Abstract: Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades. Exploring an efficient CO₂ storage method can significantly reduce CO₂ emissions in the short term. In this study, we attempted to construct sediment samples with different residual CH₄ hydrate amounts and reservoir conditions, and then investigate the potentials of both CO₂ storage and enhanced CH₄ recovery in depleted gas hydrate deposits in the permafrost and ocean zones, respectively. The results demonstrate that CO₂ hydrate formation rate can be significantly improved due to the presence of residual hydrate seeds; However, excessive residual hydrates in turn lead to the decrease in CO₂ storage efficiency. Affected by the T-P conditions of the reservoir, the storage amount of liquid CO₂ can reach 8 times that of gaseous CO₂, and CO₂ stored in hydrate form reaches 2-4 times. Additionally, we noticed two other advantages of this method. One is that CO₂ injection can enhance CH₄ recovery rate and increases CH₄ recovery by 10%-20%. The second is that hydrate saturation in the reservoir can be restored to 20%-40%, which means that the solid volume of the reservoir avoids serious shrinkage. Obviously, this is crucial for protecting the goaf stability. In summary, this approach is greatly promising for high-efficient CO₂ storage and safe exploitation of gas hydrate.

Key words: Hydrate, Depressurization, CO₂ storage, CH₄ production, Reservoir remediation

摘要： Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades. Exploring an efficient CO₂ storage method can significantly reduce CO₂ emissions in the short term. In this study, we attempted to construct sediment samples with different residual CH₄ hydrate amounts and reservoir conditions, and then investigate the potentials of both CO₂ storage and enhanced CH₄ recovery in depleted gas hydrate deposits in the permafrost and ocean zones, respectively. The results demonstrate that CO₂ hydrate formation rate can be significantly improved due to the presence of residual hydrate seeds; However, excessive residual hydrates in turn lead to the decrease in CO₂ storage efficiency. Affected by the T-P conditions of the reservoir, the storage amount of liquid CO₂ can reach 8 times that of gaseous CO₂, and CO₂ stored in hydrate form reaches 2-4 times. Additionally, we noticed two other advantages of this method. One is that CO₂ injection can enhance CH₄ recovery rate and increases CH₄ recovery by 10%-20%. The second is that hydrate saturation in the reservoir can be restored to 20%-40%, which means that the solid volume of the reservoir avoids serious shrinkage. Obviously, this is crucial for protecting the goaf stability. In summary, this approach is greatly promising for high-efficient CO₂ storage and safe exploitation of gas hydrate.

关键词: Hydrate, Depressurization, CO₂ storage, CH₄ production, Reservoir remediation