Preparation of hydrated calcium silicate phase change microcapsules and its application of temperature regulation in deep-water natural gas hydrate layer cementing process.

The effective hydration of cement at low temperatures is a critical factor affecting the sealing stability of the cement sheath. Effective hydration of cement slurry is typically accompanied by significant exotherm, and can cause the decomposition of natural gas hydrates, ultimately leading to gas migration and affecting cementing quality. To ensure effective hydration with low exothermic cement slurry, hydrated calcium silicate (C-S-H) shell phase change microcapsules (TDCSH) were prepared by oil-in-water emulsification with chemical precipitation. Compared with traditional phase change microcapsule with polymer shell, the rough C-S-H shell with large surface area improves the thermal conductive area of the microcapsules and their compatibility with the cement composition. Results showed that the TDCSH has a high phase change enthalpy of 169.9 J/g and 65.25% encapsulate efficiency compared to other inorganic shell materials. Furthermore, the addition of 3% TDCSH can reduce the hydration temperature of cement by 3.9°C and increase the compressive strength by 19.0% under the curing condition of 20°C. The mechanism of action of microcapsules in cement was analyzed. The results showed that the incorporation of TDCSH reduced the heat of hydration of cement while promoting the generation of more hydration products and increased the compressive strength of cement. [Display omitted] • Microencapsulated thermal control material containing hydrated calcium silicate was designed and synthesized. • Hydrated calcium silicate promotes effective hydration of cement slurry at low temperatures. • Rough surface of microcapsules improves interfacial bonding with cement components. • The cement's early compressive strength is increased and its heat of hydration is concurrently lowered by the microcapsules. [ABSTRACT FROM AUTHOR]