| abstract |
The present invention relates to new compositions and methods of preparation of deflocculents for water-base mud additives. The disclosed materials are low molecular weight terpolymers and graft copolymers consisting essentially of monovalent salts of (1) 5 to 50% by weight of tetrahydrophthalic acid (THPA); (2) 10 to 70% by weight of acrylic acid (AA); (3) 5 to 50% by weight of 2-acrylamido-2-methylpropane sulfonic acid (AMPS); and (4) 0 to 70% by weight of lignosulfonate units. The unique compositions and processes of terpolymers and graft copolymers provide excellent drilling fluid additives which significantly control the viscosity, yield point, gel strength, and fluid loss of drilling fluids over a wide range of temperatures and in the presence of contaminants such as salt, lime, cement, gypsum and drilled solids. |