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Water Distribution in the Ultra-Deep Shale of the Wufeng–Longmaxi Formations from the Sichuan Basin

Author

Listed:
  • Ping Gao

    (School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China)

  • Xianming Xiao

    (School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China)

  • Dongfeng Hu

    (Sinopec Exploration Branch Company, Chengdu 610041, China)

  • Ruobing Liu

    (Sinopec Exploration Branch Company, Chengdu 610041, China)

  • Yidong Cai

    (School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China)

  • Tao Yuan

    (Sinopec Exploration Branch Company, Chengdu 610041, China)

  • Guangming Meng

    (School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China)

Abstract

Recently, deep and ultra-deep shales (depth >3500 m) of the Lower Paleozoic Wufeng–Longmaxi formations (WF–LMX) have become attractive targets for shale gas exploration and development in China, and their gas contents may be influenced by the occurrence of water to some extent. However, the water content and its distribution in the different nanopores of the deep and ultra-deep shales have rarely been reported. In this study, a suite of the WF–LMX ultra-deep shale samples (5910–5965 m depth) from the Well PS1 was collected for water content measurements, and low-pressure CO 2 and N 2 adsorption experiments of both as-received and experimentally dried shale samples were carried out to investigate the distribution of water in the different nanopores. Since the studied ultra-deep shales are characterized by higher thermal maturity (equivalent vitrinite reflectance (EqVRo) > 2.5 %) and ultra-low water saturation, the pore water is generally dominated by irreducible water. The content of irreducible water of the studied shales varies from 1.57 to 13.66 mg/g, averaging 6.74 mg/g. Irreducible water may mainly occur in the clay-hosted pores, while it could also be hosted in parts of organic pores of organic-rich shales. Irreducible water is primarily distributed in non-micropores rather than in micropores of the studied shales, which mainly occurs in micopores with a diameter of 0.4–0.6 nm and mesopores with a diameter of 2–10 nm. Very low contents of irreducible water could reduce the specific surface area and volume of non-micropores of the shales to some extent, but the effect of irreducible water on the specific surface area of non-micropores was more significant than the volume of non-micropores, especially for organic-rich shale samples. The ultra-deep shale gas may be predominately composed of free gas, so low contents of irreducible water may play a limited role in its total gas contents. Overall, our findings can be helpful for a better understanding of water distribution in the highly-matured shales, and provide a scientific basis for ultra-deep shale gas exploration.

Suggested Citation

  • Ping Gao & Xianming Xiao & Dongfeng Hu & Ruobing Liu & Yidong Cai & Tao Yuan & Guangming Meng, 2022. "Water Distribution in the Ultra-Deep Shale of the Wufeng–Longmaxi Formations from the Sichuan Basin," Energies, MDPI, vol. 15(6), pages 1-17, March.
    • Handle: RePEc:gam:jeners:v:15:y:2022:i:6:p:2215-:d:773808
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    References listed on IDEAS

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    1. Xiaoyan Zou & Xianqing Li & Jizhen Zhang & Huantong Li & Man Guo & Pei Zhao, 2021. "Characteristics of Pore Structure and Gas Content of the Lower Paleozoic Shale from the Upper Yangtze Plate, South China," Energies, MDPI, vol. 14(22), pages 1-29, November.
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    Cited by:

    1. Ruolong Chi & Ping Gao & Yidong Cai & Ruobing Liu & Jinghan Du & Qin Zhou, 2023. "Pore Types and Characteristics of Ultra-Deep Shale of the Lower Paleozoic Wufeng-Longmaxi Formations in the Eastern Sichuan Basin," Energies, MDPI, vol. 16(17), pages 1-14, August.
    2. Guangming Meng & Tengfei Li & Haifeng Gai & Xianming Xiao, 2022. "Pore Characteristics and Gas Preservation of the Lower Cambrian Shale in a Strongly Deformed Zone, Northern Chongqing, China," Energies, MDPI, vol. 15(8), pages 1-25, April.
    3. Yijie Xing & Xianming Xiao & Qin Zhou & Wei Liu & Yanming Zhao, 2023. "Influence of Water on the Methane Adsorption Capacity of Organic-Rich Shales and Its Controlling Factors: A Review," Energies, MDPI, vol. 16(8), pages 1-29, April.

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