含油气盆地激光原位方解石U-Pb年龄对油气成藏年代的约束--以渤海湾盆地东营凹陷为例  

Constraint of in-situ calcite U-Pb dating by laser ablation on geochronology of hydrocarbon accumulation in petroliferous basins: a case study of Dongying sag in the Bohai Bay Basin

作　　者：郭小文[1] 陈家旭 袁圣强[2] 何生[1] 赵建新 Guo Xiaowen;Chen Jiaxu;Yuan Shengqiang;He Sheng;Zhao Jianxin(Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences,Hubei Wuhan 430074,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;Radiogenic Isotope Facility,School of Earth and Environmental Sciences,The University of Queensland,Brisbane QLD4072,Australia)

机构地区：[1]中国地质大学(武汉)构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石油勘探开发研究院,北京100083 [3]昆士兰大学地球与环境科学学院放射性同位素实验室,澳大利亚布里斯班QLD4072

出　　处：《石油学报》2020年第3期284-291,共8页Acta Petrolei Sinica

基　　金：国家科技重大专项(2016ZX05006-003-001);国家自然科学基金项目(No.41872139)资助。

摘　　要：油气成藏年代学研究是揭示油气成藏过程的关键。以渤海湾盆地东营凹陷为例,通过厘定方解石脉的发育期次,采用激光原位U-Pb同位素定年技术测定含原生烃类包裹体的方解石脉的绝对年龄,结合砂岩储层样品的流体包裹体分析,最终可综合确定油气成藏年代。流体包裹体岩相学、荧光特征和显微测温结果指示东营凹陷沙河街组存在2期油充注,但由于东营组沉积末期地层抬升剥蚀造成温度下降,采用流体包裹体方法解释的第1期油充注时间存在多解性。通过激光原位方解石U-Pb定年技术可消除第1期油充注时间的多解性,厘定第1期油充注时间在距今24~20 Ma东营组抬升剥蚀期,第2期油充注时间在距今4~3 Ma。激光原位方解石U-Pb定年技术结合流体包裹体分析可很好地用于约束油气成藏时间,提升油气成藏定年的精度,为含油气盆地特别是多旋回叠合盆地的油气成藏年代学提供更为可靠的研究方法。The geochronological study of hydrocarbon accumulation is the key to reveal the hydrocarbon accumulation process. Taking Dongying sag of the Bohai Bay Basin as an example, this study determines the absolute age of calcite veins containing primary hydrocarbon inclusions through in-situ U-Pb dating by laser ablation. Combined with analyses of the fluid inclusions in sandstone samples, the time of hydrocarbon accumulation can be finally determined. Fluid inclusion petrographies, fluorescence characteristics and microthermometry results indicate that there are 2 periods of oil charging in Shahejie Formation, Dongying sag. However, due to temperature reduction caused by the uplifting and denudation of strata at the end of Dongying Formation, the first period of oil charging interpreted by fluid inclusion method is ambiguity. This multiplicity can be eliminated based on in-situ U-Pb dating by laser ablation. The first period of oil charging occurred between 24 Ma and 20 Ma corresponding to the period of the uplifting and denudation of Dongying Formation, and the second period of oil charging occurred between 4 Ma and 3 Ma. In-situ calcite U-Pb dating by laser ablation in combination with fluid inclusion analysis can be used to well constrain the time of hydrocarbon accumulation and improve the dating accuracy, providing more reliable method for the geochronological study of hydrocarbon accumulation for petroliferous basins, especially for multi-cyclical superimposed basins.

关 键 词：激光原位方解石U-Pb定年 流体包裹体 均一温度 油气成藏年代学 东营凹陷 

分 类 号：TE122.3[石油与天然气工程—油气勘探]