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<p>Constructing salt cavern gas storage in deep layers exceeding 1500&#xa0;m is a significant strategic technology in China. The high temperatures in deep formations significantly affect the permeability characteristics of surrounding rock and influence gas flow via the slippage effect due to the extremely low permeability of rock salt. This study employs scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and mercury intrusion porosimetry to investigate the grain boundaries and porosity of rock salt. The results indicate that the pores in rock salt are significantly smaller than the micron scale, with particles and grain boundaries joined to form a discrete polycrystalline structure and no clear regularity in particle packing density at different locations. Subsequently, helium permeability tests were conducted on large rock salt samples under multiple temperature and pore pressure stages, revealing the permeability characteristics of rock salt during helium seepage under varying temperatures and pore pressures. The results show that temperature primarily influences the permeability of rock salt by altering the size of grains and their arrangement, thereby modifying the size of pore throats. The permeability of rock salt decreases as temperature increases, and the influence of temperature on the slippage effect also diminishes with higher temperatures. Simultaneous acoustic emission monitoring was conducted during the permeability tests to clarify the microcrack characteristics of rock salt during helium seepage under different temperatures and pore pressures. The results indicate that fewer microcracks are generated during high-temperature gas seepage, while more microcracks occur during low-temperature seepage. The analysis of the acoustic emission spectrum reveals that, at lower temperatures, larger intergranular cracks are predominant, whereas, at higher temperatures, smaller intergranular cracks dominate. The findings provide essential experimental evidence for the design, construction, and operational safety of salt cavern gas storage.</p>

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Experimental Study on the Evolution Law of Permeability Characteristics of Salt Rocks Under Different Temperatures and Different Pore Pressures

  • 期刊论文

  • 发表日期：

    2025年1月12日

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  • Wenbo Guo,
  • Jing Li,
  • Tongtao Wang,
  • Tao He,
  • Dongzhou Xie,
  • Youqiang Liao,
  • Chufan Liu

摘要

Constructing salt cavern gas storage in deep layers exceeding 1500 m is a significant strategic technology in China. The high temperatures in deep formations significantly affect the permeability characteristics of surrounding rock and influence gas flow via the slippage effect due to the extremely low permeability of rock salt. This study employs scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and mercury intrusion porosimetry to investigate the grain boundaries and porosity of rock salt. The results indicate that the pores in rock salt are significantly smaller than the micron scale, with particles and grain boundaries joined to form a discrete polycrystalline structure and no clear regularity in particle packing density at different locations. Subsequently, helium permeability tests were conducted on large rock salt samples under multiple temperature and pore pressure stages, revealing the permeability characteristics of rock salt during helium seepage under varying temperatures and pore pressures. The results show that temperature primarily influences the permeability of rock salt by altering the size of grains and their arrangement, thereby modifying the size of pore throats. The permeability of rock salt decreases as temperature increases, and the influence of temperature on the slippage effect also diminishes with higher temperatures. Simultaneous acoustic emission monitoring was conducted during the permeability tests to clarify the microcrack characteristics of rock salt during helium seepage under different temperatures and pore pressures. The results indicate that fewer microcracks are generated during high-temperature gas seepage, while more microcracks occur during low-temperature seepage. The analysis of the acoustic emission spectrum reveals that, at lower temperatures, larger intergranular cracks are predominant, whereas, at higher temperatures, smaller intergranular cracks dominate. The findings provide essential experimental evidence for the design, construction, and operational safety of salt cavern gas storage.