微纳米气泡−表面活性剂协同强化驱替煤中瓦斯效应与机理

Effect and mechanism of synergistic enhancement of gas displacement in coal by micro-nano bubbles and surfactants

  • 摘要: 为实现煤体瓦斯减阻增渗与强化驱替,基于微纳米气泡、表面活性剂与水介质共存特性获得了液气耦合介质,通过环管流量、旋转黏度表征了液气耦合协同增效特征,基于渗流瞬时流量、气测渗透率量化了微纳米气泡−表面活性剂协同强化驱替煤中瓦斯效应,借助达西渗流揭示了微纳米气泡−表面活性剂协同增效作用下驱替机理。结果表明:微纳米气泡−表面活性剂协同增效后,轴压/围压3、5 MPa渗流驱替时,相对蒸馏水介质,无烟煤瞬时流量分别增大1.61、2.44倍,气测渗透率分别增大1.61、2.39倍,长焰煤瞬时流量分别增大1.43、1.67倍,气测渗透率分别增大1.44、1.68倍;相对含表面活性剂介质,无烟煤瞬时流量分别增大1.08、1.21倍,气测渗透率分别增大1.08、1.13倍,长焰煤瞬时流量分别增大1.07、1.11倍,气测渗透率分别增大1.08、1.11倍。相同变质程度煤体在蒸馏水介质、含表面活性剂介质、液气耦合介质渗流驱替时,瞬时流量、气测渗透率逐渐增大,且长焰煤相对无烟煤呈现出更为明显的增强效应。随轴压/围压的增大,不同介质渗流驱替强度均呈现一定幅度的降低;但微纳米气泡−表面活性剂协同增效作用显现,相同载荷条件下,液气耦合介质渗流强度均大于蒸馏水介质与含表面活性剂介质,且不同轴压/围压之间的渗流差异明显缩小。微纳米气泡−表面活性剂协同增效衍生减阻性能与边界滑移,提供了瓦斯渗流驱替作用动力,基于孔隙渗流与边界滑移特征,将煤体内部孔隙结构类比圆管孔隙建立了减阻渗流模型,借助达西渗流表征了液气耦合介质对煤体注水渗流驱替界面特性与作用机制。微纳米气泡−表面活性剂液气耦合协同增效为煤层注水渗流驱替与增透抽采提出了新的技术方向。

     

    Abstract: In order to achieve drag reduction, permeability enhancement and enhanced displacement of coal gas, the liquid-gas coupling medium was obtained based on the coexistence characteristics of micro-nano bubbles, surfactants and water medium. The synergistic effect of the liquid-gas coupling was characterized by the flow rate of the loop and the rotational viscosity. The synergistic effect of micro-nano bubbles and surfactants was quantified based on the instantaneous flow rate of seepage and gas permeability measurement. The displacement mechanism under the synergistic effect of micro-nano bubbles and surfactants was revealed through Darcy seepage. The results show that after the synergistic effect of micro-nano bubbles and surfactants when the axial pressure/confining pressure is 3 and 5 MPa, the instantaneous flow rate of anthracite increases by 1.61 and 2.44 times and the gas permeability increases by 1.61 and 2.39 times respectively compared with distilled water, the instantaneous flow rate of long flame coal increased by 1.43 and 1.67 times and the gas permeability increased by 1.44 and 1.68 times respectively compared with the medium containing surfactant, the instantaneous flow rate of anthracite increased by 1.08 and 1.21 times and the gas permeability increased by 1.08 and 1.13 times respectively, the instantaneous flow rate of long flame coal increased by 1.07 and 1.11 times and the gas permeability increased by 1.08 and 1.11 times respectively. When the coal with the same metamorphic degree is displaced by distilled water medium, surfactant containing medium and liquid gas coupling medium, the instantaneous flow rate and gas permeability increase gradually, and the long flame coal shows a more obvious enhancement effect than anthracite coal. With the increase of axial pressure/confining pressure, the displacement intensity of different media decreased to a certain extent. However, the synergistic effect of micro and nano bubbles and surfactants shows that under the same load condition, the seepage strength of liquid gas coupling medium is greater than that of distilled water medium and surfactant containing medium and the seepage difference between different axial pressure/confining pressure is significantly reduced. The synergistic effect of micro-nano bubbles and surfactant derived drag reduction performance and boundary slip which provided the driving force for gas seepage displacement. Based on the characteristics of pore seepage and boundary slip, the resistance reduction seepage model was established by comparing the internal pore structure of coal with that of circular pipe pores. Based on Darcy seepage, the characteristics and mechanism of the interface of liquid gas coupling medium on coal water injection seepage displacement were characterized. The synergistic effect of micro nano bubble surfactant liquid gas coupling has put forward a new technical direction for coal seam water injection seepage displacement and enhanced permeability drainage.

     

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