Synthesis and characterization of a quaternary copolymer retarder for cementing in a long sealing section with large temperature difference

Abstract

Because of the contradiction between the safe thickening time of cement slurry and over-retarding at the top in the cementing of a long sealing section with large temperature difference, we synthesized a quaternary copolymerization retarder with 2-acrylamide-2-methyl propane sulfonic acid (AMPS), acrylic acid (AA), diallyl dimethyl ammonium chloride (DMDAAC) and allyl polyoxyethylene ether (APEG). The structure of the retarder was characterized by FTIR and ¹H NMR and its thermal stability was tested by TG-DSC. The results showed that the molecule contained the designed functional groups, the initial pyrolysis temperature was 364 °C, and its performance was stable in the temperature range of 90–150 °C. There was no “bulge” or “step” on the thickening curve, and the thickening time could meet the safety requirements of pumping at high temperatures. It can also ensure the development of compressive strength of cement in the low-temperature section and has excellent temperature adaptability. Through the study of its retardation mechanism, it was found that the retarder molecules formed an adsorption layer of a certain thickness on the surface of cement particles by adsorption, and the concentration of Ca²⁺ in the solution was reduced by complexation, so as to prevent cement hydration and prolong the thickening time. Generally speaking, the large temperature difference adaptability of retarders was mainly manifested in the decrease of molecular adsorption capacity and performance at low-temperature and the improvement of molecular adsorption capacity and performance at high-temperature.