This article explores the possibility to assess the flow and transport properties of loosely consolidated rock material—something that is very hard or impossible to achieve in the laboratory due to fragility of cores. We present two cases of weakly consolidated and unconsolidated rocks. We provide a solution based on pore-scale simulations and stochastic reconstructions using scanning electron (SEM) and grain optical microscopy images as input data. The hybrid reconstruction approach is based on 3D grain shape construction out of 2D optical images, packing of grains to match the target porosity measured from SEM imaging, and addition of clay and other cementing phases with the help of phase-recovery method. Note that standard digital rock protocol based on X-ray microtomography did not work for considered samples due to fine-grained particle size distribution (insufficient resolution of X-ray microtomography). After creation of 3D digital replicas of rock samples based on their SEM and optical microscopy images, we applied pore-scale modeling to obtain permeability and two-phase flow properties. Simulated permeability of 259 mD for the first sample was in surprisingly good agreement with laboratory measurements of 248 mD. For the second sample permeabilities deviated by an order of magnitude. After additional studies it was found that the mesh attached to the sample during measurements affected the results. After pore-scale simulations of the grain packing with the mesh we were able to achieve very good agreement with the experiment, confirming that the lab was basically exploring the properties of the mesh clogged with unconsolidated rock material. Thus, pore-scale hybrid rock structure reconstruction technique combined with pore-scale simulations was able to correct inaccurate laboratory assessment and obtain flow properties for unconsolidated rock sample. We believe the developed hybrid reconstruction technique to be robust enough to serve as a basis of the industrial technology for petrophysical studies of weakly and unconsolidated core material.

中文翻译：

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孔隙尺度模拟有助于克服松散岩石材料的实验室限制：基于扫描电子和光学显微镜数据的多步重建


本文探讨了评估松散固结岩石材料的流动和传输特性的可能性，由于岩心的脆弱性，这在实验室中很难或不可能实现。我们提出了弱固结和松散岩石的两种情况。我们提供基于孔隙尺度模拟和随机重建的解决方案，使用扫描电子 (SEM) 和颗粒光学显微镜图像作为输入数据。混合重建方法基于 2D 光学图像的 3D 颗粒形状构建、颗粒堆积以匹配 SEM 成像测量的目标孔隙度，以及借助相恢复方法添加粘土和其他胶结相。请注意，由于细粒度的粒度分布（X 射线显微断层扫描的分辨率不足），基于 X 射线显微断层扫描的标准数字岩石协议不适用于所考虑的样品。根据 SEM 和光学显微镜图像创建岩石样本的 3D 数字复制品后，我们应用孔隙尺度建模来获得渗透率和两相流特性。第一个样品的模拟渗透性为 259 mD，与实验室测量的 248 mD 惊人地一致。对于第二个样品，渗透率偏差了一个数量级。经过进一步的研究发现，测量过程中附着在样品上的网格会影响结果。在用网格对颗粒堆积进行孔隙尺度模拟后，我们能够与实验取得非常好的一致性，证实实验室基本上正在探索被松散岩石材料堵塞的网格的特性。 因此，孔隙尺度混合岩石结构重建技术与孔隙尺度模拟相结合，能够纠正不准确的实验室评估并获得松散岩石样品的流动特性。我们相信，所开发的混合重建技术足够强大，可以作为弱松散岩心材料岩石物理研究的工业技术基础。