页岩气储层孔隙类型及特征研究:以渝东南下古生界为例

通过薄片分析、扫描电镜及氩离子抛光技术,对渝东南下古生界含气页岩中的孔隙类型及特征进行了分类观察、描述,结合有机碳含量、X衍射、岩石物性、氮气吸附及甲烷等温吸附实验测试,分析了页岩气储层中各类孔隙的储气贡献,探讨这些孔隙对页岩中烃类运移的影响。研究认为,有机质孔隙、颗粒内孔、粒间孔隙及微裂隙是页岩气储层孔隙的4种类型,有机质表面的分散状孔隙多为nm级,石英碎屑可形成粒内或粒间孔隙,黄铁矿颗粒内部小晶体排列分布产生孔隙空间,黏土絮状沉淀形成片粒状结构孔隙,微裂隙普遍发育在页岩基质中,可达mm级。不同类型的孔隙能够为页岩气的赋存提供不同尺度的储集空间,页岩吸附含气量与表征孔隙特征的参数(TOC、BET比表面积、BJH总孔体积)具有显著的正相关关系。微裂隙与粒间孔隙对页岩中烃类的运移最有利。

Pore types and characteristics of shale gas reservoir: A case study of Lower Paleozoic shale in Southeast Chongqing

Through thin section analysis,scanning electron microscopy and argon-ion milled surfaces technique,the pore types and characteristics of Lower Paleozoic gas shales in Southeast Chongqing were observed and described.Based on the experimental methods of total organic carbon content,XRD analysis,rock porosity,nitrogen adsorption and methane isothermal adsorption,the pores' contribution to gas storage was analyzed and their impacts on hydrocarbon migration was discussed.The results showed that the organic pore,intraparticle pore,interparticle pore and microfracture are four pore types developed in Lower Paleozoic shale gas reservoir.Most dispersed pores on the organic matter are nanoscale pores,intraparticle or interparticle pores with granular quartz appeared;pore space spreads between small crystals inside pyrite;flake structures produce pores by flocculation of clay;microfractures occur within the matrix of shale,some are millimeter sized.Different types of pores could provide various sized storage space and there is an obvious linear correlation between gas adsorption capacity and pore characteristic parameters(TOC,BET surface area,BJH total pore volume).Microfractures and interparticle pores are most likely to contribute to hydrocarbon migration.