Patent ID: 7842652

Claim:
A well cement composition comprising: cement, water, and a fluid loss control additive comprising a graft copolymer, the graft copolymer comprising: a backbone comprising a humic acid salt, a first grafted monomer comprising at least one monomer selected from the group consisting of 2-acrylamido-2-methylpropanesulfonic acid, salts thereof and combinations thereof, a second grafted monomer comprising acrylamide, a third grafted monomer comprising at least one monomer selected from the group consisting of acrylic acid, salts thereof, and combinations thereof, and a fourth grafted monomer comprising diallyldimethylammonium chloride, and wherein the graft copolymer has a first grafted monomer-second grafted monomer-third grafted monomer-fourth grafted monomer mole ratio in the range of about 4:3:2:1 to about 4:1:0.5:0.1.