{"title":"Projection–Subtraction X-ray Imaging Scheme for Studying Fast Fluid-Dynamics Processes in Porous Media","authors":"","doi":"10.1007/s11242-023-02055-8","DOIUrl":null,"url":null,"abstract":"<h3>Abstract</h3> <p>Imaging of fluid flow at the pore scale in permeable media requires high spatial resolution to observe the topology of fluid in the pore system, along with high temporal resolution to study dynamic processes. The two most popular imaging techniques in modern experiments are microfluidic device imaging and X-ray micro-computed tomography, both having significant limitations as applied to the micro-level. In particular, microfluidic experiments examine flow in quasi-2D system of pores instead of natural 3D geometry of permeable media, whereas X-ray computed tomography (reconstruction of a 3D object representation from a set of 2D projections collected at different rotation angles) is considerably slow when studying fast pore-scale events. In this work, we present a novel approach to examination of local fluid dynamics by combining traditional fast X-ray microtomography and radiographic analysis of successive projections. After initial tomographic imaging of the 3D pore structure, we perform projection-wise analysis comparing differences between two successive projections. As a result, we obtain flow visualization with time resolution determined by the projection time, which is orders of magnitude faster than standard microtomographic scan time. To confirm the effectiveness of this approach, we investigate the pore-scale mechanisms of unstable water migration that occurs during gas-hydrate formation in coal media. We first show that the displacement of brine by methane gas due to cryogenic suction can lead to multiple snap-off events of brine flow in pores. Second, we study a fast local drainage process accompanied by the formation of the gradually swelling gas bubble in the center of the pore. The measured maximum interfacial velocity in our experiments varies from 1.3 to 5.2 mm/s. We also simulate this outflow process accompanied by the bubble expansion and estimate the average brine flow rate during brine-methane displacement.</p>","PeriodicalId":804,"journal":{"name":"Transport in Porous Media","volume":null,"pages":null},"PeriodicalIF":2.7000,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Transport in Porous Media","FirstCategoryId":"5","ListUrlMain":"https://doi.org/10.1007/s11242-023-02055-8","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Imaging of fluid flow at the pore scale in permeable media requires high spatial resolution to observe the topology of fluid in the pore system, along with high temporal resolution to study dynamic processes. The two most popular imaging techniques in modern experiments are microfluidic device imaging and X-ray micro-computed tomography, both having significant limitations as applied to the micro-level. In particular, microfluidic experiments examine flow in quasi-2D system of pores instead of natural 3D geometry of permeable media, whereas X-ray computed tomography (reconstruction of a 3D object representation from a set of 2D projections collected at different rotation angles) is considerably slow when studying fast pore-scale events. In this work, we present a novel approach to examination of local fluid dynamics by combining traditional fast X-ray microtomography and radiographic analysis of successive projections. After initial tomographic imaging of the 3D pore structure, we perform projection-wise analysis comparing differences between two successive projections. As a result, we obtain flow visualization with time resolution determined by the projection time, which is orders of magnitude faster than standard microtomographic scan time. To confirm the effectiveness of this approach, we investigate the pore-scale mechanisms of unstable water migration that occurs during gas-hydrate formation in coal media. We first show that the displacement of brine by methane gas due to cryogenic suction can lead to multiple snap-off events of brine flow in pores. Second, we study a fast local drainage process accompanied by the formation of the gradually swelling gas bubble in the center of the pore. The measured maximum interfacial velocity in our experiments varies from 1.3 to 5.2 mm/s. We also simulate this outflow process accompanied by the bubble expansion and estimate the average brine flow rate during brine-methane displacement.
摘要 对渗透介质中孔隙尺度的流体流动进行成像需要高空间分辨率来观察孔隙系统中流体的拓扑结构，同时还需要高时间分辨率来研究动态过程。现代实验中最常用的两种成像技术是微流体设备成像和 X 射线显微计算机断层扫描，这两种技术在微观层面的应用都有很大的局限性。特别是，微流体实验检查的是准二维孔隙系统中的流动，而不是渗透介质的自然三维几何形状，而 X 射线计算机断层扫描（从一组在不同旋转角度收集的二维投影重建三维物体表示）在研究快速孔隙尺度事件时速度相当慢。在这项工作中，我们结合传统的快速 X 射线显微层析成像和连续投影的射线分析，提出了一种检查局部流体动力学的新方法。在对三维孔隙结构进行初始层析成像后，我们进行投影分析，比较两个连续投影之间的差异。因此，我们获得了流动可视化，其时间分辨率由投影时间决定，比标准微断层扫描时间快了几个数量级。为了证实这种方法的有效性，我们研究了煤介质中瓦斯-水合物形成过程中不稳定水迁移的孔隙尺度机制。我们首先证明了甲烷气体在低温抽吸作用下对盐水的置换会导致盐水在孔隙中发生多次断流。其次，我们研究了伴随着孔隙中心逐渐膨胀的气泡形成的快速局部排水过程。实验中测得的最大界面速度为 1.3 至 5.2 mm/s。我们还模拟了伴随气泡膨胀的流出过程，并估算了盐水-甲烷置换过程中的平均盐水流速。
期刊介绍：
-Publishes original research on physical, chemical, and biological aspects of transport in porous media-
Papers on porous media research may originate in various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering)-
Emphasizes theory, (numerical) modelling, laboratory work, and non-routine applications-
Publishes work of a fundamental nature, of interest to a wide readership, that provides novel insight into porous media processes-
Expanded in 2007 from 12 to 15 issues per year.
Transport in Porous Media publishes original research on physical and chemical aspects of transport phenomena in rigid and deformable porous media. These phenomena, occurring in single and multiphase flow in porous domains, can be governed by extensive quantities such as mass of a fluid phase, mass of component of a phase, momentum, or energy. Moreover, porous medium deformations can be induced by the transport phenomena, by chemical and electro-chemical activities such as swelling, or by external loading through forces and displacements. These porous media phenomena may be studied by researchers from various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering).
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