渝东南下志留统龙马溪组页岩有机质孔隙发育特征:基于聚焦离子束氦离子显微镜(FIB-HIM)技术

doi:10.19657/j.geoscience.1000-8527.2019.04.21

现代地质 ›› 2019, Vol. 33 ›› Issue (04): 902-910.DOI: 10.19657/j.geoscience.1000-8527.2019.04.21

渝东南下志留统龙马溪组页岩有机质孔隙发育特征:基于聚焦离子束氦离子显微镜(FIB-HIM)技术

王朋飞¹^,²(), 姜振学², 金璨³, 吕鹏¹, 李鑫², 张昆², 王凯⁴, 黄璞⁵

1.中国地质调查局地学文献中心,北京 100083
2.中国石油大学(北京) 油气资源与探测国家重点实验室,北京 102249
3.中国石油化工股份有限公司上海海洋油气分公司,上海 200120
4.中国石油化工股份有限公司胜利油田分公司,山东东营 257001
5.中国石油化工股份有限公司西南油气分公司,四川成都 610051

收稿日期:2018-10-12 修回日期:2018-11-20 出版日期:2019-08-20 发布日期:2019-09-05
作者简介:王朋飞,男,博士,助理研究员,1988年出生,矿产普查与勘察专业,主要从事非常规油气成藏与地质评价及能源信息方面的研究。Email: wpfupc725@outlook.com。
基金资助:
中国地质调查局国际地质调查动态跟踪与分析项目(DD20190414);南方页岩气基础地质调查工程项目(12120114046701)

Organic Matter Pores Developments of Lower Silurian Longmaxi Shale in Southeast Chongqing: Based on Focused Ion Beam Helium Ion Microscopy (FIB-HIM)

WANG Pengfei¹^,²(), JIANG Zhenxue², JIN Can³, LÜ Peng¹, LI Xin², ZHANG Kun², WANG Kai⁴, HUANG Pu⁵

1. Geoscience Documentation Center, CGS, Beijing 100083, China
2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
3. SINOPEC Shanghai Offshore Petroleum Company, Shanghai 200120, China
4. SINOPEC Shengli Oilfield Company, Dongying, Shandong 257001, China
5. SINOPEC Southwest Oil & Gas Company, Chengdu,Sichuan 610051, China

Received:2018-10-12 Revised:2018-11-20 Online:2019-08-20 Published:2019-09-05

摘要/Abstract

摘要：

页岩中的有机质孔隙对烃类气体的赋存至关重要。为了明确渝东南下志留统龙马溪组页岩的有机质孔隙发育特征,使用聚焦离子束氦离子显微镜(FIB-HIM)技术进行观察。FIB-HIM具有极高的分辨率,分辨精度可达到亚纳米级,能够有效识别直径为0~20 nm的孔隙。结果表明:龙马溪组页岩的焦沥青内部发育大量的有机质孔隙,孔隙直径大,连通性好,大量较小直径的孔隙嵌套在直径较大的有机质孔隙中,增加了页岩有机质孔隙系统的比表面积和孔隙连通性,有利于烃类气体在页岩有机质孔隙内的赋存及有效渗流。龙马溪组页岩的固体干酪根内部有机质孔隙的发育特征与焦沥青相比存在较大差别,固体干酪根内部发育的有机质孔隙数量少,孔隙直径小,连通性差,孔隙多呈孤立状存在于固体干酪根内部。

关键词: 渝东南, 龙马溪组页岩, 固体干酪根, 焦沥青, 有机质孔隙, 聚焦离子束氦离子显微镜

Abstract:

Organic matter pores in shale are critical to the occurrence of hydrocarbon gases. The focused ion beam helium ion microscope (FIB-HIM) technique was used to determine the organic matter pore development features of the Lower Silurian Longmaxi Formation (Fm.) shale in southeastern Chongqing. The sub-nanometer resolution of FIB-HIM can effectively identify pores with 0-20 nm diameter. The results show a large amount of organic matter pores inside the pyrobitumen of the Longmaxi Fm. shale. The organic matter pore diameter is large with good connectivity. A large number of smaller pores are nested in the larger pores, which increases the connectivity of the pore system. The specific surface area and pore connectivity are beneficial to the occurrence and effective seepage of hydrocarbon gases in the pores. Development characteristics of the organic matter pores in solid kerogen of the Longmaxi Fm. shale are considerably different from those of the pyrobitumen. The organic matter pores developed in the solid kerogen are small in both size and number, and with poor connectivity that the pores are mostly isolated inside the solid kerogen.

Key words: southeastern Chongqing, Longmaxi Fm. shale, solid kerogen, pyrobitumen, organic matter pore, FIB-HIM

中图分类号:

TE121.2

王朋飞, 姜振学, 金璨, 吕鹏, 李鑫, 张昆, 王凯, 黄璞. 渝东南下志留统龙马溪组页岩有机质孔隙发育特征:基于聚焦离子束氦离子显微镜(FIB-HIM)技术[J]. 现代地质, 2019, 33(04): 902-910.

WANG Pengfei, JIANG Zhenxue, JIN Can, LÜ Peng, LI Xin, ZHANG Kun, WANG Kai, HUANG Pu. Organic Matter Pores Developments of Lower Silurian Longmaxi Shale in Southeast Chongqing: Based on Focused Ion Beam Helium Ion Microscopy (FIB-HIM)[J]. Geoscience, 2019, 33(04): 902-910.

图/表 9

图1 渝东南地区位置及龙马溪组页岩井位分布

Fig.1 Geological map of the study area in southeastern Chongqing and the well distribution in the Longmaxi Fm. shale

图2 龙马溪组页岩样品TOC含量频率分布

Fig.2 Frequency distribution of the TOC content in the Longmaxi Fm. shale samples

图3 马溪组页岩样品全岩矿物组成特征

Fig.3 Bulk-rock mineral composition of the Longmaxi Fm. shale samples

图4 龙马溪组页岩样品热演化程度(等效镜质体反射率)分布频率

Fig.4 Frequency distribution of thermal maturities(Equa-Ro) of the Longmaxi Fm. shale samples

图5 聚焦离子束氦离子显微镜仪器

Fig.5 Focused ion beam helium ion microscopy (FIB-HIM)

图6 龙马溪组页岩样品固体干酪根及其内部有机质孔隙发育特征 (JY1井,2 410.2 m;Ro,2.7%;TOC,2.9%,红色线条指示固体干酪根;黄色线条指示孔隙) (a)FIB-HIM镜下固体干酪根发育特征,固体干酪根呈块状发育,但其内部未发现有机质孔隙,固体干酪根周围可见黏土矿物层间孔;(b)FIB-SEM镜下固体干酪根、焦沥青及内部有机质孔隙发育特征,固体干酪根呈条带状发育,周围可见焦沥青。使用FIB-SEM二次电子技术,在孔隙周围可产生圈层状高亮,突出孔隙形貌,在低分辨精度下可有效识别孔隙。固体干酪根内部有机质孔隙数量少,连通性差,而焦沥青内部有机质孔隙数量多,连通性好

Fig. 6 Development features of solid kerogen and its organic matter pores in the Longmaxi Fm. shale samples

图7 FIB-HIM镜下龙马溪组页岩焦沥青及有机质孔隙发育特征 (JY1井,2 410.2 m;Ro,2.7%;TOC,2.9%,红色线条指示焦沥青;黄色线条指示孔隙) (a)龙马溪组页岩样品焦沥青发育特征;(b)龙马溪组页岩样品焦沥青及其内部有机质孔隙发育特征;(c)龙马溪组页岩样品焦沥青内部发育大量有机质孔隙,在观察比例尺为500 nm的尺度下,孔隙直径较大,分布在20~500 nm之间;(d)FIB-HIM镜下,观察比例尺为200 nm,龙马溪组页岩样品焦沥青内部有机质孔隙连片发育,在焦沥青内部表面发现直径分布在0~20 nm的有机质孔隙,同时在较大直径的有机质孔隙内部嵌套发育较小直径的有机质孔隙,增加了页岩有机质孔隙系统的比表面积及连通性

Fig.7 Pyrobitumen and organic matter pore development characteristics of the Longmaxi Fm. shale samples based on FIB-HIM

图8 FIB-HIM高分辨率镜下龙马溪组页岩焦沥青有机质孔隙发育特征 (JY1井,2 410.2 m;Ro,2.7%;TOC,2.9%,红色线条指示焦沥青;黄色线条指示孔隙) (a)龙马溪组页岩样品焦沥青内有机质孔隙大量发育,孔隙直径大,连通性好;(b)FIB-HIM高分辨精度下,龙马溪组页岩样品焦沥青表面发育大量直径分布在0~25 nm的有机质孔隙,同时较大直径的有机质孔隙内部嵌套发育较小直径的孔隙,沟通相邻的大孔,并起到渗流通道的作用,增加有机质孔隙系统的连通性及渗流能力;(c)龙马溪组页岩焦沥青内较大直径有机质孔隙壁上发育大量直径分布在0~20 nm之间的较小直径孔隙,增加了有机质孔隙系统的吸附能力;(d)龙马溪组页岩样品焦沥青内直径在100~500 nm的有机质孔隙连片发育,孔隙多呈规则椭圆状分布;(e)将(d)图中的焦沥青有机质孔隙放大一倍,发育在焦沥青表面直径在0~20 nm之间的小孔隙清晰可见,同时直径较大的孔隙内部嵌套发育着直径较小的孔隙,这些直径较小的孔隙均能增加页岩有机质孔隙的吸附能力;(f)高分辨精度下,将(e)图中的有机质孔隙继续放大观察倍数,较大直径的有机质孔隙内部隙壁上发育大量的直径在0~20 nm之间的孔隙,同时在焦沥青表面发现大量同等直径分布的有机质孔隙,这些孔隙能够增加有机质孔隙的比表面积,增强孔隙系统的吸附能力

Fig.8 Organic matter pore development characteristics of pyrobitumen in the Longmaxi Fm. shale samples based on high resolution FIB-HIM

图9 FIB-SEM镜下龙马溪组页岩焦沥青及有机质孔隙发育特征 (JY1井,2 410.2 m;Ro,2.7%;TOC,2.9%,红色线条指示焦沥青;黄色线条指示孔隙) (a)FIB-SEM镜下龙马溪组页岩样品焦沥青及其内部有机质孔隙发育特征;(b)将(a)图中的焦沥青及其内部有机质孔隙的观察倍数放大,与HIM数字照片相比,SEM的数字照片开始出现视域模糊,分辨不清的特点,在焦沥青表面及较大直径有机质孔隙壁上发育的直径在0~20 nm的有机质孔隙及较大直径有机质孔隙内嵌套发育的较小直径孔隙均未能得到有效识别;(c)在SEM镜下只能分辨龙马溪组页岩焦沥青内发育的直径20~500 nm的有机质孔隙; (d)对(c)图中的焦沥青进行二次电子轰击,围绕焦沥青内部的有机质孔隙周围产生圈层状高亮,在较低分辨率下可对直径相对较小的有机质孔隙进行有效识别,但二次电子的持续轰击会对样品产生电离辐射损伤

Fig.9 Pyrobitumen and organic matter pore development characteristics of the Longmaxi Fm. shale samples based on FIB-SEM

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渝东南下志留统龙马溪组页岩有机质孔隙发育特征:基于聚焦离子束氦离子显微镜(FIB-HIM)技术

Organic Matter Pores Developments of Lower Silurian Longmaxi Shale in Southeast Chongqing: Based on Focused Ion Beam Helium Ion Microscopy (FIB-HIM)

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