Carbon Dioxide Hydrate Formation in Porous Media Under Dynamic Conditions for CO₂ Storage in Low-Temperature Water Zones

Abstract

Injecting carbon dioxide (CO2) into subsea water zones, where the in situ temperatures are below the hydrate-forming temperature of CO2, has been recently proposed to lock CO2 inside the water zones in a solid hydrate form. It is a common concern that CO2 may form hydrates during the injection period, which would reduce well injectivity. CO2 injection into sandstone cores under simulated subsea temperatures ranging from 0 °C to 5 °C was investigated in this study. Experimental results show that flowing CO2 at Darcy velocity 0.033 cm/s begins to form hydrate in the sandstone core at dynamic pressures higher than the minimum required pressure under static conditions. At temperatures changing from 0 °C to 5 °C, the observed hydrate-forming pressure changes from 1.87 to 2.5 times the pressures required for CO2 hydrates under static conditions. The reason why the required minimum pressure for CO2 to form hydrates in dynamic conditions is higher than that in static conditions is attributed to the shear rate effect of flowing fluids that should slow down the growth of hydrate crystals and/or break down formed hydrate films in the dynamic conditions. Therefore, higher pressure energy, or fugacity, is required to promote the growth of hydrate crystals and hydrate films in dynamic conditions. More rigorous investigations in this area are needed in the future.

Keywords

• CO₂
• subsea
• storage
• hydrate
• dynamic formation
• porous media