Palaeogeographical development of two merging delta systems (Eocene Shahejie Formation) in the Bohai Bay Basin, E China and implications for hydrocarbon exploration
Palaeogeographical development of two merging delta systems (Eocene Shahejie Formation) in the Bohai Bay Basin, E China and implications for hydrocarbon exploration
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DOI：
10.1016/j.jop.2023.08.003
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发表时间：
2023-09
期刊：
影响因子：
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通讯作者：
Renchao Yang;Y. Li;Ai-Ping Fan;A. V. van Loon;Jin Li;Zuo-Zhen Han;Jie Chen
中科院分区：
文献类型：
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作者：
Renchao Yang;Y. Li;Ai-Ping Fan;A. V. van Loon;Jin Li;Zuo-Zhen Han;Jie Chen
始新世时期，在东营次盆地的一个大湖东侧同时发育了两个三角洲，东营次盆地是中国东部渤海湾盆地的一部分。形成三角洲的河流有不同的集水区，由于分选和泥质含量的差异，导致沉积物具有不同的渗透性和孔隙度。这两个三角洲都发生了扩张，经常在其前缘产生的物质流形成了横向扩张的叶瓣。这最终导致了两个三角洲的合并，这是迄今为止很少从古代沉积物中描述的特征。岩心分析和地震反射资料表明，两个三角洲的合并发生在9个阶段，这是由其间的缓慢沉积甚至暂时退积阶段决定的。来自两个三角洲的沉积物的交替和它们最终的混合使得合并的三角洲的结构比“经典的”单个三角洲的结构复杂得多。这对可能的储集层特征的空间分布的可预测性有很大影响，但详细的岩心分析表明，最好的油气储集层由三角洲平原分流河道中形成的砂体和合并三角洲前方深湖环境中形成的桑迪浊积岩组成。
Two deltas developed simultaneously during the Eocene on the eastern side of a large lake that existed in the Dongying Sub-basin, which forms part of the Bohai Bay Basin in eastern China. The rivers that built the deltas had different catchment areas, which resulted in sediments with different permeability and porosity, due to differences in sorting and mud content. Both deltas prograded, and mass flows that originated frequently on their fronts formed lobes that expanded laterally. This eventually led to merging of both deltas, a feature that has rarely been described from ancient deposits thus far. Core analysis and seismic reflection data show that the merging of the two deltas took place in nine phases, determined by phases of slower progradation or even temporary retrogradation in between. The alternation of sediments from both deltas and their eventual mixing makes the architecture of the merged deltas much more complex than that of ‘classical’ single deltas. This affects the predictability of the spatial distribution of possible reservoir characteristics significantly, but detailed core analysis shows that the best hydrocarbon reservoirs consist of sand bodies formed in distributary channels on the delta plains, and of sandy turbidites formed in the deep-lacustrine environment in front of the merged deltas.