New water-soluble ampholytic polysaccharides for oilfield drilling treatment: a preliminary study

New water-soluble ampholytic polysaccharides with carboxybetaine groups, which were prepared by grafting the zwitterionic monomer 2(2-methacryloethyldimethylammonio)ethanoate onto hydroxyethyl cellulose, have been tested for their properties as a multifunctional drilling-mud additive regarding clay hydration inhibition and mud rheological control. For the ampholytic polysaccharides investigated, an increase in carboxybetaine groups results in an enhanced inhibitive ability and the pH of the medium has an effect on the inhibition. A strong viscosifying efficiency for low-solid muds, especially for saline mud, has been observed. (C) 2001 Elsevier Science Ltd. All rights reserved.