Mechanisms and effects of amphiphilic lamellar nanofluid for enhanced oil recovery in low permeability reservoirs

Amphiphilic nanosheets have attracted more attention for enhanced oil recovery (EOR) owing to their unique properties. Here, the amphiphilic molybdenum disulfide (MoS2) nanosheets (AP-MDN) were prepared by functionalizing octadecyl amine (ODA) molecules onto the molybdenum disulfide nanosheets (MDN) surfaces. The dynamic stability and interfacial tension (IFT) measurements of AP-MDN nanofluid were evaluated. Besides, the mechanisms and effects of AP-MDN nanofluid for EOR were also systematically investigated and studied. Experimental results indicate that the dynamic stability of AP-MDN nanofluid is improved when MDN is successfully functionalized with ODA molecules. The IFT is decreased to 10(-1) mN/m and micron-emulsions ranging from 1 mu m similar to 2 mu m can be formed. In addition, the contraction rate of oil film exposed in ultra-low concentration AP-MDN nanofluid (50 mg/L) experiences two stages: a steep stage (8.5817 x 10(-5) cm/s) and a gentle stage (0.6617 x 10(-5) cm/s) owing to the generation of structuring disjoining pressure. Comprehensive mechanisms of AP-MDN nanofluid for EOR are also proposed and revealed. Moreover, oil washing efficiency of AP-MDN nanofluid is as high as 95.7 % when the soaking time is 6 hrs and temperature is 75 degree celsius. Core flooding experimental results demonstrate that the increase in shut-down time and the injection mode of multiple rounds with small slugs can better promote the interaction between AP-MDN nanofluid and crude oil in porous media. The highest oil recovery contributed by AP-MDN nanofluid is 19.1 %. These results are expected to promise AP-MDN nanofluid as an effective candidate for EOR.