Performance evaluation of trimethylolpropane ester as high-temperature resistant lubricant for high performance water-based drilling fluids

As drilling operations increasingly target large-displacement wells, horizontal wells, deep wells, and ultra-deep wells, the challenges of excessive drilling resistance and downhole safety have become more prominent. During the drilling process, one of the primary technical methods for preventing and addressing drilling safety issues is the reduction of downhole frictional resistance through the addition of lubricants to the drilling fluid. In this study, a high-temperature and high-salt-resistant drilling fluid lubricant was synthesized using raw materials such as oleic acid and trimethylolpropane. The lubricant exhibited excellent lubrication performance under high-temperature and high-salt conditions. When added at a 1.5% dosage to a 4% freshwater-based slurry, HZ-1 resulted in a 95.2% reduction in the lubrication coefficient. After aging at 200°C, the HZ-1-containing slurry maintained an 87.9% reduction, and when used with a NaCl dosage of 36%, the slurry still exhibited an 80.5% reduction. Furthermore, HZ-1 exhibited favorable compatibility with both polymer drilling fluid and polysulfone drilling fluid systems. It had basically no effect on the rheological properties of the drilling fluid and reduced filtration loss. Moreover, HZ-1 exhibited a lubrication coefficient reduction rate of 94.5% in freshwater-based slurry and 85.5% in brine-based slurry, outperforming domestic and foreign lubricants. It outperformed these comparative lubricants in terms of lubrication and drag reduction within the same period. The analysis of the lubrication and drag-reduction mechanism revealed that HZ-1, when adsorbed onto a metal surface, formed a hydrophobic and high-strength physical adsorption film. This film prevented direct contact between drilling tools and the friction surface of the well wall, resulting in a significant reduction in the lubrication coefficient. Furthermore, using the drilling fluid system containing HZ-1 lubricant, the wear scar diameter formed on the surface of the four-ball friction experimental body was the smallest, measuring only 0.78 mm. This property significantly enhances the extreme-pressure and anti-wear performance of the friction sub-surface. Consequently, HZ-1 effectively prevents complications such as pressure support, stuck drilling, and high frictional resistance, thereby significantly reducing costs and improving efficiency.