Synthesis and Performance Evaluation of a Cement Retardant AID for Oil Well

Because the binary-copolymer cement retardant that is currently used has poor thermal stability, and the component acrylamide(AM) in terpolymer retardant tends to decompose at high temperature,the AM has been replaced with N,N-dimethylacrylamide(DMAM), and three monomers were selected, including 2-acrylamide-2-methyl acrylic acid(AMPS), itaconic acid(IA)and DMAM, by which a terpolymeric retardant AID was synthesized according to the polymerization principle of free radical aqueous solution.The structure and thermal stability of AID were analyzed by gel permeation chromatography (GPC), infrared (IR) spectrometry and thermal weight loss test, which evaluated the performance and the effect on cement compressive strength. Test results showed that AID had better thermal stability and it could resist 355 ℃, in which the mass ratio of AMPS, IA and DMAM was 10:4:1, the reaction temperature was 60 ℃,the dosage of the initiator was 2.0%, with excellent synthetic effect in the reaction time of five hours. The thickening time of the slurry with 0.5% AID is over two times of that without adding AID. When the AID quantity was the same, the slurry thickening time in the range of 90-150 ℃ was over 300 min, and the cement strength developed over 14 MPa. The studies showed that the retardant AIDcould extend the slurry thickening time significantly, and possess strong temperature adaptability, but have no obvious impact on the compressive strength of set cement, which indicates that it can be used widely in the future.