The
memory effect of hydrate reformation has an important influence
on the hydrate growth mechanism and technological applications. This
paper focuses on the relation between the morphologies and memory
effects of hydrate reformation and the stability of the memory effect
using a visual research method. The results indicated that the hydrate
morphology differed between the first formation and the reformation.
A specific flocculated hydrate was observed only in the process of
hydrate reformation. Moreover, the flocculated hydrate was unstable,
and it was observed to first grow and then shrink. In this study,
the free water was observed to also become turbid during hydrate dissociation.
In addition, many gaps were generated during hydrate dissociation,
which affected the hydrate dissociation efficiency and the geological
safety of hydrate exploitation. The effects of the dissociation temperature
and pressure difference on the stability of the memory effects were
investigated. The results showed that the memory effect tended to
be stable in the closed and heating dissociation patterns. Furthermore,
depressurization significantly inhibited the memory effect of hydrate
reformation. After depressurization, the induction time of first hydrate
formation was increased 4-fold compared with the induction time before
depressurization. The experimental results are well explained by the
mechanism of dissolved gas remaining in solution after hydrate dissociation.
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