天宫堂地区位于四川盆地南部,发育大规模沉积稳定性与连续性好的海相页岩,是页岩气勘探开发的热点地区。本研究以五峰组-龙马溪组纹层状富有机质页岩为对象,基于岩心尺度描述与大薄片观察,系统分析了页岩纹层的发育特征,并对纹层组合进行了分类与定量表征。通过有机地球化学、矿物学、岩石学、孔隙结构和场发射扫描电镜等分析,表征了页岩的孔隙结构,揭示了页岩的储集物性特征。结合纹层分析结果,揭示了不同类型纹层组合内部结构差异及其控制机理。研究表明,川西南缘天宫堂构造五峰-龙一1亚段页岩主要发育递变型、块状型和砂泥互层型3类纹层组合。递变型纹层组合页岩和互层型纹层组合页岩水平渗透率远高于块状型页岩,块状型页岩的垂直渗透率最高,整体递变型纹层组合页岩物性最好。且三者孔体积和微孔比表面积均呈现由递变型纹层组合页岩、块状型页岩到互层型纹层组合页岩递减的趋势。受沉积环境和成岩作用的共同控制,具有较高TOC和发育有机质-黏土纹层的递变型纹层组合页岩相较于具有较低TOC和发育厚粉砂纹层组和黏土纹层为主的泥纹层组的互层型纹层组合页岩,有效孔隙空间更大,孔隙连通率更高,表现为孔体积更大。而相对较高的有机质含量和无序的矿物孔粒组合排列共同导致块状型页岩有效储集空间优于砂泥互层型纹层组合页岩,而劣于递变型纹层组合页岩。

The Tiangongtang area in southern Sichuan Basin is a shale gas exploration and development hotspot, famous for the development of large-scale marine deposits with good sedimentary stability and continuity. Focusing on the laminated organic-rich shale of the Wufeng-Longmaxi Formations, this paper clarifies the shale lamination types based on core description and microscopic observation of large and thin sections. By means of geochemical, mineralogical, petrograpic and pore structural analyses and field emission scanning electron microscope observation, the pore structure and reservoir physical properties are revealed. Accordingly, the internal structural differences and control mechanisms of different lamination combinations are revealed. Shales of the Wufeng-Long1-1 submember mainly develops three lamination combinations: graded, massive and sand-mud interbedded. Graded laminated and interlaminated shale assemblages have much higher horizontal permeability than the massive while the latter has the highest vertical permeability; the graded has the best reservoir physical properties. Moreover, the pore volume and specific surface area of fractures show a decreasing trend from the graded to massive to interlaminated. Under the control of sedimentary environment and diagenesis, graded laminated shales with higher TOC and organic-clay laminae have larger effective pore space, higher pore connectivity and larger pore volume than the interlaminated with lower TOC and thick silty and clay laminae. With relatively high organic content and disordered porous media massive shales have better quality effective storage spaces than sand-mud interbedded shales but worse quality than graded laminated shales.