Synthesis and retarder mechanism study of a novel amphoteric composite high temperature-resistant retarder for oil well cement.

An amphoteric composite polymer (hereinafter referred to as PAADM) as a high temperature-resistant cement retarder was prepared by intercalated polymerization method with 2-crylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA) and two diallyl dimethyl ammonium chloride (DMDAAC) as monomers, and modified montmorillonite as an active polymerization filler. The synthetic composite polymer was characterized by Fourier transform infrared spectroscopy (FT-IR), H nuclear magnetic resonance (H-NMR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results of the aforementioned characterization showed that the synthesized copolymer (PAADM) has an intercalation/exfoliation composite structure and excellent thermal stability. Performance evaluation evidenced that the cement slurry containing PAADM has good retarding property in the range of 120-200 °C, and demonstrated the rapid development of compressive strength under high temperature and low temperature conditions, this property could guarantee that the retarder PAADM could be applied to the construction of deep wells and long interval wells. Moreover, the retarding mechanism of PAADM was studied through calcium binding capacity, adsorption amount, zeta potential, XRD and SEM analysis, and it was found that "adsorption deposition" and "calcium complexation" should be responsible for this retarder delaying the hydration process of cement grains.