Amidocyanogen silanol as a high-temperature-resistant shale inhibitor in water-based drilling fluid

Abstract To meet the technical requirements of high-temperature deep wells, highly inhibitive, high-temperature-resistant shale inhibitors are essential. This paper reports for the first time the use of amidocyanogen silanol (ANS-1), a newly developed oligomer with an amino siloxane structure, as a potential shale inhibitor. Its inhibitive properties were evaluated by linear swell testing, cutting dispersion testing, bentonite inhibition testing, and mud pellet disintegration testing, and the results were compared with the properties of other current conventional inhibitors. The inhibition mechanism was investigated by X-ray diffraction, adsorption, Fourier transforms infrared spectroscopy, contact angle, zeta potential and transmission electron microscope. The results indicated that ANS-1 can inhibit the hydration swelling and dispersion of water-sensitive clay minerals effectively, performing better than other inhibitors. Furthermore, ANS-1 provides reliable thermal stability as high as 140 °C and has potential application in high-temperature deep wells. ANS-1 can adsorb into the surface of clay, which changes the wettability of the clay surface and increases the resistance of water molecules to bond with the clay. In addition, ANS-1 can intercalate into the clay interlayer, occupying water adsorption sites, and into the interlayer channel, thus inhibiting the hydration swelling of clay. The introduction of siloxane groups in the ANS-1 molecular chain led to a firm chemical adsorption between ANS-1 and clay, which increased the adsorption capacity of ANS-1 at high temperature, thus improving its inhibition performance.