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
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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。
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.
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.
引文
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[10]聂海宽,金之钧,马鑫,等.四川盆地及邻区上奥陶统五峰组—下志留统龙马溪组底部笔石带及沉积特征[J].石油学报,2017,38(2):160-174.
[11]唐相路,姜振学,李卓,等.渝东南地区龙马溪组高演化页岩微纳米孔隙非均质性及主控因素[J].现代地质,2016,30(1):163-171.
[12]纪文明,宋岩,姜振学,等.四川盆地东南部龙马溪组页岩微-纳米孔隙结构特征及控制因素[J].石油学报,2016,37(2):182-195.
[13]耿一凯,金振奎,赵建华,等.页岩储层孔隙类型控制因素研究——以川东焦石坝地区龙马溪组为例[J].石油实验地质,2017,39(1):71-78.
[14]黄家国,许开明,郭少斌,等.基于SEM,NMR和X-CT的页岩储层孔隙结构综合研究[J].现代地质,2015,29(1):198-205.
[15]曹涛涛,刘光祥,曹清古,等.有机显微组成对泥页岩有机孔发育的影响——以川东地区海陆过渡相龙潭组泥页岩为例[J].石油与天然气地质,2018,39(1):40-53.
[16]赵建华,金之钧,金振奎,等.岩石学方法区分页岩中有机质类型[J].石油实验地质,2016,38(4):514-520.
[17]王香增,张丽霞,雷裕红,等.低熟湖相页岩内运移固体有机质和有机质孔特征——以鄂尔多斯盆地东南部延长组长7油层组页岩为例[J].石油学报,2018,39(2):141-151.
[2] SLATT R M,O'BRIEN N R. Pore types in the Barnett and Woodford gas shales:Contribution to understanding gas storage and migration pathways in fine-grained rocks[J]. AAPG Bulletin,2011,95(12):2017-2030.
[3] LOUCKS R G,REED R M,RUPPEL S C,et al. Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores[J]. AAPG Bulletin,2012,96(6):1071-1098.
[4] MILLIKEN K L,RUDNICKI M,AWWILLER D N,et al. Organic matter-hosted pore system,Marcellus formation(Devonian),Pennsylvania[J]. AAPG Bulletin,2013,97(2):177-200.
[5] LOUCKS R G,REED R M. Scanning-electron-microscope petrographic Evidence for distinguishing organic-matter pores associated with depositional organic matter versus migrated organic matter in mudrocks[J]. Gcags Transactions,2014,3:51-60.
[6] JIAO K,YAO S,LIU C,et al. The characterization and quantitative analysis of nanopores in unconventional gas reservoirs utilizing FESEM-FIB and image processing:An example from the lower Silurian Longmaxi Shale, Upper Yangtze region, China[J]. International Journal of Coal Geology,2014,128:1-11.
[7] GUO X,SHEN Y,HE S. Quantitative pore characterization and the relationship between pore distributions and organic matter in shale based on Nano-CT image analysis:A case study for a lacustrine shale reservoir in the Triassic Chang 7 member,Ordos Basin,China[J]. Journal of Natural Gas Science and Engineering,2015,27:1630-1640.
[8] WANG P F,JIANG Z X,JI W M,et al. Heterogeneity of intergranular,intraparticle and organic pores in Longmaxi shale in Sichuan Basin,South China:Evidence from SEM digital images and fractal and multifractal geometries[J]. Marine and Petroleum Geology,2016,72:122-138.
[9] WANG P F,JIANG Z X,CHEN L,et al. Pore structure characterization for the Longmaxi and Niutitang shales in the Upper Yangtze Platform,South China:Evidence from focused ion beam-He ion microscopy,nano-computerized tomography and gas adsorption analysis[J]. Marine and Petroleum Geology,2016,77:1323-1337.
[10]聂海宽,金之钧,马鑫,等.四川盆地及邻区上奥陶统五峰组—下志留统龙马溪组底部笔石带及沉积特征[J].石油学报,2017,38(2):160-174.
[11]唐相路,姜振学,李卓,等.渝东南地区龙马溪组高演化页岩微纳米孔隙非均质性及主控因素[J].现代地质,2016,30(1):163-171.
[12]纪文明,宋岩,姜振学,等.四川盆地东南部龙马溪组页岩微-纳米孔隙结构特征及控制因素[J].石油学报,2016,37(2):182-195.
[13]耿一凯,金振奎,赵建华,等.页岩储层孔隙类型控制因素研究——以川东焦石坝地区龙马溪组为例[J].石油实验地质,2017,39(1):71-78.
[14]黄家国,许开明,郭少斌,等.基于SEM,NMR和X-CT的页岩储层孔隙结构综合研究[J].现代地质,2015,29(1):198-205.
[15]曹涛涛,刘光祥,曹清古,等.有机显微组成对泥页岩有机孔发育的影响——以川东地区海陆过渡相龙潭组泥页岩为例[J].石油与天然气地质,2018,39(1):40-53.
[16]赵建华,金之钧,金振奎,等.岩石学方法区分页岩中有机质类型[J].石油实验地质,2016,38(4):514-520.
[17]王香增,张丽霞,雷裕红,等.低熟湖相页岩内运移固体有机质和有机质孔特征——以鄂尔多斯盆地东南部延长组长7油层组页岩为例[J].石油学报,2018,39(2):141-151.