One-Step Process of Mixed Oleic Acid Esters and Its High Temperature Lubrication Properties in Bentonite Gelling Suspension

In recent years, with the increase in requirements for horizontal wells, ultra-high depth wells, small wells and branching wells, it has become increasingly important to deal with the conflict between drilling safety and bottomhole friction. In order to meet the requirements of complex boreholes and deepwater drilling processes, it is crucial to improve the performance of ester-based lubricants. Oleic acid esters are relatively stable and have high lubricity at low temperature, however, these can be hydrolyzed at high temperature. However, the structure of carboxylic acids and alcohols can significantly affect the performance of synthetic esters. In order to solve the problem of balancing the high-temperature performance and low temperature performance of oleic acid esters with different structures, we propose a new oleic acid esterification process. After mixing methanol and ethylene glycol, it is reacted with oleic acid, and the mixed oleate prepared is named MEO-21, and the optimal esterification conditions are obtained as follows: the reaction time is 3 h, the reaction temperature is 150 °C, and concentrated sulfuric acid is the catalyst. MEO-21 not only achieves an extreme pressure lubrication coefficient reduction rate (Δf) of 86.57% at room temperature, but maintains a stable performance after hot rolling at high temperatures. Hot rolling at 150 °C for 16 h, Δf was 85.25%, hot rolling at 180 °C for 16 h, Δf was 89.56%. MEO-21 was used as a base oil with other industrial by-product oils to compound and produce a high-temperature-resistant lubricant that was named L-541, L-541′s Δf was 90.39% at room temperature. L-541 was hot-rolling at 120 °C, 150 °C and 180 °C for 16 h, the Δf was stabled at 89%.