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GEOCHEMICAL CHARACTERISTICS OF TECTONIC GAS IN HUTUBI UNDERGROUND GAS STORAGE
ZHANG Lei, GAO Xiao-qi, BAO Chuang, LI Jing, LI Xu-mao
SEISMOLOGY AND GEOLOGY
2018, 40 (5):
1059-1071.
DOI: 10.3969/j.issn.0253-4967.2018.05.007
The migrating and enriching of fault gas during dynamic load-unload process are important indexes to evaluate the stress state and tectonic activity of underground medium. The Hutubi underground gas storage provides a natural experiment site for the analysis of the relationship between the gas geochemistry and the stress-strain status. In this paper, the soil gas concentrations of Rn, CO2, Hg and H2 during the gas injection in the Hutubi underground gas storage were analyzed. The results show that the soil gas contents and changing trend are close to the background value in the non-reservoir area and fault zone, which may reveal the weak activity of the fault. Significantly higher concentrations of soil gas H2 and Hg are observed in the gas storage area, where H2 maximum reaches 5.551×10-4 and Hg maximum reaches 53ng/m3. Moreover, the abnormal soil gas H2 and Hg measurement locations are more consistent. The variation trends of soil gas Hg, H2, Rn, and CO2may be related to the different gas generation and response mechanisms. The concentrations of soil gas H2 and Hg are sensitive to the variation of pressure and the development of cracks in the underground gas storage, and they can reveal gas injection's effect on fault activity. This study provides a new basis for analyzing the influence of gas injection and withdrawal in Hutubi underground gas storage on fault activity.
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