Adsorption of imidazolium-based ionic liquid on sodium bentonite and its effects on rheological and swelling behaviors

Abstract Clay is closely associated with the drilling of oil and gas by influencing the shale wellbore stability and the rheology of drilling fluids. In this work, four imidazolium-based ionic liquids (ILs) were used to modify the typical clay (i.e., sodium bentonite (Na-Bent)), and their effects on the Na-Bent rheological and swelling properties were evaluated by shear rheological measurements, immersion experiment, linear swelling measurements. The mechanisms involved were identified by using fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Zeta-potential and environmental scanning electron microscopy (ESEM) analysis. Evaluation experiment results showed that the adsorption of each IL could both significantly affect the Na-Bent rheological property and inhibit the Na-Bent swelling, which strongly depended on ILs' structures and concentrations. The mechanism study revealed that the cationic groups of ILs could adsorb on Na-Bent prior to water molecules, followed by expelling water and compressing the double electrode layers, and therefore inhibit the Na-Bent swelling. The adsorption of ILs could also change aggregation behaviors of the Na-Bent particles, by which the “house of cards” structures in Na-Bent dispersions were improved or destroyed, resulting in changes in rheological properties of Na-Bent dispersions.