Effect of thermal aging and electrolyte on bentonite dispersions: Rheology and morphological properties

In this work, the effect of thermal aging and electrolyte on the theological and morphological properties of bentonite dispersion was studied. Previous studies reported the effect of electrolyte concentration and thermal aging on bentonite rheological properties but detailed morphological studies of the effect of electrolyte and thermal aging of bentonite dispersion have never done before. Dynamic and steady shear rheological experiments were performed at 25 degrees C and data were fitted to two different models (Herschel-Bulkley and Cross models) to study the rheological behavior of thermally aged and electrolyte treated bentonite dispersions. The bentonite dispersion was thermally aged at 120 degrees C in the rolling oven for 24 h prior to rheological measurements. The electrolyte treated bentonite dispersion was formulated by mixing 0.1 M NaCl in bentonite dispersion with constant stirring for 24 h. It was noticed that electrolyte treated bentonite dispersions have low rheological properties (viscosity, yield stress, and gel strength) compared to the base bentonite dispersion. Thermal aging of bentonite dispersion resulted in the immense increase in rheological properties of bentonite dispersion compared to the base dispersion. XRF, XRD, and TGA were used to study the chemical composition and thermal stability of the bentonite. Scanning electron microscope (SEM) analysis and transmission electron microscope (TEM) analysis were performed to understand the effect of electrolyte and thermal aging on the morphology of bentonite dispersions. The d-spacing of bentonite platelets were calculated from XRD analysis and compared with the interlayer distance measured with TEM analysis. The morphology of electrolyte treated bentonite dispersion showed the aggregation of bentonite platelets while thermal aging resulted in flocculation of the bentonite platelets. This work will help to understand the effect of electrolyte and thermal aging on rheology and morphological properties of bentonite-based drilling fluids. The comparative study of the effect of electrolyte and thermal aging on bentonite morphological properties using SEM, XRD and TEM analysis has never studied before in the literature. (C) 2018 Elsevier B.V. All rights reserved.