湘西北下古生界黑色页岩扫描电镜孔隙特征

Scanning-electron-microscopic micropore characteristics of the Lower Paleozoic black shale in northwestern Hunan Province

利用扫描电镜对湘西北下古生界下寒武统牛蹄塘组和下志留统龙马溪组的黑色页岩样品进行了观察,进一步分析了黑色页岩中的微观孔隙类型、特征及其形成演化过程。区内两套黑色页岩内部发育多种储集空间类型,可概括分为3大类:矿物基质孔、有机质孔、微裂缝,其中矿物基质孔又可细分为粒间骨架孔、凝絮成因孔、溶蚀孔和基质晶间孔,有机质孔主要包括生物骨架孔和生烃残留孔。原始的沉积环境与成岩过程决定了泥页岩中的孔隙和微裂缝系统,不同的成岩阶段控制着页岩中孔隙结构的演化过程,进而影响着页岩气的赋存状态。泥页岩中这种复杂的微观孔隙网络系统为油气储集提供了有效空间,也为页岩气的渗流提供了主要通道,对页岩气的成藏和开发有重要意义。

This paper scanned systematically the black shale samples of the Lower Paleozoic Niuti- tang Formation of Lower Cambrian and Longmaxi Formation of Lower Silurian in northwestern Hunan using scanning electron microscope （SEM）. The micropore types, characteristics, forming and evolution process were further analyzed. A variety of pores developed in the two sets of black shale can be summarized into three broad categories： Mineral matrix pore, organic pore and microfracture. The mineral matrix pore can be subdivided into intergranular skeleton pore, floccule pore, dissolution pore and matrix intercrystal pore. The organic pore mainly include biological skeleton pore and residual pore of hydrocarbon generation. Original depositional environment and diagenetic process determine the pore system in the shale, and dif- ferent diagenetic stages control the evolution of pore texture as well as affect the occurrence of shale gas. The complex network of micropores in shale provides the effective space for oil or gas reservoir and the main channel for shale gas seepage, which has an important significance to shale gas accumulation and de-velopment.