川东南地区志留系龙马溪组页岩微观孔隙结构特征

Micropore structure characteristics of the Silurian Longmaxi Formation shale in southeast Sichuan Province

以川东南地区为例,运用氩离子抛光扫描电镜技术对龙马溪组页岩孔隙结构特征进行研究。结果表明,该地区龙马溪组页岩孔径主要为纳米级,孔隙可分为有机质孔、无机孔(微裂缝、微孔道、絮状物孔隙、晶间孔、晶内孔),以有机质孔为主。结合前人研究成果,建立了泥页岩微观孔隙组合模式。通过氮气吸附实验,确定龙马溪组页岩气储层为Ⅱ类吸附曲线,表明其孔隙主要由纳米孔组成,结构具有一定的无规则(无定形)孔特征,颗粒内部孔结构具有平行壁的狭缝状孔特征,且含有多形态的其他孔。

Taking the southeast Sichuan Province as an example, the micropore structures of the Longmaxi Formation shale by using argon-ion polishing scanning electron microscope （SEM） technology were systematically studied. The result reveals that the shale pores are dominated by nano-scale pores, and can be divided into organic pores and inorganic pores （microfissure, micro-channels, floc pores, intercrystalline pores and intracrystal pores）, with predominant organic pores. Combining with the previous studies, a combina- tion model for micropores in shales was established. The Silurian Longmaxi Formation reservoir belongs to class II adsorption curve sug- gested by nitrogen adsorption tests. It is inferred that the Longmaxi shale gas reservoir is mainly dominated by nano-scale pore, and that the structure has certain irregular （amorphous） pore features. The intracrystal pores are narrow, with parallel wall, and contain many shapes of other pores.