Impact of Particle Size on Gas Hydrate Formation in Porous Media under Dynamic Porous Flow

Methane migration and transformation in marine environments constitute a critical pathway within the global carbon cycle, where hydrate formation serves as a pivotal physical carbon sequestration mechanism to capture submarine methane seepage. Despite its significance, the dynamics of hydrate formation and its consequent impacts on fluid transport behaviors within porous media under active methane seepage conditions remain poorly understood. This study systematically investigated methane hydrate formation mechanisms in variable-sized porous media (150–840 μm particle diameters) through real-time visualization using X-ray computed tomography. Quantitative analysis revealed particle size exerts dual control over gas migration channel evolution and hydrate formation efficiency. In the 158–178 μm small-particle system, high flow resistance leads to the formation of macroscopic preferential channels. Hydrates grew along the channel walls, forming a solidified framework that enhanced the fluid migration but limited further hydrate formation due to the limited surface area. In contrast, the 710–840 μm large-particle system had lower flow resistance and gas displaces the liquid between particles formed a multibranch microchannel network. Although the permeability was only 1/10 of the small-particle system, the abundant gas–liquid interfaces promoted the formation of hydrate, resulting in 1.65 times more hydrate. These findings highlight the complex influence of particle size on gas transport mechanisms and hydrate formation, offering valuable insights for gas migration models and hydrate-related studies.