A comprehensive study of the effect of multi-walled carbon nanotubes as an additive on the properties of oil-based drilling fluids

Carbon tubes, due to their unsurpassed aspect ratio, are a unique nanomaterial. The effect of carbon nanotube additions on the rheology of nanosuspensions is much more significant compared to spherical nanoparticles. This makes their use for improving drilling fluids very attractive. The work shows that with the help of nanoparticle additives it is possible to control the functional properties of drilling fluids over a very wide range. The article presents the findings of comprehensive experimental studies on the effect of multi-walled carbon nanotubes (MWCNTs) as additives, on the main functional characteristics of mineral oil-based emulsions used as drilling fluids (DF). Such systematic studies on oil-based DFs have been carried out for the first time. Nanotubes have been used to modify the formulations of typical DFs containing 65% of hydrocarbon phase. The weight concentration of nanotubes in emulsions was varied from 0.1 to 0.5%. The composition formula and preparation technique of stable DFs with CNT additives have been developed. The rheology, filtration and antifriction properties, temperature, and colloidal stability of oil-based DFs, modified by carbon nanotubes, have been studied. In general, the study has shown that adding MWCNTs even at low concentrations are capable of modulating significantly the characteristics of drilling oil-based emulsions. The addition of MWCNTs allows increasing the effective viscosity by 1.5 times and enhances the yield point of DFs, decreasing filtration loss by four times, and friction coefficient, by 20%, as well as increasing the stability of the emulsion by 2.7 times. The findings of this study can help for better understanding that the addition of MWCNTs to control the properties of hydrocarbon drilling fluids is a very promising direction in the development of drilling technologies in difficult mining and geological conditions. Graphical abstract