Investigation of dihydroxyl ionic liquids as high-performance shale inhibitors and their inhibition mechanism

Ionic liquids (ILs) are incredibly efficient additives to solve wellbore instability resulting from shale hydration. The influence of the molecular structure of ILs on their inhibition performance has been investigated intensively, and hydroxyl is regarded as the significant group to improve their inhibition performances. In this study, three novel dihydroxyl ionic liquids (DHILs) including [C 4 DIPA]Br, [C 8 DIPA]Br, and [C 12 DIPA]Br were successfully synthesized. Then their thixotropy and inhibition properties were evaluated via three-interval thixotropy tests (3ITTs), hot-rolling recovery tests, immersion tests, and linear swelling tests. [C 12 DIPA]Br exhibited the optimal inhibition ability at a low concentration (0.5 wt%) and was more effective than the conventional inhibitor KCl (2 wt%). Various techniques were used to analyze the inhibition mechanism of DHILs including contact angle measurements, zeta potential , X-ray diffraction, and Flourier transform infrared spectroscopy . The results demonstrated that the synergistic effects of hydrogen bonding , electrostatic interaction, and hydrophobic shield should be responsible for the excellent inhibition performance and great thermal stability of [C 12 DIPA]Br. Finally, the proposed mechanism was supported by the control experiments using other three ILs inhibitors and molecular dynamics simulation . Our work provided unique perspectives on developing rationally designed and efficient ILs inhibitors.