Salt-Resistant Lubricant for Deep Water Drilling Fluids

In deepwater drilling, drilling fluids are affected by seawater, highly mineralized brine, and polyvalent metal ions. Conventional lubricants such as mineral oils, vegetable oils, and fatty acids often exhibit poor dispersion and incompatibility in high salinity environments,separating out as oily or cheese like pastes, which reduces or even eliminates the lubricating performance of the drilling fluid. Currently, there are limited efficient lubricants in China suitable for brine-based drilling fluids, making it difficult to meet the demands of deepwater operations.To address this issue, this study reviews and analyzes international research progress on high performance water-based drilling fluids and salt-resistant lubricants for deepwater drilling. Laboratory evaluations were conducted on six lubricants with different compositions. The results show that all of them suffer from poor compatibility and fail to meet the required lubrication coefficient standards in seawater-based fluids.Based on these findings, a high-efficiency lubricant suitable for brine drilling fluids was developed using long-chain modified fatty acid esters compounded with non-ionic surfactants. This lubricant demonstrates good compatibility with seawater and brine-based fluids, with no separation of oily or cheese-like substances. It can reduce the lubrication coefficient of seawater-based fluids prepared with inorganic and organic salts to below 0.10. After hot rolling at 185℃, no oily material separates on the surface of the slurry, and the lubricating performance remains stable. Additionally, the lubricant does not cause foaming, does not affect the rheological properties of the drilling fluid, is environmentally friendly, has low biotoxicity, and does not harm the marine environment.