卸压煤层瓦斯抽采渗透率演化模型研究

Research on permeability evolution model for coal seam being drained by pressure relief

为研究井下卸压抽采时瓦斯流动规律,建立煤层渗透率演化模型。为建该模型将煤体简化为有2组相互垂直节理发育的等效连续介质,假定瓦斯在煤体裂隙中的流动符合立方定律,考虑煤基质对吸附性气体的吸附膨胀作用和外荷载对煤的压缩变形作用,不考虑孔隙压力对裂隙张开的影响。从应力条件和孔隙压力2个方面,结合煤样渗透率试验,对该模型进行有效性验证。结果表明,渗透率模型能反映应力和低孔隙压力对煤样渗透率的影响,但不能体现高孔隙压力对煤样损伤导致的渗透率增大作用。

For the sake of studying changes in coal seam permeability as a result of gas drainage from a relief coal seam,a permeability model was built. For the purposes of building the model,the coal was treaded simply as an equivalent continuous medium having two mutually perpendicular joints,Gas flow in coal fissures was hypothesized to meet the cubic law,adsorption strain and elastic strain on the fracture aperture were taken into account,but the impact of high pore pressure on the cracks opening was neglected.According to the permeability testes on different samples of the coal under different load conditions and pore pressure,the permeability model was verified. The results showed that permeability model can well reflect the influence of stress and low pore pressure on the permeability of coal samples,but can not reflect the relationship between the increase in permeability and the damage effects caused by high pore pressure.