页岩储层成岩作用及其对储层脆性的影响 ——以渝西地区五峰组—龙马溪组深层页岩为例

页岩粒度细小、岩石致密、微观非均质性显著，在成岩作用改造下发育形成页岩气储层，成岩作用的研究可以为优质页岩储层发育机理提供依据。以渝西地区綦江观音桥剖面、南川泉浅1井、南川三泉剖面、大足Z-203井等代表性剖面、钻孔为例，通过X射线衍射、氩离子抛光—场发射扫描电镜、能谱、岩石薄片/光片显微观察、有机地球化学测试、力学特征测试等手段，对储层成岩作用及其对储层力学脆性的影响展开系统研究。结果表明，研究区五峰组—龙马溪组页岩物质组分、岩石结构、力学性质存在层段性差异，成岩作用阶段介于晚成岩作用阶段至极低级变质作用阶段之间；储层主要成岩作用类型可以划分为压实作用等物理性成岩作用、矿物溶蚀作用等矿物相关化学性成岩作用和有机质生烃作用等有机质相关化学性成岩作用三类。研究区五峰组—龙马溪组底部存在部分脆性矿物高于80%的超高脆性矿物含量层段，碳质—硅质富层理页岩在特殊储层成岩作用的影响下形成大量自生微晶石英，构成以微晶石英+赋孔有机质为主的显微物相组合，兼具良好的力学脆性与储集能力，而其他层段缺乏持续演化不断形成微晶石英的物质基础。储层成岩作用发生的物质基础、岩石结构、类型、作用强度在层段间的差异，是储层脆性矿物与力学性质差异的关键影响因素，应纳入储层评价与优质储层机理研究的关注范畴。

Diagenesis of a Shale Reservoir and Its Influence on Reservoir Brittleness:Taking the deep shale of the Wufeng-Longmaxi Formation in western Chongqing as an example

Shale is developed with a small grain size and strong microscopic heterogeneity， forming gas reservoirs during the transformation of diagenesis process. The research of diagenesis provides a basis for a deeper understanding of high-quality reservoir forming mechanisms. This paper studies reservoir diagenesis and its effect on shale using the Qijiang Guanyinqiao section， Nanchuan Sanquan section， Quanqian-1 well， and Dazu Z-3 well in the western Chongqing area as an example using X-ray diffraction （XRD）， argon ion polishing-field emission scanning electron microscopy （AIP-FESEM）， Energy Dispersive X-Ray Spectroscopy （EDS）， microscopical observation， and geochemical and mechanical tests. The results show that the Wufeng-Longmaxi Formation has interval differences in material component， rock structure， and mechanical properties. The reservoir diagenesis is between the late diagenetic stage and very-low-grade metamorphism stage and is divided into three categories: physical diagenesis （e.g.， Compaction）， mineral related chemical diagenesis （e.g.， mineral dissolution）， and organic matter related chemical diagenesis （e.g.， hydrocarbon generation of organic matter）. Carbonaceous-siliceous shale layers with more than 80% brittle minerals and a large amount of authigenic microcrystalline quartz exist in the Wufeng and bottom Longmaxi Formation with microfacies of microcrystalline quartz and pore-bearing organic matter under the influence of special diagenesis process. In contrast， other intervals in the Wufeng-Longmaxi Formation lack the material base for the continuous development of authigenic quartz. The material basis， rock structure， type， and influence degree of diagenesis show interval differences， which is a key factor that influences brittle minerals and mechanical properties and should be included in the scope of reservoir evaluation and high-quality reservoir mechanisms.