FLUID LOSS CONTROL AGENTS FOR DRILLING FLUIDS CONTAINING DIVALENT CATIONS

摘要

Low and high solids drilling fluids containing high levels (i.e., at least 10,000 ppm) of divalent cations are provided with improved fluid loss control by employing high molecular weight water-in-oil emulsion copolymers of acrylamide and a water soluble salt of acrylic acid. The copolymers, produced by the copolymerization in water-in-oil emulsion form of acrylamide and acrylic acid or the salt thereof in molar ratios of 70:30 to 95:5, are particularly effective in drilling fluids containing high levels of calcium ions.