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尧春洪, 李波波, 高 政, 李建华, 许 江. 孔隙压力升降条件下煤岩双孔隙渗透率模型研究[J]. 煤炭科学技术, 2022, 50(11): 116-121.
引用本文: 尧春洪, 李波波, 高 政, 李建华, 许 江. 孔隙压力升降条件下煤岩双孔隙渗透率模型研究[J]. 煤炭科学技术, 2022, 50(11): 116-121.
YAO Chunhong, LI Bobo, GAO Zheng, LI Jianhua, XU Jiang. Study on dual pore permeability model of coal under the conditions of pore pressure rise and fall[J]. COAL SCIENCE AND TECHNOLOGY, 2022, 50(11): 116-121.
Citation: YAO Chunhong, LI Bobo, GAO Zheng, LI Jianhua, XU Jiang. Study on dual pore permeability model of coal under the conditions of pore pressure rise and fall[J]. COAL SCIENCE AND TECHNOLOGY, 2022, 50(11): 116-121.

孔隙压力升降条件下煤岩双孔隙渗透率模型研究

Study on dual pore permeability model of coal under the conditions of pore pressure rise and fall

  • 摘要: 孔隙压力是控制煤岩渗透率的关键因素,为探究煤岩渗透率在孔隙压力升降过程的响应机制,利用含瓦斯煤三轴渗流试验装置,分别开展不同平均应力条件下孔隙压力升高和降低的渗流试验。基于煤岩具备的双孔隙结构介质的特性,综合升压过程中煤岩力学效应、滑脱效应、吸附膨胀及吸附层厚度变化等因素,构建包含基质与裂隙的双孔隙渗透率模型。通过引入修正函数L(p),进一步量化降压过程中煤岩渗透率变化情况,并利用试验数据验证新建渗透率模型的合理性。研究结果表明:①当平均应力一定时,基质渗透率随孔隙压力增大呈先急剧减小后缓慢减小的变化趋势,裂隙渗透率的变化规律与煤岩总渗透率的变化规律较为接近;②当平均应力一定时,孔隙压力升降过程中的煤岩总渗透率均呈“V”型变化,但对于同一孔隙压力,降压过程总渗透率要低于升压过程总渗透率;③利用渗流试验数据对模型进行验证,发现新建双孔隙渗透率模型能够与试验结果保持一致;④修正函数L(p)中的敏感性系数c影响渗透率随孔隙压力变化的曲线斜率,敏感性系数d影响渗透率曲线整体高度。

     

    Abstract: Pore pressure is the key factor to control the permeability of coal and rock. In order to explore the response mechanism of coal and rock permeability in the process of pore pressure increasing and decreasing, the 3-axis seepage test device for gas bearing coal was used to carry out seepage tests on the increase and decrease of pore pressure under different average stress conditions. Based on the characteristics of dual pore structure medium of coal and rock, considering the mechanical effect of coal, slippage effect, adsorption expansion, and thickness change of adsorption layer in the process of pressure boost, a dual pore permeability model including matrix and fracture was constructed. By introducing a modified function L(p), the change of coal and rock permeability during depressurization was further quantified, and the rationality of the new permeability model was verified by using test data. The research results show that:①When the average stress is constant, the matrix permeability decreases sharply at first and then slowly with the increase of pore pressure, and the change law of fracture permeability is close to that of the total permeability of coal and rock. ②When the average stress is constant, the total permeability of coal and rock in the process of pore pressure increasing and decreasing shows a “V” shape. But for the same pore pressure, the total permeability in the process of pressure drop is lower than that in the process of pressure rise. ③The model is verified by seepage test data, and it is found that the new dual pore permeability model is consistent with the test results. ④With the change of pore pressure, the sensitivity coefficient c in the correction function L(p) affects the slope of the permeability curve,and the sensitivity coefficient d affects the overall height of the permeability curve. ④The sensitivity coefficient c in the modified function L(p) affects the slope of the permeability curve, and the sensitivity coefficient d affects the overall height of the permeability curve.

     

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