Rheological study on the invert emulsion fluids with organoclay at high aged temperatures

Abstract

Invert emulsion fluids stabilized by organoclays are important for applications in thixotropic fluids and petrochemical industry, especially in the field of oil extraction. Among these applications, improvement of the rheological properties of invert emulsion fluids at high temperatures lacks detailed study. In the current work, three different organoclays, including organo-sepiolite (OSEP), organo-hectorite (OSHCA) and organo-montmorillonite (OMMT) were prepared through chemical modification of unmodified clays using DODMAC. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that DODMAC is not only adsorbed on the surface of particles, but also inserted into the layers of OMMT and OSHCA. For OSEP particles, DODMAC can only be adsorbed on the surface of particles. Interestingly, the results of optical microscopy and rheology indicate that the OSHCA particle-stabilized invert emulsion fluid provides better rheological properties than the other two organoclays at high temperature. Such high rheological properties is ascribed to the weak flocculation of OSHCA particles. Due to its nonreactive Mg−OH surface groups, OSHCA maintains the rheology of high-temperature aged invert emulsions by reconstructing weak flocculation structure. On the other hand, on the particle surface of OMMT and OSEP, Al−OH may react with OH− under alkaline conditions, which will destroy the weak flocculation due to increased repulsion interaction. These results clearly shed light on the relationship between the performance of invert emulsion at high aged temperature and particle weak flocculation, and also are beneficial to the applications which need stable emulsion at high temperature.