摘要
采用GC—MS分析技术,对东海盆地西湖凹陷31个原油样品进行了分子指纹研究。原油碳同位素值偏高,Pr/Ph值高,甾烷系列以C_(29)甾烷占优,萜烷以二萜类为主,富含降异海松烷、异海松烷、扁枝烷等,C_(24)四环萜烷含量高,伽马蜡烷含量低,富含奥利烷,表明原油的烃源岩形成于偏氧化的沉积环境,其成烃母质主要来源于高等植物。原油含有丰富的金刚烷类化合物,总含量可达877～9 797μg/g_油,其中以单金刚烷系列占绝对优势(754～9 333μg/g_油),体现出高成熟原油的特征。认为西湖凹陷西部缓坡带平湖组原油主要来源于平湖组烃源岩的生烃晚期,并在储层中发生了不同程度的裂解;中央洼陷带花港组原油主要为高成熟油或裂解油与未裂解的、成熟度较低原油的混合油,其中成熟度较低的原油主要来自于花港组烃源岩的生烃高峰期。平湖组或其下伏烃源岩在高—过成熟阶段形成的大量凝析油、天然气,甚至深层储层原油发生裂解形成的轻质烃类进入浅部花港组储层,与储层内早期原油发生混合是造成西湖凹陷浅部原油富含金刚烷类化合物的主要原因。
Molecular geochemical characteristics of thirty-one crude oil samples recovered from the Xihu Depression in the East China Sea were studied comprehensively by GC-MS analysis.The result shows that the oils have relatively high Pr/Ph ratios,heavier carbon isotope,C29 steranes preference in C27-C28-C29 series, diterpane preference such as abundant nor-isopotonane,isopotonane, phyllocladene, also abundant C24 tetracyclic terpanes and oleanane, while low abundance of gammacerane.The molecular composition characteristics indicate an oxydic sedimentary environment and a higher-plant organic source input. Adamantanes presents in abundance with a total amount reached 877-9 797ptg/goi], dominated by monoamantane series, showing a characteristic of high-mature oil.Maturity parameters of adamantanes and alkylphenanthrene implied that the crude oils from Pinghu Formation distributed in the East Slope mainly originated from the Pinghu source rock at a late generation period and had experienced variable degrees of thermal-cracking.The crude oil in the Huagang Formation of the central depression belt is a mixture mainly composed of highly-matured oil or cracking oil and uncracked maturity oil, which sourced from the Huagang Formation during the main oil generation window. A large amount of condensate oil, natural gas generated from the high-over mature source rocks in the Pinghu Formation and light oil cracked from the lower reservoir oils contribute to the high abundance of adamantanes in shallow oil reservoirs distributed in Xihu Depression.
作者
王勇刚
田彦宽
詹兆文
汤睿
Wang Yong-gang;Tian Yan-kuanJ;Zhan Zhao-wen;Tang Rui(Shanghai Branch of CNOOC Ltd.,Shanghai 200335,China;Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2019年第4期582-592,共11页
Natural Gas Geoscience
基金
国家科技重大专项"大型油气田及煤层气开发"(编号:2016ZX05027-001)
国家自然科学基金项目(编号:41502121)联合资助
