石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (5): 1279-1289.doi: 10.11743/ogg20230516

• 油气地质 • 上一篇    

珠江口盆地恩平凹陷恩平17洼油气动态成藏过程

史玉玲1,2(), 龙祖烈1,2, 张向涛1,2, 温华华1,2, 马晓楠1,2   

  1. 1.中海石油(中国)有限公司 深圳分公司,广东 深圳 518054
    2.中海石油深海开发有限公司,广东 深圳 518054
  • 收稿日期:2023-03-30 修回日期:2023-07-04 出版日期:2023-10-01 发布日期:2023-10-19
  • 第一作者简介:史玉玲(1987—),女,高级工程师,资源评价和油气运移成藏。E-mail:shiyl5@cnooc.com.cn
  • 基金项目:
    中国海洋石油集团有限公司重大科技项目(KJGG2022-0403)

Exploring the dynamic hydrocarbon accumulation process of the Enping 17 sub-sag in the Enping Sag, Pearl River Mouth Basin

Yuling SHI1,2(), Zulie LONG1,2, Xiangtao ZHANG1,2, Huahua WEN1,2, Xiaonan MA1,2   

  1. 1.Shenzhen Branch of CNOOC (China) Limited,Shenzhen,Guangdong 518054,China
    2.Deepwater Development Limited,CNOOC,Shenzhen,Guangdong 518054,China
  • Received:2023-03-30 Revised:2023-07-04 Online:2023-10-01 Published:2023-10-19

摘要:

基于地化分析明确了珠江口盆地恩平凹陷恩平17洼油气来源及分布特征,优选断层属性有效参数,定量评价了不同时期断层的输导性;借助MOVE软件再现了23.03 Ma以来主要层面的古构造形态,揭示了T70古构造面形态变化对纵向上及不同构造带间油气调整分配的影响,最终恢复了油气动态成藏过程,也预测了潜在的油气勘探方向。研究认为:恩平17洼原油主要来自始新统文昌组三段、四段及五段烃源岩,断距在100 ~ 130 m的断层可以向恩平组输导油气,断距大于130 m的断层有利于油气穿过恩平组向中、浅层垂向输导。恩平17洼油气经历了早期近源、中期南向、晚期南-北双向3个阶段的运聚过程,由于洼陷带晚期断层垂向输导油气能力较弱,使得恩平组成为纵向上及不同构造带间油气调整分配的枢纽。10.00 Ma之前,油气主要在T70古构造面之下近源运聚;10.00 ~ 5.33 Ma,油气主要沿恩平组输导层向南部构造带运聚;5.33 Ma之后,油气开始在洼陷带T70古构造面之下向北运移调整,整体油气运移趋势进入南-北双向运聚阶段。沿NW向构造脊发育的古近系构造圈闭及北部古隆起周缘恩平组构造-岩性或地层-岩性圈闭是今后较为有利的勘探方向。

关键词: 原油成因类型, 古构造面形态, 输导体系, 成藏过程, 恩平17洼, 珠江口盆地

Abstract:

In this study, we determine the hydrocarbon sources and distribution in the Enping 17 sub-sag, Pearl River Mouth Basin (PRMB) through geochemical analyses. Using the selected optimal fault attributes, we quantitatively evaluate the hydrocarbon transport capacity of faults during different geologic periods. Furthermore, we reproduce the paleotectonic morphologies of primary seismic reflectors in the Enping 17 sub-sag since 23.03 Ma with the aid of the MOVE software, revealing the influence of the paleotectonic morphological changes of seismic reflector T70 on hydrocarbon redistribution in the vertical direction and among various tectonic zones. Finally, we reconstruct the dynamic hydrocarbon accumulation process and predict potential hydrocarbon exploration targets. The results are as follows. (1) The crude oil of the Enping 17 sub-sag originates primarily from source rocks in the 3rd, 4th, and 5th members of the Eocene Wenchang Formation. Faults with throws ranging from 100—130 m can transport hydrocarbons to the Enping Formation, while those with throws exceeding 130 m may create conducive conditions for hydrocarbons to migrate vertically toward the medium and shallow reservoirs through the Enping Formation. (2) The hydrocarbons in the sub-sag underwent three migration and accumulation stages: the migration and accumulation near sources in the early stage, the southward migration and accumulation in the middle stage, and the S-N two-way migration and accumulation in the late stage. Due to the weak vertical hydrocarbon transport capacity of faults in the late stage, the Enping Formation served as a hub for hydrocarbon redistribution in the vertical direction and among various tectonic zones. Prior to 10.00 Ma, hydrocarbon migration and accumulation primarily occurred near sources under the paleostructural surface on seismic reflector T70. From 10.00 Ma to 5.33 Ma, hydrocarbons migrated to and accumulated in the southern tectonic zones along the carrier beds of the Enping Formation. After 5.33 Ma, hydrocarbon migration was diverted northward under the paleostructural surface on T70, signaling the general commencement of S-N two-way migration and accumulation. In conclusion, the favorable exploration targets in the Enping 17 sub-sag include the Paleogene structural traps along NW-trending structural ridges, as well as the tectono-lithologic or stratigraphic-lithologic traps in the Enping Formation at the edge of the northern paleo-uplift.

Key words: genetic type of crude oil, morphology of the paleostructural surface, migration pathway, accumulation process, Enping 17 sub-sag, Pearl River Mouth Basin (PRMB)

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