Improving the Lubricity of Extended Reach Well Drilling Equipment Using Non-Fluorescent Extreme Pressure Cationic Lubricants

In this study, non-fluorescent cationic extreme pressure lubricant JDLUB-1 was prepared to improve the lubricity for extended reach well drilling. The lubricant was mainly composed of synthetic base oil, oil-soluble and spherical nano-silica, sulfur-phosphorus-molybdenum anti-friction and anti-extreme pressure additives. The mixture was emulsified with primary emulsifier cycloalkane group condensed fatty amines and a fatty alcohol polyoxyethylene ether co-emulsifier. The fluorescence level did not exceed 4, satisfying the standard requirements. The properties including extreme pressure lubrication, temperature resistance and compatibility with conventional drilling fluid additives were evaluated. The results indicated that the extreme pressure lubricity coefficient could reach 0.0283 after addition of JDLUB-1. Meanwhile, the product was stable at high temperature of 130 °C, and compatible with common additives. The lubricity mechanism of JDLUB-1 was investigated by measuring the zeta potential, particle size distribution, adsorption, and anti-wear evaluation at extreme pressure. The results indicated that the positively charged lubricant oil droplets could be actively adsorbed onto the surface of N80 steel casing coupon. An adsorption film composed of oil soluble and spherical nano-silica and sulfur-phosphorus-molybdenum compounds was formed with a low melting point and low shear strength. During friction, the formation of molybdenum disulfide film leads to repair of the metal surface and formation of a stable sliding friction between the drill string and the wellbore with a low friction coefficient. The JDLUB-1 lubricant was successfully applied in several high-angle deviated wells and extended reach wells in Jidong oilfield (China). The results demonstrated that JDLUB-1 could effectively reduce torque and drag and show potential field application in the future