The applications of nanotechnology in oilfields have attracted the attention of researchers to nanofluid injection as a novel approach for enhanced oil recovery. To better understand the prevailing mechanisms in such new displacement scenarios, micromodel experiments provide powerful tools to visually observe the way that nanoparticles may mobilize the trapped oil. In this work, the effect of silicon oxide nanoparticles on the alteration of wettability of glass micromodels was investigated in both experimental and numerical simulation approaches. The displacement experiments were performed on the original water-wet and imposed oil-wet (after aging in stearic acid/n-heptane solution) glass micromodels. The results of injection of nanofluids into the oil-saturated micromodels were then compared with those of the water injection scenarios. The flooding scenarios in the micromodels were also simulated numerically with the computational fluid dynamics (CFD) method. A good agreement between the experimental and simulation results was observed. An increase of 9% and 13% in the oil recovery was obtained by nanofluid flooding in experimental tests and CFD calculations, respectively.

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. Graphical Abstract

Energy storage in carbonate and basalt reservoirs: Investigating secondary imbibition in H2 and CO2 systems