束鹿凹陷中部古近系沙河街组第三段下部层序特征

Stratigraphic sequence features in lower part of the third member of Shahejie formation in the middle part of Shulu sag

通过岩心观察、薄片鉴定、地化分析,钻井地层层位划分与对比、地震层位标定和追踪等项工作的研究,结合区域构造、沉积演化特征等分析认为,冀中坳陷束鹿凹陷中部古近系沙河街组第三段下部是一个完整的三级层序。该层序顶底界面特别是顶界面的识别标志分别是:岩性上,碳酸盐岩含量高且稳定;电性上,电阻率曲线呈块状高阻、自然伽马值普遍较低;地震上,反射特征清楚,顶界面为一明显顶超面;地化指标显示界面上下有机碳含量迥异。

Based on stratigraphic correlation, core observation, thin section identifying, geochemistry analyzing and seismic horizon calibrating and tracing, and in combination with the analysis of regional tectonic and sedimentary evo- lution characteristics, an entire third- sequence is considered to be existed in lower part of the third member of Shahejie Formation in the Middle part of Shulu Sag of the middle Depression of Hebei Province. Indicators of sequence boundary, especially the top boundary were identified by using the data of lithologic character, well logging, seism, geochemistry analyzing and so on. These indicators are: the content of carbonate rock is high and steady: the exhibition of the resistivity curves is massive and high value, the natural gamma value is very low; the seismic reflection is very good and the top surface is a good toplap surface and the abundance of organic material is very different.