A hybrid lubricant for invert emulsion drilling fluids (IEDFs), especially for high density (ρ>1.8 g/cm3) IEDFs, was synthesized with expanded graphitic oxide, 1,3-dichloro-2-propanol and N,N-dimethylhexadecylamine in our laboratory. The characterization of the hybrid lubricant was studied through scanning electron microscope (SEM), nuclear magnetic resonance hydrogen spectroscopy (1H NMR) and thermogravimetry analysis (TGA). The results demonstrated that the structure of the hybrid lubricant was consistent with design. This lubricant can adhere to the wellbore and the string directionally and then form a dense protective lubricant film, which causes a drastic reduction of coefficient of friction (CoF) between the rotating drill string and the casing or the rock formation. Application tests in IEDFs with various density showed that 50-70% CoF reduction was observed with 1.0-1.5 w/v% hybrid lubricant. In contrast, CoF reduction of conventional lubricants was only 30-40% at the same condition. And the hybrid lubricant even performs well under high temperature up to 180oC in the drilling fluids with a high density of 2.5 g/cm3 and has little influence on the rheology of drilling fluids. Additionally, the hybrid lubricant is proved easily degradable.
