Inhibiting the surface hydration of shale formation using preferred surfactant compound of polyamine and twelve alkyl two hydroxyethyl amine oxide for drilling

The surface hydration of shale has severe effect on the wellbore stability during drilling through the shale formation. In this paper, a novel method was developed to measure wettability of shale power by determining real contact angle. A variety of methods including measurements of Zeta potential, uniaxial compressive strength, shale stability indexes, surface hydration water, linear swelling, and cuttings hot-rolling dispersion experiment were used to evaluate the inhibition of surfactants. Meanwhile, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD) were used to investigate the interaction between surfactants and shale particles. Results revealed that the surface hydration of shale could be inhibited by using suitable surfactants. The surfactants compound of PA and THAO possessed stronger surface hydrating inhibition and capacity of restraining osmotic hydration. This is because the compound can enhance the surface hydrophobicity after adsorption onto the surface of shale particles, restrained osmotic hydration through swapping out inorganic cations in the clay interlayer, thus reducing the zeta potential and bounding clay gall together.