Enhanced oil recovery using silica nanoparticles in the presence of salts for wettability alteration

This study focuses on the performance of nanosilica particles in the injected brine with different salt concentrations. For investigating the effect of SiO2-water-salt nanofluid in improving oil recovery, a set of experiment was conducted in both static and dynamic conditions. Interfacial Tension (IFT) measurement, contact angle measurements on glass surfaces, adhesion tests on sandstone grains and micromodel flooding tests were conducted. IFT results showed that although presence of nanoparticles can decrease the interfacial tension between injected brine and oil, but this change is not significant. The effect of nanofluid and salt concentration on the surface/fluid interaction was investigated by contact angle tests and new adhesion tests using grains of rocks. Both tests confirm that presence of nanofluid and salt can shift the wettability of rock surfaces towards more water wet condition. A glass micromodel was constructed for conducting flooding test to compare the capability of the nanofluid solution with/without salt, for improving oil recovery in dynamic conditions. The obtained results of all experiments demonstrated that silica nanoparticles are able to improve the wettability of both glass and sandstone surfaces towards more water-wet conditions. Wettability alteration by electrical double layer (EDL) and multicomponent ion exchange (MIE) are the dominant mechanisms in glass and sandstone surfaces during LSW injection and disjoining pressure is the major mechanism during nanofluid flooding. The presence of salts in the nanolfuids also showed to have a pronounced positive effect on the level of wettability alteration due to more adsorption of nanoparticles on the rock surface. [GRAPHICS] .