synthesis and use of amphoteric carboxymethylcellulose graft copolymers in the environmentally-acceptable water-based drillingfluids as a water-sensitive shale stabilizer

water soluble amphoteric graft copolymers of polysaccharide were synthesized via grafting of cationic monomer onto the sodium carboxymethylcellulose ()cmc)( and then used as a shale stabilizer in the water-based drilling fluids. accordingly, five types of cmc-graft copolymers with different ratios of acrylamide am)( and diallyldimethylammonium chloride dadmac)( were synthesized. grafting of monomer()s)( onto the cmc was verified by ft-ir spectroscopy. results showed that grafting percentage is strongly affected by the monomer type as well as the weight ratio of monomers. synthesized cmc-graft copolymers were used in the formulation of water-based drilling fluid. drilling fluid was then subjected to the rheological, fluid loss and shale recovery tests. it was found that ability of cmc in the shale stability enhances by grafting of cationic monomer onto cmc. fluid loss is also controlled in the acceptable region in the presence of cmc-graft copolymers. among graft copolymers, cmc-grafted with pure cationic monomer exhibited higher efficiency in the fluid loss control and more important in the shale stability.