Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (1): 185-199.doi: 10.11743/ogg20240113

• Petroleum Geology • Previous Articles    

The Jinqiu gas field in the Sichuan Basin: A typical helium-bearing to helium-rich gas field with the Mesozoic sedimentary rocks as helium source rocks

Baoshou ZHANG1(), Benjian ZHANG1, Hua WANG1, Jianfa CHEN2, Kaixuan LIU2, Shuang DOU1, Xin DAI1, Shuangling CHEN1   

  1. 1.Research Institute of Exploration and Development,Southwest Oil & Gas Field Company,PetroChina,Chengdu,Sichuan 610041,China
    2.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
  • Received:2023-07-27 Revised:2023-12-05 Online:2024-02-01 Published:2024-02-29

Abstract:

The lack of studies over an extended period leads to an unclear understanding of helium accumulation conditions and mechanisms, along with fierce controversy over the types and formation conditions of helium source rocks. Focusing on the helium-bearing to helium-rich Jinqiu gas field, this study presents the following key findings through detailed analysis: (1) The Jinqiu gas field exhibits a helium content ranging from 0.05 % to 0.10 % primarily, with an average of 0.07 %. In some wells, the helium content exceeds 0.10 %, reaching a maximum of 0.20 %. Isotope analysis reveals that helium in the gas field originates from the crust, without any contribution from the mantle. (2) The Jinqiu gas field is identified as of a typical helium-bearing to helium-rich type with the Mesozoic sedimentary rocks serving as helium source rocks. Both the Upper Triassic Xujiahe Formation and the Jurassic strata demonstrate high uranium and thorium contents, along with considerable thickness. They exhibit a high helium-generating intensity in the Jinqiu area, serving as helium source rock basis for the formation of helium-bearing to helium-rich gas reservoirs. Helium is presumed to primarily originate from the Jurassic reservoirs rather than the hydrocarbon source rock sequence of the Upper Triassic Xujiahe Formation. (3) The formation of the Jinqiu gas field is primarily under three factors. First, helium source rocks with a high helium-generating intensity act as a sound material basis. Second, the presence of hydrocarbon gases with a moderate charging intensity contributes to helium enrichment. Last, the uplift and erosion of strata, accompanied by a decrease in temperature and pressure, result in the exsolution of in-situ dissolved helium, conducive to helium gas enrichment.

Key words: charging intensity, solubility, exsolution amount, helium-generating intensity, helium source rock, helium gas, Jinqiu gas field, Sichuan Basin

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