[NVim]Br and Poly([NVim]Br-Co-AM): Synthesis and Effects on Inhibiting Clay Swelling and Dispersion and the Mechanisms

To solve the downhole problems correlated with clay hydration swelling and dispersion under high-temperature conditions, a 1-aminoethyl-3-vinylimidazolium bromide ([NVim]Br) and a [NVim]Br/acrylamide copolymer (poly([NVim]Br-co-AM)) are synthesized and used as inhibitors. The molecular structures of [NVim]Br and poly([NVim]Br-co-AM) are characterized by FT-IR and ¹H-NMR. The inhibition properties of [NVim]Br and poly([NVim]Br-co-AM) are evaluated by free swelling and dispersion tests, linear swelling, hot roll recovery experiments and thermogravimetric analyses.The inhibition mechanisms were revealed by X-ray diffraction, zeta potential, wettability analysis and ESEM observation. The results showed that both [NVim]Br and poly([NVim]Br-co-AM) has significantly superior inhibition performance compared with the common inhibitors KCl, polyether amine D230 and polyquaternium-7. Both [NVim]Br and poly([NVim]Br-co-AM) can resist 250 °C. [NVim]Br performed excellently in inihibiting both crystalline and osmotic swelling, which depended on the strong electrostatic adsorption and hydrogen bonds of imidazole cations and primary amine in [NVim]⁺. Poly([NVim]Br-co-AM) exerted excellent inhibition by minimizing osmotic swelling, reducing hydrophilicity and increasing clay bonding. The results are important for understanding the rational design of novel efficient inhibitors for drilling high-temperature shale formation.