西湖凹陷始新统宝石组烃源岩分布差异及控制因素  

Distribution differences and controlling factors of source rocks of Eocene Baoshi Formation in Xihu Sag

作　　者：丁飞 蒋一鸣 赵洪 刁慧 于仲坤 王皖丽 DING Fei;JIANG Yiming;ZHAO Hong;DIAO Hui;YU Zhongkun;WANG Wanli(CNOOC China Limited,Shanghai Branch,Shanghai 200335,China)

机构地区：[1]中海石油(中国)有限公司上海分公司,上海200335

出　　处：《中国海上油气》2024年第5期68-82,共15页China Offshore Oil and Gas

基　　金：“十三五”国家科技重大专项“东海盆地天然气资源潜力评价(编号:2016ZX05027-001)”;“十四五”全国油气资源评价“中海油矿业权区及周边空白区油气资源评价(编号:QGYQZYPJ2022-3)”;中国海洋石油有限公司重大科技专项“东海西湖凹陷大中型气田勘探方向及关键技术研究(编号:KJZX-2023-0101)”部分研究成果。

摘　　要：始新统宝石组是东海西湖凹陷重要烃源岩,不同地区烃源岩品质差异及控制因素尚不明确,限制了勘探进一步拓展。基于已钻井烃源岩有机地球化学分析,开展不同地区烃源岩有机地球化学特征研究,结合有机质来源与沉积保存环境判识,剖析烃源岩发育控制因素,建立了烃源岩分布模式。西湖凹陷斜坡带宝石组烃源岩有机质丰度呈现南、北低,中段高的特征;有机质类型在斜坡北段及中段以Ⅱ2型干酪根为主,斜坡南段为典型Ⅲ型干酪根。宝石组烃源岩有机质来源以陆生高等植物为主,自北向南陆生植物贡献呈逐渐增加趋势,沉积与保存环境以氧化条件下的淡水—半咸水沉积为主。宝石组烃源岩相较平湖组具有品质略差、有机质母质浮游动植物贡献相对略高、有机质沉积水体盐度略高、沉积与保存环境氧化还原条件相当的特征。有机质来源是控制斜坡中段优质烃源岩发育的主要因素,陆生植物输入多,对应有机质丰度高的Ⅱ2型优质烃源岩,陆生植物输入相对少,对应有机质丰度相对低的Ⅱ2—Ⅲ型烃源岩。宝石组烃源岩是斜坡高部位主要供烃灶,是斜坡低部位平湖组烃源岩的有效补充,在斜坡中段平北区品质较好。Eocene Baoshi Formation is an important source rock in Xihu Sag,East China Sea.The quality differences and controlling factors of source rocks in different areas are still unclear,which limits further exploration.Based on the organic geochemical analysis of drilled source rocks,the organic geochemical characteristics of source rocks in different areas were studied.According to the identification of the organic matter source and sedimentary and preservation environment,the controlling factors of source rock development were analyzed,and the distribution model of source rock was established.The organic matter abundance of the source rocks in Baoshi Formation in the slope zone of Xihu Sag is poor in the southern and northern sections and rich in the middle section.The organic matter types are mainly typeⅡ2kerogen in the northern and middle sections of the slope and typeⅢkerogen in the southern sections of the slope.The source of organic matter of Baoshi Formation is mainly terrestrial higher plants,showing agradual increase in the contribution of terrestrial plants from north to south.The sedimentary and preservation environment is dominated by freshwater-brackish water deposits under oxidizing conditions.The quality of the source rock of Baoshi Formation is slightly worse than that of the Pinghu Formation.The contribution of zooplankton and plants to the organic matter material is relatively higher;the salinity of the sedimentary water is slightly higher,and the redox conditions of the sedimentary and preservation environment are similar.The source of organic matter is the main factor controlling the development of high-quality source rocks in the middle section of the slope.More terrestrial plant input indicates high organic matter abundance of typeⅡ2high-quality source rocks,while less terrestrial plant input indicates relatively low organic matter abundance of typeⅡ2-Ⅲsource rocks.The source rocks of Baoshi Formation are the main hydrocarbon source in the high zone of the slope and an effective supplem

关 键 词：东海 西湖凹陷 宝石组 烃源岩 有机质来源 沉积与保存环境 分布模式 

分 类 号：TE122.1[石油与天然气工程—油气勘探]