Development of An Epoxy Phosphate Retarder and A High Temperature Cement Slurry Resistant to 220 °C

In designing the molecular structures of cement slurry retarders, monomers with the target groups are selected to produce retarders which can control the thickening time of oil well cement slurries at stable values at temperatures above 200 °C. The molecular structure is designed on the basis of functional structure of the polymers. A high temperature penta-polymer retarder NPAAS-1 is developed based on the molecular structure design clue with five monomers, which are AMPS, SAS, NVP, AM and epoxypropyl phosphate. Characterization of the molecular structure of NPAAS-1 shows that the final product is the expected product. Weight loss on heating of NPAAS-1 at 300 °C is only 22.30%. NPASS-1 has good retarding capacity at temperatures above 200 °C, and the thickening time of the cement slurry is in a linear relationship with the concentration of NPSSA-1. A cement slurry of moderate density working normally at 220 °C was formulated with NPAAS-1 as the retarder, HTFLA-A as the filter loss reducer, HTDA-6 as the dispersant and HTSA-2 as the suspending agent. At concentration of 3.5% NPAAS-1, the thickening time of the cement slurry is 297 min; while at concentration of 4.5%, the thickening time becomes 530 min. Using this retarder NPAAS-1, the hydration speed of cement can be effectively controlled at ultra-high temperatures.