扫描电镜分析参数对定量评价页岩微观孔隙的影响

doi:10.11743/ogg20190520

摘要/Abstract

摘要： 以四川盆地龙马溪组富有机质页岩为研究对象，基于氩离子束抛光结合扫描电镜表征技术，研究不同扫描电镜分析参数下页岩微观孔隙结构，并通过“最佳阈值法”提取相同视域下的孔隙定量信息来探讨改变电镜分析参数对定量评价页岩微观孔隙的影响。结果表明，电镜分析参数中电子束流和加速电压对孔隙定量信息提取的准确性影响较大；束流超过170 PA时，电压调整的越高提取出的大孔面积反而越小；电压超过15 kV时，束流较低，孔隙提取的反而更完整；当束流低于86 PA时，扫描时间越长孔隙提取的越完整，而当束流超过86 PA时，扫描时间对孔隙提取的影响不大；亮度与对比度值过低或过高都对孔隙提取不利，而当其值分别为47.5和85时孔隙提取的最完整。最终结果表明电镜分析参数对提取有机质孔隙的影响较大，且选择合适的参数可显著提高页岩微观孔隙定量数据提取的准确性，从而得到更加真实的页岩微观孔隙结构信息。

关键词: 场发射扫描电镜, 扫描电镜参数, 加速电压, 电子束流, 微观孔隙提取, 页岩, 龙马溪组, 四川盆地

Abstract: We studied the microscopic pore structure of the organic-rich Longmaxi Formation shale in Sichuan Basin through Argon Ion milling-Field Emission Scanning Electron Microscopy characterization with different SEM parameters,and investigated the effect of electron microscopic parameter variation on the quantitative evaluation of the microscopic pores of shale based on the pore data extracted by the "optimal threshold method" within the same field of view.The results show that the probe current and accelerating voltage among these electron microscopic parameters,have greater influence on the accuracy of quantitative pore data extraction.When the beam exceeds 170PA,the higher the voltage is adjusted to,the smaller the large pore area is extracted.When the voltage exceeds 15KV,the beam current is lower,and the pores extracted are relatively more complete; while as the beam current is lower than 86PA,the longer the scanning time is,the more completely the pore is extracted,but as it exceeds 86PA,the scanning time has little effect on pore extraction.In addition,luminance and contrast values of excessive lowness or highness are detrimental to pore extraction,and the pore extraction comes to the most complete when their values are 47.5 and 85 respectively.In conclusion,the parameters of electron microscopy have a remarkable influence on the extraction of organic pores,and the proper selection of parameters can significantly improve the accuracy of quantitative data extraction for shale micropores,in a bid to obtain more realistic data of shale micropore structure.

Key words: Field Emission Scanning Electron Microscopy, SEM parameter, accelerating voltage, electron beam current, micropore extraction, shale, Longmaxi Formation, Sichuan Basin

中图分类号:

TE135

赵日新,卢双舫,薛海涛,等. 扫描电镜分析参数对定量评价页岩微观孔隙的影响[J]. 石油与天然气地质, 2019, 40(5): 1141-1154. doi: 10.11743/ogg20190520 Zhao Rixin,Lu Shuangfang,Xue Haitao,et al. Effect of SEM parameters on quantitative evaluation of shale micropores[J]. Oil & Gas Geology, 2019, 40(5): 1141-1154. doi: 10.11743/ogg20190520

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