Novel silicon quantum dots for efficient imbibition oil recovery in low permeability reservoirs

In this work, the active sulfonated silicon quantum dots (S-SiQDs) nanofluid composed of S-SiQDs nanoparticles and bitetradecyl sulfobetaine (BS) was prepared to enhance oil recovery of low permeability reservoir by spontaneous imbibition. Firstly, a facile hydrothermal synthesis method was proposed to fabricate silicon quantum dots (SiQDs), followed by sulfonated modification of SiQDs to obtain S-SiQDs. The average particle size of S-SiQDs was 5.4 nm and it can remain stable at 120 degrees C and 5 wt% NaCl for 7 days. In addition, the active SSiQDs nanofluid had better abilities in interfacial tension reduction, wettability alteration, and oil detachment than single surfactants and single S-SiQDs due to the synergistic effect. Compared with single S-SiQDs (12.8 %) and BS surfactant (17.5 %), the active S-SiQDs nanofluid can significantly improve the imbibition recovery to 29.9 %. Finally, the spontaneous imbibition mechanism of this active S-SiQDs nanofluid was proposed through nuclear magnetic resonance and theoretical analysis. This work develops an active S-SiQDs nanofluid with ultrasmall size, excellent temperature and salinity resistance, and high interfacial activity, which can efficiently improve oil recovery of low permeability reservoirs.