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高校地质学报 ›› 2024, Vol. 30 ›› Issue (05): 622-633.DOI: 10.16108/j.issn1006-7493.2023055

• • 上一篇    

早寒武世玉尔吐斯组烃源岩沉积环境与有机质富集机制

孙候雪1,2 ,郝 芳1, 2,王 奇1, 2*,田金强1, 2   

  1. 1. 中国石油大学(华东)地球科学与技术学院,青岛 266580;
    2. 深层油气全国重点实验室,中国石油大学(华东),青岛 266580
  • 出版日期:2024-10-20 发布日期:2024-10-20

Sedimentary Environment and Organic Matter Enrichment Mechanism of the Yuertusi Formation Source Rocks during Early Cambrian Period

SUN Houxue1,2,HAO Fang1,2,WANG Qi1,2*,TIAN Jinqiang1,2   

  1. 1. School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China;
    2. National Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao 266580, China
  • Online:2024-10-20 Published:2024-10-20

摘要: 早寒武世玉尔吐斯组烃源岩发育机制是塔里木盆地深层油气勘探研究的重点之一,近些年台盆区超深层的钻井完钻前寒武系地层,为盆地内的寒武系烃源岩发育机制研究提供了理想窗口。为探究寒武系烃源岩沉积期的古海洋环境与古生产力,并阐明有机质的富集机制,文章对塔北地区典型单井系统开展了TOC、主微量元素及碳氧同位素分析。结果表明,玉尔吐斯组下段处于缺氧—硫化的沉积环境,生产力较高;上段处于贫氧的沉积环境,生产力逐渐减弱,处于低生产力水平;碳氧同位素等指标表明玉尔吐斯组下段沉积于广泛海侵的背景下,且存在上升流作用,受上升洋流及轻度热液活动影响,营养物质的输入导致该时期初级生产力勃发,有机质的富集主要受控于较高的生产力及良好的保存条件;玉尔吐斯组上段沉积时基本无热液活动,生产力水平逐渐降低,水体的还原性也开始减弱,表现为上段高位体系域的低生产力水平和贫氧的沉积环境,最终导致有机质的丰度较低。

关键词: 沉积环境, 生产力, 热液活动, 玉尔吐斯组, 塔里木盆地

Abstract: The development mechanism of source rocks of the early Cambrian Yuertusi Formation is one of the key points of deep oil and gas exploration in the Tarim Basin. The completion of ultra-deep drilling of pre-Cambrian strata in the basin in recent years provides an ideal window for the study of the development mechanism of Cambrian source rocks in the basin. In order to investigate the sedimentary environment and paleo-productivity during the deposition of source rocks and clarify the enrichment mechanism of organic matter, a systematic analysis of TOC, major and trace elements and carbon and oxygen isotopes was carried out in a typical well of the Tabei area. The results show that the lower part of the Yuertusi Formation was in anoxic-sulfuration environment with high primary productivity. In comparison, the upper section was formed in the oxygen-poor sedimentary environment, and the productivity was gradually weakened to a low productivity level. Carbon and oxygen isotopes indicate that the lower member of the Yuertusi Formation was deposited under the background of extensive transgression with upwelling. The coupling of upwelling currents and mild hydrothermal activities provides abundant nutrients for the bloom of primary productivity during this period, and the enrichment of organic matter was mainly controlled by high productivity and good preservation conditions. There was basically no hydrothermal activities in the upper member of the Yuertusi Formation when it was deposited, the productivity level gradually decreased, and the reductibility of the water body also began to weaken, which was manifested in the low productivity level and the depositional environment of the upper system domain in the upper member, and eventually resulted in the low abundance of organic matter.

Key words: depositional environment, productivity, hydrothermal activity, Yuertusi Formation, Tarim Basin

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