Effect of Temperature and PH on Wettability Alteration and Adsorption of Amphiphilic Polymer-Coated SiO<sub>2</sub> Nanoparticle on Oil-Wet Porous Media

Wettability alteration of the oil-wet reservoir rocks to the water-wet state is an important factor for enhanced oil recovery (EOR). One of the main challenges of applying nanoparticles for wettability alteration is related to the colloidal stability and poor adsorption of the nanofluids in the harsh conditions of the reservoirs. In the present work, comparative studies were followed between polymer-coated silica nanoparticles by polyethylene glycol (Mn ~ 2000) and amphiphilic polymer-coated silica nanoparticles by polyethylene glycol (Mn ~ 2000 or 5000) and propyl chains to determine wettability alteration and adsorption of these modified nanoparticles on porous media. Water contact angle and UV–Vis adsorption measurements showed which the efficiency of amphiphilic polymer-coated nanoparticles depends on the wettability state of glass and it was improved significantly by oil-wet glass substrates due to the existence of the hydrophobic polymer on the surface of the nanoparticles. Moreover, effective parameters including temperature, and pH were studied. The better performance was obtained for the modified silica nanoparticles by polyethylene glycol (Mn ~ 5000) and propyl chains at 1000 ppm concentration in pH of 6 and the temperature range of 25-55°C. Our study demonstrated amphiphilic polymer-coated silica nanoparticles can be considered as a promising agent which has the potential for EOR purposes.