Abstract In drilling fluid industry, few shale inhibitors commonly used can simultaneously meet the requirements of strong inhibition and environmental performance. In our previous study, polyamino acid materials showed great potential to be used as environmental-friendly and efficient shale inhibitors. Herein, four polyamino acids with different functional groups, polyglycine (PGly), polyglutamic acid (PGlu), polylysine (PLys), and polyarginine (PArg), were successfully synthesized to study the influence of amino acid composition on inhibition performance. Results indicated that PGly and PGlu mainly exerted their inhibition by decreasing the clay swelling degree, while PLys and PArg mainly showed their inhibition on decreasing the clay dispersion degree. In detail, PGly and PGlu could enter the interlayer region of sodium bentonite (Na-BT) and decrease the interlayer spacing, which could reduce the Na-BT swelling degree to 83.8% and 85.8%, respectively. However, their inhibition on shale dispersion at high temperatures was not satisfactory. Meanwhile, PLys and PArg displayed superior thermal stability and could improve the shale recovery to 66.85% and 74.45% at 150 °C. They could strongly adsorb onto the surface of Na-BT particles, encapsulate them, and decrease the ζ potential to −2.06 and −15.9 mV, thus forming stable aggregates. Compared with PGly and PGlu, PLys and PArg would cause limited change of the interlayer spacing of Na-BT. In all, PArg was preferred to be used as a biodegradable and effective shale inhibitor at high-temperature wells. In the future, different polyamino acid combinations can be designed as more highly effective inhibitors for water-based drilling fluids.

中文翻译：

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不同聚氨基酸在水基钻井液中的缓蚀性能比较

摘要 在钻井液行业，很少有常用的页岩缓蚀剂能同时满足强缓蚀和环保性能的要求。在我们之前的研究中，聚氨基酸材料显示出用作环保高效页岩抑制剂的巨大潜力。在此，成功合成了四种不同官能团的聚氨基酸，聚甘氨酸（PGly）、聚谷氨酸（PGlu）、聚赖氨酸（PLys）和聚精氨酸（PArg），以研究氨基酸组成对抑制性能的影响。结果表明，PGly和PGlu主要通过降低粘土溶胀度发挥抑制作用，而PLys和PArg主要通过降低粘土分散度发挥抑制作用。详细，PGly和PGlu可以进入钠基膨润土(Na-BT)的层间区域，减小层间距，使Na-BT溶胀度分别降低到83.8%和85.8%。然而，它们在高温下对页岩分散的抑制并不令人满意。同时，PLys 和 PArg 表现出优异的热稳定性，可以将页岩采收率提高到 150 °C 时的 66.85% 和 74.45%。它们可以强烈吸附在 Na-BT 颗粒的表面，将它们包裹起来，并将 ζ 电位降低到 -2.06 和 -15.9 mV，从而形成稳定的聚集体。与 PGly 和 PGlu 相比，PLys 和 PArg 会导致 Na-BT 层间距的变化有限。总之，在高温井中，首选 PArg 作为可生物降解的有效页岩抑制剂。将来，