Xylitol Based Ternary Deep Eutectic Solution: An Effective Shale Inhibitor for Drilling Fluids

Shale hydration-induced wellbore instability remains a major technical challenge in oil and gas drilling. The development of efficient and environmentally friendly shale inhibitors is crucial for ensuring downhole safety. Current research trends show a shift from traditional inorganic salts and small-molecule polymers toward multifunctional materials, with emphasis on higher efficiency, lower toxicity, and simplified synthesis. Deep eutectic solvents (DESs), as green solvents characterized by low biotoxicity, high stability, and facile preparation, demonstrate significant potential for shale hydration inhibition. In this study, a series of ternary DES inhibitors (Xyl-ter-DES) with multiple active sites were synthesized via a one-step method using xylitol (a natural organic compound) as hydrogen bond donor, with choline chloride and tetramethylammonium chloride as hydrogen bond acceptors. Comprehensive characterization through surface tension measurement, X-ray diffraction (XRD), and zeta potential analysis revealed the inhibition mechanism involving surface tension reduction, interlayer spacing contraction, and capillary effect weakening. Performance evaluation demonstrated that 1 wt% Xyl-ter-DES aqueous solution reduced the bentonite linear swelling rate from 84.77% (in water) to 45.32%, while increasing the shale recovery rate from 15.35% (in water) to 80.65% in hot-rolling tests (90 ℃). The developed Xyl-ter-DES inhibitor exhibits advantages of simple preparation, environmental compatibility, superior performance, and good adaptability to water-based drilling fluids, offering both theoretical insights and technical references for next-generation shale inhibitor development.