Investigating the Synergistic/Antagonistic Effects of Mixing SiO2 Nanoparticles and Ionic Liquid, Nonionic Emulsifier, and Gemini Surfactants on the Main Mechanisms of Crude Oil Production

In this study, the synergistic/antagonistic effects between hydrophilic SiO2 nanoparticles, synthesized from rice husk ash, and various surfactant types including a cationic imidazolium-based ionic liquid ([C12mim]­[Cl]), a twin-branched tailed anionic gemini surfactant (AOT), and a nonionic emulsifier (Tween 80) on the reduction of interfacial tension (IFT), the change of wettability of dolomite rock (analyzed using energy-dispersive X-ray (EDX) and field-emission scanning electron microscopy (FESEM)), the formation of the microemulsion, spreading coefficient (S C), and capillary number during injection of mixing of SiO2 nanoparticles and surfactants in the fracture and nonfracture oil reservoirs were investigated. The results showed that the addition of 100 ppm of SiO2 nanoparticles to seawater changed the wettability of dolomite rock from the neutral state to strongly water-wet (contact angle was decreased from 89 to 20°), but it did not have much effect on the IFT value (IFT was changed from 8.7 to 7.8 mN/m). Even though the IFT values of surfactant solutions were almost unaffected by the addition of SiO2 nanoparticles, an antagonistic effect was observed for wettability; by adding AOT, [C12mim]­[Cl], and Tween 80 surfactants to the aqueous solution containing 100 ppm of SiO2 nanoparticles, the contact angle increased from 20 to 140, 140, and 127°, respectively. Furthermore, from comparison to the literature data, it is found that the best spreading coefficient and capillary number can be achieved for AOT and [C12mim]­[Cl] in the absence of SiO2, respectively. The AOT surfactant was proposed as an appropriate agent, especially in the fractured reservoir, due to its capability to reduce IFT and change the wettability of carbonate rock to the water-wet state (modifying the imbibition mechanism), thus resulting in a spreading coefficient of near zero value (S C = −0.04), and provide the most desirable microemulsion condition (formation of Type III microemulsion).