Sedimentary characteristics of the source rocks in fluctuation from lake facies: an example from the Well Niu-38 in the Dongying Depression, China

以东营凹陷牛38井为例,研究显示,该井沙河街组沙三段烃源岩的沉积特征具有明显的波动性．宏观上体现为, 构造因素控制湖盆的整体升降和沉积构造旋回,但季节性气候及其它因素的影响使湖盆呈现次级旋回的复合性沉积．微观上表现为纹层的不连续性及生物扰动构造等事件性沉积.古湖面不同幅度的波动和变化导致相对稳定的泥岩沉积的不稳定性,有机质的分布也呈现较显著的非均质性．湖泊的沉积过程影响了微量元素、有机质以及烃源物质的分布,水体较深、盐度较高的沙三段下部多数微量元素含量较高以及B/Ca、Sr/Ba呈现高值;水体较浅、盐度较低的沙三段中部各元素的分布较为稳定,B/Ca、Sr/Ba比值及Sr的含量均显著降低.波动性沉积导致烃源岩呈现明显的优劣性分布,沙三段下部中的有机质富集,为优质烃源岩;沙三段中部的有机质分布较为分散,生排烃的资源潜力有限．;The sedimentary course controls the distribution of minerals and source rocks. The characteristics of source rocks in the Member 3 of Shahejie Formation in Dongying Depression revealed the obvious fluctuation of the sedimentary course of lake. Tectonic movement controlled the rise and settle of the whole lake, and with the influence of climate and the other geological factors, the lake deposit was a result of complex sedimentary course which was a main sedimentary cycle contained many hypo-cycles. The heterogeneity and the unstable deposition in the stable deposition of source rocks were believed as a result of the lacustrine cyclothemic sedimentation and the Jake-level fluctuation. The environment of deep water-body and high salinity in the Member 3 of Shahejie Formation was characterized by high content of many trace elements and high value of B/Ca, Sr/Ba. The deposition in fluctuation contributed to the distribution of organic matter in different manners; organic matter was enrichment in the lower part of the Member 3 ol Shahejie Formation, and it was source rocks in high quality; the organic matter was dispersed in the middle part of the Member 3 of Shahejie Formation, whose resource potential for hydrocarbon generation and expulsion was restricted.