Volume 324, Part A, 15 September 2022, 124436

Full Length Article
Evolution of hydrate habit and formation properties evolution during hydrate phase transition in fractured-porous medium

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Hydrate synthesis and decomposition occur simultaneously throughout phase transition process.

Hydrate growth habit is not monotonous change in fractured-porous medium sandstone at different stages of phase transition.

Hydrate occurences in fractured-porous medium differs from that in porous matrix system.

The preferential occurence of hydrates in fracture leads to significantly permeability changes.


Natural gas hydrate, as an efficient and clean energy resource, are naturally distributed in porous and fractured-porous medium. With the most recent development of advanced micro-scale imaging techniques, hydrate habits evolution, hydrate occurrences, and pore structure evolution as well as seepage characteristics during hydrate phase transition in porous hydrate-bearing sediments have been studied extensively at pore scale. However, there are few studies on gas hydrates in fractured-porous sediment. In this work, xenon hydrate phase transition experiment by excess-gas method is carried out in a fractured sandstone core with in-situ micro computed tomography (micro-CT) scanning to explore the evolution of hydrate habits and physical parameters of the host sediment. The results indicate that hydrate-bearing sediment is a dynamic equilibrium system as hydrate synthesis and decomposition occur simultaneously at each moment of hydrate phase transition induced by pressure change. The hydrate occurrences in fractured hydrate reservoirs include contiguous-sheet, clustered and isolated, which are slightly different from that of porous hydrate formation; and the contiguous-sheet hydrate is the occurrence that dominantly determines the seepage characteristics of fractured hydrate-bearing sediments. In addition, the logic diagram for hydrate growth paths in fractured-porous medium is presented for the first time. These findings are significant for detailed understanding of pore-scale hydrate distribution throughout phase transition process and provide theoretical basis for precise modeling of permeability in host sediments.


Hydrate Habit
Hydrate Morphology
Fractured-Porous Medium
Seepage Capacity

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