Colloidal Properties and Clay Inhibition of Sodium Silicate in Solution and Montmorillonite Suspension

Abstract

To investigate the interaction mechanism, clay inhibition and compatibility of sodium silicates as shale inhibitor in water based drilling fluid, a variety of properties were characterized. Zeta potential, activity, colloidal stability and particle size were employed to characterize the colloidal properties. Adsorption, cuttings hot-rolling dispersion, linear swelling, pressure and osmosis transmission tests were used to determine the inhibition properties. Results showed that the zeta potential of sodium silicate solution ranging from −45 mV to 0 mV, increased in magnitude with increasing the sodium silicate modulus and pH of solution in the initial stage and decreased with the concentration of monovalent inorganic salts. With the increase of modulus and concentration of sodium silicate, the solution activity generally decreased or colloidal polysilicic acid began to form at a solution concentration above 70 g/L of Na₂O⋅2.8SiO₂ (2.8SS). The diameter of polysilicic acid increased with 2.8SS concentration, modulus, pH and salt concentration. Adsorption of 2.8SS onto montmorillonite through chemical bonding was boosted with increasing 2.8SS concentration regardless of cuttings addition. The adsorption also rose exponentially with temperature. The activity of the montmorillonite suspension was reduced by the addition of 2.8SS and further decreased by salt addition. 2.8SS was found to exhibit superior inhibition performance compared to KCl, organosilicon, sulfonate asphalt and polyglycol. The pressure transmission was retarded effectively, resulting in the improvement of membrane efficiency of shale clays.