at 20000 ppm nacl.