Combined Effects of Nanofluid and Surfactant on Enhanced Oil Recovery: An Experimental Study

The synergistic effects of nanofluid-surfactant hybrid systems on enhanced oil recovery (EOR) were systematically investigated by using modified MoS₂-NSs and SiO₂-NPs. Traditional surfactants face limitations such as poor stability and high adsorption loss, while nanomaterials offer complementary advantages in interfacial activity and thermal resilience. In this study, KH-560-modified SiO₂-NPs and ODA-functionalized MoS₂-NSs were synthesized and combined with an SDS surfactant. Stability, wettability alteration, interfacial tension (IFT), and imbibition performance were evaluated under varying temperatures and salinity conditions. Results demonstrated that surfactant addition significantly enhanced colloidal stability and reduced IFT by forming dense interfacial layers via coadsorption. MoS₂-NSs exhibited superior wettability modification and thermal stability in medium-salinity conditions (>3000 mg·L^-1 cations), achieving a 5.3% higher oil recovery compared to SiO₂-NPs. Both nanomaterials achieved >15% incremental oil recovery in high-permeability cores (>1 mD), but their efficiency declined in ultralow-permeability cores (<1 mD) due to pore-throat accessibility constraints. The hybrid systems enhanced structural disjoining pressure and imbibition efficiency, particularly at elevated temperatures. These findings highlight the potential of surfactant-nanomaterial synergy for EOR in moderate-to-high permeability reservoirs while underscoring the need for nanoparticle size optimization in low-permeability formations.