Temperature regulation effect of low melting point phase change microcapsules for cement slurry in nature gas hydrate-bearing sediments

Nature gas hydrates are only stable at low temperatures and high pressures; consequently, the hydration heat of cement slurry can easily decompose hydrates. Therefore, low-heat cement slurry systems need to be used during well cementing in nature gas hydrate-bearing sediments. In this study, temperature-regulated microcapsules having binary alkanes as the core material and CaCO3 as the shell were prepared by self-assembly. In addition, the hydrophobic modified graphite was added into core material to improve the temperature sensitivity. The morphology, thermal properties, and hydrophilicity of the microcapsules were characterized by multiple techniques. The hydration property, setting behavior, pore distribution and compressive strength of cement slurry/stone containing the microcapsules was studied. Furthermore, the effect of cement slurry hydration on hydrate-bearing sediments was tracked by a hydrate-bearing sediment-damage simulation device. The results demonstrated that the microcapsules have good temperature regulating properties. The addition of modified graphite increased the sensitivity of the microcapsules to temperature changes. Compared to the standard group, the maximum hydration temperature of the cement slurry decreased by 3.7 °C upon the addition of microcapsules. The simulation trail showed that the addition of microcapsules impeded the damage to hydrate-bearing sediments that were associated with the hydration of the cement slurry.