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SiO_2的赋存状态对页岩气开发具有重要意义,其成因机制与成岩系统具有密切关系。综合利用野外露头、钻井岩心等资料,采用X-射线衍射分析、阴极发光、扫描电镜及能谱分析等分析手段,系统研究了渝东南龙马溪组页岩成岩系统主控因素、成岩过程模型及成岩系统过程对SiO_2赋存状态的影响。渝东南地区龙马溪组页岩成岩现象丰富,成岩系统过程也相当复杂;早期成岩主控因素受沉积机制影响较大,中后期受成岩机制制约,晚期主要受到构造机制的影响;后期构造运动使得页岩成岩系统具有明显的阶段性特征,喜山期页岩地层的大幅度隆升,不仅使页岩与外界系统连通性加强,溶蚀作用和微裂缝变得发育,还导致页岩储层物性、有机质生烃演化、油气保存条件等发生了明显的变化;在成岩演化不同阶段,不同的化学流体特征制约着页岩中硅质成因,页岩中SiO_2赋存状态在早期主要以陆源石英及蛋白石为主,中后期以微晶自生石英为主,晚期在石英脉体中发育中—粗晶石英。
The occurrence of SiO_2 is of great significance to the development of shale gas, and its genetic mechanism is closely related to the diagenetic system. By comprehensively using the data of outcrops and drilling cores, the main controlling factors and diagenetic processes of shale diagenesis system of Longmaxi Formation in southeast Chongqing were systematically studied by X-ray diffraction, cathodoluminescence, scanning electron microscopy and energy spectrum analysis. Influence of Diagenetic System on the Occurrence of. The diagenetic system of Longmaxi Formation is rich in diagenesis in the southeastern Chongqing area. The diagenetic system is also quite complicated. The main controlling factors of early diagenesis are greatly influenced by sedimentary mechanism, and are controlled by diagenetic mechanism in the middle and late stages. The latter is mainly affected by tectonic mechanism. Shale diagenetic system has obvious stage characteristics. The sharp uplift of shale formation in the Himalayan period not only enhanced the connectivity of shale with the external system, but also enhanced the dissolution and microcrack development. It also resulted in the physical property of shale , Organic hydrocarbon generation evolution, oil and gas preservation conditions have undergone significant changes. At different stages of diagenetic evolution, different chemical fluid characteristics restrict the silicagenesis of shale. The occurrence of SiO 2 in shale is dominated by terrigenous quartz and Mainly opal, in the latter part of microcrystalline self-born quartz, late in the quartz veins in the development - coarse grain quartz.