涠西南凹陷A洼及周缘含油构造油藏地球化学性质及成藏特征  

Oil geochemical and accumulation characterization in the A sag and surrounding oil-bearing structures of the Weixinan depression,Beibuwan Basin

作　　者：满勇 魏琳[2] 邓勇 李文龙 胡德胜 马潇潇 尹嘉 MAN Yong;WEI Lin;DENG Yong;LI Wenlong;HU Desheng;MA Xiaoxiao;YIN Jia(Hainan Branch of CNOOC(China)Co.Ltd.,Haikou 570311,China;School of Energy Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中海石油(中国)有限公司海南分公司,海口570311 [2]中国地质大学(北京)能源学院,北京100083

出　　处：《石油科学通报》2022年第2期155-173,共19页Petroleum Science Bulletin

基　　金：中国地质大学(北京)基本科研业务费(35832019035);中海油南海西部油田上产2000万方关键技术研究“南海西部在生产油气田提高采收率技术研究”(CNOOC-KJ 135 ZDXM 38 ZJ)资助。

摘　　要：通过对北部湾盆地涠西南凹陷A洼及其周缘区域不同井典型原油样品的地球化学特征进行分析,将原油划分为3类:Ⅰ类原油为重质油,碳同位素轻,4-甲基甾烷丰度低,成熟度低;ⅡI类原油为轻质油,碳同位素重,4-甲基甾烷丰度高,成熟度高;Ⅱ类原油整体地球化学特征介于两者之间。涠西南A洼主体原油为Ⅱ类和ⅡI类原油。烃源岩地球化学特征对比结果表明,涠西南凹陷发育上中下3套烃源岩。上源岩沉积环境偏氧化,以藻类生源为主,有一定的陆源高等植物贡献;中源岩沉积环境偏氧化,陆源高等植物输入增多;下源岩沉积环境为弱还原+弱氧化,4-甲基甾烷含量高,藻类勃发。精细的油源对比结果表明:Ⅰ类和Ⅱ类原油来源于上源岩,Ⅲ类原油来源于下源岩。结合成藏期次和输导体系综合分析,可知I类原油为上源岩第一期早期充注,通过砂体垂向运移至烃源岩上覆砂体成藏,Ⅱ类原油为上源岩第二期早期充注,通过断裂和砂体近距离运移至A洼周缘浅层圈闭成藏,Ⅲ类原油为下源岩晚期充注,通过构造脊和层间断层远距离侧向运移后聚集。该研究成果对北部湾盆地涠西南凹陷A洼的油气勘探突破具有一定的指导意义。Based on geochemical characteristics analysis of crude oil samples from different typical wells in the Weixinan sag A and its surrounding areas in the Beibuwan Basin,the crude oils in this area can be divided into three types(Ⅰ,Ⅱ,andⅢ).The first type of crude oil(Ⅰ)mainly distributed in the shallow reservoirs has relatively heavier oil density,relatively lighter isotopic value,relatively lower abundance of 4-methyl sterane and lower thermal maturity.The third type of crude oil(Ⅲ)mainly distributed in the deep reservoirs has relatively lower oil density,relatively heavier carbon isotopic value,relatively higher abundance of 4-methyl sterane and the highest thermal maturity.The overall geochemical characteristics of second type of crude oils(Ⅱ)mainly distributed in the shallow reservoirs are in between.Most of the crude oil of the Weixinan sag A belong to classⅡand classⅢ.The comparison of geochemical characteristics of source rocks samples shows that there are three sets of source rocks developing in the Weixinan Sag.The upper part source rocks that deposited in an oxidizing environment are dominated by algal input with certain contribution from terrigenous higher plants.The sedimentary environment of the middle part source rocks was more oxidized,and higher plants contributed more to its source materials.The lower part source rocks were formed in a weak reducing-oxidizing environment with large amounts of algal inputs.Oil-source correlation results show that typeⅠand typeⅡoils are mainly derived from the upper part source rocks,and typeⅢoils are chiefly derived from the lower part source rocks.Considering the comprehensive analysis of generation stages,accumulation stages,and migration pathways,this study concludes that typeⅠoil,which mainly derived from the first hydrocarbon charging stage of the upper part source rocks,is accumulated in the overlying reservoir by migrating upward through sand bodies.TypeⅡoil came from the second hydrocarbon charging stage from the upper part source roc

关 键 词：涠西南凹陷 油藏地球化学 生物标志化合物 油源对比 运移成藏 供烃组合 

分 类 号：P618.13[天文地球—矿床学]