Phase change composite materials of sodium alginate-SiO2 aerogel loaded with sodium sulfate decahydrate for cementing of natural gas hydrate layers

Currently, the encapsulated organic phase change materials (PCMs) used in cementing slurries for NGH layers have problems such as difficulty in realizing applications, poor compatibility with cement slurries after leakage, and contamination of the environment at the bottom of the well. Furthermore, there is a dearth of perceptive investigation about the impact of PCMs on the hydration mechanism of cement. This study presents a new idea of using inorganic hydrated salt PCMs to control the heat released of cementing slurries during the hydration process. For the first time, sodium sulfate decahydrate-type composite inorganic hydrated salt PCMs (FH) loaded with SA-SiO₂ were synthesized and analyzed. The effect of FH on cement hydration mechanism was investigated and the changes of cement hydration products were analyzed qualitatively and quantitatively. The results showed the phase transition temperature of FH varied between 20.83 and 43.45 ℃, accompanied with a significant latent heat of phase change of 117.93 J/g. This attribute has the capacity to greatly reduce the rise in temperature during the process of cement hydration and the overall total release of heat. FH did not modify the cement hydration mechanism, but it extended the NG stage and reduced the hydration effect of the I stage, resulting in an increased level of hydration. FH improves the hydration procedure for cement, resulting in an augmented production of calcium-silicate-hydrate (C-S-H) compounds and enhances the compaction and arrangement the C-S-H. The inclusion of FH in the cement slurry did not lead to the dissociation of NGH during the hydration process.