青海隆务峡三叠系深水重力流体系的沉积过程与地层构型

Deepwater gravity-flow systems are not only archives of such scientific information as paleoclimate and paleoenvironment, but are of great significance for oil and gas exploration. However, the general paucity of research on changes of depositional processes in plan view and on 3D quantitative characterization of stratigraphic architecture hinders our understanding and prediction of such systems. Focusing on these issues, this study intends to qualitatively and quantitatively analyse the processes and architecture of the outcropping gravity flow system in Longwu Gorge, Qinghai, by using traditional field techniques, UAV digital outcrop technology and laboratory methods. Analysis of sedimentary logs and thin sections will be carried out in order to understand the genesis of lithofacies. Following this, the 3D distribution characteristics of lithofacies will be examined by using the photo-realistic outcrop model established by digital outcrop technology, in order to clarify the plan-view evolutionary patterns of depositional processes. Based on sedimentary logs and the photo-realistic outcrop model, this study will quantitatively analyse the types and hierarchy of architectural elements, and extract quantitative parameters concerning spatial configurations of architectural elements. It is expected that this study will not only help to solve the above scientific problems regarding gravity flow systems and promote the development of this discipline, but also provide an analogous outcrop model for reservoir prediction, reducing the risk of hydrocarbon exploration and development.

深水重力流体系不仅记录着古气候、古地理等重要科研信息，而且拥有巨大油气勘探意义；但目前对其沉积过程研究缺乏平面上的规律探索，而在地层构型方面三维定量表征不足，阻碍了对重力流体系的理解和预测。本项目围绕这两方面的科学问题，拟以青海隆务峡地区出露良好的深水重力流体系为研究对象，通过传统野外研究方法、无人机数字露头技术和室内分析测试，对重力流沉积过程与地层构型开展定性、定量综合分析。拟根据野外实测剖面与室内薄片分析，揭示岩相成因机制；在此基础上，利用数字露头技术建立的拟真露头模型分析岩相三维分布特征，从而阐明沉积过程的平面演化规律；结合实测剖面与拟真露头模型，定量分析构型要素的类型与级次，并拾取构型要素空间配置关系的定量参数，进而建立三维定量化构型模型。本项目研究成果不仅有助于上述两方面科学问题的解决，促进深水重力流学科发展，而且可以为油气储层预测提供可类比的露头范例，降低油气勘探开发风险。

深水重力流体系不仅记录着古气候、古地理等重要科研信息，而且拥有巨大油气勘探意义。深水重力流由于不可预测性和巨大破坏性等特点而难以直接观测，往往需要通过岩石地层记录来研究，尤其是出露良好的野外地质露头。本项目以青海省隆务峡地区出露的重力流体系为研究对象，通过传统野外研究方法、无人机数字露头技术和室内分析测试，对重力流沉积过程与地层构型开展系统性研究。在野外露头岩性岩相和垂向沉积序列分析的基础上，项目明确研究区为一深水沉积环境，认为该区发育的主要沉积体系类型为水道化的朵叶体；研究发现该区深水朵叶体中发育具有二元结构特征的、以再沉积碳酸盐岩颗粒为主的巨厚事件层，并建立了碎屑流-浊流相互转化的混合事件层沉积模式；此外，研究揭示了深水朵叶体内部构型叠加特征：在大尺度上，朵叶体或朵叶复合体横向厚度变化较小，呈现席状特征，在小尺度上，朵叶体要素的厚度横向变化快，它们交错叠置，呈现出补偿性叠加的样式。本项目研究成果不仅对研究区宏观古地理背景重建具有约束作用，而且可以为油气储层预测提供可类比的露头范例，降低油气勘探开发风险。除此之外，本项目对目前研究较少的碳酸盐岩再搬运形成的重力流沉积，尤其是混合事件沉积提供了一些新的认识，一定程度上丰富和发展了原有理论模型。