Hydrothermal synthesis of bentonite carbon composites for ultra-high temperature filtration control in water-based drilling fluid

In this study, bentonite hydrothermal carbon composites (BHCCs) were fabricated by green and facile hydrothermal carbonization, employing glucose as the carbon source and bentonite as the template. BHCCs were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effects of the BHCCs on the rheological and filtration properties of bentonite dispersions were investigated before and after thermal aging at 220 °C and 240 °C, respectively. The results demonstrated that, unlike conventional synthetic polymers, the BHCCs exhibited a minor influence on the rheology of bentonite dispersion and had extraordinary filtration control both before and after ultra-high-temperature aging. The incorporation of BHCCs helped introduce the oxygenated groups with carbon species, thereby enhancing the dispersion stability of bentonite particles. The spherical nano-sized carbon particles in BHCCs filled the gaps between large particles in the filter cake. The above factors contributed to excellent filtration control under hostile, high-temperature conditions.