Microstructural investigation of gas shales in two and three dimensions using nanometer-scale resolution imaging
Microstructural investigation of gas shales in two and three dimensions using nanometer-scale resolution imaging
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DOI：
10.1306/08151110188
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发表时间：
2012-04-01
期刊：
影响因子：
3.5
通讯作者：
Rai, Chandra S.
中科院分区：
文献类型：
--
作者：
Curtis, Mark E.;Sondergeld, Carl H.;Rai, Chandra S.
利用聚焦离子束（FIB）铣削和扫描电子显微镜（SEM）的结合，研究了来自9个不同地层的气页岩样品的微观结构。FIB剖面页岩表面的背散射电子（BSE）图像显示出复杂的微观结构，不同地层之间存在差异。页岩横截面的能量色散谱分析表明，粘土、碳酸盐、石英、黄铁矿和干酪根是最常见的成分。在疯牛病图像中，观察到干酪根区域穿插着无机颗粒。在干酪根和无机基质中均观察到孔隙，孔隙的大小、形状和数量随页岩样品的不同而不同。通过连续重复地使用FIB磨矿和SEM成像，可以为每个页岩样品生成三维（3-D） SEM图像数据集。根据这些图像重建了页岩的三维体积。通过在灰度上设置阈值，将干酪根和孔隙网络在重建的页岩体中分割出来并显示出来。对重建页岩体积的干酪根和孔隙体积百分比进行了估算，干酪根和孔隙体积百分比分别为0 ~ 90.0%和0.2 ~ 2.3%。对孔隙大小分布的估计表明，尽管半径约为3nm的孔隙在数量上占主导地位，但它们不一定占总体积贡献的主导地位。扫描电子显微镜图像和三维重建强化了页岩非常不同的事实，它们的微观结构是高度可变和复杂的。
The microstructure of gas shale samples from nine different formations has been investigated using a combination of focused ion beam (FIB) milling and scanning electron microscopy (SEM). Backscattered electron (BSE) images of FIB cross sectioned shale surfaces show a complex microstructure with variations observed among the formations. Energy dispersive spectroscopy of the shale cross sections indicates that clay, carbonate, quartz, pyrite, and kerogen are the most prevalent components. In the BSE images, areas of kerogen are observed interspersed with the inorganic grains. Pores are observed in both the kerogen and inorganic matrix with the size, shape, and number of pores varying among the shale samples. By using FIB milling and SEM imaging sequentially and repetitively, three-dimensional (3-D) data sets of SEM images have been generated for each of the shale samples. Three-dimensional volumes of the shales are reconstructed from these images. By setting thresholds on the gray scale, the kerogen and pore networks are segmented out and visualized in the reconstructed shale volumes. Estimates of kerogen and pore volume percentages of the reconstructed shale volumes have been made and range from 0 to 90.0% for the kerogen and 0.2 to 2.3% for pores. Estimates of pore-size distributions suggest that although pores with radii of approximately 3 nm dominate in number, they do not necessarily dominate in total volumetric contribution. Scanning electron microscopy images and 3-D reconstructions reinforce the facts that shales are quite different and that their microstructures are highly variable and complex.