砂泥成岩系统内成岩物质交换及其对砂岩溶蚀和胶结的影响

The dissolution and cementation of sandstones are mainly driven by the geochemical system consist of diagenetic fluid and diagenetic material, which both were key factors. This proposal selected Paleogene turbidite sandstones in eastern faulted basin, and mainly analyzed the control of diagenetic fluid and diagenetic material to sandstones dissolution and cementation, by dense sampling and other analysis methods such as thin section, scanning electron microscope, X ray diffraction, cathodeluminescence, electronic probe microscopy and fluid inclusion analysis. To illustrate the source-sink relationship in sandstone-shale diagenetic system, we study the mechanism of fluid flow and mass transport. To clarify the control of fluid concentration variation and selective dissolution to sandstone diagenesis, we study the associated mineral assemblage and thermodynamic equilibrium in the process of sandstone dissolution and cementation. To define the net change of sandstone porosity in that process, we study the influences of mass transport to the sandstone pore volumes. We hope to get the clearly mechanism of sandstone dissolution and cementation, and the porosity variation in microscope, which would help the scientific research of diagenesis and porosity predication.

砂岩的溶蚀和胶结作用受成岩流体和成岩物质组成的地球化学系统驱动，二者起到了关键作用。本次研究选择东部断陷盆地古近系深埋藏浊积扇砂岩为研究对象，通过密集采样与测试，利用岩石薄片、扫描电镜、X衍射、阴极发光、电子探针和流体包裹体测试等实验手段，分析封闭的砂泥成岩系统中成岩流体和成岩物质对砂岩溶蚀和胶结的影响和控制。主要研究成岩系统内成岩流体的迁移和成岩物质的转移机制，阐明砂泥成岩系统中的源-汇关系；研究砂岩溶蚀和胶结作用过程中的"共生矿物组合"与热力学平衡关系，阐明微观尺度下成岩流体浓度变化和选择性溶蚀对砂岩溶蚀和胶结起到的关键作用；研究孔隙流体及成岩物质转移对砂岩孔隙体积的影响，明确砂岩孔隙度的净变化程度。希望通过本次研究在微观尺度下把握砂岩溶蚀和胶结作用机理及孔隙变化规律，为成岩演化和孔隙预测提供科学依据。

利用铸体薄片、扫描电镜、阴极发光、X衍射、包裹体测试等手段，详细分析了济阳坳陷渤南洼陷沙三段连续取心砂岩段的溶蚀作用和胶结作用特征，以及该砂体周围泥岩的成岩作用特征。研究表明，砂岩的溶蚀和胶结作用与周围泥岩的成岩作用之间存在流体和成岩物质交换，相互产生了影响；进一步通过对比泥岩和砂岩的成岩产物和“共生矿物组合”综合分析了这一系统内的成岩物质交换过程和机理，并对比了四川盆地须家河组类似砂岩的成岩作用、物性特征和孔隙演化过程，总结了这种流体和物质交换对砂岩溶蚀与胶结作用、孔隙形成和改造、物性差异的影响，同时认为砂岩成岩和孔隙演化的定量研究有待适当探索。