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 (CVSh) 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 CVSh, where increasing CVSh indicates enhanced hydrate heterogeneity and suppresses the extent of permeability increase.