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<p>Low permeability is a key factor restricting efficient coalbed methane extraction in China. Liquid nitrogen (LN<sub>2</sub>) fracturing, as an unconventional method for enhancing permeability, has emerged as one of the focal points. Meanwhile, coal reservoirs are greatly affected by fracture structure and permeability changes caused by mining stress. In order to ensure high efficiency and cost control of LN<sub>2</sub>-induced fracturing, it is necessary to conduct a detailed study on the seepage heat transfer characteristics of LN<sub>2</sub>-induced fracturing coal under the influence of mining stress. Therefore, in this experiment, a loaded gas injection tester was employed to conduct triaxial stress loading and unloading experiments on anthracite samples treated with different durations of LN<sub>2</sub> exposure under specific stress paths. A simulation model was established to analyze LN<sub>2</sub> injection into coal seam drilling holes. The experimental results indicate that the coal body's permeability exhibited an inverse “Z” shaped variation pattern as mining progresses; specifically, it initially decreased before subsequently increasing. The permeability increased by nearly 10 × at its peak, with distinct differences observed among various stages. However, in this experiment, mining dynamic stress had an effect on reducing the permeability of coal samples, with a reduction from 74.2 to 44%. Multiple instances of LN<sub>2</sub> fracturing can enhance the permeability of coal samples up to 15.02 × . After LN<sub>2</sub> treatment of coal samples, only minor increases in injection pressure were required to enhance their permeability further. In simulations reflecting the increased duration of LN<sub>2</sub> injection time, there is a significant expansion in the temperature variation range. After 1.5&#xa0;h, complete fracturing within the coal body is essentially achieved.</p>

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Seepage Characteristics and Heat Transfer Law of Coal Body by Liquid Nitrogen Fracturing Under Stress Disturbance Condition

  • 期刊论文

  • 发表日期：

    2026年1月3日

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  • Lei Zhang,
  • Shipan Zeng,
  • Ting Ren,
  • Cun Zhang,
  • Xijian Li,
  • Songzhao Li

摘要

Low permeability is a key factor restricting efficient coalbed methane extraction in China. Liquid nitrogen (LN2) fracturing, as an unconventional method for enhancing permeability, has emerged as one of the focal points. Meanwhile, coal reservoirs are greatly affected by fracture structure and permeability changes caused by mining stress. In order to ensure high efficiency and cost control of LN2-induced fracturing, it is necessary to conduct a detailed study on the seepage heat transfer characteristics of LN2-induced fracturing coal under the influence of mining stress. Therefore, in this experiment, a loaded gas injection tester was employed to conduct triaxial stress loading and unloading experiments on anthracite samples treated with different durations of LN2 exposure under specific stress paths. A simulation model was established to analyze LN2 injection into coal seam drilling holes. The experimental results indicate that the coal body's permeability exhibited an inverse “Z” shaped variation pattern as mining progresses; specifically, it initially decreased before subsequently increasing. The permeability increased by nearly 10 × at its peak, with distinct differences observed among various stages. However, in this experiment, mining dynamic stress had an effect on reducing the permeability of coal samples, with a reduction from 74.2 to 44%. Multiple instances of LN2 fracturing can enhance the permeability of coal samples up to 15.02 × . After LN2 treatment of coal samples, only minor increases in injection pressure were required to enhance their permeability further. In simulations reflecting the increased duration of LN2 injection time, there is a significant expansion in the temperature variation range. After 1.5 h, complete fracturing within the coal body is essentially achieved.