湖相富有机质泥页岩中的事件沉积作用：以鄂尔多斯盆地长7-8段为例

The latest studies show large amounts of mudrock can also be deposited by episodic events, challenging the traditional view that a still water environment is necessary for mudrock deposition. However, the characteristics of episodic deposition in organic-rich mudrock is poorly understood, and the scanty studies concentrate on marine system. The hydrocarbon-bearing organic-rich mudrock were mostly deposited in lacustrine environment, but its episodic depositional characteristics still are poorly understood. Here we study the episodic deposition in organic-rich mudrock of the 7th-8th member of Yanchang Formation in Ordos Basin, using integrated outcrops, cores, well-logging, and testing data. This is the first time to systematically study the episodic deposition in organic-rich mudrock of the Ordos Basin. It successively studies the: 1) the types and recognition criteria of episodic deposits in organic-rich mudrock, 2) the small-scale (millimeters to centimeters) to large-scale (more than several meters) distribution law, 3) the controlling factors and depositional models of episodically deposited organic-rich mudrock, 4) the hydrocarbon significance of episodically deposited organic-rich mudrock. This study promotes the study of episodic deposition of lacustrine fine-grained sediments from relatively shallow-water to deep-water organic-rich mudrock, and thus providing a new perspective for lacustrine source rock evaluation and shale reservoir prospecting.

泥页岩总是在静水环境中缓慢悬浮沉积的传统认识正面临巨大挑战，现有研究表明突发性事件作用也可大量沉积泥页岩，但研究集中于国外海相沉积；我国广泛发育湖相含油气富有机质泥页岩，一直缺少对其事件沉积作用的系统研究。本申请项目拟以鄂尔多斯盆地延长组7-8段为对象，利用露头、岩心、分析测试、测录井等资料，首次系统研究鄂尔多斯盆地富有机质深湖泥页岩中的事件沉积作用，区分事件泥页岩成因类型并建立识别标志，揭示高精度地层格架下各类型事件泥页岩从准层序到三级层序的时空分布规律及演化特征，分析事件泥页岩沉积的主控因素并建立沉积模式，探讨事件泥页岩的油气地质意义。本申请项目将细粒物质事件沉积作用的研究从海相泥页岩推进到我国广泛发育的富有机质深湖泥页岩中，为湖相烃源岩和页岩油气储层精细预测提供了一个全新视角。

本项目以鄂尔多斯盆地延长组7-8段为对象，综合利用露头、岩心、分析测试、测录井等资料，首次系统研究了鄂尔多斯盆地富有机质深湖泥页岩中的事件沉积作用特征，系统区分事件泥页岩成因类型并建立了相应识别标志，从而揭示了事件泥页岩从准层序到三级层序的时空分布规律及演化特征，分析了事件泥页岩沉积的主控因素并建立相应沉积模式，探讨事件泥页岩的油气地质意义。本项目将细粒物质事件沉积作用的研究从海相泥页岩推进到我国广泛发育的富有机质深湖泥页岩中，为湖相烃源岩和页岩油气储层精细预测提供了新视角。