破碎煤岩体瓦斯-水相对渗透特性试验研究
Experimental study on gas-water relative permeability characteristics of broken coal and rock mass
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摘要: 为探究瓦斯抽采钻孔孔周破碎煤岩体中瓦斯-水相对渗透特性，利用自主研发的破碎岩体气液耦合渗透试验系统，采用稳态渗透法开展了瓦斯-水耦合渗透试验，得到了煤样渗透参数随渗透压和轴向压力的变化特征，并分析了渗透参数间的相互影响关系。结果表明：承压破碎煤岩体孔隙度随轴向压力的增加呈快速下降、缓慢下降和趋于稳定的阶段性特征；随着含水饱和度的增加，煤样气体相对渗透率快速下降，水相对渗透率线性上升，气体和水相对渗透率表现出竞争关系，且气体渗透率对于含水饱和度的敏感程度更高；气体和水的总渗透率随有效应力的增加而减小，服从指数函数关系，有效应力会影响破碎煤岩体孔隙结构的变形过程，随孔隙度的减小，气体有效渗透率降低，相对渗透率增加；渗透压对于水和气体相对渗透率的影响可分为气体占优阶段、等渗阶段和水占优阶段，临界渗透压取值范围为0.4~0.6 MPa。Abstract: In order to explore the relative permeability characteristics of gas-water in the crushed coal rock mass around the drilling hole of gas extraction, the gas-water coupling permeation test system of the crushed rock mass was used to carry out the gas-water coupling permeation test by using the steady-state osmosis method, and the variation characteristics of the coal sample permeability parameters with osmotic pressure and axial pressure were obtained, and the interaction relationship between the permeation parameters was analyzed. The results show that the porosity of the crushed coal mass under pressure shows a rapid decline, a slow decline and stabilization with the increase of axial pressure. With the increase of water saturation, the relative permeability of coal-like gases decreases rapidly, the relative permeability of water increases linearly, the relative permeability of gases and water shows a competitive relationship, and the sensitivity of gas permeability to water saturation is higher. The total permeability of gas and water decreases with the increase of the effective force, obeying the exponential function relationship, the effective force will affect the deformation process of the pore structure of the crushed coal rock mass, and with the decrease of porosity, the effective permeability of the gas decreases and the relative permeability increases. The influence of osmotic pressure on the relative permeability of water and gas can be divided into gas dominant stage, isotonic stage and water dominant stage, and the critical osmotic pressure extraction value ranges from 0.4 MPa to 0.6 MPa.
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Keywords:
- gas extraction /
- broken coal sample /
- relative permeability /
- porosity /
- water saturation /
- effective stress
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