Gasaway Carley, Mastalerz Maria, Krause Fed, Clarkson Chris, Debuhr Chris
Department of Geological Sciences, Indiana University, Bloomington, Indiana, U.S.A.
Indiana Geological Survey, Indiana University, Bloomington, Indiana, U.S.A.
J Microsc. 2017 Jan;265(1):60-72. doi: 10.1111/jmi.12463. Epub 2016 Sep 6.
Samples of Late Devonian/Early Mississippian New Albany Shale from the Illinois Basin, having maturities ranging from early mature to postmature, were analysed using micro-Fourier transform infrared (FTIR) spectroscopy, ImageJ processing software and scanning electron microscopic X-ray spectroscopy to explore the distribution, connectivity and chemical composition of organic matter, clay minerals, carbonate minerals and quartz, and to further test the applicability of micro-FTIR mapping to study shale heterogeneity. Each sample was analysed in planes parallel and perpendicular to the bedding to investigate anisotropy in component distribution, with a possible implication for better understanding anisotropy in porosity and permeability in organic-matter-rich shales. Our results show that for low-maturity samples, organic matter is better connected in the plane parallel to the bedding than in the plane perpendicular to the bedding. Organic matter connectivity decreases with increasing maturity as a result of kerogen transformation. Clay minerals are very well connected in both planes, whereas carbonate minerals are not abundant whilst dominantly isolated in most samples, independent of maturity. This study demonstrates that micro-FTIR mapping is a valuable tool for studying shale heterogeneity on a micrometre to millimetre scale that becomes even more powerful in combination with scanning electron microscopy techniques, which extend observations to a nanometre scale. However, to obtain meaningful and comparable results, micro-FTIR mapping requires very careful standardization, precise selection of peak heights/areas and mapping conditions (such as aperture size, scan numbers, resolution, etc.) well suited for the analysed samples.
对来自伊利诺伊盆地的晚泥盆世/早密西西比世新奥尔巴尼页岩样本进行了分析，这些样本的成熟度范围从早期成熟到过成熟。分析采用了显微傅里叶变换红外（FTIR）光谱、ImageJ处理软件和扫描电子显微镜X射线光谱，以探究有机质、粘土矿物、碳酸盐矿物和石英的分布、连通性及化学成分，并进一步测试显微FTIR映射在研究页岩非均质性方面的适用性。每个样本在平行和垂直于层面的平面上进行分析，以研究组分分布的各向异性，这可能有助于更好地理解富含有机质页岩孔隙度和渗透率的各向异性。我们的结果表明，对于低成熟度样本，有机质在平行于层面的平面上比在垂直于层面的平面上连接性更好。由于干酪根转化，有机质连通性随成熟度增加而降低。粘土矿物在两个平面上连接性都很好，而碳酸盐矿物在大多数样本中含量不高且主要呈孤立状态，与成熟度无关。这项研究表明，显微FTIR映射是一种在微米到毫米尺度上研究页岩非均质性的有价值工具，与扫描电子显微镜技术结合时变得更加强大，扫描电子显微镜技术将观测扩展到纳米尺度。然而，为了获得有意义且可比的结果，显微FTIR映射需要非常仔细的标准化，精确选择适合分析样本的峰高/面积和映射条件（如孔径大小、扫描次数、分辨率等）。
