川东北深层页岩储层成岩作用及对孔隙发育的影响OA北大核心CSTPCD

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.