Synthesis and Application of a New High Temperature High Performance Salt Resistant Shale Inhibitor

Quaternary ammonium salts and cationic inhibitive agents presently used are not strong enough in shale inhibition, Polyamine (such as JY-1), although strong enough, has deficiencies in molecular stability and high temperature tolerance. To improve the molecular stability and high temperature tolerance of polyamine inhibitive agents, a high temperature salt resistant low molecular weight polyamine, JY-2, was synthesized, based on the profiling and re-design of molecular structure of JY-1. The optimum synthesis condition of JY-2 is as follows:reaction temperature 220-240℃, reaction time 4-5 h, catalyst concentration 0.10%, molar ratio of monomer B and a polyhydric alcohol 1:1.8, reducing agent concentration 1.0%. IR spectroscopy showed that the actual molecular structure of JY-2 is conforming to the designed molecular structure, containing secondary amine and tertiary amine groups. JY-2 has moderate molecular weight (508 g/mol), is nontoxic and contains no weak ether bonds. Laboratory analyses recommended that the molecular formula of JY-2 should be C₂₃H₆₆N₇O₄.JY-2 has inhibitive capacity similar to that of polyamines produced abroad, and is much more inhibitive than those presently used in China. JY-2 has good long-time inhibitive performance, and good compatibility with other additives used in fresh water base and saltwater base drilling fluids. Optimum treatment of JY-2 is 0.5%-1.0%. Water base drilling fluid using JY-2 as the main additive has been used the well Gu693-104-Ping104 in Daqing, solving the extremely water sensitive shale and clay stones of the Nenjiang Formation and Yaojia Formation. Percent of hole enlargement (hole section drilled with the JY-2 mud) was only 7.1%, and ROP was 7.11 m/h. Study and field application show that JY-2 has outstanding inhibitive capacity, good molecular stability and is tolerant to high temperatures to 180℃, and can be used in drilling highly water sensitive shale formations.