The second member of Kongdian Formation (Ek₂) of Cangdong Sag represents an excellent hydrocarbon source rocks interval target for crude oil and shale oil production in the Bohai Bay Basin. To reconstruct the palaeoenvironmental conditions and reveal the mechanisms of organic matter enrichment of the Ek₂ shales, a series of analyses (total organic carbon (TOC), Rock-Eval pyrolysis, major and trace element analyses, and X-ray diffraction (XRD)) were performed on samples collected from the borehole of Cangdong Sag. The Ek₂ consists of fine-grained rocks deposited in a lacustrine environment, and it can be further subdivided into four members (Ek₂⁴ to Ek₂¹). The results show that the Ek₂ contains a high abundance of thermally mature Type I and II kerogen, and most of the samples show good to excellent generative potential. The mineralogical compositions, dominated by quartz, feldspar, and dolomite, with subordinated calcite, clay minerals, and analcime. Specific major and trace elements were employed to analyze the changes in paleoclimate conditions, lake water chemistry, and the detrital influx of Ek₂. The vertical changes of paleoenvironmental indicators suggest that during the sedimentary period of Ek₂, the climate changed from semi-humid to arid, with the input of terrigenous detrital gradually decreased, and the salinity of the water increased. The relationship among the primary productivity, redox conditions, detrital influx indicators and TOC content suggests that primary productivity was the most critical factor in controlling organic enrichment, and the input of terrigenous debris promotes the increase in productivity. The high primary productivity, together with anoxic bottom water conditions, resulted in the greatest enrichment of organic matter in the lower part of Ek₂ shale (Ek₂³). The upper part (Ek₂¹) is mainly composed of moderate-TOC calcareous shale, which is deposited under arid paleoclimate, with low detrital input, moderate productivity, and favorable preservation conditions.

沧东凹陷孔店二段（Ek ₂）代表了渤海湾盆地原油和页岩油生产的优良烃源岩层段。为了重建古环境条件并揭示 Ek ₂页岩有机质富集的机制，一系列分析（总有机碳 (TOC)、Rock-Eval 热解、主要和微量元素分析以及 X 射线衍射 (XRD)） ) 是对从沧东凹陷钻孔采集的样品进行的。Ek ₂由沉积在湖相环境中的细粒岩石组成，它可以进一步细分为四个成员（Ek ₂ ⁴至 Ek ₂ ¹）。结果表明，Ek ₂含有高丰度的热成熟 I 型和 II 型干酪根，大部分样品显示出良好至极好的成矿潜力。矿物成分以石英、长石、白云石为主，次要方解石、粘土矿物、方沸石。采用特定的主量和微量元素分析古气候条件、湖水化学和Ek ₂碎屑流入量的变化。古环境指标的垂直变化表明 Ek ₂沉积期，气候由半湿润转为干旱，陆源碎屑输入逐渐减少，水体盐度增加。初级生产力、氧化还原条件、碎屑流入指标和TOC含量之间的关系表明初级生产力是控制有机富集的最关键因素，陆源碎屑的输入促进了生产力的提高。较高的初级生产力以及底水缺氧条件导致 Ek ₂页岩下部(Ek ₂ ³ )有机质最富集。上部 (Ek ₂ ¹) 主要为中-TOC 钙质页岩，沉积于干旱古气候条件下，碎屑输入量低，产能适中，保存条件良好。