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.

Automated summary

In this study, an active sulfonated silicon quantum dots (S-SiQDs) nanofluid was prepared using a facile hydrothermal synthesis method and sulfonated modification. The active S-SiQDs nanofluid demonstrated better interfacial tension reduction, wettability alteration, and oil detachment compared to single surfactants and single S-SiQDs. It significantly improved the imbibition recovery of low permeability reservoirs to 29.9%. The active S-SiQDs nanofluid possesses ultrasmall size, excellent temperature and salinity resistance, and high interfacial activity.