Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (6): 1365-1375.doi: 10.11743/ogg20210611

• Petroleum Geology • Previous Articles     Next Articles

Application of laser in-situ U-Pb dating of calcite to determination of the absolute time of hydrocarbon accumulation in polycyclic superimposed basins: A case study on Tahe oilfield, Tarim Basin

Jiaxu Chen1(), Bin Wang1,2, Xiaowen Guo1,*(), Zicheng Cao3, Yongli Liu3, Feng Geng3, Xuyou Zhang1, Hao Xu1, Jianxin Zhao1,4   

  1. 1. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan, Hubei 430074, China
    2. Wuxi Research Institute of Petroleum Geology, Petroleum Exploration and Production Research Institute, SINOPEC, Wuxi, Jiangsu 214126, China
    3. Research Institute of Exploration and Production, Northwest Oilfield Branch Company, SINOPEC, Urumqi, Xinjiang 830011, China
    4. Radiogenic Isotope Facility, School of Earth and Environment Sciences, University of Queensland, Brisbane 4072, Australia
  • Received:2020-01-02 Online:2021-12-28 Published:2021-12-16
  • Contact: Xiaowen Guo E-mail:jiaxuchen@cug.edu.cn;guoxw@cug.edu.cn

Abstract:

The absolute time of hydrocarbon accumulation in polycyclic superimposed basins has always been a major problem to be solved in the research of hydrocarbon accumulation. Based on the observation of oil inclusions and fluorescence spectrum analysis, we classify the generation of calcite crystallization into four stages by cathodoluminescence and trace elements analysis carried out in the Tahe oilfield, Tarim Basin; then determine the absolute time of hydrocarbon accumulation by laser in-situ U-Pb dating of calcite generated in these stages. The results show that two types of oil inclusions with yellow and blue-white fluorescent respectively are developed in calcite veins of the Ordovician in the study area. The differences of cathodoluminescence and micro-area trace elements indicate two stages of calcite veins contain primary oil inclusions with yellow fluorescent, the ages of which just correspond to the two charging episodes of yellow fluorescent crude oil. The laser in-situ U-Pb isotope dating results of calcite veins show that the first episode of yellow fluorescent crude oil charging occurred during 329.7 Ma±1.6 Ma, the second ran from 249.3 Ma±2.6 Ma to 220.5 Ma±7.3 Ma. An integration of the isotope dating technique and hydrocarbon fluid inclusion analysis can effectively determine the absolute time of hydrocarbon accumulation in polycyclic superimposed basins, and is of great significance to reconstructing the dynamic process of hydrocarbon accumulation.

Key words: laser in-situ U-Pb dating, fluid inclusion, calcite vein, hydrocarbon accumulation geochronology, Tahe oilfield, Tarim Basin

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