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

Abstract Wellbore instability caused by the hydration of shale formations during the drilling process is the main technical problem in drilling engineering. The existing shale inhibitors mainly inhibit shale hydration through charge neutralization, intercalation, activity reduction, and/or plugging. Few shale inhibitors focus on reverse the wettability of shale surface. In the paper, the shale inhibition performance of silicone quaternary ammonium salt (SQAS), a material that can reverse the wettability of shale surface, was evaluated and the shale inhibition mechanism of SQAS was studied via particle size, zeta potential, contact angle, scanning electron microscopy (SEM), and shale water absorption analyses. The experimental results show that the use of SQAS could result in a relatively lower linear swelling rate of clay, and its rolling recovery rate of easily hydrated shale was as high as 64.25%, which is better than those of polyamine inhibitors. The study on the inhibition mechanism revealed that SQAS can chemically react with the shale surfaces to form a seamless hydrophobic film. The water contact angle on the shale surface was increased from 28.7° to 110.7°, which greatly reduces water penetration into shale and the water absorption capacity of clay minerals. The results of this study provide new technical ideas for the development of high-performance shale inhibitors.