Computer X-ray microtomography (µXCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than 1 order of magnitude. This effect increases towards smaller pore sizes, as shown in this study, in which nanostructural features related to clay minerals reduce the permeability of tight reservoir sandstone samples. Focussed ion beam scanning electron microscopy (FIB-SEM) tomography was applied to determine the permeability effects of illites at the nanometre scale, and Navier–Stokes equations were applied to calculate the permeability of these domains. With these data, microporous domains (porous voxels) were defined using microtomography images of a tight reservoir sample. The distribution of these domains could be extrapolated by calibration against size distributions measured in FIB-SEM images. For this, we assumed a mean permeability for the dominant clay mineral (illite) in the rock and assigned it to the microporous domains within the structure. The results prove the applicability of our novel approach by combining FIB-SEM with X-ray tomographic rock core scans to achieve a good correspondence between measured and simulated permeabilities. This methodology results in a more accurate representation of reservoir rock permeability in comparison to that estimated purely based on µXCT images.

中文翻译：

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结合计算机X射线显微照相术和聚焦离子束扫描电子显微镜成像，模拟致密砂岩中粘土矿物纳米孔的渗透率降低

计算机X射线断层摄影术（µXCT）是研究多孔岩石物理性质的有力工具。尽管通过这种方法确定的计算出的孔隙率通常与实验测量值相符，但计算出的渗透率往往被高估了1个数量级以上。如本研究所示，这种影响随着孔径的减小而增加，其中与粘土矿物有关的纳米结构特征降低了致密储层砂岩样品的渗透性。聚焦离子束扫描电子显微镜（FIB-SEM）层析成像技术被用于确定伊利石在纳米尺度上的渗透率效应，而Navier-Stokes方程被用于计算这些畴的渗透率。利用这些数据，使用致密储层样品的显微断层图像来定义微孔区域（多孔体素）。这些域的分布可以通过针对FIB-SEM图像中测量的尺寸分布进行校准来推断。为此，我们假设岩石中的主要粘土矿物（伊利石）具有平均渗透率，并将其分配给结构内的微孔区域。结果通过将FIB-SEM与X射线断层扫描岩心扫描相结合，在测量的渗透率和模拟的渗透率之间取得了良好的对应关系，证明了我们新颖方法的适用性。与纯粹根据以下方法估算的储层渗透率相比，该方法可以更准确地表示储层岩石渗透率 我们假设岩石中的主要粘土矿物（伊利石）具有平均渗透率，并将其分配给结构内的微孔区域。结果通过将FIB-SEM与X射线断层扫描岩心扫描相结合，在测量的渗透率和模拟的渗透率之间取得了良好的对应关系，证明了我们新颖方法的适用性。与纯粹根据以下方法估算的储层渗透率相比，该方法可以更准确地表示储层岩石渗透率 我们假设岩石中的主要粘土矿物（伊利石）具有平均渗透率，并将其分配给结构内的微孔区域。结果通过将FIB-SEM与X射线断层扫描岩心扫描相结合，在测量的渗透率和模拟的渗透率之间取得了良好的对应关系，证明了我们新颖方法的适用性。与纯粹根据以下方法估算的储层渗透率相比，该方法可以更准确地表示储层岩石的渗透率µ XCT图像。