Novel lignosulfonate/N,N‐dimethylacrylamide/γ‐methacryloxypropyl trimethoxy silane graft copolymer as a filtration reducer for water‐based drilling fluids

ABSTRACT The redox system consisting of ammonium persulfate and sodium bisulfite was used as initiator, N , N ‐dimethylacrylamide (DMAA) and γ‐methacryloxypropyl trimethoxy silane (KH570) were grafted onto sodium lignosulfonate (LS) in aqueous solution as reaction monomers, and a novel LS/KH570/DMAA graft copolymer filtrate reducer was synthesized. The structure of the copolymer was characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance instrument. The result revealed that DMAA and KH570 were successfully grafted onto sodium LS. In addition, the thermal stability of the copolymer was determined by thermogravimetric analyzer and the micromorphology of filter cake of water‐based drilling fluids (WBDFs) containing LS/KH570/DMAA was analyzed by scanning electron microscopy. At the same time, the rheological and filtration properties of WBDFs containing copolymer with different concentrations were further evaluated. The results showed that when the copolymer concentration was 3 wt %, the fluid loss of bentonite‐based drilling fluids was only 6.2 mL before aging, and 9.8 mL after aging at 180 °C for 16 h. The fluid‐loss control mechanism of LS/KH570/DMAA was investigated through clay particle distribution analysis and zeta potential measurement of WBDFs. Moreover, the WBDFs containing copolymer exhibit excellent performance in reducing fluid loss under the invasion of calcium salts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48274.