Effect of surface chemistry of silica nanoparticles on contact angle of oil on calcite surfaces in concentrated brine with divalent ions.

Hypothesis: For an oil droplet on calcite with an intervening brine film, the water contact angle θ may be reduced markedly (greater water wetness) with surface modified silica nanoparticles (NP). Modification with cationic, anionic, and nonionic ligands may be used to control the nanoparticle adsorption and interactions at the oil-brine and brine-calcite interfaces to influence the rate and degree of reduction in θ.

Experiments: The colloidal stability at 25 °C was determined in concentrated divalent brine (8 wt% NaCl and 2 wt% CaCl) with dynamic light scattering, and the NP adsorption was determined on calcite.