| 講演要旨(和文) | | ガス気泡を含む地層水中を伝播する音波速度は、気泡の振動によって周波数依存性を持ち, 地層水中を伝播する音波に対しガス気泡が共振する事によって高音波速度異常が発生する. 速度の周波数依存性は個々の気泡の大きさ, 及び全体に占めるガス飽和度によって決定される. ゆえに音波速度と周波数を定量的に把握できれば, 複数周波数を用いた地層音波速度計測によって地層水中のガス飽和度を推定することが可能となる. 本研究では, 液体中の気泡の振動特性, 気泡を含む地層水中の音波速度の周波数依存性と気泡の体積, 飽和度の関係を, 共振周波数を考慮しつつ理論的, 数値的に明らかにし, 高音波速度異常を利用して, 地層水中のガス飽和度の推定手法を開発した. |
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| | 講演要旨(英文) | | Sonic velocities in liquids that contain gas bubbles have frequency dependency because of the oscillation of the bubbles. High sonic velocity anomaly could be observed when the bubbles resonate against incident sonic waves near the resonant frequencies. The frequency dependence of sonic velocity depends on gas saturation and bubble sizes. Therefore it becomes possible to estimate gas saturation in formation water using multi-frequency sonic velocity measurements if we know sonic velocity and its frequency. In this study, we showed the oscillation property of bubbles in liquids for estimating the relationship between the frequency dependency of sonic velocity and the gas saturation of formation water that contains gas bubbles, considering the resonance frequency of gas bubbles theoretically and numerically. These results suggest that a method could be applied to estimate the gas saturation in formation water using the high sonic velocity anomalies. |
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