CO

2

hydrate-based sequestration in submarine sediments shows great potential for carbon emission reduction. Considering the proportional relationship of CO

2

and water for hydrates formation

their existing ratio largely determines the CO

2

sequestration density and phase state. Here

this work focuses on determining the optimal ratio of CO

2

to seawater in sediments simulated with 20-40 mesh (0.42-0.85 mm) quartz sand

in order to maximize CO

2

hydrate conversion in sediments. The results show that the conversion rate of CO

2

hydrate increases with the initial water saturation

reaching 15.3% at 80% initial water saturation. The optimal CO

2

hydrate formation occurs at 30% initial water saturation

with the corresponding CO

2

storage density in hydrate form of 33.09 kg·m

-3

and the hydrate saturation of 22.3%. However

CO

2

hydrate conversion rate is 10%

which implies that most CO

2

still exists in liquid state

despite the presence of free water. The total CO

2

sequestration density is negatively correlated with the initial water saturation

and at 10% initial water saturation

398.73 kg·m

-3

of CO

2

is sequestered

of which only 18.02 kg·m

-3

is hydrated. Additionally

the lower initial water saturation corresponds to the shorter time to achieve

t

90

of CO

2

consumption

and the

water conversion rate to hydrate reaches 90% at 10% initial water saturation. In summary

adjusting the volume ratio of liquid CO

2

to seawater can effectively increase the sequestration amount of CO

2

hydrates

but methods to increase CO

2

conversion to hydrate still need to be established.