岩矿测试2026，Vol.45Issue(1)：31-44,14.DOI:10.15898/j.ykcs.202506060152
基于主微量元素和生物标志物重建东海西湖凹陷始新世烃源岩发育古环境
Reconstruction of Paleoenvironment of the Eocene Source Rocks in the Xihu Sag,East China Sea,Based on Major and Trace Elements and Biomarkers
摘要
Abstract
The Xihu sag of the East China Sea Shelf Basin is dominated by low-to ultra-low-permeability natural gas resources.The Eocene Gemstone Formation and Pinghu Formation are the two main source rock formations in the sag.Although previous studies have extensively addressed their geochemical characteristics and sedimentary facies,the differences in paleosalinity,evolution of redox conditions,and paleoclimate fluctuations are still unclear,which restricts the study of the correlation between low-to ultra-low-permeability resources and paleoenvironment.Here,the mudstone samples of Well N1 in the Pinghu slope zone of Xihu sag were taken as the research object.The main elements were analyzed by X-ray fluorescence spectrometry(XRF),the trace elements were analyzed by inductively coupled plasma-mass spectrometry(ICP-MS),and the saturated hydrocarbon content of biomarkers was analyzed by gas chromatography-mass spectrometry(GC-MS).Based on the analysis results,the paleosedimentary environment of the source rocks of the Baoshi Formation and Pinghu Formation in Well N1 was reconstructed.The results show that Sr/Ba(<0.5),Rb/K and wax index jointly reveal that the sedimentary period of Baoshi Formation and Pinghu Formation is freshwater-brackish water environment.U/Th<0.75,V/Cr<2,δU<1 and Pr/Ph>2 synergistically indicate that the oxidation environment is dominant,and the elements are consistent with the biomarker parameters.It is confirmed that the oxidation is gradually enhanced from the Baoshi Formation to the Pinghu Formation;the climate indices C>0.6 and Sr/Cu<10 support warm and humid sedimentary paleoclimate,with vertical fluctuations.The ratios of steroids to terpenoids C27R/C29R and C19TT/C23TT indicate that the Pinghu Formation received more terrigenous input than the Baoshi Formation.Multivariate geochemical parameters provide important evidence for the reconstruction of paleoenvironment in the Eocene sedimentary period of Xihu sag.The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202506060152.关键词
古环境重建/主微量元素/生物标志物/烃源岩/西湖凹陷Key words
reconstruction of ancient environment/main trace elements/biomarkers/hydrocarbon source rocks/Xihu sag分类
天文与地球科学引用本文复制引用
刁慧,蒋一鸣,陈忠云,丁飞,于仲坤,徐靖琦,余箐,王皖丽..基于主微量元素和生物标志物重建东海西湖凹陷始新世烃源岩发育古环境[J].岩矿测试,2026,45(1):31-44,14.基金项目
中海石油(中国)有限公司"十四五"重大科技项目"海上深层/超深层油气勘探技术"(KJGG2022-0402) （中国）
中海石油(中国)有限公司上海分公司生产性科研(SCKY-2024-YJY01) （中国）
中海石油(中国)有限公司上海分公司生产性科研(SCKY-2025-YJY05) （中国）
