Microfluidic study of hydrate propagation during CO2 injection into cold aquifers

• Hydrate propagation during CO 2 injection is studied in a cold microfluidic system. • CO 2 injection reduces spatial randomness and shortens the hydrate induction time. • CO 2 hydrate propagation in porous media shows a collective cascade behavior. • The growth rate of CO 2 hydrate depends on subcooling and increases with saturation. Understanding the interplay between hydrate formation and CO 2 injection is crucial for advancing submarine carbon sequestration, yet it remains underexplored. This study employs a high-pressure, low-temperature microfluidic system to investigate hydrate formation and propagation during CO 2 injection in porous media. This approach enables direct visualization of pore-scale and chip-scale hydrate formation dynamics across thousands of pores, offering critical insights into large-scale submarine CO 2 storage processes. We systematically assess the effects of injection rate, temperature (1.1–9.4 °C), and pressure (6.9–13.8 MPa) on hydrate formation kinetics. CO 2 injection reduces spatial stochasticity, with nucleation occurring primarily near the injection zone due to localized subcooling. Hydrate propagation follows a cascade mechanism over a broad saturation range (9–94%). Two key parameters—induction time and propagation velocity—are identified: induction time decreases with higher injection rates, while propagation velocity remains stable. Propagation velocity follows a power-law dependence on subcooling (exponent=2) but is diminished in porous media due to the effects of tortuosity and CO 2 saturation degree. Pressure variations have minimal influence on hydrate growth, confirming that subcooling is the dominant factor controlling hydrate formation kinetics. Our findings suggest potential injection strategies for CO 2 storage as hydrates in submarine environments.