Morphology of Gas Bubbles in Mud: A Microcomputed Tomographic Evaluation
Morphology of Gas Bubbles in Mud: A Microcomputed Tomographic Evaluation
复制标题
泥浆中气泡的形态：微计算机断层扫描评估
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Y. Furukawa
中科院分区：
文献类型：
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作者：
A. Reed;B. Boudreau;C. Algar;Y. Furukawa
摘要：表层沉积物中的游离气通常会形成气泡，这些气泡会衰减和衰减声波，影响边坡的稳定性，并导致温室气体浓度升高。因此，确定控制气泡形状、大小、生长和迁移的机制对声学沉积物表征和其他学科非常重要。以前，气泡的形状、大小和分布是使用“低分辨率”(~500微米)医学计算机断层扫描(CT)来量化的。最近，“高分辨率”(至30微米。在几个MR岩心中，气泡形成为垂直取向的扁平球体，其SAR值约为1.6(长宽比为5：1)，而在其他MR岩心中，气泡形成横跨岩心宽度的拉长裂缝，因此无法准确确定SAR。在CH泥浆中，当空气通过毛细管递增注入时，形成的气泡为扁球形(即硬币形)，其SAR为~5.0(长宽比为30：1)。气泡的形状(即SAR)和取向似乎与沉积物的物理性质和局部非均质性有关。XMCT图像显示，气泡是通过断裂力学而不是沉积物的弹性膨胀来生长的。图像还显示，气泡的大小是医学CT无法分辨的，而且通常是随着主轴垂直方向生长的。XMCT能够表征比之前评估的气泡小得多的气泡，从而进一步加深了我们对气泡形成和生长的机理的理解。
Abstract : Free gas in surficial sediments commonly forms gas bubbles that attenuate and dampen acoustic waves, influence slope stability, and contribute to greenhouse gas concentrations. Therefore, determining the mechanisms that control bubble shape, size, growth, and migration is important to acoustic sediment characterization and other disciplines. Previously, gas bubble shape, size, and distribution was quantified using "low-resolution" (~500 micron) medical computed tomography (CT). Recently, "high-resolution" (to 30 microns. In several MR cores, gas bubbles formed as vertically oriented oblate spheroids with SARs of ~1.6 (5:1 ratio of length to width), yet in other MR cores, gas bubbles formed elongated fractures that spanned the core width, consequently, a SAR could not be accurately determined. In the CH mud, a gas bubble formed as an oblate spheroid (i.e., coin-shape) with a SAR of ~5.0 (30:1 ratio of length to width) as air was injected incrementally through a capillary tube. It appears that bubble shape (i.e., SAR) and orientation are correlated with sediment physical properties and localized heterogeneity. XMCT images show that gas bubbles grow by fracture mechanics rather than by elastic expansion of the sediments. The images also show that the bubbles exist at sizes that are not resolvable with medical CT and often grow with the principal axis oriented vertically. XMCT has enabled the characterization of gas bubbles that are significantly smaller than those evaluated previously, thus furthering our mechanistic understanding of gas bubble formation and growth.