Study of a gemini surface active ionic liquid 1,2-bis(3-hexylimidazolium-1-yl) ethane bromide as a high performance shale inhibitor and inhibition mechanism

It is an urgent subject to search high-performance shale inhibitors used in water-based drilling fluids for drilling safety. In the present work, two imidazolium-based ionic liquids (ILs), 1-hexyl −3-methylimidazolium bromide (BMH) and its corresponding gemini type, 1,2-bis(3-hexylimidazolium-1-yl) ethane bromide (HMH), were introduced as promising shale inhibitors. The inhibition performances were assessed and compared with the conventional inhibitors potassium chloride and polyether diamine (PDA) via the inhibition evaluation tests including sodium bentonite (Na-bent) pellets immersing tests, linear swelling tests and shale hot-rolling recovery tests. Both ILs inhibitors, especially HMH, shown terrific inhibition performance with lower dosages and maintained high-performance at temperature up to 160 °C. The inhibition mechanism was analyzed by FTIR, X-ray diffraction (XRD), Zeta potential tests, particle size distribution measurement, contact angle measurement and surface tension measurement. The results demonstrated both BMH and HMH effectively inhibit the shale hydration and swelling. HMH, with two positively charged headgroups and two hydrophobic tails, was better than BMH in entering the interlayer space of clay, reducing Zeta potential, forming hydrophobic shield and reducing the surface tension, which was responsible for its superior inhibition performance.