南海北部湾盆地乌石凹陷原油地球化学特征与油源对比  

Geochemical Characteristics and Oil-Source Rock Correlation of Crude Oil in Wushi Sag,Beibuwan Basin,South China Sea

作　　者：尹嘉 魏琳[1] 侯读杰[1] 范彩伟 满勇 胡德胜 Yin Jia;Wei Lin;Hou Dujie;Fan Caiwei;Man Yong;Hu Desheng(School of Energy and Resources,China University of Geosciences,Beijing 100083,China;Zhanjiang Branch,China National Offshore Oil Corporation(CNOOC),Zhanjiang 524057,China)

机构地区：[1]中国地质大学能源学院,北京100083 [2]中海石油(中国)有限公司湛江分公司,广东湛江524057

出　　处：《地球科学》2023年第11期4135-4152,共18页Earth Science

基　　金：中国地质大学(北京)基本科研业务费项目(No.35832019035);国家自然科学基金项目(No.41702133);中海油南海西部油田上产2000万方关键技术研究项目“南海西部在生产油气田提高采收率技术研究”(No.CNOOC⁃KJ135ZDXM38ZJ).

摘　　要：为了探究乌石凹陷的油气来源,对原油及烃源岩样品进行地球化学分析.研究结果表明,乌石凹陷原油可分为3类:Ⅰ类原油分布在深洼带的涠洲组和流沙港组一段储层,成熟度整体偏高,C_(19)三环萜烷、C_(24)四环萜烷、奥利烷丰度均相对较高,C_(23)三环萜烷、C_(30)4-甲基甾烷丰度相对较低,体现出水生低等生物与陆源高等植物双重输入的特征.Ⅱ类和Ⅲ类原油主要分布在反转构造带和缓坡带的流沙港组二段、三段储层中,成熟度整体低于Ⅰ类原油,C_(19)三环萜烷、C_(24)四环萜烷、奥利烷丰度均较低,C_(23)三环萜烷、C_(30)4-甲基甾烷丰度相对较高,表明其母质来源以低等水生生物为主.相对Ⅱ类原油,Ⅲ类原油的Pr/Ph值更低,全油稳定碳同位素偏轻.油源对比表明,I类原油主要来源于流沙港组二上亚段烃源岩;II类及Ⅲ类原油均来自流沙港组二下亚段烃源岩.To study the genetic relationship between oil and source rock in Wushi sag,geochemical analyses of crude oil and source rock samples were carried out in this paper.The results show that crude oils in Wushi sag can be classified into three groups:groupⅠcrude oil is distributed in the Weizhou Formation and 1-member of Liushagang Formation reservoir in the deep sag belt.The maturity of this crude oil is relatively high,and the abundances of C_(19)tricyclic terpenes,C_(24)tetracyclic terpenes,and oleanane are relatively high,while the abundances of C_(23)tricyclic terpenes and C_(30)4-methylsteranes are relatively low,which reflects the characteristics of double input of lower aquatic organisms and terrigenous higher plants.GroupⅡand groupⅢcrude oil is mainly distributed in the 2-member and 3-member of the Liushagang Formation reservoir in the reversal tectonic belt and gentle slope belt,and their maturity is overall lower than that of group I crude oil.The abundances of C_(19)tricyclic terpanes,C_(24)tetracyclic terpanes,and oleanane of these oils are relatively low,and the abundances of C_(23)tricyclic terpanes and 4-methylsteranes are relatively high,indicating their parent material is mainly from lower aquatic organisms.The difference between the two groups of crude oils mainly lies in the Pr/Ph value and the stable carbon isotope characteristics of whole oil.Compared with groupⅡcrude oil,groupⅢcrude oil has a lower Pr/Ph value and lighter stable carbon isotope.The oil-source rock correlation shows that the group I crude oil mainly comes from the upper sub-member of 2-member of Liushagang Formation source rock.Both group II and groupⅢoils are derived from the lower sub-member of the 2-member of Liushagang Formation source rock.

关 键 词：地球化学特征 生物标志化合物 油源对比 钻井 乌石凹陷 石油地质 

分 类 号：P59[天文地球—地球化学]