Visual Study of Methane Hydrate Effects on Permeability: Insights from a Microchip

Permeability is a crucial factor in the gas production of natural gas hydrates, significantly influenced by the saturation and distribution of hydrates. In this study, a high-pressure visual microchip system is developed that enables in situ observation of hydrate formation/dissociation while simultaneously measuring permeability. The experimental results demonstrate that hydrate morphology is strongly influenced by the initial gas–water distribution, leading to distinct permeability responses. Four contact patterns are identified: when gas bubbles are dispersed in the water phase, hydrates form around the bubbles; when small water droplets are dispersed in the gas phase, only limited hydrate forms on one side of each droplet; when extensive gas–water contact occurs, hydrates grow abundantly within the gas phase; when only water is present, no hydrate forms. Furthermore, a variation coefficient ( CV Sh ) is defined to characterize the spatial heterogeneity of hydrate saturation. During hydrate dissociation, permeability exhibits a two-stage behavior, with a gradual increase at the early stage followed by a rapid recovery at the later stage. This behavior is closely associated with the evolution of CV Sh, where increasing CV Sh indicates enhanced hydrate heterogeneity and suppresses the extent of permeability increase.