Dynamics and Morphology of CO ₂ Hydrate Growth: Implications for CO ₂ Transport and Storage

The safe transportation of carbon dioxide (CO2) is paramount for Carbon Capture, Utilization, and Storage (CCUS). The ubiquitous presence of water with CO2 naturally leads to CO2 hydrates, which pose flow assurance risks through potential accumulation and blockage. This study investigated the distinct growth and morphology of CO2 hydrates in vapor (277.2 K, 3.6 MPa) and liquid (277.2 K, 6.0 MPa) phases under controlled laboratory conditions. We report a higher extent of hydrate formation in liquid CO2 than in vapor. Notably, CO2 hydrates from both phases demonstrated volume expansion, reaching over three times the initial water volume in liquid CO2 under the tested conditions. This expansion is attributed to a porous morphology and capillary-driven water transport along wall surfaces. Cryo-scanning electron microscopy revealed that hydrates formed in liquid CO2 possessed larger pores and surface domes compared to those formed in the vapor phase. We propose a mechanism for this abnormal swelling: the high buoyancy of liquid CO2 provides a strong driving force for water to spread along the wall, while larger capillaries remain open longer. These findings suggest potential implications for flow assurance within the experimental scope and indicate the need for further investigation into management strategies for CCUS infrastructure.