Investigation of silica nanoparticles grafted with sulphonated polymer for enhanced oil recovery at high temperature and high salt

Nano-fluids' application for enhanced oil recovery (EOR) has attracted noticeable attention and formed a new research area in recent years. Currently, the greatest challenge in this area is to formulate stable nano-fluids for oil reservoirs with high temperatures and salinity. To overcome the limitations of its application in high-temperature drilling, polymer-coated nanoparticles (SiO2-PAMPS NPs) were prepared via solution polymerization of 2-acrylamide-2-methyl-1-propane sulphonic acid (AMPS) from the surface of aminopropyl-functionalized silica nanoparticles. The SiO2-PAMPS NPs were characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and dynamic light scattering (DLS). The results indicated that the AMPS was successfully grafted onto the surface of silica nanoparticles, and the average diameter of SiO2-PAMPS NPs was about 16 nm. The nano-fluids showed noticeable stability in American Petroleum Institute (API) brine (2 wt.% CaCl2 and 8 wt.% NaCl) at 90 degrees C beyond 46 days. When amphipathic nanoparticles were introduced to brine at 90 degrees C, the potential of the nano-fluids in recovering oil was evaluated by investigating the interfacial tension with kerosene oil and the oil contact angle in the nano-fluids. The contact angle of the glass sheet surface before treatment was about 144 degrees, while after SiO2-PAMPS NPs treatment for 72 h, it became about 92 degrees. Meanwhile, the nano-fluids showed an excellent enhancing emulsibility property, which plays a vital role in promoting the development of EOR in high-temperature and high-salt environments.