Review of hydrate-bearing sediment permeability for natural gas hydrate exploitation: Measurement and application development

Natural gas hydrate-bearing sediment permeability, which influences the flow behavior of fluids, is a key physical parameter used to determine the exploitation efficiency of hydrate. However, no comprehensive overview of existing research related to its measurement and application development has been conducted to date. In this review, the related advances in sediment permeability are systematically summarized in terms of experiments, models, numerical simulations, and its influence on hydrate exploitation. The sediment permeability measurement and their influencing factors have been comprehensively analyzed. In particular, the effects of hydrate phase transition on sediment permeability are discussed in detail. In addition, the normalized models of sediment permeability and numerical simulations of sediment structure are investigated. However, no universal normalized models of sediment permeability and numerical simulation of hydrate phase transition are available. The mechanism by which sediment permeability magnitude and anisotropy influence the hydrate exploitation efficiency has also been discussed. Finally, future efforts should focus on dynamic evolution, highprecision measurement, multifactor coupling effect, generalization of models, and optimization of numerical simulations, which are beneficial to improve guidance for the commercial exploitation of hydrate.