Choi Chae-Soon, Lee Yong-Ki, Song Jae-Joon
Department of Energy Resources Engineering, Research Institute of Energy and Resources, Seoul National University, Seoul 04750, Korea.
Materials (Basel). 2020 Jun 8;13(11):2619. doi: 10.3390/ma13112619.
Pore-scale modeling with a reconstructed rock microstructure has become a dominant technique for fluid flow characterization in rock thanks to technological improvements in X-ray computed tomography (CT) imaging. A new method for the construction of a pore channel model from micro-CT image analysis is suggested to improve computational efficiency by simplifying a highly complex pore structure. Ternary segmentation was applied through matching a pore volume experimentally measured by mercury intrusion porosimetry with a CT image voxel volume to distinguish regions denoted as "apparent" and "indistinct" pores. The developed pore channel model, with distinct domains of different pore phases, captures the pore shape dependence of flow in two dimensions and a tortuous flow path in three dimensions. All factors determining these geometric characteristics were identified by CT image analysis. Computation of an interaction flow regime with apparent and indistinct pore domains was conducted using both the Stokes and Brinkman equations. The coupling was successfully simulated and evaluated against the experimental results of permeability derived from Darcy's law. Reasonable agreement was found between the permeability derived from the pore channel model and that estimated experimentally. However, the model is still incapable of accurate flow modeling in very low-permeability rock. Direct numerical simulation in a computational domain with a complex pore space was also performed to compare its accuracy and efficiency with the pore channel model. Both schemes achieved reasonable results, but the pore channel model was more computationally efficient.
借助X射线计算机断层扫描（CT）成像技术的改进，利用重建的岩石微观结构进行孔隙尺度建模已成为表征岩石中流体流动的主要技术。本文提出了一种基于微观CT图像分析构建孔隙通道模型的新方法，通过简化高度复杂的孔隙结构来提高计算效率。通过将压汞法实验测量的孔隙体积与CT图像体素体积进行匹配，应用三元分割来区分“明显”孔隙和“不明显”孔隙区域。所开发的孔隙通道模型具有不同孔隙相的不同区域，能够捕捉二维流动中孔隙形状的依赖性以及三维中的曲折流动路径。通过CT图像分析确定了所有决定这些几何特征的因素。使用斯托克斯方程和布林克曼方程对明显孔隙域和不明显孔隙域的相互作用流态进行了计算。成功模拟了耦合过程，并根据达西定律得出的渗透率实验结果进行了评估。孔隙通道模型得出的渗透率与实验估计值之间发现了合理的一致性。然而，该模型在极低渗透率岩石中仍无法进行精确的流动建模。还在具有复杂孔隙空间的计算域中进行了直接数值模拟，以将其精度和效率与孔隙通道模型进行比较。两种方案都取得了合理的结果，但孔隙通道模型的计算效率更高。
