Aperture Field Anisotropy Control on Immiscible Displacement Patterns in Rough Fractures

IF 4.6 1区 地球科学 Q2 ENVIRONMENTAL SCIENCES
Kun Xing, Xiaoqing Shi, Zhibing Yang, Xueyuan Kang, Siyuan Qiang, Jichun Wu
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引用次数: 0

Abstract

Two-phase flow displacement in rock fractures is crucial for various subsurface mass transfer processes and engineering applications. In fractures, the displacement of a less viscous fluid by a more viscous one (i.e., viscosity ratio M > 1) involves viscous forces help stabilizing the displacement front in presence of capillary pressure fluctuations. Although previous studies have reported displacement patterns in isotropic fractures, the impact of anisotropic fractures on displacement patterns has not been systematically examined. In this study, we conducted flow-rate-controlled drainage experiments to examine how anisotropic aperture fields affect displacement patterns. We observed the transition of displacement patterns from capillary fingering (CF) to crossover zone (CZ) to compact displacement pattern (CD) based on variations in transverse pore-filling event (TPFE) frequency, which characterizes the competition between capillary and viscous forces. Increasing aperture correlation length in the transverse direction leads to increased TPFE frequency at a low flow rate, destabilizing displacement front. While the increasing aperture correlation length in longitudinal direction suppressed TPFE frequency, stabilizing displacement front. Therefore, the critical capillary number (CaCF-CZ), which indicates the onset of the CF-CZ transition, decreases as the aperture field varies from transversely to longitudinally correlated. At high flow rates, TPFEs almost disappeared, indicating that anisotropy did not affect CZ-CD transition (CaCZ-CD). Furthermore, we modified theoretical models of CaCF-CZ and CaCZ-CD by incorporating the aperture anisotropy factor, achieving a good fit with the experimental data. This study demonstrates the critical role of aperture field anisotropy in controlling two-phase displacement patterns and provides a theoretical framework for predicting multiphase flow behavior in natural fractures.
孔场各向异性控制粗糙断裂中的不溶位移模式
岩石裂缝中的两相流动位移对于各种地下传质过程和工程应用至关重要。在裂缝中,粘度较低的流体被粘度较高的流体(即粘度比 M > 1)位移时,粘滞力有助于在毛细管压力波动的情况下稳定位移前沿。尽管之前的研究已经报道了各向同性裂缝的位移模式,但尚未系统研究各向异性裂缝对位移模式的影响。在本研究中,我们进行了流速控制排水实验,以研究各向异性孔场如何影响位移模式。根据横向孔隙充填事件(TPFE)频率的变化,我们观察到了位移模式从毛细指状(CF)到交叉区(CZ)再到紧密位移模式(CD)的转变过程。增加横向孔径相关长度会导致低流速下的 TPFE 频率增加,从而破坏位移前沿的稳定性。而纵向孔径相关长度的增加会抑制 TPFE 频率,使位移前沿趋于稳定。因此,表示 CF-CZ 过渡开始的临界毛细管数(CaCF-CZ)会随着孔径场从横向相关到纵向相关的变化而降低。在高流速下,TPFE 几乎消失,这表明各向异性并不影响 CZ-CD 过渡(CaCZ-CD)。此外,我们修改了 CaCF-CZ 和 CaCZ-CD 的理论模型,加入了孔径各向异性因子,与实验数据实现了很好的拟合。这项研究证明了孔场各向异性在控制两相位移模式中的关键作用,并为预测天然裂缝中的多相流行为提供了一个理论框架。
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来源期刊
Water Resources Research
Water Resources Research 环境科学-湖沼学
CiteScore
8.80
自引率
13.00%
发文量
599
审稿时长
3.5 months
期刊介绍: Water Resources Research (WRR) is an interdisciplinary journal that focuses on hydrology and water resources. It publishes original research in the natural and social sciences of water. It emphasizes the role of water in the Earth system, including physical, chemical, biological, and ecological processes in water resources research and management, including social, policy, and public health implications. It encompasses observational, experimental, theoretical, analytical, numerical, and data-driven approaches that advance the science of water and its management. Submissions are evaluated for their novelty, accuracy, significance, and broader implications of the findings.
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