Stability of Aqueous Silica Nanoparticle Dispersions under Subsurface Conditions

摘要

We present quantification methods for nanoparticle stability analysis using non-intrusive analytical techniques to study the stability of silica nanoparticle dispersions and the effects of pH, temperature and electrolytes that would be encountered in oil field brines in a reservoir. Spectral analysis of the Si-0 bond at wavenumber of 1110 cm~(-1) with the attenuated total reflectance, Fourier transform infrared (ATR-FTIR) indicates a structural change on the surface of silica particles as the dispersion pH changes. We define a critical salt concentration (CSC) for, NaCl, CaCl_2, BaCl_2 and MgCl_2, above which the silica dispersion becomes uastablc. Divalent cations Mg~(2+), Ca~(2+) and Ba~(2+) are. more effective in destabilizing silica nanoparticle dispersion than the monovalent cation Na~+. The CSC for Na~+ is about 100 times more than for Ca~(2+), Ba~(2+) and Mg~(2+). Among the divalent cations studied, Mg~(2+) is the most effective in destabilizing the silica particles. The CSC is independent of silica concentration, and lowers at high temperature.