Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades. Exploring an efficient CO

2

storage method can significantly reduce CO

2

emissions in the short term. In this study

we attempted to construct sediment samples with different residual CH

4

hydrate amounts and reservoir conditions

and then investigate the potentials of both CO

2

storage and enhanced CH

4

recovery in depleted gas hydrate deposits in the permafrost and ocean zones

respectively. The results demonstrate that CO

2

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 CO

2

storage efficiency. Affected by the

T-P

conditions of the reservoir

the storage amount of liquid CO

2

can reach 8 times that of gaseous CO

2

and CO

2

stored in hydrate form reaches 2-4 times. Additionally

we noticed two other advantages of this method. One is that CO

2

injection can enhance CH

4

recovery rate and increases CH

4

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 great

ly promising for high-efficient CO

2

storage and safe exploitation of gas hydrate.