Development and Performance Evaluation of High Temperature Salt Resistant Drilling Lubricant

Using boric acid, polyols and long-chain fatty acids, a high temperature salt resistant drilling lubricant SOB has been developed to deal with high torque high friction encountered in deep and ultra-deep well drilling. SOB has good lubricity at high temperatures and high salinities. A 5% base mud treated with 1% SOB has its friction coefficient reduced by 92.7%, and the adhesion coefficient of the mud cake produced by that mud is reduced to 0.0405, meaning that SOB has a sustainable lubricity under extreme pressure condition. Percent reduction of friction coefficient at 210 ℃ is generally 90.2%, percent reduction of friction coefficient of a mud containing 35%NaCl at 210 ℃ is generally 81.3%. At high temperature and high salinity conditions, SOB has good compatibility with other components of a high density drilling fluid. After aging at 200 ℃, the rheology of the drilling fluid was not affected, the mud filtration rate can be reduced, and the coefficient of friction of the mud was reduced by 45.09%, meaning that SOB has better lubricity than conventional drilling lubricants. The reason for this phenomenon is that SOB can be effectively adsorbed on the surfaces of the drill strings, forming a layer of film with strong hydrophobicity. The existence of this film changes the direct contact between the drill strings and the borehole wall to a contact between two films of the lubricant, thereby effectively reducing the friction therebetween.