第三紀堆積岩を用いたガスと水の浸透係数の比較と Klinkenberg 効果  [in Japanese] Comparison of Nitrogen Gas and Water Permeabilities in Tertiary Sedimentary Rocks in the Light of Klinkenberg Effects  [in Japanese]

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Abstract

地下深部におけるガスの浸透係数は, 天然ガスの貯留・移動問題を解明するうえで重要な水理パラメータである. また, ガスで求めた固有浸透係数を水の固有浸透係数として代用する場合と, 水-ガスの二相流問題を解析する場合においてガスと水の固有浸透係数の違いおよび各々の特徴を把握する必要がある.<BR>本研究では, 室温高封圧下の有効圧サイクル試験により, 同一試料におけるガスと水の固有浸透係数の測定および比較を行った. いずれの試料においてもガスの固有浸透係数は水の固有浸透係数に比べて2~10倍ほど高い値を示し, また強い間隙圧依存性を示した. 固有浸透係数はサイクル数および有効圧の増加とともに減少していったが, その減少量はガスと水の固有浸透係数の差に比べて非常に小さかった. ガスの固有浸透係数の間隙圧依存性を表すKlinkenberg効果をもとに水の固有浸透係数を推定すると, 実際に測定した水の固有浸透係数とほぼ同じ値を示した. このことはガスと水の固有浸透係数の違いがKlinkenberg効果によることを示唆する. とくに固有浸透係数が10<SUP>-18</SUP>mm<SUP>2</SUP>より低い場合かつ間隙差圧が0.3MPaより低い条件下でガスの固有浸透係数を測定した場合には, Klinkenberg効果によるガスと水の固有浸透係数の違いは無視できなくなる.

Knowing the difference between gas and water permeabilities is significant not only for solving gas-water two-phase flow problems, but also for quick measurements of permeability using gas as pore fluid. We have thus measured intrinsic permeability of porous sedimentary rocks from Western Foothills of Taiwan, using nitrogen gas and water as pore fluids, during several effective-pressure cycling tests at room temperature. The observed difference in gas and water permeabilities have been analyzed in view of the Klinkenberg effect. This effect is primarily due to slip flow of gas at pore walls which enhances gas flow when pore sizes are very small. Experimental results show (1) that gas permeability is larger than water permeability by several times to one order of magnitude, (2) that gas permeability increases with increasing pore pressure, and (3) that water permeability slightly increases with increasing pore-pressure gradient across the specimen. The results (1) and (2) can be explained by the Klinkenberg effect quantitatively with an empirical power law for the Klinkenberg constant. Thus water permeability can be estimated from gas permeability. The Klinkenberg effect is important when permeability is lower than 10<SUP>-18</SUP> mm<SUP>2</SUP> and at low differential pore pressures, and its correction is essential for estimating water permeability from the measurement of gas permeability. A simple Bingham-flow model of pore water with a fixed pore size can explain the overall trend of the result (3) above. More sophisticated models with a pore-size distribution and with realistic rheology of water film is needed to account for the observed deviation from Darcy's law, i. e., the dependence of water permeability on the pore-pressure gradient.

Journal

  • Journal of the Japan Society of Engineering Geology

    Journal of the Japan Society of Engineering Geology 47(3), 131-139, 2006-08-10

    Japan Society of Engineering Geology

References:  17

Codes

  • NII Article ID (NAID)
    110004793108
  • NII NACSIS-CAT ID (NCID)
    AN00026635
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    02867737
  • NDL Article ID
    8067558
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-263
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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