In recent years, lithofacies identification and classification have been a hot topic in shale gas research. Even if some previous works are considering the distribution characteristics of lithofacies in different system tracts (third-order sequences), only few studies systematically reveal the lithofacies distribution and reservoir characteristics. In this study, we focus on transgressive systems tract (TST) section which is characterized by high TOC content and highest gas content in the Long-1 member and divided the third-order TST into five Units (parasequences) according to graptolite biozonation, gamma ray (GR) and acoustic (AC) logging data. Twenty-six samples were analyzed for total organic carbon (TOC) content, mineral and elemental composition, porosity, pore type, pore size distribution and pore connectivity. The results show that Unit 1 is predominantly composed of S-3 and S-4 lithofacies, and Units 2–5 is predominantly composed of S-4 and M-2 lithofacies. The S-4 lithofacies was associated with high primary productivity of organic matter, and anoxic bottom water conditions. Redox conditions changed from anoxic to dysoxic condition and the productivity decreased through Unit 1 to Unit 5. Compared to other units, Units 1 and 2 are characterized by higher porosity and better pore connectivity. The S-3/S-4 and M-2 lithofacies exhibit different reservoir quality, especially in pore structure. Mineralogical composition is the key factor to determine lithofacies type and affects the characteristics of pore structure. Besides, TOC plays an important role in the development of organic matter pores. Anoxic bottom water conditions and high paleo-salinity contributed to the preservation of organic matter.

近年来，岩相的识别和分类一直是页岩气研究的热点。即使先前的一些研究考虑了岩相在不同系统区域（三阶序列）中的分布特征，也只有很少的研究系统地揭示了岩相分布和储层特征。在这项研究中，我们重点研究海侵系统道（TST）断面，该断面的特征在于Long-1成员中的TOC含量高且气体含量最高，并根据笔石生物分区，γ将三阶TST分为五个单位（副序列）。射线（GR）和声学（AC）记录数据。分析了26个样品的总有机碳（TOC）含量，矿物质和元素组成，孔隙率，孔类型，孔径分布和孔连通性。结果表明，第1单元主要由S-3和S-4岩相组成，第2–5单元主要由S-4和M-2岩相组成。S-4岩相与有机物的高初级生产力和缺氧的底水条件有关。氧化还原条件从缺氧条件变为低氧条件，并且通过单元1到单元5降低了生产率。与其他单元相比，单元1和2具有更高的孔隙率和更好的孔隙连通性。S-3 / S-4和M-2岩相表现出不同的储层质量，尤其是在孔隙结构方面。矿物学组成是确定岩相类型的关键因素，并影响孔隙结构的特征。此外，TOC在有机物孔隙的发育中也起着重要作用。