南海珠江口盆地惠州凹陷东南缘远源凸起带油气成因及来源  

Crude oil in the uplifts of the Huizhou depression,Pearl River Mouth Basin,South China Sea: Source and formation mechanisms

作　　者：段威 田金强 李三忠[1,2] 于强 陈瑞雪 龙祖烈[5] DUAN Wei;TIAN Jinqiang;LI Sanzhong;YU Qiang;CHEN Ruixue;LONG Zulie(Institute for Advanced Ocean Study and College of Marine Geosciences/Frontiers Science Center for Deep Ocean Multispheres and Earth System/MOE Key Lab of Submarine Geosciences and Prospecting Techniques,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266100,China;School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;CNOOC Central Laboratory Shenzhen Branch,Huizhou 516000,China;Shenzhen Branch of CNOOC China Limited,Shenzhen 518000,China)

机构地区：[1]中国海洋大学海洋高等研究院和海洋地球科学学院/深海圈层与地球系统前沿科学中心/海底科学与探测技术教育部重点实验室,山东青岛266100 [2]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,山东青岛266100 [3]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [4]中海油实验中心深圳实验中心,广东惠州516000 [5]中海石油(中国)有限公司深圳分公司,广东深圳518000

出　　处：《地学前缘》2022年第5期176-187,共12页Earth Science Frontiers

基　　金：国家自然科学基金青年科学基金项目(41602136);中央高校基本科研业务费专项(202072002,862001013146)。

摘　　要：惠州凹陷是中国南海珠江口盆地东部最重要的富生烃凹陷,位于其东南缘的远源凸起带普遍缺失烃源岩地层,距离油源远,是典型的源外远源油气藏,油藏中原油成因及来源尚未明确。通过对惠州凹陷内原油和烃源岩样品进行生物标志化合物、同位素特征的系统对比,结合对断裂-砂体-不整合运移通道和遮挡条件的分析,应用Pathway软件模拟分析三维油气运移路径,跳出静态模式的禁锢,从动态的角度分析油气成藏过程。本文认为,惠州凹陷东南缘远源凸起带原油主要来源于文昌组烃源岩,其生物标志物主要表现为低C_(19)/C_(23)三环萜烷值(<0.7)、低C_(20)/C_(23)三环萜烷值(<0.8)、高C_(27)重排甾烷/C_(27)规则甾烷值(>0.25)、低ETR值(<0.4)、高4-甲基甾烷/ΣC_(29)甾烷值(>0.4)和低双杜松烷T/C_(30)藿烷值(<1)。油气三维运移路径模拟结果显示,油气在惠州凹陷H26洼生成后,在惠-流构造脊控制下沿优势运移路径向东沙隆起方向运移,并在构造脊顶端的远源凸起带L11-1油田聚集成藏。远源凸起带的原油与同一优势运移路径上的其他油田原油样品的生物标志物特征和碳同位素特征具有非常高的相似性。故本文推断,远源凸起带原油主要来自惠州凹陷H26洼陷文昌组中深湖相烃源岩。The Huizhou depression is the most important hydrocarbon-rich depression in the eastern Pearl River Mouth Basin,South China Sea.The uplifts,located in the southeastern margin of the Huizhou depression,are far from source rocks with no in-situ deposition of source rock strata.They are typical remotely sourced petroleum reservoirs,whose source and formation mechanisms are not yet known.This study systematically compared the biomarker compositions and isotopic characteristics between crude oil and source rock samples from the Huizhou depression.Combined with analysis of the fault-sand-unconformity migration pathways and blocking conditions,the Pathway software was used to simulate and analyze the three-dimensional hydrocarbon migration pathways,and the hydrocarbon accumulation process was analyzed in dynamic mode to overcome the limitations of static analysis.We suggest the source rock of the Wenchang formation is responsible for the crude oil in the uplifts.The crude oil samples were characterized by low C_(19)/C_(23) tricyclic terpane ratio(<0.7),low C_(20)/C_(23) tricyclic terpane ratio(<0.8),high C_(27) rearranged sterane/C_(27) regular sterane ratio(>0.25),low ETR value(<0.4),high 4-methylsterane/C_(29) sterane ratio(BBB>4),and low bicadinane T/C_(30) hopane ratio(<1).The simulated three-dimensional hydrocarbon migration pathways indicated that under the control of the Hui-Liu mid-ocean ridge,hydrocarbon generated in sag H26 of the Huizhou depression migrated to the Dongsha uplift along the dominant migration pathway and accumulated in the L11-1 oilfield in the uplifts far from the source rocks at the top of the mid-ocean ridge.The biomarker and carbon isotopic characteristics of crude oil samples from the uplifts were similar to those from other oilfields along the same predominant migration pathway.Therefore,we infer that the crude oil in the uplifts is predominantly sourced from the middle-deep lacustrine source rock of the Wenchang formation of sag H26.

关 键 词：珠江口盆地 惠州凹陷 远源凸起带 生物标志化合物特征 油气成因及来源 

分 类 号：P597[天文地球—地球化学] P618.13[天文地球—地质学]