The spatial and temporal evolution of the sandbody architecture of shallow-water deltas in open lacustrine basins is controlled by the classification of allocyclicity and autocyclicity. On the southwestern margin of the Ordos Basin, a braided river system deposited a shallow-water delta in the Late Triassic Period. Based on the principle of sequence stratigraphy and the hierarchical analysis of reservoir architecture, the spatial and temporal evolution of individual sandbodies in the Chang 8 1 member of the Yanchang Formation in the Zhenbei Oilfield is interpreted by utilizing data from cores, wells and outcrops. The research ideas are as follows: large deposition scale architectural elements (first- to third-order cycles, as defined by Miall) of different sequence levels are affected by allocyclicity associated with changes in tectonic activity, provenance, and sea level, and small deposition scale architectural elements (fourth- to fifth-order cycles, as defined by Miall) of different sedimentary facies mainly consist of individual sandbodies that are affected by autocyclicity associated with lake-level changes caused by various river processes. Based on previous studies, the results are as follows. The sedimentary characteristics of shallow-water deltas have been verified by core and outcrop data. In addition, three ultrashort-term cycles are identified on the basis of boundary sequences and lithofacies’ sequences in the outcrop section of the Rui River, and three sedimentary evolution stages of the delta front are defined. Finally, according to well data, five types of architectural elements at the level of single sandbodies are identified. The vertical superimposition and lateral contact relationships of different architectural elements indicate that during the three sedimentary evolution stages, the hydrodynamics weakened, strengthened slightly, and finally weakened substantially. Among the 20 kinds of architectural element spatial combination patterns formed by single sandbodies, primary and secondary sandbodies have great potential for hosting remaining oil. In the process of architectural spatiotemporal evolution, the geometry and connectivity of the underwater distributary channel gradually weakened, and the spatial relationship between the underwater distributary channel and other architectural elements increased. This article proposes a new method for researching shallow-water deltas and has some guiding significance for exploiting the remaining oil in oil fields.

中文翻译：

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湖泊开放盆地浅水辫状河三角洲前缘由单循环和自循环控制的单个砂体的时空演化

开放湖泊湖盆地浅水三角洲砂体构造的时空演化受同位循环性和自循环性的分类控制。在鄂尔多斯盆地的西南边缘，一条辫状的河系在三叠纪晚期沉积了一个浅水三角洲。基于层序地层学原理和储层构造层次分析，利用岩心，井眼和露头数据解释了镇北油田延长组长8 1段单个砂体的时空演化特征。研究思路如下：不同序列水平的大型沉积规模建筑元素（如Miall定义的一阶到三阶循环）受构造活动变化相关的同周旋影响，不同沉积相的物源，海平面和较小的沉积规模建筑元素（由Miall定义为第四级到第五级循环）主要由单个砂体组成，这些砂体受与各种河流引起的湖面变化相关的自周期性影响流程。根据以前的研究，结果如下。岩心和露头数据已经证实了浅水三角洲的沉积特征。另外，根据瑞河露头段的边界层序和岩相序列，确定了三个超短期循环，并定义了三角洲前缘的三个沉积演化阶段。最后，根据油井数据，确定了单个砂体水平上的五种建筑元素。不同建筑元素的垂直叠加和横向接触关系表明，在三个沉积演化阶段，水动力减弱，轻微增强，并最终显着减弱。在单个沙体形成的20种建筑元素空间组合格局中，初级和次级沙体具有蕴藏剩余油的巨大潜力。在建筑时空演变过程中，水下分水渠的几何形状和连通性逐渐减弱，水下分水渠与其他建筑要素之间的空间关系增加。本文提出了一种研究浅水三角洲的新方法，对开发油田剩余油具有一定的指导意义。