Geochemical characteristics and hydrocarbon generation history of Mesozoic-Cenozoic lacustrine source rocks in the South Yellow Sea Basin, offshore eastern China

被引：0
作者：
Li Z. [1 ]
Yang B. [1 ]
Wang J. [1 ]
Han Z. [1 ]
Wu Q. [1 ]
机构：
[1] Tianjin Branch,CNOOC(China)Ltd., Tianjin
来源：
Oil and Gas Geology | 2022年 / 43卷 / 02期
关键词：
Biomarker compound; Funing Formation; Lacustrine source rocks; Mesozoic-Cenozoic; Subei Basin; Taizhou Formation; Thermal maturity;
D O I：
10.11743/ogg20220214
中图分类号：
学科分类号：
摘要：
No commercial oil or gas discovery has ever been made in the South Yellow Sea Basin (SYSB), offshore eastern China so far. This is probably due to the lack of study on the development and hydrocarbon generation history of the three sets of Mesozoic-Cenozoic lacustrine source rocks in the basin. Rock pyrolysis, trace elements, X-ray diffraction and chromatography-mass spectrometry analyses on 41 samples collected from the source rocks show that the second member of the Taizhou Formation (K2 t2) (one of the three sets) is rich in sapropel of Type Ⅱ1 kerogen, mainly the result of aquatic organic matter (OM) input as indicated by a dominant C27 regular sterane. The member has high content of carbonate minerals, suggesting a transgression influence that caused an anoxic and saline paleoenvironment, favorable for OM preservation. The second member of Funing Formation (E1 f2) shares the paleoenvironment with K2 t2 but has dramatically higher content of C28 regular sterane and a dual OM input of dominant algae with a small amount of terrestrial material, suggesting typical lacustrine source rocks. The fourth member of Funing Formation (E1 f4) contains mostly C29 regular sterane and has high terrestrial /aquatic ratio (TAR), indicating terrestrial OM input and oxic ancient water body with low salinity that is not favorable for OM preservation. The complex OM input mix and paleoenvironment conditions make it difficult to evaluate the thermal maturity of the source rocks. It is recommended to treat with caution the "immature" characteristic expressed by the ratios such as sterane 20S/(20S+20R) or Ts/(Ts+Tm). The hydrocarbon generation process of potential source beds is established base on analysis of structural background transformation from fault-depression period to depression period. It suggests that volcanic activities facilitated the generation process and that the depressions in the north experienced an early hydrocarbon generation and those in the south went through both early and late hydrocarbon generation but with a major generation period occurring during the deposition of the Sanduo Formation. The study may serve to guide the next step of oil and gas exploration in the basin.. © 2022, OIL & GAS GEOLOGY Editorial Board. All right reserved.
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页码：419 / 431
页数：12
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