Silica Nanofluids in Low Salinity Water for Wettability Alteration of the Mineral Surface and the Effect of Surface Roughness
Gomathi Rajalakshmi Seetharaman, Devakumar N. P, Jitendra S. Sangwai
Abstract
Surface roughness plays a crucial role in oil recovery operation. Wenzel’s equation relates the contact angle of a liquid droplet on a rough surface to its intrinsic contact angle and surface roughness. Herein, we report the impact of surface roughness on the wettability of rough quartz surfaces using silica nanofluid in low-salinity (low-sal) water under different temperature and pressure conditions. We employed atomic microscopy to analyze the roughness of a quartz surface that shows varying degrees of roughness. The results of nanofluid stability reveal that one of the key factors enhancing the colloidal stability of silica nanoparticles is the electrolyte’s pH. Increasing the surface roughness of the quartz substrate from 34.6 to 415 nm decreased the contact angle of crude oil from 63 to 30°. Furthermore, a decrease in contact angle with an increase in temperature is prominent for the nanofluid on highly rough surfaces. Likewise, a slight increase in surface roughness exaggerates the effect of pressure on the contact angle of the quartz surface. Scanning electron microscopy and energy-dispersive X-ray analyses confirm the dendritic structure of the low-sal-silica nanofluid on the rough surface. Our study strengthens the hypothesis that surface roughness together with surface chemistry is the key factor in determining quartz surface wettability.