地学前缘 ›› 2009, Vol. 16 ›› Issue (1): 290-295.

• 论文 • 上一篇    下一篇

利用自生伊利石激光加热40Ar-39Ar定年技术探讨惠州凹陷新近系油气充注时间

  

  1. 1同济大学 海洋与地球科学学院, 上海 200092
    2中海石油(中国)有限公司 深圳分公司研究院, 广东 广州 510240
    3中国科学院 广州地球化学研究所, 广东 广州 510640

  • 出版日期:2009-02-02 发布日期:2009-02-02
  • 作者简介:施和生(1962—),男,高级工程师,主要从事构造、沉积、层序地层与油气勘探综合研究。E-mail: shihsh@cnooc.com.cn
  • 基金资助:

    中国海洋石油总公司综合科研项目(海油科字2004-37号)

 Timing of hydrocarbon fluid emplacement in sandstone reservoirs in Neogene in Huizhou Sag, Southern China Sea, by authigenic illite 40Ar39Ar laser stepwise heating

  1. 1School of Ocean and Earth Science, Tongji University,  Shanghai 200092, China
    2Research Institute, CNOOC China LimitedShenzhen,  Guangzhou 510240, China
    3Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

  • Online:2009-02-02 Published:2009-02-02

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摘要：

油气成藏年代学是新兴的学科发展方向。烃类充注之后, 砂岩储层中自生伊利石停止生长, 故可利用自生伊利石的年龄来推断储集层中油气藏形成的最老年龄。砂岩样品中存在的有机质在质谱仪离子源中产生的覆盖40Ar峰的有机碎片离子m/e36m/e40将导致错误的同位素分析和年龄谱结果。经预处理后的伊利石样品加热后在质谱仪离子源中确实产生了有机碎片离子m/e36m/e44,为获得可靠的分析结果,必须完全清除有机杂质气体。在攻克了有机杂质气体纯化技术之后,笔者开展了珠江口盆地惠州凹陷内3个富油气二级构造带油气藏砂岩自生伊利石40Ar39Ar法定年研究,采取样品清洗、循环冷冻—加热法破碎样品、经苯甲醇混合试剂洗油、采用离心机分离粘土矿物。自生伊利石激光阶段加热40Ar39Ar定年最初低温阶段综合年龄结果表明,惠州凹陷珠海组和珠江组自生伊利石加权平均年龄分别为(121±11) Ma 和(99±12) Ma,惠州凹陷新近系油气成藏关键时间为10 Ma左右。结合该区断裂发育史、油气成藏组合和流体包裹体均一化温度等资料进一步分析认为,中中新世末—晚中新世末的晚期断层活化加强了新近系油气的成藏。

关键词: 自生伊利石40Ar39Ar定年;油气充注时间;流体包裹体;均一化温度;砂岩储层;珠江口盆地;新近系

Abstract:

Abstract:  Timing of oil or gas emplacements is a new subject in isotopic geochronology and petroleum geology. The principle of the illite KAr age as expounded by Hamilton et al. is that the illite is often the last or one of the latest mineral cements to form prior to hydrocarbon accumulation, and since the displacement of formation water by hydrocarbons will cause silicate diagenesis to cease, KAr ages for illite will constrain the timing of this event and also constrain the maximum age of formation of the trap structure. In this study, the possibility of authigenic illites 40Ar39Ar dating has been investigated. The illite samples were separated from the Tertiary sandstones in three rich oil reservoir belts within the Huizhou sag by cleaning, fractured by coolingheating cycling，Soxhletextracting with solvents of benzene and methanol and separated with centrifugal machine. If oil is present in the separated samples, ionized organic fragments with m/e ratios of 36 to 40 covering the argon isotopes will be yielded by the ion source of a mass spectrometer, resulting in wrong argon isotopic analyses and wrong 40Ar39Ar ages. The preliminary experiments of illite by heating did show the presence of ionized organic fragments with m/e ratios of 36 to 44. In order to clean completely up the organic gases and obtain reliable analysis results, a special purification apparatus has been established by Qiu et al. and proved valid by the sequent illite analyses. All the illite samples by 40Ar39Ar IRlaser stepwise heating yield stairup age spectra in lower laser steps and plateaux in higher laser steps. The youngest apparent ages corresponding to the beginning steps are reasonable to be interpreted as the hydrocarbon accumulation ages. The weighted mean ages of the illites from the Zhuhai and Zhujiang Formations are 12.1±1.1 Ma and 9.9±1.2 Ma respectively. Therefore, the critical emplacement of petroleum accumulation in Zhujiang Formation in Huizhou sag took place in ca 10 Ma. Later fault activity strengthened the entrance of hydrocarbon fluids into the oil systems based on the data of the fault evolvement history, petroleum system combinations and homogeneous temperatures of fluid inclusions.

Key words:

Key words: 40Ar39Ar dating of authigenic illite; timing of petroleum entrance; fluid inclusions; homogeneous temperature; sandstone reservoir; Pearl River Mouth Basin; Neogene

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