Permeability Measurements Using Oscillation Method and an Application for Deformed Rock Specimen

  • TAKAHASHI Miki
    Japan National Oil Corporation, present at Institute of Geoscience, National Institute of Advanced Industrial Science and Technology(AIST)
  • KANEKO Takanobu
    Geocsience Research Laboratory Co., Ltd.

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Other Title
  • 間隙圧オシレーション法による浸透率・比貯留率測定方法と岩石の変形試料に対する適用例
  • カンゲキアツ オシレーションホウ ニ ヨル シントウリツ ヒ チョリュウリツ ソクテイ ホウホウ ト ガンセキ ノ ヘンケイ シリョウ ニ タイスル テキヨウ レイ

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Abstract

Oscillation method is one of the most instructive methods to evaluate lower permeability and storage capacity coincidently. Constant sinusoidal pore pressure changes at upstream side of the specimen give rise to a response of sinusoidal pressure changes at downstream reservoir with amplitude attenuation and phase retardation. By measuring the attenuation and the retardation, the permeability and the storage capacity can be calculated. If the specimen has lower permeability, the pressure of downstream reservoir responds smaller amplitude and larger retardation against pressure wave at upstream reservoir. The usual graphical analysis estimates how the range of the attenuation and the retardation measured can produce most accurate values of permeability and storage capacity respectively. The most accurate value of the permeability can be required at 0.08 of attenuation and -87° of retardation, and that of the storage capacity is at 0.12 of attenuation and -117° of retardation. However, the graphical analysis is inefficient because of requires lot of data set of permeability and storage capacity. Then, we developed a calculation program to increase the calculation efficiency by using the iterated Newton method.<BR>As examples, we investigate the permeability and the storage capacity changes while a fault in sandstone entrained low-permeable siltstone along sandstone surface during the sliding. To obtain the amplitude and the phase of both pressure waves of upstream and downstream reservoirs, Fourier transform was adopted. This Fourier analysis occurs periodic errors with twice frequency of the oscillation test on the data of the amplitude attenuation and the phase retardation. These periodic errors on the attenuation and the retardation induced more 2 orders of magnitude variations on the result of storage capacity when the attenuation and the retardation are lower. With these reductions, the variation of storage capacity becomes less than one order of magnitude. On the other hand, the permeability resulted from the oscillation method is independent on the pressure conditions and the accuracy is higher than that of the storage capacity.

Journal

  • Shigen-to-Sozai

    Shigen-to-Sozai 119 (8), 501-507, 2003

    The Mining and Materials Processing Institute of Japan

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