川东地区上二叠统龙潭组泥页岩基本特征及页岩气勘探潜力

四川盆地晚二叠世龙潭期沉积相类型多样，为落实不同沉积相带的页岩气勘探潜力，针对不同相带典型井开展了系统的页岩气形成条件分析，四川盆地晚二叠世龙潭期富有机质页岩主要发育在潮坪—潟湖相和陆棚相，其中潮坪—潟湖相泥页岩分布在资阳—永川—綦江一带，岩性组合复杂，泥岩、页岩、泥质碳酸盐岩不等厚互层，煤层全段均有发育，具有“高TOC、高黏土、高孔隙度、高含气量”的四高特征，有机质类型主体为Ⅲ型；浅水混积陆棚相龙潭组分布在广安—长寿—南川一带，煤层减少，灰质增加，龙潭组二段煤层基本不发育，有机质类型为Ⅱ₂-Ⅱ₁型，具有厚度稳定、TOC中等、脆性矿物含量高、有机孔发育的特点，气测普遍活跃；深水陆棚相上二叠统吴家坪组分布在石柱—万县以及广元—梁平一带，煤层仅在吴家坪组底部发育，吴家坪组二段以硅质页岩、泥岩为主，具有“高TOC、高脆性矿物含量、高孔隙度、高含气量、高含气饱和度”等五高特征，有机质类型为Ⅱ₁型，有机质孔普见，是目前二叠系页岩气勘探开发的主力层系。 

Basic characteristics and exploration potential of shale gas in Longtan Formation of Upper Permian in eastern Sichuan Basin

Various types of sedimentary facies were developed during the Longtan period of the Late Permian, Sichuan Basin. To discover the shale gas exploration potential of belts with different sedimentary facies, a systematic analysis of shale gas generation conditions was carried out on the basis of different typical wells. The organic-rich shale developed in the Sichuan Basin during the Late Permian Longtan period was mainly distributed in tidal flat-lagoon and shelf facies. With complex lithological combinations, the tidal flat-lagoon facies shale was distributed in the Ziyang-Yongchuan-Qijiang areas. Mudstone, shale, and argillaceous carbonate rocks were interbedded with varying thickness and coal seams were also developed in all sections. Furthermore, it has the characteristics of "high TOC, clay and gas contents, and high porosity". The main organic matter type is type Ⅲ. The shallow water, mixed shelf facies in the Longtan Formation was mainly distributed in the Guang'an-Changshou-Nanchuan area, with reduced coal seams and increased ash content. Coal seams were barely developed in the second member of the Longtan Formation. Its organic matter type is Ⅱ₂-Ⅱ₁, with stable thickness as well as medium TOC and brittle mineral contents. Gas logging was anomalous. The deep-water shelf facies in the Wujiaping Formation were mainly distributed in Shizhu-Wanxian and Guangyuan-Liangping. Coal seams were only developed at the bottom of the Wujiaping Formation. Moreover, the second member of the Wujiaping Formation is composed of siliceous shale and mudstone, which has the characteristics of "high TOC content, high brittle mineral content, high porosity, high gas content, and high gas saturation". Its organic matter type is Ⅱ₁, with widespread organic pores. It is currently the main strata for the exploration and development of Permian shale gas in the Sichuan Basin.