In the long-term exploitation of natural gas hydrate, the stress change intensifies the creep effect and leads to the destruction of pore structures, which makes it difficult to predict the permeability of hydrate reservoir. Although permeability is crucial to optimize gas recovery for gas hydrate reservoirs, until now, accurately modeling the permeability of hydrate-bearing clayey-silty sediments during the creep process remains a significant challenge. In this study, by combining the nonlinear fractional-order constitutive model and the Kozeny-Carman (KC) equation, a novel creep model for predicting the permeability of hydrate-bearing clayey-silty sediments has been proposed. In addition, experimental tests have been conducted to validate the derived model. The proposed model is further validated against other available test data. When the yield function F < 0, the permeability decreases gradually due to the shrinkage of pore space. However, when the yield function F ≥ 0, the penetrating damage bands will be generated. Results show that, once the model parameters are determined appropriately by fitting the test data, the model can also be used to predict permeability under any other stress conditions. This study has a certain guiding significance for elucidating the permeability evolution mechanisms of hydrate-bearing clayey-silty sediments during the extraction of marine gas hydrates.

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Keywords: Hydrate-bearing clayey-silty sediments, Creep behaviors, Permeability, Fractional-order constitutive model