Influence of the interaction between surfactants and sepiolite on the rheological properties and thermal stability of organo-sepiolite in oil-based drilling fluids

摘要

The influence of interaction between organic surfactants and sepiolite (Sep) on the structure and rheological properties of organo-sepiolite (OSep) in oil-based drilling fluids was investigated. Sep was modified with three kinds of cationic surfactant. X-ray diffraction, scanning electron microscope, surface properties, thermal analysis and X-ray photoelectron spectroscopy (XPS) were applied to characterize the structures of OSep and interaction between surfactants and Sep. Gel volume and dynamic rheological behavior were used to appraise the rheological properties of OSep/oil fluids. OSep keeps the crystal structure of sepiolite after organic modification and shows the more dispersed fibers. XPS results demonstrated that organic surfactants are in electronic interaction with sepiolite. Surfactants block the micropores of sepiolite by partially inserting and covering, resulting in the decrease of specific surface area. The size of the surfactants plays an important role to insert the channels. The partially insertion of surfactants into the channels leads to better rheological properties and thermal stability of OSep in oil-based drilling fluids.