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Depositional Environment of E s 4 u and E s 3 l Shales Based on Biomarkers from the Boxing Sag of Dongying Depression, East China
Author(s) -
WANG Ying,
LIU Luofu,
MENG Jianghui,
JIANG Zhenxue,
GAO Yongjin,
LIU Shuhui
Publication year - 2014
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12318
Subject(s) - oil shale , sedimentary depositional environment , geology , phytane , facies , geochemistry , pristane , sedimentary rock , source rock , brackish water , sterane , mineralogy , structural basin , hydrocarbon , paleontology , hopanoids , chemistry , oceanography , organic chemistry , salinity
The Boxing Sag is located in the southwest of Dongying Depression, southern Bohai Bay Basin of East China. It is one of the main petroliferous sags in the Dongying Depression, and has two major source rocks, namely the upper 4 th Member (E s 4 u ) and lower 3 rd Member (E s 3 l ) shales of Eocene Shahejie Formation, which are the new exploration targets in recent years. In this study, 16 core samples were collected from E s 4 u and E s 3 l shales in the Boxing Sag, and the saturate hydrocarbons were analyzed by gas chromatography (GC) and gas chromatography‐mass spectrometry (GC‐MS), respectively. The results show that E s 4 u shale has obvious phytane and gammacerane predominance, higher concentration of tricyclic terpanes and regular steranes, and very low concentration of 4‐methly steranes; E s 3 l shale has pristane predominance, lower concentration of tricyclic terpanes, gammacerane and regular steranes, and higher concentration of 4‐methly steranes. The E s 4 u shale can be further divided into two types based on the distribution of n ‐alkanes in gas chromatograms: normal distribution and double peak pattern. The biomarker characteristics and sedimentary facies distribution show that E s 4 u shale was deposited in the saline‐hypersaline semi‐deep (Type A E s 4 u shale, sag center) to shallow (Type B E s 4 u shale, sag edge) lacustrine environments, E s 3 l shale was deposited in the freshwater‐brackish semi‐deep‐deep lacustrine environments, and the former sedimentary facies maps of E s 4 u and E s 3 l in the Boxing Sag are further modified.