Salinity-Sediment Interactions Governing CO₂ Hydrate Formation, Kinetics and Stability in Marine Environments

Area of Science:

• Geochemistry
• Marine Geology
• Chemical Engineering

Background:

• Carbon dioxide (CO2) sequestration in marine gas hydrates is a key climate change mitigation strategy.
• Salinity in marine environments can inhibit CO2 hydrate formation and stability.
• Natural sediments play a crucial role in hydrate formation and storage.

Purpose of the Study:

• To investigate the combined effects of salinity and natural sand on CO2 hydrate formation, dissociation, and stability.
• To compare hydrate behavior in gas-water systems versus gas-water-sand systems under varying pressures and salinity.
• To understand the role of Adriatic Sea sand in CO2 sequestration via hydrates.

Main Methods:

• Experimental investigation using a 1 L high-pressure reactor.
• Systematic comparison of binary gas-water and three-phase gas-water-sand systems.
• Testing with and without 3 wt% NaCl salinity at 25 and 35 bar.

Main Results:

• Natural sand significantly mitigates salinity-induced inhibition, increasing hydrate density and water utilization in saline systems.
• Pressure controls the overall CO2 hydrate formation rate, with sand transitioning growth from bulk to pore-controlled at higher pressures.
• Salinity dictates dissociation rates, while sand modifies CO2 release patterns by altering hydrate distribution within pores.

Conclusions:

• Natural sand enhances CO2 hydrate formation and stability in saline marine conditions, partially compensating for salinity inhibition.
• Sand influences hydrate kinetics and morphology, shifting stability towards less restrictive conditions.
• The findings support the potential of using natural sediments for effective marine CO2 sequestration through gas hydrates.