Rheological investigation of polymer/clay dispersions as potential drilling fluids

Abstract

The rheological properties of poly(ethylene glycol)(PEG)/Laponite® RD (Lap) and poly(propylene glycol)(PPG)/Lap aqueous dispersions, with 2% polymer and different clay concentrations, were investigated at 25 °C in order to establish the optimal composition to formulate a system applicable as drilling fluid. Some of the most important parameters, such as low shear rate viscosity, plastic viscosity, yield stress and flow behavior index, were determined and discussed. The PEG/Lap and PPG/Lap dispersions containing more than 2.55% and 3.10% clay, respectively, could be considered in the formulation of drilling fluids. The yield point value of dispersions, which is suitable for drilling fluid applications, increased while their plastic viscosity decreased in the presence of NaCl. By addition of NaCl, the complex viscosity of these samples becomes independent of temperature in the range 10 °C – 65 °C. Zeta potential value decreases as the Lap concentration increases up to about 3% clay and, higher clay content no longer affects it. • Laponite® RD (Lap) aqueous dispersions in presence of PEG or PPG were investigated. • Rheological results suggest Lap suitability for drilling fluids. • Effect of salt and temperature on viscoelastic properties was evaluated. • Zeta potential as function of clay content and polymer structure was analysed. • Structure of Lap dispersions in presence/absence of PEG or PPG was discussed.