Preparation and characterization of a novel amphoteric polymer for oil well cementing with superior performances

A novel amphoteric polymer TH-1 was synthesized using the monomers of 2-acrylamido-2-methylpropane sulfonic acid, acrylic acid, acrylamide, and cationic monomer through radical copolymerization as filtrate loss reducer in oil well cementing. Optimal synthesis conditions of TH-1 were obtained by an orthogonal experiment. The composition of copolymer (TH-1) was characterized by Fourier-transform infrared spectrum and proton nuclear magnetic resonance spectroscopy. The thermal stability of the synthesized copolymer was tested by thermogravimetric analysis. The fluid loss (FL) control and thickening performance of cement slurry incorporating TH-1 were evaluated at different temperatures. The filtration reduction mechanism of TH-1 was finally discussed. Results suggest that the amphoteric polymer is the target product polymerized by all the monomers, which presents excellent filtrate reduction property, high thermal stability, and strong saline tolerance under 200°C. The amphoteric polymer TH-1 includes cationic and anionic group in a molecule structure, which can adsorb firmly onto the surface of cement particles through electrostatic attraction and form adsorption membrane of viscoelastic polymer. In this way, compact cement filter cakes are formed, thereby efficiently reducing the FL.