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<p>To reveal the differences between the stress damage behaviors of fracture–pore networks in deep and shallow coal reservoirs during drainage and stimulation processes, five cyclic loading–unloading experiments of coal samples collected at six depths (249, 350, 478, 1161, 2721 and 2992 m) from the Junggar Basin were conducted under varying effective stresses (2–35 MPa). The samples from both deep and shallow coal reservoirs exhibited triphasic permeability and porosity evolution trends with increasing effective stress comprising rapid decrease, significant deceleration, and stabilization. Under an effective stress of 35 MPa, the permeability loss rate (<i>PLR</i><sub>k</sub>) of deep coal was 86.54%, whereas that of shallow coal was 95.83%. The porosity loss rate (<i>PLR</i><sub>P</sub>) of deep coal reached 26.16%, whereas that of shallow coal reached 42.95%. The key parameters of deep coal, namely, the compressibility coefficient (<i>C</i><sub>f</sub>), permeability stress sensitivity coefficient (<i>SSC</i><sub>k</sub>), porosity stress sensitivity coefficient (<i>SSC</i><sub>P</sub>), irreversible permeability loss rate (<i>IPLR</i><sub>k</sub>), and irreversible porosity loss rate (<i>IPLR</i><sub>P</sub>), were consistently lower than those of shallow coal. With increasing cyclic loading, <i>SSC</i><sub>k</sub> and <i>SSC</i><sub>P</sub> of shallow coal gradually decreased, whereas <i>SSC</i><sub>k</sub> of deep coal initially increased before stabilizing. Notably, <i>IPLR</i><sub>k</sub> of shallow coal (29.56–50.39%) was 6–8 times greater than that of deep coal, and <i>IPLR</i><sub>P</sub> (4.45–7.91%) was 3 times greater. Compared with their shallow counterparts, deep coal reservoirs exhibit lower stress sensitivity and less irreversible damage, indicating superior mechanical stability and greater damage resistance.</p>

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Investigation of Permeability Stress Induced Damage Evolution of Shallow and Deep Coal Reservoirs in the Junggar Basin, China

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Zhenzhi Wang,
  • Junjie Xiong,
  • Yaqiong Zhang,
  • Guangbiao Tao,
  • Jienan Pan,
  • Qinghe Niu

摘要

To reveal the differences between the stress damage behaviors of fracture–pore networks in deep and shallow coal reservoirs during drainage and stimulation processes, five cyclic loading–unloading experiments of coal samples collected at six depths (249, 350, 478, 1161, 2721 and 2992 m) from the Junggar Basin were conducted under varying effective stresses (2–35 MPa). The samples from both deep and shallow coal reservoirs exhibited triphasic permeability and porosity evolution trends with increasing effective stress comprising rapid decrease, significant deceleration, and stabilization. Under an effective stress of 35 MPa, the permeability loss rate (PLRk) of deep coal was 86.54%, whereas that of shallow coal was 95.83%. The porosity loss rate (PLRP) of deep coal reached 26.16%, whereas that of shallow coal reached 42.95%. The key parameters of deep coal, namely, the compressibility coefficient (Cf), permeability stress sensitivity coefficient (SSCk), porosity stress sensitivity coefficient (SSCP), irreversible permeability loss rate (IPLRk), and irreversible porosity loss rate (IPLRP), were consistently lower than those of shallow coal. With increasing cyclic loading, SSCk and SSCP of shallow coal gradually decreased, whereas SSCk of deep coal initially increased before stabilizing. Notably, IPLRk of shallow coal (29.56–50.39%) was 6–8 times greater than that of deep coal, and IPLRP (4.45–7.91%) was 3 times greater. Compared with their shallow counterparts, deep coal reservoirs exhibit lower stress sensitivity and less irreversible damage, indicating superior mechanical stability and greater damage resistance.