Montmorillonite Modified by Cationic and Nonionic Surfactants as High-Performance Fluid-Loss-Control Additive in Oil-Based Drilling Fluids

Abstract

This work reports the modification of montmorillonite (MMT) by nonionic surfactant sorbitan monooleate (Span 80) and cationic surfactant cetyltrimethylammonium bromide (CTAB), which can be used as fluid-loss-control additive for preventing the fluid invasion into the porous pristine formation and avoiding the collapse of borehole wall in oil-drilling excavation. Transmission electron microscopy imaging revealed modified MMT with small particle size display high dispersibility compared with that of pristine MMT in white oil. Experimental results of small-angle x-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy showed that a bilayer of CTAB and Span 80 was intercalated into the interlayer space of the MMT. The synthesized organo-clays as a fluid-loss-control additive performed well in oil phase. The organo-clays modified with 2.0 cation-exchange capacity (CEC) CTAB and 2.0 CEC Span 80 yielded 100% colloid fraction in colloid fraction tests, showed low filtration loss of 5.7 mL, and left a filter cake approximately 68 µm thick in American Petroleum Institute filtration tests, showing that the synthesized organo-clays can be potentially used as fluid-loss-control additive in oil-drilling excavation.