川东地区龙马溪组页岩不同岩相孔隙结构特征及其主控因素  

Characteristics and controlling factors of pore structures of various lithofacies in shales of Longmaxi Formation,eastern Sichuan Basin

作　　者：霍建峰 高健[2] 郭小文[1] 易积正[3] 舒志国[3] 包汉勇[3] 杨锐[1] 罗涛 何生[1] Huo Jianfeng;Gao Jian;Guo Xiaowen;Yi Jizheng;Shu Zhiguo;Bao Hanyong;Yang Rui;Luo Tao;He Sheng(Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences(Wuhan),Wuhan,Hubei 430074,China;Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100083,China;Research Institute of Exploration and Development of Jianghan Oilfield Company,SINOPEC,Wuhan,Hubei 430223,China)

机构地区：[1]中国地质大学(武汉)构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石化石油勘探开发研究院,北京100083 [3]中国石化江汉油田分公司勘探开发研究院,湖北武汉430223

出　　处：《石油与天然气地质》2020年第6期1162-1175,共14页Oil & Gas Geology

基　　金：国家自然科学基金项目(41690134,41872139)。

摘　　要：四川盆地川东地区是中国页岩气主要产区,目前发现的页岩气主要产自五峰-龙马溪组的富泥硅质页岩,而对富硅泥质和混合质页岩研究较少。为了确定川东地区龙马溪组富硅泥质和混合质页岩的孔隙发育特征,在对龙马溪组页岩岩相划分的基础之上,通过二氧化碳吸附,氮气吸附,高压压汞以及孔隙度测定,X-衍射,场发射扫描电子显微镜(FE-SEM)等实验手段,对比不同岩相页岩孔隙结构特征,研究不同岩相页岩孔隙结构的主控因素。研究结果表明:(1)川东地区富有机质页岩可划分为富硅泥质页岩相、硅/泥混合页岩相和富泥硅质页岩相,不同岩相页岩孔隙度范围在2.62%~5.65%;(2)页岩储层中孔隙体积以介孔为主,大约占总孔隙的50%~60%,其次是微孔和宏孔,大约占总孔隙的15%~20%,比表面积主要贡献来自微孔和介孔,分别占总比表面积的70%和30%;(3)龙马溪组页岩孔隙发育主要受有机质丰度的控制,粘土矿物含量不是控制页岩孔隙发育主要因素,高有机质丰度页岩可能由于骨架颗粒支撑较弱遭受更剧烈的压实作用使大部分孔隙消失;(4)高有机质丰度富泥质页岩和硅/泥混合页岩也具有较高的孔隙度,与大部分富泥硅质页岩具有相似的孔隙结构,表明富硅泥质页岩相和硅/泥混合页岩相页岩也能发育一定量的纳米级孔隙,可为页岩气赋存提供空间。The eastern Sichuan Basin is one of the major shale gas producing areas in China.However,with gas being mostly found in the clay-rich siliceous shale,the silica-rich argillaceous and mixed argillaceous/siliceous shales in the Wufeng-Longmaxi formation have been largely neglected.This study focuses on pore structure features of the shales by comparing the structural features of diverse lithofacies and investigating their main controlling factors based on the lithofacies classification of the shale samples from the Longmaxi Formation by means of low pressure N2/CO2 gas adsorption,high pressure mercury intrusion,porosity measurement,XRD analyses,FE-SEM and so on.The results show that the organic-rich shales in the eastern Sichuan Basin can be divided to silica-rich argillaceous,mixed argillaceous/siliceous and clay-rich siliceous lithofacies with a porosity ranging from 2.62%to 5.65%.Pore volume of the shale reservoirs is primarily contributed by mesopores,accounting for 50%to 60%of the total,followed by micropores and macropores,accounting for 15%to 20%of the total;while the total specific surface area is mainly contributed by micropores and mesopores,accounting for 70%and 30%of total respectively.The pore development is chiefly controlled by the abundance of organic matters instead of the clay mineral content.Shale with high abundance of organic matters may contain less pores as it could not withstand intense compaction with its soft matrix.The organic-rich shale of silica-rich argillaceous and mixed argillaceous/siliceous lithofacies is high in porosity and shares the similar pore structure with most of the clay-rich siliceous shale,suggesting that the silica-rich argillaceous and mixed argillaceous/siliceous shales can also generate certain amount of nano-scaled pores for shale gas storage.

关 键 词：孔隙结构 有机孔隙 页岩气 龙马溪组 四川盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]