Synthesis of amphiphilic silicon quantum dots and its application in high efficiency imbibition oil recovery in low permeability reservoirs

In this work, a novel three-step method was used to modify the surface of silicon quantum dots to synthesize amphiphilic silicon quantum dots (A-SiQDs) with higher interfacial activity. The particle size of A-SiQDs was only 3.5 nm. By adding a small amount of dodecyl dimethyl betaine (BS-12), the performance of A-SiQDs was further improved. Through particle size and zeta potential testing, it can be seen that the mixed system of ASiQDs and BS-12 had good temperature and salinity resistance, and can be stable at 120 degrees C and 50,000 mg/L NaCl. Meanwhile, the mixed system exhibited superior interfacial activity compared with individual A-SiQDs and BS-12. The mixed system can lower the interfacial tension from 32.15 mN/m to 1.82 mN/m and transform the rock surface from an oil-wet to a strong water-wet state. This ensured the excellent imbibition ability of the mixed system, which can increase the oil recovery to 35.7 %. Finally, from the perspective of force, the influence of nanofluids on oil stripping and migration was analyzed to reveal the imbibition mechanism. This paper proposes a facile three-step method for synthesizing A-SiQDs, and also provides a novel nanomaterial for high efficiency imbibition in low-permeability reservoirs.