Methane Hydrate Behavior under High Pressure

Hisako Hirai, Tadashi Kondo, Masashi Hasegawa, Takehiko Yagi, Yoshitaka Yamamoto, Takeshi Komai, Kazushige Nagashima, Mami Sakashita, Hiroyuki Fujihisa, Katsutoshi Aoki

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)


Phases changes in a water-methane system were investigated in a pressure range from 0.2 to 5.5 GPa using a diamond anvil cell. In-situ X-ray diffractometry and optical microscopy revealed methane hydrate behavior from growth to decomposition into high-pressure ice and solid methane at room temperature. Methane hydrate crystallized at 0.2-0.3 GPa from liquid, and it was compressed continuously until 2.3 GPa, maintaining structure I. Below 0.7 GPa the cage occupancy was unchanged. At 1.5 GPa methane hydrate partly decomposed to ice IV and fluid methane. The remaining methane hydrate kept structure I, but the cage occupancy was changed; i.e., small cages became vacant. At 2.1 GPa, coexisting ice VI transformed to ice VII and fluid methane solidified to phase I, while methane hydrate remained. At this pressure, structure I of methane hydrate was still maintained, and an additional change of cage occupancy occurred. The change in the cage occupancy is consistent with the change in compressibility observed on the compression curve. At 2.3 GPa, all of the methane hydrate decomposed into ice VII and phase I of solid methane.

Original languageEnglish
Pages (from-to)1429-1433
Number of pages5
JournalJournal of Physical Chemistry B
Issue number7
Publication statusPublished - 2000 Feb 24
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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