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程先振, 陈连军, 栾恒杰, 王春光, 蒋宇静. 基质-裂隙相互作用对煤渗透率的影响:考虑煤的软化[J]. 岩土工程学报, 2022, 44(10): 1890-1898. DOI: 10.11779/CJGE202210015
引用本文: 程先振, 陈连军, 栾恒杰, 王春光, 蒋宇静. 基质-裂隙相互作用对煤渗透率的影响:考虑煤的软化[J]. 岩土工程学报, 2022, 44(10): 1890-1898. DOI: 10.11779/CJGE202210015
CHENG Xian-zhen, CHEN Lian-jun, LUAN Heng-jie, WHANG Chun-guang, JIANG Yu-jing. Influences of softening behaviour of coal on evolution of its permeability by considering matrix-fracture interactions[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(10): 1890-1898. DOI: 10.11779/CJGE202210015
Citation: CHENG Xian-zhen, CHEN Lian-jun, LUAN Heng-jie, WHANG Chun-guang, JIANG Yu-jing. Influences of softening behaviour of coal on evolution of its permeability by considering matrix-fracture interactions[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(10): 1890-1898. DOI: 10.11779/CJGE202210015

基质-裂隙相互作用对煤渗透率的影响:考虑煤的软化

Influences of softening behaviour of coal on evolution of its permeability by considering matrix-fracture interactions

  • 摘要: 瞬态渗透率是提高煤层气产量的重要依据。为了得到基质-裂隙压力相互作用出现煤的软化行为对渗透率演化的影响。基于理论分析建立含模量软化系数的双重孔隙介质渗透率模型,并基于脉冲瞬态试验与COMSOL有限元数值模拟软件进行渗透率模型的验证。结果表明:根据曲线变化特征,将应变分为初始,快速增长和平衡阶段。在快速增长阶段,注气压力从1 MPa增大到3 MPa应变曲线的斜率分别为83.77,270.54,440.92 m/s。模量软化系数是应变的函数,其值也增大;其次,通过提出张开型和闭合型裂隙几何概念模型,得到含模量软化系数的双孔渗透率模型;最后,试验数据与改进的渗透率模型结果一致,证明模量软化系数主导了渗透率的动态演化。与试验方法相比,数值模拟方法能够监测煤基质的压力,基质与裂隙之间气体压力的变化揭示了煤渗透率演化机理。

     

    Abstract: The evolution of dynamic permeability is an important basis for improving the production of coal bed methane. In order to obtain the influences of the softening behavior of coal from matrix-fracture pressure interactions on the evolution of its permeability, a dual-pore permeability model with modulus reduction ratio from differential pressure is obtained through theoretical analysis and is validated based on the permeability transient method tests and the finite element numerical simulation software COMSOL. The experimental results show that the strain is divided into the initial, rapid growth and equilibrium phases based on the characteristics of the curve change. During the rapid growth phase, the slope of the strain curve increases from 1 to 3 MPa with slopes of 83.77, 270.54, 440.92 m/s respectively. The modulus-softening coefficient is a function of the strain and its value increases. Furthermore, a dual-pore permeability model with modulus-softening coefficient is obtained by proposing a conceptual model for open and closed fractures. The experimental data are consistent with the results of the improved permeability model, demonstrating that the modulus-softening coefficient dominates the dynamic evolution of the permeability. Finally, the numerical simulation method can be used to monitor the pressure in the coal matrix compared to the experimental method. Thus, the pressure difference between the matrix and the fracture reveals the mechanism of permeability evolution in coal samples.

     

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