Study on the Adsorption Laws and Enhanced Oil Recovery of Nanofluid Prepared by Amphiphilic Nanosheets in the Low-Permeability Porous Media

The nanofluid prepared by spherical nanoparticles has a good enhanced oil recovery effect in low-permeability reservoirs. However, a huge adsorption loss has been produced in the process of oil displacement, reducing the oil recovery and increasing the production cost. In this paper, the static adsorption experiments under different influence factors, the dynamic desorption experiment on porous media, and the core flooding experiment are carried out with the nanofluids prepared by self-developed amphiphilic nanosheets (ODA-MoS2). Furthermore, the laws of adsorption kinetics and thermodynamics of the ODA-MoS2 nanofluid on the porous media surfaces are proposed, and the effect on improving oil recovery is clarified ulteriorly. The results show that the physical adsorption of the system on the surface of oil sand is caused by diffusion (concentration difference), electrostatic interaction, and hydrogen bonding. There is a monolayer adsorption existing on the porous media surface, which is consistent with Langmuir isothermal adsorption model. The salinity and temperature have an inhibitory effect on the adsorption of the ODA-MoS2 nanofluid; the adsorption capacity increases with the increase in concentration and reaches the equilibrium value of 1.68 mg/g at 75 mg/L. Moreover, the adsorption rate of the ODA-MoS2 nanofluid is the lowest, only 14.71% compared to that of SiO2, whereas the oil recovery increases by 18.59% compared to primary water flooding under the concentration of 75 mg/L. Therefore, the ODA-MoS2 nanofluid with a lower adsorption capacity is more effective in improving oil recovery in low-permeability reservoirs, and it is expected to be applied on a large scale for oil extraction in low-permeability reservoirs.