欢迎访问《高校地质学报》官方网站,今天是
分享到:

高校地质学报 ›› 2019, Vol. 25 ›› Issue (6): 801-.DOI: 10.16108/j.issn1006-7493.2019081

• 烃源岩地球化学专栏 •    下一篇

渤海湾盆地东濮凹陷古近系古湖盆氧化还原条件及其优质烃源岩的发育模式

马小祥,姚素平,张柏林,张云献,彭君   

  1. 1. 南京大学地球科学与工程学院,南京 210023;
    2. 中国石化中原油田分公司,濮阳 457001
  • 收稿日期:2019-10-12 修回日期:2019-11-12 出版日期:2019-12-20 发布日期:2020-01-06

Redox Conditions of Paleogene Paleolake and Development Models of High-quality Source Rocks in the Dongpu Sag, Bohai Bay Basin

MA Xiaoxiang,YAO Suping,ZHANG Bolin,ZHANG Yunxian,PENG Jun   

  1. 1. School of Earth Sciences and Engineening, Nanjing University, Nanjing 210023, China;
    2. Zhongyuan Oilfiedld Branch Company, SINOPEC, Puyang 457001, China
  • Received:2019-10-12 Revised:2019-11-12 Online:2019-12-20 Published:2020-01-06

摘要: 通过分析东濮凹陷古近系沙河街组烃源岩样品的主微量元素含量,研究了东濮凹陷沙河街组优质烃源岩形成时的古氧化还原条件、古生产力水平及古水体的局限性,探讨了沙河街组沙三段优质烃源岩的发育模式。研究结果表明,东濮凹陷的北部沙三段优质烃源岩发育属于“深水窄盆水体分层沉积”模式。水体主要是咸水—超咸水,水体局限性较强,深度较深形成了稳定的盐度分层,从而造成底层水处于稳定的缺氧条件,有利于有机质的保存。根据主微量元素分析及古生产力的还原,沙三段沉积时水体表层富氧,发育大量有机质,生物死亡后有机质发生絮凝,在氧化还原界面吸附于铁锰氧化物的表面,沉降到底部,底部水体缺氧到还原的性质,适合保存有机质。东濮凹陷南部沙三段优质烃源岩发育属于“浅水广盆凹盆缺氧沉积”模式。湖泊水体为淡水,湖水局限性很弱,属于开阔水域,由于地表河流及洪水带来大量营养物质,表层水体古生产力较高,缺乏缺氧的保存条件,有机质生化阶段消耗较多,但是局部也可以发育弱还原水体,进而形成优
质烃源岩。

关键词: 东濮凹陷, 古近系, 烃源岩, 氧化还原, 古生产力, 保存条件, 发育模式

Abstract:  Based on the analysis of major and trace elements in source rock samples of the Paleogene Shahejie Formation in the Dongpu sag, the paleoredox conditions, paleoproductivity level and limitations of paleo-water body during the formation of high-quality source rock of the Shahejie Formation in the Dongpu sag were studied, and the development model of high-quality source rock of Shahejie Formation was discussed. The results show that the development of high-quality source rocks in the third member of Shahejie Formation in the north of Dongpu sag belongs to the model of“stratified sedimentation of deep-water narrow basin water body”. The water body is mainly brackish-super-brackish water, which has strong limitations and deep salinity stratification, which results in stable anoxic conditions of bottom water and is conducive to the preservation of organic matter. According to the analysis of major and trace elements and the reduction of paleoproductivity, the surface layer of Sha 3 member is rich in oxygen, and a large amount of organic matter is developed. After biological death, organic matter 1flocculates, adsorbs on the surface of ferromanganese oxide at the redox interface, and settles to the bottom, and the bottom water is anoxic to reductive, which is suitable for preserving organic properties. The development of high-quality source rocks in the third member of Shahejie Formation in the south of Dongpu sag belongs to the model of“shallow wide basin and basin anoxic deposition”. The lake water body is fresh water, and its limitation is very weak. It belongs to open water area. Because surface rivers and floods bring a lot of nutrients, surface water body has high paleoproductivity, lacking of oxygen-deficient preservation conditions, and consumes more organic matter in biochemical stage. However, weak reducing water body can also be developed locally, thus forming high-quality hydrocarbon source rocks.

Key words: Dongpu sag, Paleogene, source rocks, redox, paleoproductivity, preservation conditions, development model