High-strength metakaolin-based hollow-core microspheres as an internal curing agent for mitigation of autogenous shrinkage of well cement

摘要

High-strength metakaolin-based hollow-core microspheres (HMHM), prepared by the combination of inverse suspension polymerization and high-temperature sintering, was proposed in this paper. The research objective was designed to utilize HMHM in the cement slurry to reduce autogenous shrinkage, without negatively affecting other properties of cement slurry. In this study, HMHM was developed and the liquid absorption and strength performance of HMHM were evaluated. And then the properties of cement slurry with different dosage of HMHM were investigated. The microstructure of hardened cement with HMHM was analyzed. Further, mitigation of autogenous shrinkage of well cement, with HMHM, was tested. Results showed that HMHM, with many pores on the shell, had the ability to absorb liquid and the liquid absorption ability is stable in cement slurry. The settlement stability of cement slurry with HMHM could be guaranteed by adding microsilica. HMHM can reduce the shear value of the cement slurry at high rotational speeds and increase the shear value at low rotational speeds. Due to the high strength of HMHM, when the dosage of HMHM is lower than 10%, with the increased dosage of HMHM, the compressive strength of hardened cement increases. The scanning electron microscope results showed that the interface between HMHM and the cement matrix was tight. Microscopic observation results showed that the hollow-core of HMHM still existed in hardened cement. HMHM could be used as the internal curing agent for oil well cement to reduce autogenous shrinkage. (C) 2020 Elsevier Ltd. All rights reserved.