Clean Technology 2010
C.O. Metin, Q.P. Nguyen, L.W. Lake
The University of Texas at Austin, US
silica nanoparticle, aqueous stability, aggregation kinetics, surface structure, electrolyte, subsurface
The potential application of nanotechnology has significantly advanced into the upstream oil and gas industry. However, harsh subsurface conditions such as high temperature and saline environment are generally incompatible to most commercially available engineered nanoparticles. The injection of nanoparticles in an aqueous phase is preferable for most subsurface applications. It is thus crucial that the aqueous dispersion remain stable upon the desired functions of nanoparticles are fully utilized. In this work, we conducted a systematic study of aqueous dispersion of silica nanoparticles under subsurface conditions. The ability to improve nanoparticle dispersivity in an aqueous phase was also investigated. New methods for identifying nanoparticle phase behavior were developed, using Fourier transform infrared (ATR-FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometer, and dynamic light scattering (DLS). These methods allow accurate evaluation of the effects of pH, temperature, and electrolytes on the aqueous stability of silica nanoparticles. Spectral analysis of Si-O bond at 1110 cm-1 with ATR-FTIR indicates a structural change on the surface of silica particles as the dispersion pH changes. Silica nanoparticle dispersion becomes unstable as electrolyte concentration exceeds a critical value called critical stability concentration (CSC). CSC was found to be strongly dependent on electrolyte types and temperature.