基于扫描电镜和X射线能谱的页岩矿物分析方法  

A mineral analysis method for shale based on SEM and X-ray EDS

作　　者：周尚文[1,2,3] 薛华庆 郭伟[1,2,3] 

机构地区：[1]中国石油勘探开发研究院 [2]国家能源页岩气研发(实验)中心 [3]中国石油非常规油气重点实验室

出　　处：《中国石油勘探》2017年第6期27-33,共7页China Petroleum Exploration

基　　金：国家重点基础研究发展计划(973)项目"中国南方海相页岩气高效开发的基础研究"(2013CB2281)

摘　　要：页岩气系统主要由富含黏土矿物的致密泥页岩组成,自生自储是其显著特征。采用高分辨率扫描电镜分析页岩微观孔隙结构及矿物成分时,基于样品制备的需要,在镜下观察时必须进行样品表面的氩离子抛光。氩离子抛光给扫描电镜带来了更好的图像效果,但由于破坏了矿物的自生形态而加大了镜下矿物识别的难度。为了更加直观地识别和分析页岩矿物组成,基于双束扫描电镜和X射线能谱的分析结果,总结出抛光后页岩样品中各类主要矿物的扫描电镜图像和能谱特征,并且建立了相应的图版。应用该图版可以对页岩中的矿物组成进行定性和定量的分析。定性识别结果与能谱面扫描结果较为一致;借助软件进行矿物分割提取后计算的矿物组分含量与X射线衍射实验结果有较大误差,基于图像分析的矿物定量计算方法还需进一步优化。A shale gas system is mainly composed of clay mineral-rich shale and its remarkable characteristic is self-generating and self- preserving. When the high-resolution scanning electron microscope （SEM） is used to analyze the micro pore structures and mineral compositions of shale, the surface of the samples shall be polished by means of argon ion to meet the requirements of sample preparation. The argon ion polishing can improve the quality of SEM images, but in the meantime, it deteriorates the anthigenic forms of the minerals, increasing the difficulty of SEM mineral identification. In order to identify and analyze the mineral compositions of shale more intuitively, the SEM images and EDS （energy dispersive spectnma） characteristics of main minerals in the polished shale samples were summarized based on the analysis results of FIB-SEM （focused ion beam-scanning electron microscope） and X-ray EDS. Then, the corresponding chart was established. And by virtue of this chart, the mineral compositions of shale can be analyzed qualitatively and quantitatively. It is shown that the qualitative identification results are consistent with the EDS scanning results. The error between the mineral compositions calculated by means of the software after the mineral division and extraction and the X-ray diffraction experiment results is larger. And it is recommended to optimize the quantitative mineral calculation method based on image analysis.

关 键 词：页岩气 矿物分析 扫描电镜 能谱 氩离子抛光 

分 类 号：TE125[石油与天然气工程—油气勘探]