沙南凹陷古近系烃源岩地球化学特征及其发育主控因素  

Differences characteristics and controlling factors of Paleogene high-quality source rocks in Shanan Sag

作　　者：王德英 田宏钰 肖述光 赵弟江 郭一凡 Wang Deying;Tian Hongyu;Xiao Shuguang;Zhao Dijiang;Guo Yifan(Tianjin Branch of CNOOC Ltd.,Tianjin 300452;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083;China University of Geosciences(Beijing),Beijing 100083)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300452 [2]中国石油勘探开发研究院致密油研究所,北京100083 [3]中国地质大学(北京),北京100083

出　　处：《地质科学》2024年第5期1256-1267,共12页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中海油重大科技专项(编号:CNOOC-KJ135ZDXM36TJ08TJ)资助。

摘　　要：沙南凹陷位于渤中凹陷和岐口凹陷之间的过渡位置,埋深相对较浅,经历了复杂的构造演化,盆内油气分布及烃源岩地化特征表现出强烈的非均质性,是制约该凹陷油气勘探发现的难点。本研究采用有机地球化学、有机岩石学和元素地球化学相结合的方法,对沙南凹陷古近系4个层段的烃源岩特征进行了系统对比分析。结果显示:沙南凹陷古近系不同层段烃源岩的有机质丰度、类型等存在明显差异,其中沙三中亚段、东三段烃源岩品质为好—优质,沙一二段次之,沙三上亚段烃源岩品质相对较差;不同层段有机质来源与组成不同,沙三中段有机质主要来源于淡水藻类,而东三段陆源有机质最多。生物标志物特征对比表明,姥鲛烷、植烷、伽马蜡烷、C_(27)-C_(29)规则甾烷和4-甲基甾烷等指标可以较好地区分各层段烃源岩。沙三中和东三段沉积期控凹断层活动强烈,沉积水体较深,水体弱分层至中等分层的缺氧沉积环境有利于优质烃源岩的发育。古气候和断裂活动控制着沙南凹陷古近纪烃源岩的发育和展布,而优质烃源岩的形成通常要求较高的断层活动速率和较低的砂质输入。本次研究对更好地认识全球其它陆相盆地在相似条件下沉积的湖相优质烃源岩发育规律与油气勘探提供参考。Shanan Sag is located in the transitional position between Bozhong and Qikou sags with relatively shallow burial depth,and has undergone complex structural evolution.The distribution of oil and gas in the basin and the geochemical characteristics of hydrocarbon source rocks show strong heterogeneity,which has been the difficulty of oil and gas exploration in the Bohai Sea.In this study,the organic geochemistry,organic petrology and inorganic geochemistry are systematically used to analyze the source rock characteristics in four layers from the third member of Shahejie Formation(Es_(3))to third member of Dongying Formation(Ed_(3))in the Shanan Sag.The results show that there are significant differences in the organic matter abundance and type of Paleogene source rocks in the Shanan Sag.The middle section of third member of Shahejie Formation(Es_(3)^(m))and Ed_(3) source rocks are high-quality,followed by the first(Es_(1))and second(Es_(2))members of Shahejie Formation,and the upper section of third member of Shahejie Formation(Es_(3)^(u))is the worst.The source and organic matter composition of different source rocks shows that the Es_(3)^(m) organic matter mainly comes from freshwater algae,the Ed_(3) source rock has the highest amount of terrestrial organic matter.Detailed comparative analysis of biomarkers shows that the indicators,such as pristane,phytane,gammacerane,ααα20R regular sterane and 4-methylsterane can be better used to distinguish the different source rocks.During the Es_(3)^(m) and Ed_(3) sedimentary period,the activities of boundary faults were strong,and the sedimentary water was deep.The hypoxic sedimentary environment with weak to moderate stratification was conducive to the development of high-quality source rocks.Paleoclimate and fault activity control the development and distribution of Paleogene source rock in Shanan Sag,while the formation of high-quality source rock usually requires a higher fault activity rate and lower sand body input.The paleoclimate and fault activity control the

关 键 词：沙南凹陷 古近系 优质烃源岩 烃源岩地球化学特征 生物标志物鉴定 控制因素 

分 类 号：P618.13[天文地球—矿床学] TE122.1+13[天文地球—地质学]