Development Of Wideband Retarder And Long Sealing Cement Slurry System

With the development of oilfields, more and longer formations are needed to be sealed. Low density cement slurry are usually used to cement in one time under such situation. However, cement curing time of the top cement slurry is much longer than the bottom, and the possibility of leakage and gas channeling is higher. This article develops a kind of wideband retarder and long sealing cement slurry system to solve such problems.Based on radical polymerization and mechanism of dominate functional groups, AMPS and maleic are selected as complex monomer, ammonium persulfate and sodium bisulfite as initiator. Results shows that synthetic polymer has the lowest temperature sensitivity when the ratio of AMPS and maleic is 3:1. According to orthogonal experiment, the synthesis conditions of wideband retarder are as following: the ratio of monomer (AMPS and maleic) is 3:1; initiator concentration is 0.5%; reaction temperature is 45℃; pH value is six. The effects of factors on the retarder AS is ordered as followed: temperature> pH value> initiator concentration. This polymer can be demonstrated as the binary copolymer of AMPS and maleic by the infrared spectroscopic analysis. Experiment on cement slurry performance shows that the retarder has good retardation performance and low temperature sensitivity, and has good compatibility with other cement additive. Therefore, this can solve the problem that cement curing time of the top cement slurry is much longer than the bottom.In order to cement long segment, this article composites quaternary low density cement slurry system with a density of 1.38g/cm~3 using this wideband retarder AS as main agent. This cement slurry has good rheology, with rational thickening time and low water loss, whose density can be changed from 1.20 to 1.28 g/cm~3. Experiment results show that cement slurry have good performance and can meet cementing operation requirements.