Study on synthesis of temperature resistant polycarboxylic acid dispersant and its application in oil well cement

Abstract

Abstract Polycarboxylic acid dispersant has the advantages of good dispersion performance and environmental protection, and has a good application prospect in oil well cement. However, the current polycarboxylate dispersant has poor temperature resistance, which limits its application in high temperature formation cementing. In this study, a polycarboxylic acid dispersant (NLPC) that can be applied to high temperature cementing was synthesized by free radical copolymerization of monomer isoprenol polyoxyethylene ether, maleic acid, 2-acrylamido-2-methylpropanesulfonic acid and N-vinyl-2-pyrrolidone. The structure of NLPC was characterized by Fourier transform infrared spectroscopy, gel permeation chromatography and 1H nuclear magnetic resonance spectroscopy. The effects of NLPC on the fluidity, rheological properties, thickening time and mechanical strength of cement paste at different temperatures were tested, and compared with the traditional sulfonated acetone-formaldehyde polycondensate (SAF) dispersant. The mechanism of dispersant and its effect on cement hydration behavior were systematically studied by total organic carbon, Zeta potential, particle size analysis, thermogravimetric analysis and X-ray diffraction analysis. The effect of dispersant on the microstructure of hardened cement was analyzed by scanning electron microscopy. The results show that NLPC has excellent high temperature dispersion performance. At 150 ℃, NLPC can significantly reduce the consistency coefficient of cement paste, increase the fluidity index of cement paste, significantly improve the rheological properties of cement paste, and the paste has excellent thickening performance, and the initial consistency is lower than SAF. In addition, due to the good dispersion of cement particles by NLPC, the early mechanical strength of cement stone after solidification is also improved. The mechanism analysis shows that NLPC improves the dispersion performance of oil well cement paste mainly through electrostatic repulsion and steric hindrance effect. In short, NLPC overcomes the shortcomings of low efficiency and heavy pollution of SAF dispersant and low applicable temperature of conventional polycarboxylic acid dispersant, and ensures the smooth progress of high temperature deep well cementing construction.