メタンハイドレートを胚胎する砂質堆積物の特徴とメタンハイドレート胚胎メカニズムへの影響 Features of Methane Hydrate-bearing Sandy-sediments of the Forearc Basin along the Nankai Trough : Effect on Methane Hydrate-Accumulating Mechanism in Turbidite

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著者

    • 鈴木 清史 SUZUKI Kiyofumi
    • 独立行政法人産業技術総合研究所メタンハイドレート研究センター Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST)
    • 海老沼 孝郎 EBINUMA Takao
    • 独立行政法人産業技術総合研究所メタンハイドレート研究センター Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST)
    • 成田 英夫 NARITA Hideo
    • 独立行政法人産業技術総合研究所メタンハイドレート研究センター Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST)

抄録

 Methane hydrate-bearing sediments taken by a Pressure Temperature Core Sampler (PTCS), were recovered from the NE-Nankai Trough to clarify the accumulating mechanisms whereby methane hydrate accumulates in pore spaces. The sediments were of the sand and mud alternation layer, which were turbidities and hemi-pelagic mud, respectively. Their sediment features such as grain size, porosity, and methane hydrate saturation of pore spaces were analyzed systematically.<br> Relationships among grain size distribution, Bouma's sequence and hydrocarbon gas volume produced by methane hydrate dissociation were confirmed, thus we understood the correspondence of the features of turbidities features and methane hydrate saturation; <i>i.e.</i>, we understood that the part of high methane hydrate saturation had a porosity of 50-55%, median of 1.9-3.3φ, and grain sorting of from -1.4 to -0.4. These features indicate the lower section of turbidite called as Ta and/or Tb. Other sections of turbidite had small amounts of methane hydrate.<br> From these results, we estimated that only permeable sections could maintain the accumulation of methane hydrate from first to last stage. If their pores had been filled with gas-saturated water and the pressure/temperature condition was sufficient for methane hydrate, the methane hydrate would precipitate homogeneously in sediments from its initial accumulation. However, methane hydrate precipitation reduces permeability because methane hydrate growth in pores causes a reduction of pore volume. During accumulation, it is inevitable that gas-rich fluid could not reach into low permeable layers, although it could still be supplied into high permeable layers. This mechanism does not need any cap rock or some trap system in sediments, and it is quite a different mechanism from conventional oil and gas accumulation.

収録刊行物

  • 地學雜誌

    地學雜誌 118(5), 899-912, 2009-10-25

    Tokyo Geographical Society

参考文献:  13件中 1-13件 を表示

被引用文献:  6件中 1-6件 を表示

各種コード

  • NII論文ID(NAID)
    10030366575
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    0022135X
  • NDL 記事登録ID
    10503756
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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