构造-物源供给对湖相断陷盆地异重流沉积的控制机理：以东营凹陷沙河街组为例

On the basis of triggering mechanisms, deep-water sediment gravity flows can be divided into two main categories, including well-documented, slump-induced, intra-basinal gravity flows and understudied, flood-induced, extral-basinal gravity flows. As compared to those in continental margins or depressed basins, how tectonics and sediment supply determined hyperpycnal flows and resultant depositions in steep and gentle slope zones of tectonically active rift basins still remain underappreciated. The present study employs Shahejie Formation of the Dongying sag rich in geological and geophysical data on the exploration and development on turbidites, constrained by deep-water outcrop study and physical experiments, to investigate the controls of topographic variations, sediment composition, type of flows on lakes hyperpycnites. Firstly, this study uses cores, microscopic structures of FMI database, grain size, flow dynamic interpretation of depositional structures, coupled with physical experiments, to reconstruct hyperpycnal flow processes in steep and gentle slope zones. Secondly, lithofacies, facies sequence, and 3D seismic sedimentology approach are employed to analyze depositional units and architectural styles, which, compare with slump-induced gravity-flow depositional systems, is used to address sedimentary responses to depositional processes and associated flow transformation. This, in turn, will be used to establish architectural models of hyperpycnites in both steep and gentle slope zones, providing insights into the hydrocarbon exploration and production. This research will contribute to a better understanding of the controlling of tectonics and sediment supply on depositional mechanisms and depositional models of hyperpycnal flows in rift basins.

据触发机制，深水沉积物重力流可分为内源滑塌成因重力流和目前认识程度相对较低的外源洪水成因的异重流。与被动陆缘或坳陷盆地相比，目前对构造活跃的断陷盆地陡坡带、缓坡带中构造和物源供给条件对异重流沉积的控制机理仍缺乏深入的认识。以“浊积岩”研究资料丰富的渤海湾盆地东营凹陷沙河街组为例，拟在露头解剖和沉积物理模拟实验约束下研究地形变化、沉积物组成和入湖流体类型对异重流沉积过程及响应的控制作用。首先，利用多井岩心、FMI资料显微结构、粒度资料、沉积构造的动力学解释，结合物理模拟结果重建陡坡带和缓坡带异重流沉积作用过程，探究异重流的流体转换机制。然后，利用岩相及其组合、3D地震沉积学解释分析沉积单元及构型样式，与滑榻型浊积体系比较，探讨异重流沉积过程及其转换的沉积响应，建立陡坡带、缓坡带异重流沉积模式，指导油气勘探开发。预计将在构造、物源供给对异重流沉积机制的控制和断陷湖盆异重流沉积模式方面取得突破。

本项目以“浊积岩”勘探开发资料丰富的渤海湾盆地东营凹陷沙河街组为例，在露头解剖和沉积物理模拟实验约束下研究地形变化、沉积物组成和入湖流体类型对异重流沉积过程及响应的控制作用。利用多井岩心、FMI资料显微结构、粒度资料、沉积构造的动力学解释，结合物理模拟结果重建陡坡带和缓坡带异重流沉积作用过程，探究异重流的流体转换机制。然后利用岩相及其组合、3D地震沉积学解释分析沉积单元及构型样式，与滑榻型浊积体系比较，探讨异重流沉积过程及其转换的沉积响应，建立陡坡带、缓坡带异重流沉积模式，指导油气勘探开发。通过本项目的研究，深化了湖相重力流沉积触发机制、沉积过程及沉积响应规律的认识，在以下几方面取得了重要进展与成果：（1）提出断陷盆地盆缘断裂带（陡坡带）洪水沉积作用可细分为溃坝型和季节型两种类型。前者受断层活动影响，主要发育于构造活跃期及平面上断裂活跃带；后者受气候控制，主要发育于构造稳定期或构造活跃期的断层稳定区带。据此，明确了断裂活动强度、降雨量变化等气候条件控制下的盆缘断裂带沉积模式；（2）提出断裂生长与连接作用对斜向洪水成因浊积体系沉积类型与构型模式的控制规律。提出断层软连接阶段，斜坡地貌格局仅受少量影响而无整体改变，斜向洪水成因异重流以浊积扇沉积为特征；而进入到断层硬连接阶段，斜坡地貌受到断裂活动控制而呈现沟槽分隔状，导致斜向异重流以断槽型水道沉积为特征；（3）针对断层活动较弱的缓坡带地区，提出基准面控制下的浊积岩成因及构型差异性模型，深入解剖了4级旋回内洪泛期与枯水期重力流触发机制差异，以及基准面控制下的沉积构型模型。围绕上述进展已经发表科技论文18篇，正投稿论文2篇。其中，SCI论文11篇（含正投稿论文2篇），中文核心期刊论文9篇。研究期间，参加国内外学术交流活动14人次，其中国际学术会议6人次，国内学术会议8人次。