四川盆地红星地区二叠系页岩岩相及其微观孔隙结构特征

四川盆地红星地区二叠系是页岩气勘探的重要接替领域，目前整体勘探程度低，页岩岩相类型不清、储层微观孔隙结构特征不明。利用铸体薄片、扫描电镜、X射线衍射、总有机碳(total organic carbon, TOC)和低温氮气吸附实验等技术手段，明确了二叠系茅口组四段-吴家坪组页岩岩相类型及其微观孔隙结构特征，探讨了优质储层主控因素。结果表明：(1)红星地区二叠系页岩发育高碳高硅类、高碳低硅类、低碳高硅类、高黏土类和灰质混合类共5种岩相类型；(2)高碳高硅类岩相储集特征以微孔-小孔为主，高碳低硅类页岩储集特征以微孔为主，低碳高硅类页岩储集特征以小孔-中孔为主，高黏土类页岩储集特征以中孔-大孔为主；灰质混合类页岩储集特征以大孔为主；(3)高碳高硅类岩相孔隙度、孔体积和比表面积最大，其次为高碳低硅类、高黏土类和低碳高硅类，灰质混合类岩相最小；(4)微孔主要受有机质含量控制，微孔体积与有机质含量成正比，小孔体积与长英质矿物含量成正比，中孔体积与黏土矿物含量成正比，大孔基本不发育；(5)综合岩相发育占比和储集特征认为，高碳高硅类和高碳低硅类岩相是最优质的岩相类型，高黏土类和低碳高硅类次之，灰质混合...

Lithofacies and characteristics of micro-pore structure of Permian shale in Hongxing area , Sichuan Basin

The Hongxing area of Sichuan Basin is a significant replacement area for the exploration of shale gas in the Permian Formation. Currently, the overall exploration level is low, and the lithofacies types of shale are unclear, and the characteristics of the micropore structure of the reservoir are unknown. In this study, techniques such as thin sections, scanning electron microscopy, X-ray diffraction, total organic carbon analysis, and low-temperature nitrogen adsorption experiments were used to clarify the lithofacies types and micropore structure characteristics of the fourth member of Maokou Formation -Wujiaping formation shale and to explore the main controlling factors of high-quality reservoirs. The results show that: (1) There are five types of lithofacies of the fourth member of Maokou Formation -Wujiaping formation of the Permian shale in Hongxing area, including High carbon-high siliceous shale, High carbon-low siliceous shale, Low carbon-high siliceous shale, High clay shale, and Carbonate-mixed shale. (2) the High carbon-high siliceous shale lithofacies are mainly characterized by micropores and small pores, High carbon-low siliceous shale lithofacies are mainly characterized by micropores, Low carbon-high siliceous shale lithofacies are mainly characterized by small to medium pores, the High clay shale lithofacies are mainly characterized by medium to large pores, and the Carbonate-mixed shale lithofacies are mainly characterized by large pores. (3) the lithofacies of High carbon-high siliceous shale have the highest porosity, pore volume, and specific surface area, followed by the High carbon-low siliceous shale, High clay shale, and Low carbon-high siliceous shale, while Carbonate-mixed shale have the smallest values. (4) The volume of micropores is proportional to the organic matter content, the volume of small pores is positively correlated with the content of siliceous, the volume of medium pores is controlled by the content of clay, and large pores are not well developed. (5) Based on the development proportion of lithofacies and reservoir characteristics, the lithofacies of High carbon-high siliceous shale and High carbon-low siliceous shale are the most favorable lithofacies types, followed by the High clay shale and Low carbon-high siliceous shale, while the lithofacies of Carbonate-mixed shale are relatively the least favorable.