Gas hydrate saturation and distribution in the Kumano Forearc Basin of the Nankai Trough

Jihui Jia, Takeshi Tsuji, Toshifumi Matsuoka

研究成果: ジャーナルへの寄稿記事

10 引用 (Scopus)

抄録

The Kumano Forearc Basin is located to the south-east of the Kii Peninsula, Japan, overlying the accretionary prism in the Nankai Trough. The presence of gas hydrate in submarine sediments of the forearc basin has resulted in the widespread occurrence of bottom simulating reflectors (BSRs) on seismic profiles, and has caused distinct anomalies in logging data in the region. We estimated the in situ gas hydrate saturation from logging data by using three methods: effective rock physics models, Archie's equation, and empirical relationships between acoustic impedance (AI) and water-filled porosity. The results derived from rock physics models demonstrate that gas hydrates are attached to the grain surfaces of the rock matrix and are not floating in pore space. By applying the empirical relationships to the AI distribution derived from model-based AI inversion of the three-dimensional (3D) seismic data, we mapped the spatial distribution of hydrate saturation within the Kumano Basin and characterised locally concentrated gas hydrates. Based on the results, we propose two different mechanisms of free gas supply to explain the process of gas hydrate formation in the basin: (1) migration along inclined strata that dip landwards, and (2) migration through the faults or cracks generated by intensive tectonic movements of the accretionary prism. The dipping strata with relatively low AI in the forearc basin could indicate the presence of hydrate formation due to gas migration along the dipping strata. However, high hydrate concentration is observed at fault zones with high pore pressures, thus the second mechanism likely plays an important role in the genesis of gas hydrates in the Kumano Basin. Therefore, the tectonic activities in the accretionary wedge significantly influence the hydrate saturation and distribution in the Kumano Forearc Basin.

元の言語英語
ページ(範囲)137-150
ページ数14
ジャーナルExploration Geophysics
48
発行部数2
DOI
出版物ステータス出版済み - 6 2017

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forearc basin
gas hydrate
troughs
hydrates
trough
saturation
accretionary prism
acoustics
gases
acoustic impedance
strata
physics
basin
rock
rocks
tectonics
dipping
porosity
gas supply
prisms

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geology

これを引用

Gas hydrate saturation and distribution in the Kumano Forearc Basin of the Nankai Trough. / Jia, Jihui; Tsuji, Takeshi; Matsuoka, Toshifumi.

:: Exploration Geophysics, 巻 48, 番号 2, 06.2017, p. 137-150.

研究成果: ジャーナルへの寄稿記事

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