Pak Tannaz, Rabbani Harris Sajjad, Qaseminejad Raeini Ali, Shokri Nima
Engineering Department, Teesside University, Middlesbrough TS1 3BX, U.K.
Department of Petroleum Engineering, Texas A&M University at Qatar, Education City, Doha 23874, Qatar.
ACS Omega. 2023 Jan 22;8(4):3889-3895. doi: 10.1021/acsomega.2c06295. eCollection 2023 Jan 31.
Advances in computational and image acquisition capabilities have made direct simulation of multiphase fluid flow through porous media possible. An example is application of volume of fluid modeling on images produced using the X-ray computed micro-tomography technique. Analysis of such high-resolution (both temporal and spatial) data sets provides new insights into pore-scale dynamics of previously less well-known processes. We present the outcomes of a high-resolution direct-simulation two-phase fluid displacement study performed on a series of five two-dimensional images of sandy porous media produced using erosion and dilation algorithms. This has enabled us to study the pore-scale dynamics systematically in models that are similar in connectivity but different in the morphology (pore sizes and aspect ratio). Our results show that the drainage and imbibition processes result in very distinct fluid displacement patterns in these models at the pore scale. As a result of drainage, the more open (eroded grains) models accommodate large oil clusters, while the tighter (dilated grains) models trap smaller oil clusters. The imbibition process is dominated by oil trapping in two ways: (i) bypassing larger oil clusters in the eroded models and (ii) local trapping of smaller clusters in the dilated models. This behavior is shown to arise from the relatively larger average aspect ratios of the dilated models compared to those of the eroded models. This promotes snap-off at pore throats (in competition with piston-like displacement), resulting in local trapping of the non-wetting phase. Both of these pore-scale trapping regimes seen here allow trapping of oil in as much as 50% of the pore space. Through the use of erosion and dilation operations, we show that a power-law relationship exists between the average pore size and the average grain size for these sandy media. This relationship is useful in designing engineered porous materials where pore sizes need to be estimated based on grain sizes.
计算能力和图像采集能力的进步使得直接模拟多相流体在多孔介质中的流动成为可能。一个例子是将流体体积建模应用于使用X射线计算机显微断层扫描技术生成的图像。对这种高分辨率（时间和空间）数据集的分析为以前了解较少的过程的孔隙尺度动力学提供了新的见解。我们展示了一项高分辨率直接模拟两相流体驱替研究的结果，该研究是对使用侵蚀和扩张算法生成的一系列五个二维砂质多孔介质图像进行的。这使我们能够在连通性相似但形态（孔径和纵横比）不同的模型中系统地研究孔隙尺度动力学。我们的结果表明，在这些模型的孔隙尺度上，排水和吸渗过程导致非常不同的流体驱替模式。由于排水，更开放（侵蚀颗粒）的模型容纳大的油团簇，而更致密（扩张颗粒）的模型捕获较小的油团簇。吸渗过程以两种方式受油捕集主导：（i）在侵蚀模型中绕过较大的油团簇，（ii）在扩张模型中局部捕集较小的油团簇。这种行为被证明是由于扩张模型的平均纵横比相对于侵蚀模型相对较大。这促进了孔隙喉部的液桥断裂（与活塞式驱替竞争），导致非润湿相的局部捕集。这里看到的这两种孔隙尺度捕集机制都允许在多达50%的孔隙空间中捕集油。通过使用侵蚀和扩张操作，我们表明这些砂质介质的平均孔径和平均颗粒尺寸之间存在幂律关系。这种关系在设计需要根据颗粒尺寸估计孔径的工程多孔材料时很有用。
