四川盆地吴家坪组—大隆组海相页岩具备良好的页岩气成藏条件,是四川盆地未来天然气勘探的重要接替领域.但受混合沉积作用的影响,不同岩相之间成岩作用及孔隙演化差异显著,影响了对其储层分布及勘探潜力的评价.综合应用X衍射、扫描电镜、能谱、薄片观察等多种实验方法,对川东北地区DY1H井吴家坪组—大隆组页岩开展了岩相划分、成岩作用与微观孔隙结构研究,讨论了其成岩作用与孔隙发育的耦合关系.结果表明:DY1H井吴家坪组—大隆组页岩主要发育硅质、混合质、钙质、黏土质4类页岩岩相.其中硅质页岩相的TOC最高.硅质页岩中石英来源于陆源碎屑与硅质生物,抗压实能力强,保留下的微孔隙可为有机质迁移与富集提供空间,并且随着埋藏深度的增加,有机质热演化作用也可形成大量有机质孔.得益于优质的物质基础和良好的储集空间条件,硅质页岩成为川东北地区吴家坪组—大隆组页岩中的有利岩相.建立了有利岩相的成岩-孔隙演化模式,为海相页岩孔隙成因研究与储层分布预测提供了借鉴和参考.

The marine shales of Wujiaping Formation and Dalong Formation in Sichuan Basin have favorable conditions for shale gas accumulation,making them significant replacement fields for natural gas exploration in the future.However,due to mixed sedimentation influences,diagenesis and pore evolution vary significantly among different lithofacies.The lithofacies classification,diagenesis,and microscopic pore structure of Wujiaping Formation and Dalong Formation shales of Well DY1H in northeast Sichuan Basin are confirmed by useing X-ray diffraction,scanning electron microscopy,energy spectrum analysis,and thin section observation techniques.We also discuss the coupling relationship between diagenesis and pore development.The results reveal that four types of shale lithofacies are predominantly present in well DY1H:siliceous,mixed,calcareous,and clay-rich shales.The siliceous shale has the highest TOC.Part of the quartz in the siliceous shale comes from the transformation of siliceous organisms in the early diagenesis.This early cementation enhances the compaction resistance of the reservoir,and the retained micropores can provide space for the migration and enrichment of organic matter.With the increase of burial depth,a large number of organic pores can be formed under the thermal evolution of organic matter.Due to their high-quality material foundation and favorable storage conditions,siliceous shales have become preferred lithofacies within the Wujiaping Formation and Dalong Formation shales in northeast Sichuan Basin.Finally,a diagenetic pore evolution model is established specifically for these favorable lithofacies which can serve as a reference for studying pore genesis and reservoir distribution prediction in marine shales.