AMPS/DMAM/FA-A Graft Copolymer Humic Acid Fluid Loss Reducer for Well Cementing

A high temperature cement slurry fluid loss reducer, G85L, was synthesized with 2-acrylamido-2-methyl propane sulfonic acid (AMPS), N,N-dimethylacrylamide (DMAM) and fumaric acid (FA) through radical polymerization under the following conditions:AMPS:DMAM:FA=1:0.38:0.08, mass ratio of total monomers to sodium humate=1:0.2, initiation temperature 60℃, and pH (of the monomer solution)=7. G85L was a viscous black liquid containing 20% solids. Analysis of the residual monomers and IR characterization showed that the synthesized product was a graft copolymer, and thermogravimetric analysis indicted that the property of the G85L remained stable at 265℃. Filtration experiment (done in accordance with API RP 10B-2 2013) demonstrated that addition of 4%G85L reduced filter loss of cement slurry to 40 mL at low temperatures, and to less than 50 mL at 200℃. No evidences of side effect of G85L on the thickening time and compressive strength of cement slurry have been observed during experiments. G85L shows good compatibility with many cement slurry formulations and is a universal high temperature filter loss reducer for cement slurries.