鄂尔多斯盆地南部延长组湖相泥质重力流沉积特征与形成机制

Mudstone olistolites, mudstone debrites, mudstone turbidites, mudstone hyperpycnites, etc. lacustrine slurry gravity flow deposits were well developed in the YC7 oil member Yanchang Formation, Ordos Basin. However, instead of scarce research on slurry gravity flow deposits, most of the existed literatures were focused on sandstone reservoirs. With deepening studies on exploration and exploitation of shale oil and gas, more and more attentions will be paid to depositional mechanisms of fine-grained sediments, such as mudstone, shales and interbedded siltstone. .In order to distinguish slurry gravity flows generated fine-grained sediments and to understand their sedimentary characteristics and identifying criteria, this study aims at lacustrine fine-grained sediments in the YC7 oil member by means of large scale observations and sketches on field profiles and cores, observations on ultra-scale slices, scanning electron microscopy and energy spectrum analysis, micro-zone X-ray diffractions, laser particle size analysis, and cathode luminescence analysis. Combining with flume simulation experiments, this project study on slurry gravity flows generated fine-grained sediments, in order to: ① study on slurry gravity flows transformations, ② analyze their dynamics depositional processes, ③ probe into their transportation and deposition mechanisms, and ④ establish their depositional models. This research project has not only scientific values to theoretical study on sedimentology of lacustrine slurry gravity flow generated fine-grained sediments, but also has important practical significances to probe into forming mechanisms of lacustrine shales reservoirs and their reserve capability, distribution regularities and brittle mineral components industrial parameters.

鄂尔多斯盆地三叠系延长组长7油层组湖相细粒沉积岩中发育泥质滑塌岩、泥质碎屑岩、泥质浊积岩、泥质异重岩等重力流沉积，但此前的研究多聚焦于砂岩储层，对泥质重力流沉积极少关注。随着页岩油气勘探开发研究的不断深入，泥、页岩及其所夹粉砂岩等细粒沉积岩的沉积机理必将受到越来越多的重视。本项目以长7油层组湖相细粒沉积岩为研究对象，通过大比例尺野外（岩心）观测与素描、大尺寸薄片观测、扫描电镜及能谱分析、X-射线微区衍射分析、激光粒度分析、阴极发光分析，识别泥质重力流沉积，把握其沉积特征与鉴识标志。结合水槽模拟实验，研究泥质重力流流体类型的转化，分析泥质重力流沉积动力学过程，探索泥质重力流对细粒物质的搬运-沉积机理，建立泥质重力流沉积模式。本项目不仅对于湖相细粒物质沉积学研究具有科学价值；而且对于湖相页岩油气储层形成机理、储集性能、分布规律及脆性矿物组分工业参数研究具有重要的现实意义。

鄂尔多斯盆地三叠系延长组长7油层组湖相细粒沉积岩中发育泥质滑塌岩、泥质碎屑岩、泥质浊积岩、泥质异重岩等重力流沉积，但此前的研究多聚焦于砂岩储层，对泥质重力流沉积极少关注。随着页岩油气勘探开发研究的不断深入，泥、页岩及其所夹粉砂岩等细粒沉积岩的沉积机理必将受到越来越多的重视。.本项目以长7油层组湖相细粒沉积岩为研究对象，通过大比例尺野外（岩心）观测与素描、大尺寸薄片观测、扫描电镜及能谱分析、X-射线微区衍射分析、激光粒度分析、阴极发光分析，识别泥质重力流沉积，把握其沉积特征与鉴识标志。研究泥质重力流流体类型的转化，分析泥质重力流沉积动力学过程，探索泥质重力流对细粒物质的搬运-沉积机理，建立泥质重力流沉积模式。. 项目研究主要取得以下成果和认识：. 鄂尔多斯盆地三叠系延长组湖相泥页岩结构类型多样，发育泥质块体流沉积、泥质碎屑流沉积、泥质浊流沉积和泥质异重流沉积等多种重力流沉积类型。.泥质重力流沉积体系与砂质、砾质重力流沉积一样，受构造活动和气候的控制。细粒沉积物重力流可以在三角洲前缘至深湖沉积环境中广泛发育。因此，利用深水细粒沉积物的特征和沉积环境变迁，可以反馈气候的变化和构造活动的变化。. 泥质重力流沉积不仅在大型坳陷型湖盆发育，而且可以存在于断陷湖盆、裂谷盆地等多种沉积盆地之中。. 源自陆地洪水河流的大量淡水注入，不仅将大量的陆源有机物质（如植物碎屑、动物遗体等）作长距离搬运输入至深水沉积区，从而有利于深水区富有机质沉积物的埋藏和保存；而且大量的淡水输入可以改变汇水盆地的古盐度、古生态。. 重力流沉积将相对粗粒沉积物搬运至深水细粒沉积区，有利于增加深水细粒沉积物中碎屑颗粒的含量，从而有利于非常规油气储层的压裂改造。. 本项目研究成果不仅对于湖相细粒物质沉积学研究具有科学价值；而且对于湖相页岩油气储层形成机理、储集性能、分布规律及脆性矿物组分工业参数研究具有重要的现实意义。