Use of silicone quaternary ammonium salt for hydrophobic surface modification to inhibit shale hydration and mechanism study

•Silicone quaternary ammonium salt was used as shale inhibitor in drilling fluid.•SQAS can chemically react with the shale and form a seamless hydrophobic film.•SQAS can significantly increase the contact angle of water on the shale surface.•SQAS can effectively inhibit the hydration of shale and stabilize wellbore.