Abstract The most important sedimentary facies comprising shallow-water lacustrine deltas are distributary channels, and these form abundant ribbon-shaped sand bodies that are excellent petroleum reservoirs. However, distributary channel sandstones are notoriously difficult to correlate and characterize in the subsurface based on well data alone. Here, we show how seismic geomorphology can be used to map lacustrine deltaic sedimentary successions in the First Member of the Kongdian Formation within the Zilaitun Oilfield, Huanghua Depression (China). Using core and wireline logs, this study identified distributary channels as the dominant sedimentary facies. Together with mottled gray-green or maroon mudstones and locally shingled progradational seismic reflection architecture, this indicates that deltas were built in a weakly-oxidized shallow-water lacustrine environment. Next, core observations were linked to seismic data to produce a successive series of stratal slices and root mean square amplitude attribute (RMSAA) maps. The RMSAA maps allowed distributary channel, mouth bar, and beach bar facies to be identified and mapped across the study area. Two patterns of distributary channels emerged from the data: (1) a distributive pattern with a lower concentration of distributary channels; and, (2) an anastomosing deltaic pattern with a high concentration of bifurcated distributary channels. Based on the seismic geomorphological analysis we show that the succession records three phases of delta evolution - retrogradation, aggradation, and progradation - which combine to form 3rd-order sequences. From a petroleum reservoir point of view, the distributive pattern yields narrower, thicker, and less connected sand bodies than the anastomosing pattern. This is consistent with observations from modern shallow-water lacustrine delta systems, providing independent support for the interpretation and highlighting the effectiveness of using seismic geomorphology.

中文翻译：

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渤海湾盆地古新世黄骅坳陷浅水湖相三角洲地震地貌特征

摘要 浅水湖相三角洲最重要的沉积相是分流河道，这些河道形成了丰富的带状砂体，是优良的油藏。然而，众所周知，仅根据井数据很难在地下关联和表征分流河道砂岩。在这里，我们展示了如何使用地震地貌学来绘制黄骅坳陷自来屯油田孔店组一段的湖相三角洲沉积序列图。本研究使用岩心和电缆测井确定分流河道作为主要沉积相。连同斑驳的灰绿色或栗色泥岩和局部叠瓦前积地震反射结构，这表明三角洲建在弱氧化的浅水湖泊环境中。接下来，岩心观测与地震数据相关联，以生成一系列连续的地层切片和均方根振幅属性 (RMSAA) 地图。RMSAA 地图允许在整个研究区域识别和绘制分流河道、河口坝和海滩坝相。数据中出现了两种经销渠道模式：（1）经销渠道集中度较低的经销模式；(2) 具有高浓度分叉分流河道的吻合三角洲模式。基于地震地貌分析，我们表明该序列记录了三角洲演化的三个阶段——退积、加积和进积——它们结合形成了三阶序列。从石油储层的角度来看，分布模式比吻合模式产生更窄、更厚、连接更少的砂体。这与现代浅水湖相三角洲系统的观测结果一致，为解释提供了独立的支持，并突出了使用地震地貌学的有效性。