AUTHOR=Shi Xukai , Liu Yan , Wang Deying , Liu Feng , Wang Feilong , Wen Zhigang , Xie Xiaomin , Wu Yuanzhe , Lu Zhongdeng 

TITLE=Geochemical characteristics of crude oil in the eastern of Qinnan sag, Bohai Bay Basin, Eastern China

JOURNAL=Frontiers in Earth Science

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.998152

DOI=10.3389/feart.2022.998152

ISSN=2296-6463

ABSTRACT=<p>The oil and gas exploration degree of Qinnan sag is low. In this paper, all the 17 crude oil samples from the four reservoirs in the eastern Qinnan sag were taken as the research object. Research methods include GC-MS, stable carbon isotopic of crude oil and group components and other analytical methods. The geochemical characteristics of crude oil were studied by the main parameters, Pr/ph, γ/C<sub>31</sub> hopane, Ts/Tm, 4MSI and C<sub>29</sub> sterane isomerization. The results show that most of the hydrocarbon generating parent materials of all the 17 crude oils are reductive lacustrine sedimentary organic matter with higher salinity. The crude oil of Es<sub>12</sub> is mainly derived from low aquatic algae, and the crude oil of Ed<sub>3</sub>, Ek and Mz shows the characteristics of a mixed source. The maturation characteristics of crude oils are low mature-mature. The stable carbon isotope of oil and the components is in the range of −30‰ to −26‰, which shows the distribution characteristics of δ<sup>13</sup>C<sub>ST</sub> &lt;δ<sup>13</sup>C<sub>ASP</sub> &lt;δ<sup>13</sup>C<sub>NOS</sub> &lt;δ<sup>13</sup>C<sub>AR</sub>. The characteristics in B-6, C-1 and C-3 of crude oils show the heavy δ<sup>13</sup>C<sub>ASP</sub> and high abundance of hopane, indicating that there is more contribution from bacterial sources. The crude oil from Es<sub>12</sub> is mainly the contribution of Es<sub>1</sub> source rocks. The crude oil of Mz, Ek and Ed<sub>3</sub> is mainly the mixed source of Es<sub>1</sub> and Es<sub>3</sub> source rocks, and Es<sub>3</sub> is the main source, and the oil source may mainly come from the southeast subsag. The carbon isotope of the component in Block D can be divided into two kinds of crude oil, which may contribute to the oil source of the Bozhong sag. The eastern of Qinnan sag has great hydrocarbon potential.</p>