Mechanism of active silica nanofluids based on interface-regulated effect during spontaneous imbibition

The ultra-low permeability reservoir is regarded as an important energy source for oil and gas resource development and is attracting more and more attention.In this work,the active silica nanofuids were prepared by modifed active silica nanoparticles and surfactant BSSB-12.The dispersion stability tests showed that the hydraulic radius of nanofuids was 58.59 nm and the zeta potential was−48.39 mV.The active nanofuids can simultaneously regulate liquid-liquid interface and solid-liquid interface.The nanofuids can reduce the oil/water interfacial tension(IFT)from 23.5 to 6.7 mN/m,and the oil/water/solid contact angle was altered from 42°to 145°.The spontaneous imbibition tests showed that the oil recovery of 0.1 wt%active nanofuids was 20.5%and 8.5%higher than that of 3 wt%NaCl solution and 0.1 wt%BSSB-12 solution.Finally,the efects of nanofuids on dynamic contact angle,dynamic interfacial tension and moduli were studied from the adsorption behavior of nanofuids at solid-liquid and liquid-liquid interface.The oil detaching and transporting are completed by synergistic efect of wettability alteration and interfacial tension reduction.The fndings of this study can help in better understanding of active nanofuids for EOR in ultra-low permeability reservoirs.