高邮凹陷深凹带戴一段古水体特征

Study on characteristics of connate water in the first member of Dainan Formation, deep concave belt of Gaoyou sag

在油气勘探和开发研究中,对于古水体盐度、古气候、古水深等方面的基础研究十分薄弱。利用粘土矿物、古生物、微量元素分析古盐度,利用孢粉特征分析古气候,利用泥岩颜色分析古水深,从而分析高邮凹陷深凹带戴一段古水体特征。研究区粘土矿物以绿泥石为主,其次为蒙伊混层,伊利石含量较少; 古生物主要有介形类、轮藻和腹足类等; 锶钡比值平均为0.98,铷钾比值平均为0.0039,硼镓比值平均为3.95,说明研究区戴一段处于陆相淡水湖泊环境; 孢粉特征反映高邮凹陷戴一段沉积时期气候温暖而潮湿。泥岩颜色反映了研究区水体深度不大,常常暴露于地表,处于氧化环境。纵向上,研究区岩心泥岩颜色由深灰色—棕红色—灰色—深灰色变化,反映了古水深逐渐增加的过程。

In recent few years, in the research of the exploration and the exploitation of the oilfield, the research on the paleosalinity, paleoclimate and palaeobathymetry is very limited. In this research, we use the result of the tests, such as the clay mineral, microelement, palaeontology and palynomorph, to infer the information of the paleosalinity, paleoclimate and palaeobathymetry. The characteristic of palaeontology shows that the environment of the deep concave belt of Gaoyou sag in the first member of the Dainan Formation is freshwater lake of continental facies, and by the analysis of the microelement, the paleosalinity of the research area changed from the brackish water to freshwater. And, we use the color of the mud stone to analyze the palaeobathymetry , and in the well, the color of the mud stone changed from the deep grey to brown, grey, and to deep grey again, this shows that the palaeobathymetry is increased in the process.