海陆过渡相煤系页岩孔隙结构特征及其对含气性的影响  

Pore structure characteristics of a marine-continental coal-bearing shale reservoir and its effect on the shale gas-containing property

作　　者：张吉振[1,2,3] 李贤庆 邹晓艳[1,4] 谢增业 张学庆[1,4] 李阳阳 王飞宇[6,7] ZHANG Ji-zhen;LI Xian-qing;ZOU Xiao-yan;XIE Zeng-ye;ZHANG Xue-qing;LI Yang-yang;WANG Fei-yu(State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology(Beijing),Beijing 100083,China;Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education,Yangtze University,Wuhan 430100,China;College of Resources and Environment,Yangtze University,Wuhan 430100,China;College of Geosciences and Surveying Engineering,China University of Technology(Beijing),Beijing 100083,China;Research Institute of Petroleum Exploration and Development,PetroChina,Langfang 065007,China;State Key Laboratory of Petroleum Resource and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国矿业大学(北京)煤炭资源与安全开采国家重点实验室,北京100083 [2]长江大学油气资源与勘探技术教育部重点实验室,湖北武汉430100 [3]长江大学资源与环境学院,湖北武汉430100 [4]中国矿业大学(北京)地球科学与测绘工程学院,北京100083 [5]中国石油勘探开发研究院天然气地质研究所,河北廊坊065007 [6]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 [7]中国石油大学(北京)地球科学学院,北京102249

出　　处：《地球化学》2021年第5期478-491,共14页Geochimica

基　　金：国家自然科学基金(U1810201,41572125);国家重点基础研究发展计划(2012CB214702);湖北省科技厅自然科学基金(2020CFB370);湖北省教育厅科研计划(Q20201310)。

摘　　要：本次研究以四川盆地南部(川南地区)上二叠统龙潭组煤系页岩为例,利用场发射扫描电镜(FE-SEM)对页岩孔隙进行定性观察分析,联用高压压汞实验、N_(2)与CO_(2)吸附-脱附实验,以及CH_(4)等温吸附实验开展海陆过渡相煤系页岩全孔径孔隙结构特征的定量表征,并探讨孔隙结构对含气性的影响。海陆过渡相煤系页岩粒间孔、粒内孔和有机质孔等基质孔隙较为发育,微裂缝较少。孔隙形态以平板狭缝状和墨水瓶状为主,具有较好的开放性特征。页岩全孔径孔容分布曲线呈两极化分布,孔径小于30 nm和大于5μm的孔隙大量发育。宏孔(>50 nm)、介孔(2~50 nm)和微孔(<2 nm)的孔容贡献率依次降低,分别占42.2%、36.3%和21.4%。页岩孔比表面积分布曲线呈单峰型分布,随着孔径增大,孔比表面积减小,微孔尤其是孔径值小于8 nm的孔隙提供较大的孔比表面积。微孔、介孔和宏孔的孔比表面积贡献率依次降低,分别占72.7%、25.0%和2.3%。龙潭组页岩总含气量为2.61~6.02 m^(3)/t,其中吸附气比例占优势,含量为1.88~4.70 m^(3)/t,受孔隙比表面积影响较强,主要吸附于微孔和介孔中;游离气含量为0.60~1.34 m^(3)/t,主要受孔隙体积影响,主要赋存于宏孔中。In this study,using Upper Permian Longtan shale as an example,shale pore morphology was qualitatively observed by FE-SEM,and the full-scale pore structure characteristics were quantitatively characterized by combining the high-pressure mercury injection test,N_(2),and CO_(2) gas adsorption-desorption experiments.The impacts of these characteristics on the shale gas content were also clarified.The results indicated that the matrix pores were well developed including interparticle pores,intraparticle pores,and organic matter pores,whereas the microfractures in the Longtan shale were less developed than those in marine shales.Flat slits,slit pores,and ink-bottle pores with good open features were mainly developed in the Longtan shale.The pore volume distribution curves of full-scale pores presented a polarized distribution,thereby indicating that the pores with diameter ranges of<30 nm and>5 m were well developed.The contribution rate of macropores(>50 nm),mesopores(2-50 nm),and micropores(<2 nm)to the total pore volume decreased successively,accounting for 42.2%,36.3%,and 21.4%,respectively.As the pore diameter increased,the pore specific surface area decreased.The micropores with a diameter smaller than 8 nm had a large contribution rate to the total pore specific surface area.The contribution rate of the pore specific surface area of micropores,mesopores,and macropores to the total pore specific surface area decreased successively,accounting for 72.7%,25.0%,and 2.3%,respectively.The total gas content of the Longtan shale ranged from 2.61 m^(3)/t to 6.02 m^(3)/t.The adsorption gas content was predominant(1.88-4.70 m^(3)/t),which dominated the specific surface area,followed by the free gas content of 0.60-1.34 m^(3)/t,which was affected by pore volume and enriched in macropores.

关 键 词：海陆过渡相 煤系页岩 孔隙结构 含气性 龙潭组 四川盆地 

分 类 号：P593[天文地球—地球化学] P618.11[天文地球—地质学]