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<p>Accurately assessing the permeability evolution of the damaged zone surrounding underground salt caverns is critical for ensuring their long-term tightness as gas storage. During high-frequency injection–withdrawal operations, the surrounding rock salt undergoes humidity cycling that activates self-healing mechanisms to alter its permeability. In this study, the transient pulse method was employed to continuously measure the damaged rock salt’s permeability under humidity cycling. A three-stage degradation trend was identified: a gradual decline in the early stage (0–18 cycles), a rapid decrease in the intermediate stage (18–30 cycles), and a progressive stabilization in the late stage (30–42 cycles). To elucidate the underlying self-healing mechanisms, water migration and void evolution in the rock were derived from nuclear magnetic resonance (NMR) relaxation spectra and subsequently parameterized and calibrated using geometrical features quantified by computed tomography (CT). Integrated analysis of these characterization results reveals that recrystallization driven by distortion energy is delayed by approximately one week relative to diffusion mass transfer but proved more effective in blocking seepage paths. Exponential decay and Gaussian functions were adopted to describe the rate of the basic self-healing effect and the recrystallization-enhanced effect, respectively, while the genus number was introduced to characterize the healing progression. An evolution model of key seepage parameters in rock, including wall roughness and tortuosity, was then established. Accordingly, a modified Kozeny–Carman (KC) model incorporating this self-healing progress was proposed, and its predictions showed strong agreement with experimental data, confirming its reliability. By developing a self-healing characterization framework incorporating multi-source data, this study establishes a trans-scale quantitative relationship between micron-scale healing behaviors and macroscale permeability, thereby improving the accuracy of tightness assessments for salt cavern gas storage and offering a new paradigm for studying the geomaterials’ permeability evolution.</p>

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Permeability degradation in self-healing rock salt under humidity cycling: experimental and modeling study using multiple characterization techniques

  • 期刊论文

  • 发表日期：

    2026年3月19日

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  • Zhen Zeng,
  • Hongling Ma,
  • Jingcui Li,
  • Wei Liang,
  • Xuan Wang,
  • Zhuyan Zheng,
  • Rui Liang,
  • Kai Zhao

摘要

Accurately assessing the permeability evolution of the damaged zone surrounding underground salt caverns is critical for ensuring their long-term tightness as gas storage. During high-frequency injection–withdrawal operations, the surrounding rock salt undergoes humidity cycling that activates self-healing mechanisms to alter its permeability. In this study, the transient pulse method was employed to continuously measure the damaged rock salt’s permeability under humidity cycling. A three-stage degradation trend was identified: a gradual decline in the early stage (0–18 cycles), a rapid decrease in the intermediate stage (18–30 cycles), and a progressive stabilization in the late stage (30–42 cycles). To elucidate the underlying self-healing mechanisms, water migration and void evolution in the rock were derived from nuclear magnetic resonance (NMR) relaxation spectra and subsequently parameterized and calibrated using geometrical features quantified by computed tomography (CT). Integrated analysis of these characterization results reveals that recrystallization driven by distortion energy is delayed by approximately one week relative to diffusion mass transfer but proved more effective in blocking seepage paths. Exponential decay and Gaussian functions were adopted to describe the rate of the basic self-healing effect and the recrystallization-enhanced effect, respectively, while the genus number was introduced to characterize the healing progression. An evolution model of key seepage parameters in rock, including wall roughness and tortuosity, was then established. Accordingly, a modified Kozeny–Carman (KC) model incorporating this self-healing progress was proposed, and its predictions showed strong agreement with experimental data, confirming its reliability. By developing a self-healing characterization framework incorporating multi-source data, this study establishes a trans-scale quantitative relationship between micron-scale healing behaviors and macroscale permeability, thereby improving the accuracy of tightness assessments for salt cavern gas storage and offering a new paradigm for studying the geomaterials’ permeability evolution.