Earth Science Frontiers ›› 2025, Vol. 32 ›› Issue (5): 258-277.DOI: 10.13745/j.esf.sf.2024.10.17

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Breakthrough in exploration of helium rich natural gas in Well Datan 1 of Sichuan Basin and main control factors for reservoir formation

LIU Xiangbai1(), TAO Shizhen1,*(), YANG Dailin2, XIE Wuren1, ZHAO Rongrong3, TIAN Xingwang2, WANG Yunlong4, GAO Jianrong1, LIU Zhuangxiaoxue1, LI Chaozheng1, SONG Zezhang5, CHEN Yanyan1, YANG Yiqing1, CHEN Yue1   

  1. 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
    2. Exploration and Development Research Institute, PetroChina Southwest Oil & Gasfield Company, Chengdu 610041, China
    3. Exploration Division, PetroChina Southwest Oil & Gasfield Company, Chengdu 610041, China
    4. PetroChina Southwest Oil & Gasfield Company, Chengdu 610051, China
    5. College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China
  • Received:2024-04-12 Revised:2024-09-18 Online:2025-09-25 Published:2025-10-14
  • Contact: TAO Shizhen

Abstract:

Recently, the second and fourth members (Deng 2 Member and Deng 4 Member) of the Sinian Dengying Formation in Well Datan 1, Sichuan Basin, obtained natural gas at rates of 42×104 m3/d and 81×104 m3/d, respectively. Helium content in both members reached 0.1%, meeting the criterion for helium-rich natural gas. To investigate geological conditions of hydrocarbon accumulation and helium enrichment mechanisms, we researched the geochemical characterization of natural gas in Well Datan 1, clarifying its genesis and helium source. Comprehensive analysis of basement tectonic conditions explored main controlling factors of helium enrichment, deepening the understanding for future exploration. Results show hydrocarbon composition characteristics are similar to those of the Weiyuan, Ziyang, and Anyue gas fields. The dominant hydrocarbon is CH4, and main non-hydrocarbon components are CO2 and N2. Helium content is higher in Well Datan 1 and the Weiyuan Gas Field, lower in the Anyue Gas Field, and variable (locally high) in the Ziyang Gas Field. Helium in Well Datan 1 and Dengying Formation reservoirs of the Weiyuan Gas Field is primarily of crustal, radiogenic origin. The widely developed granite basement beneath Well Datan 1 and Weiyuan Gas Field is its main source. Extensively developed through-source fractures provide migration pathways for basement-derived helium, enabling helium enrichment in Well Datan 1. Good preservation conditions are also critical. We propose a new exploration concept: targeting helium-rich reservoirs by identifying tectonically modified traps in positive tectonic units, combined with hydrocarbon source rocks and radioactive-element-rich rocks (e.g., ancient basement granites) in negative tectonic units. Establishing effective trap-fault-source configurations is essential.

Key words: helium, Well Datan 1, Dengying Formation, Sichuan Basin

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