Abstract Sepiolite modified by surfactants has been used in adsorption, catalysts, etc. While few studies focus on organo-sepiolite (OSep) which is used in oil-based drilling fluid. In this paper, a kind of cationic-anionic organo-sepiolite (CA-OSep) was prepared to be applied in oil-based drilling fluids. The structure and properties of OSep were characterized by X-ray diffraction, FTIR spectrum, thermal analysis and surface contact angle (SCA) analysis. The effect of dosage and chain length of surfactants, and the ratio of cationic to anionic surfactants on OSep were discussed as well as the rheological properties of OSep/diesel system. Cationic surfactant of long chains had better adhesion to the surface of sepiolite than surfactants of short chains. Compared with cationic organo-sepiolite (C-OSep), CA-OSep has an advantage in thermal stability. The apparent viscosity, plastic viscosity and yield value of oil-based drilling fluids with OSep as additives were further studied at different temperatures. Results indicated that organic surfactants had been adsorbed on the surface of sepiolite, and the CA-OSep had higher surface polarity and better thermal stability in 5# diesel oil than C-OSep. CA-OSep presented a new kind of potential rheological control additive for oil-based drilling fluids, and would exhibit excellent thermal stability.

中文翻译：

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不同表面活性剂改性有机海泡石及其在油基钻井液中的流变行为比较

摘要 表面活性剂改性的海泡石已被用于吸附、催化剂等方面，而对用于油基钻井液的有机海泡石（OSep）的研究较少。本文制备了一种用于油基钻井液的阳离子-阴离子有机海泡石（CA-OSep）。OSep的结构和性质通过X射线衍射、FTIR光谱、热分析和表面接触角(SCA)分析来表征。讨论了表面活性剂用量和链长、阳离子与阴离子表面活性剂的比例对OSep的影响以及OSep/柴油体系的流变特性。长链阳离子表面活性剂对海泡石表面的附着力优于短链表面活性剂。与阳离子有机海泡石（C-OSep）相比，CA-OSep在热稳定性方面具有优势。进一步研究了以OSep为添加剂的油基钻井液在不同温度下的表观粘度、塑性粘度和屈服值。结果表明，有机表面活性剂已吸附在海泡石表面，CA-OSep在5#柴油中的表面极性高于C-OSep，热稳定性更好。CA-OSep 提出了一种新型潜在的油基钻井液流变控制添加剂，并具有优异的热稳定性。