Development of silicon quantum dots based nano-fluid for enhanced oil recovery in tight Bakken cores

A novel silicon quantum dots (SiQDs) based nano-fluid was first developed for effectively recovering Bakken Oil. The Bakken Formation is one of the largest contiguous deposits of unconventional oil in the USA and Canada. However, the oil recovery rate is only 5% - 10% due to the existence of abundant tiny pores and ultra-low permeability. In this work, a novel nano-fluid was developed using ultra-small sized silicon quantum dots (SiQDs) coated with a zwitterionic surfactant. The nano-fluid exhibited good stability in synthetic high salinity brine containing divalent cations at high temperature and excellent capabilities in reducing interfacial tension and altering wettability, making it a good enhanced oil recovery (EOR) agent for tight Bakken Formation. Experimental results showed that the developed nano-fluid recovered 25.72 %OOIP (original oil-in-place) from Bakken core samples by spontaneous imbibition, which was 7.49 %OOIP higher than using surfactant alone. Similar results were obtained in the core flooding tests, where 41.98 %OOIP was finally recovered by the nanofluid, compared to 30.28% in surfactant case. Herein, the mechanisms of disjoining pressure and synergistic effects between surfactant and nanoparticles have also been put forward. In short, the developed quantum dots based nano-fluid has played an instructive and a reference role in the application of oil field and would be a potential oil displacing agent for EOR.