Geochemical characteristics and hydrocarbon generation mode of source rocks of Dongying Formation in Bozhong sag, Bohai Bay Basin

被引：0
|
作者：
Li G. [1 ,2 ]
Liu C. [1 ,2 ]
Wang F. [3 ]
Tang G. [3 ]
Yang H. [1 ,2 ]
Zeng X. [1 ,2 ]
Wu Y. [1 ,2 ]
Yang X. [1 ,2 ]
机构：
[1] State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing
[2] College of Geosciences, China University of Petroleum, Beijing
[3] Tianjin Branch, CNOOC China Limited, Tianjin
来源：
Shiyou Xuebao/Acta Petrolei Sinica | 2022年 / 43卷 / 11期
关键词：
Bozhong sag; Dongying Formation; low-mature oil; source rock; two-stage hydrocarbon generation;
D O I：
10.7623/syxb202211005a
中图分类号：
学科分类号：
摘要：
The unclear understanding of the characteristics and hydrocarbon generation mechanism of source rocks in Dongying Formation has restricted the study on hydrocarbon accumulation and resource evaluation in Bozhong sag, Bohai Bay Basin. By use of organic petrology, macerals, sporopollen identification and geochemical parameters related to crude oil, this paper systematically evaluates the geochemical characteristics of source rocks and crude oil in Dongying Formation, and also investigates the influencing factors and modes of hydrocarbon generation from organic matters. The results show that source rocks in Dongying Formation are mainly clay-bearing felsic mudstone and mixed mudstone, of which the mineral composition is dominated by quartz and clay minerals, followed by feldspar and carbonate minerals; the average total organic carbon content (TOC) of Member 3 and the lower submember of Member 2 of Dongying Formation are 1.94% and 0.87%, respectively, indicating that the source rocks are generally of good and premium quality; macerals are mainly composed of exinite, and Type H II1 and H II2 organic matter are dominant, currently in the low-mature to mature thermal evolution stage. The source rocks of Dongying Formation is characterized by two-stage hydrocarbon generation; in the early stage, the hydrocarbon generation peak corresponds to a vitrinite reflectance (R。) of 0.6%, and the low-mature hydrocarbons are mostly produced; in the late stage, the hydrocarbon generation peak corresponds to a R。 of 1.0%, and the mature hydrocarbons are mostly generated. The physical properties and biomarkers of crude oil indicate that crude oil in Dongying Formation is dominated by mature oil, supplemented by a small quantity of low-mature oil, which is characterized by low density, viscosity and sulfur content, high wax content, ratio of saturated hydrocarbon to aromatic hydrocarbon, Pr/Ph ratio and C19/C23 tricyclic terpane ratio, as well as low gammacerane index and low 4-methylsterane index, and belongs to the light-medium crude oil generated under the joint action of mixing organic matter, weak oxidation-weak reduction deposition conditions, and freshwater sulfur-poor lacustrine environment. The components such as amorphous benthic algae and Pinaceae sporopollen in exinite play an important role m hydrocarbon generation by source rocks in low-mature and mature stages; clay and carbonate minerals and formation overpressure have certain influence on the hydrocarbon generation evolution of source rocks. The development of source rocks of Dongying Formation is jointly controlled by the factors including freshwater lake, special organism, inorganic mineral and overpressure, which endows the source rocks with a bimodal hydrocarbon generation mode. This research can provide important reference for oil and gas exploration in the Dongying Formation of Bozhong sag as being the main hydrocarbon kitchen. © 2022 Science Press. All rights reserved.
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页码：1568 / 1584
页数：16
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