Application of Hydrothermal Carbon/Bentonite Composites in Improving the Thermal Stability, Filtration, and Lubrication of Water-Based Drilling Fluids

With the increasing harsh drilling environments encountered more frequently than ever before, developing environmentally benign and multifunctional additives is essential to formulate high performance drilling fluids. Herein, hydrothermal carbon/bentonite composites (HCBCs) were prepared by a hydrothermal carbonization reaction using soluble starch and sodium bentonite as raw materials. A systematic investigation was conducted into the effects of HCBC concentration on the rheological, filtration, and lubricating characteristics of xanthan gum, modified starch, and high-temperature polymer slurries. These properties were evaluated before and after exposure to hot rolling at different temperatures. The hydroxyl radical scavenging properties of HCBC were evaluated. Observation showed plentiful micro- and nano-sized carbon spheres deposited on the bentonite particles, endowing the bentonite with better dispersion. HCBCs could maintain stability of the water-based drilling fluids’ rheological profile, decrease filtration loss, and improve the lubrication with relatively low concentrations. The excellent properties were attributed to the highly efficient scavenging of free radicals and the stabilization of bentonite particle dispersion.