Effect of lubricating additives on the tribological properties of polymer-clay drilling fluid in a metal-to-metal sliding contact

Introduction. The article addresses the problem of improving the lubricating capacity of drilling fluids to reduce the coefficient of friction in a ”metal-to-metal“ pair, which is crucial for preventing stuck pipe incidents and reducing equipment wear during directional and horizontal drilling. Methods and materials. An analysis of modern approaches to the use of lubricating additives in drilling fluids is presented. The effect of various types of additives – paraffins, ”EZО“ nano-additive, fatty acids, waste oil, as well as compositions with surfactants – on the coefficient of friction and friction reduction efficiency in a polymer-clay fluid was experimentally studied. Tests were conducted on an OFITE E.P. lubricity tester at additive concentrations ranging from 0.2–2.0% by volume. It was shown that the greatest effect is achieved with the combined use of surfactants and nano-hydrocarbon components, providing a reduction in the coefficient of friction of up to 71% at an oil content of 2%. Results and discussion. Optimal component concentrations were established and synergy effects were identified upon the combined introduction of additives. The obtained results allow recommending the developed nano-compositions for use under high-load conditions in a ”metal–metal“ friction pair during high-angle drilling. Conclusion. Based on the conducted research, it was established that the highest efficiency (reduction of the friction coefficient up to 71%) is achieved with the combined use of surfactants and waste oil at a concentration of 2%. A synergistic effect was revealed upon the combined introduction of additives, and it was also established that exceeding the oil concentration above 0.5% reduces the efficiency of most additives, with the exception of compositions with surfactants. The developed formulations are recommended for use as a cost-effective and efficient alternative for lubricating ”metal-to-metal“ sliding contact during horizontal drilling.