基于沉积过程分析的砂质辫状河储层中细粒沉积成因机制与分布模式研究

The fine-grained deposition in this application is mudstone and siltstone in sandy braided river reservoirs. They are the key to the paleogeography and paleo-sedimentology of paleoriver depositions and also the key to heterogeneity characterization of braided river reservoirs. But the fine-grained deposition hasn’t been studied enough. The key scientific problems have not been resolved including its types, genesis mechanism and distribution model. In this application, study of modern river, outcrops and dense-well net block data is carried on. Experiment methods, including aerial photography with unmanned aerial vehicle, ‘4D’ high resolution satellite data, geological radar, trench and outcrop profile analysis, flow velocity measurement and numerical deposition simulation, and repeated measurement of modern deposition, dynamic and static data analysis of dense well net are used. The key scientific problems mentioned are explored with analysis of its static characteristics and deposition process. Through this study, the fine-grained deposition’s types and characteristics in sandy braided rivers will be summarized, the changes of deposition process and hydrodynamic forces with time and space will be analyzed, genesis mechanism and distribution model of different fine-grained depositions will be revealed, and the knowledge base for fine-grained deposition’s characteristics will be built. The above results will be used and examined in dense well net development block. This study is to improve the development of fluvial sedimentology and has wide application prospect in braided river reservoir research. It has important significance of academic innovation and social economic value.

本申请中的细粒沉积指砂质辫状河储层中的泥岩和粉砂岩，它是打开河流古地理和古沉积学信息的钥匙，也是精细表征辫状河砂体非均质性的关键，但长期以来对其研究关注不够，细粒沉积研究中的关键科学问题——细粒沉积的发育类型、成因机制和分布模式，尚未认识清楚。本申请开展现代沉积、露头和密井网区研究，采用无人机航拍、“四维”高分辨率卫星资料、地质雷达、探槽及露头测量、水流测速、沉积数值模拟等实验方法和现代沉积的不同时间多次观测，结合密井网解剖区动静态分析，从细粒沉积的静态特征和沉积过程两方面，探究上述关键科学问题。通过研究，总结砂质辫状河中细粒沉积发育类型和特征，分析其沉积过程及水动力条件的时空变化，揭示不同类型细粒沉积成因机制和分布模式，建立砂质辫状河细粒沉积特征知识库，并在密井网区应用和验证。本研究是对河流沉积学的发展完善，同时在辫状河油气储层研究中应用前景广阔，具有重要的学术创新意义和社会经济价值。

砂质辫状河内的细粒沉积对沉积事件和沉积过程有重要的指示意义，同时也是地下辫状河沉积的油气储层结构表征的重要依据。本项目开展五方面研究：1）采用无人机测绘建模、地质雷达探测及露头测量等方法，开展了砂质辫状河现代沉积和露头的研究；2）利用沉积数值模拟等实验方法开展不同类型细粒沉积单元的成因机制研究；3）通过露头区、现代沉积和地下密井网解剖区的分析，总结细粒沉积的分布规律和分布模式；4）开展细粒沉积单元的沉积特征知识库研究；5）将总结的细粒沉积分布规律应用于实际地下油藏。通过项目研究取得几点认识：1）识别了砂质辫状河沉积中的四种细粒沉积类型，包括落淤层、堤岸和溢岸沉积、坝顶洼地充填、废弃河道；2）分析了辫状河内部的复杂水动力条件，恢复了心滩复合体形成和演化过程以及伴随的水动力空间差异性，总结了以坝顶洼地和落淤层为主要类型的心滩内部细粒沉积的形成机制；3）建立了包含不同细粒沉积的砂质辫状河沉积相模式；4）在露头研究中，通过无人机测绘和地质雷达探测构建的三维露头沉积模型，定量展示了落淤层和坝顶洼地充填沉积的空间发育特征及发育规模；5）对三个典型砂质辫状河沉积的油田进行了精细刻画，包括委内瑞拉奥里诺科重油带砂质辫状河沉积、大港埕海油田馆陶组和南大港羊二庄油田馆陶组砂质辫状河沉积，在建立的细粒沉积模式指导下刻画了辫状河储层内部结构，对油田开发提供了有效指导。通过本项目回答了砂质辫状河沉积中细粒沉积发育类型、成因机制和分布模式这一关键科学问题，丰富了河流沉积学理论认识，并能够应用于地下油气储层表征和现代辫状河的河流治理与环境研究，具有显著的科学意义和社会经济价值。