Microencapsulated phase change material-cement composites for cementing the natural gas hydrate layer

•A MPCM suitable for cementing NGH layer was prepared.•The strength and hydration heat release of MPCM-cement composite were analyzed.•The action mechanism of MPCM on cement hydration was summarized.•The influence model of MPCM content on thermal stability of NGH was established. To cement natural gas hydrate (NGH) layers in the deep and ultra-deep water environment, cement slurries must display both low heat of hydration (HOH) and high early strength. Herein, chemical precipitation was used to prepare a microencapsulated phase change material (MPCM) comprising a core of phase change materials and a shell of silica. The MPCM could effectively control the temperature increase during cement hydration and improve the early strength of cement pastes by accelerating hardening. Comprehensive physical and chemical analyses were carried out to identify a suitable ratio of MPCM and its underlying mechanisms. A laboratory device was further used to test the effect of MPCM-cement composite slurries on the thermal stability of NGHs. The properties of this new cement slurry system meet the requirements for cementing NGH layers in deep and ultra-deep water areas. This cement composite has broad application potential in the oil and natural gas industry.