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

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 polycarboxylic acid 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 slurry 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 °C, NLPC can significantly reduce the consistency coefficient of cement slurry, increase the fluidity index of cement slurry, significantly improve the rheological properties of cement slurry, 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 slurry mainly through electrostatic repulsion and steric hindrance effect. In a word, NLPC overcomes the shortcomings of low efficiency and heavy pollution of SAF dispersant and the low applicable temperature of current polycarboxylic acid dispersant products, which is of great significance to ensure the smooth operation of high temperature deep well cementing and improve the cementing quality. Highlights: NLPC improves the temperature resistance of polycarboxylic dispersant. NLPC improves the rheological properties of oil well cement slurry at high temperature. The mechanism of NLPC is steric hindrance and electrostatic repulsion. NLPC has good compatibility with other oil well cement additives and has no adverse effect on the implementation of cementing engineering. [ABSTRACT FROM AUTHOR]