四川盆地涪陵地区五峰组-龙马溪组海相页岩岩相类型及储层特征

页岩岩相划分及其储层品质研究是页岩气勘探开发地质评价的基础性研究工作。以钻井资料为基础，综合利用全岩X-衍射、镜下薄片等资料建立了海相页岩岩相划分方案，并结合总有机碳含量、孔隙结构、孔渗特征、纹层特征和含气性等地化测试资料，对五峰组-龙马溪组一段不同页岩岩相的储层品质进行系统分析。涪陵地区五峰组-龙马溪组一段发育3大类页岩岩相，其中主要岩相有5亚类，即粘土质硅质页岩、含钙粘土质硅质页岩、硅质粘土页岩、粘土质硅质混合页岩和含钙粘土质硅质混合页岩。不同岩相储层品质具有较大差异，硅质类页岩具有高TOC、高孔隙度和高含气性等特征，为优质页岩岩相。沉积地质背景在控制页岩岩相发育的同时，进一步影响了页岩储层品质发育特征。五峰组和龙马溪组一段下部硅质页岩沉积期，频繁的火山活动为浮游生物爆发提供了大量富营养物质，并形成贫氧和厌氧环境，有利于有机质保存，发育富碳硅质页岩；龙马溪组一段中部和上部发育的混合类页岩和粘土类页岩分别受底流和陆源碎屑物质供给影响，沉积环境渐变为富氧环境，有机质保存条件变差，总有机碳含量较低，含气性降低。

Lithofacies types and reservoir characteristics of marine shales of the Wufeng Formation-Longmaxi Formation in Fuling area,the Sichuan Basin

Lithofacies identification and reservoir characteristics study of shale are fundamental to the geological evaluation of shale gas exploration and development.Based on the drilling data,X ray diffraction and thin section analysis,we proposed a scheme for lithofacies classification of marine shale.Then,we systematically analyzed the reservoir quality of varying shale lithofacies from the Wufeng Formation-Longmaxi Formation's first member,based on geochemical test results such as the total organic carbon(TOC) content,pore structure,porosity-permeability properties,lamina features,gas-charging properties,etc.The stratigraphic member developed three categories of shale lithofacies in the Fuling area,which can be subdivided into five major lithofacies(argillaceous-siliceous shale,dolomitic-argillaceous-siliceous shale,siliceous-clay shale,mixed argillaceous-siliceous shale,and mixed dolomitic-argillaceous-siliceous shale).There is a significant difference in reservoir characteristics between various lithofacies:the siliceous shale is a high-quality lithofacies with high TOC,high porosity and high gas content.The sedimentary setting determines reservoir quality development,while also controlling the shale lithofacies development.During the sedimentation of siliceous shale in the lower Wufeng Formation-Longmaxi Formation's first member, frequent volcanic activities provided abundant nutrients for plankton outburst,and induced an oxygen-poor and anaerobic environment which is conducive to the preservation of organic matter and the development of organic carbon-rich siliceous shale.The mixed shale and argillaceous shale developed in the middle and upper part of the first member are affected by bottom current and terrigenous debris supply respectively,which led to an oxygen-rich depositional environment,deteriorating the preservation condition of organic matters,thus lower content of TOC and less gas generation.