Representative Elementary Volumes, Hysteresis, and Heterogeneity in Multiphase Flow From the Pore to Continuum Scale
Representative Elementary Volumes, Hysteresis, and Heterogeneity in Multiphase Flow From the Pore to Continuum Scale
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DOI：
10.1029/2019wr026396
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发表时间：
2020-06-01
影响因子：
5.4
通讯作者：
Krevor, S.
中科院分区：
文献类型：
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作者：
Jackson, S. J.;Lin, Q.;Krevor, S.
代表性基本体积和非均质性是连续多相流中的关键概念，但它们在孔隙尺度上的表现及其对流态的影响还不是很清楚。我们使用多尺度实验和模拟方法来阐明转速、滞后和非均质性在两种不同的水润湿本特海默砂岩中的多相流中的作用。在稳态排水和渗吸过程中进行的实验观察发现，孔隙空间为6微米，视场最大可达12×12×65毫米，同时测量流体流动过程中的压差。两个样品的孔隙率和毛细管压力的REV约为2 mm(3)，相对不确定度为5%。相反，由于宏观毛细压力的非均质性，饱和度的REV在3.4mM到157.5 mm(3)之间变化，这取决于分流。对这种REV不确定性的准确了解对于评估连续尺度模型的有效性和预测性至关重要。我们通过预测在均匀介质的REV不确定性范围内的多个渗吸状态下观察到的非润湿流体的连通性，直接验证了Land陷阱模型。这样，当考虑连通饱和度时，测量的相对渗透率中观察到的滞后被完全消除，验证了基于连通路径流的概念滞后模型。结果表明，毛管压力中的REV尺度非均质性对流动和圈闭特征有影响；当建立具有滞后的三维连续尺度数值模型时，我们能够预测不同非均质结构的两个样品之间的圈闭和相对渗透率的变化。本文的实验数据集为未来连续尺度建模框架的发展提供了一个很好的基准。
Representative elementary volumes (REVs) and heterogeneity are key concepts in continuum multiphase flow, yet their manifestation from the pore-scale and associated impacts with the flow regime are not well understood. We use a multi-scale experimental and modeling approach to elucidate the role of REVs, hysteresis, and heterogeneity in multiphase flow in two distinct water-wetting Bentheimer sandstones. Experimental observations during steady-state drainage and imbibition resolve the pore space at 6 mu m across a field of view up to 12 x12x 65 mm with simultaneous measurements of differential pressure during fluid flow. The REV for porosity and capillary pressure is approximate to 2 mm(3) for both samples, with 5% relative uncertainty. In contrast, due to macroscopic capillary pressure heterogeneities, the REV for saturation varies between 3.4 and 157.5 mm(3), dependent on the fractional flow. Accurate knowledge of this REV uncertainty is critical in assessing continuum scale model validity and predictiveness. We validate the Land trapping model directly by predicting observed non-wetting fluid connectivity at multiple imbibition states to within the REV uncertainty for homogeneous media. With this, observed hysteresis in the measured relative permeability is entirely removed when considering the connected saturation, validating conceptual hysteresis models based on connected pathway flow. REV scale heterogeneities in capillary pressure are shown to impact flow and trapping characteristics; when built into 3D continuum scale numerical models with hysteresis we are able to predict the variations in trapping and relative permeability observed between the two samples with different heterogeneity structures. The experimental data set herein provides an excellent benchmark for future development of continuum scale modeling frameworks.