不同变质程度煤解吸过程渗透率回弹率变化规律

Change of Permeability Rebound Rate of Different Metamorphic Coal in Process of Desorption

定量描述煤解吸过程中渗透率变化是客观认识注氮驱替煤层气的重要基础。通过引入解吸率曲率把煤解吸过程中的渗透率回弹率划分为敏感回弹、过渡回弹和缓慢回弹3个阶段,构建了解吸过程只考虑煤基质收缩效应的渗透率回弹率数学模型,并进行了不同变质程度煤解吸过程中的渗透率回弹率实验研究。研究表明:低阶煤在解吸过程中的渗透率回弹率随孔隙压力的降低呈类似直线变化,随着煤变质程度的增加,渗透率回弹率呈2~3倍增加,并且这一增加趋势在敏感回弹阶段更为显著。

Quantitative description of permeability change in coal desorption process is an important basis for the objective understanding of nitrogen gas injection. The recovery rate of the coal sample was divided into three stages： sensitive rebound,transition rebound and slow rebound by introducing the curvature of the desorption rate, a mathematical model of permeability recovery rate considering the effect of shrinkage of coal matrix is established, and the experimental study on permeability and rebound rate of coal with different metamorphic degrees during desorption was carried out. The results show that： low rank coal permeability rebound in the process of desorption is similar to linear change with the decreasing of pore pressure, with the increase of coal metamorphic degree, permeability is increased by 2 to 3 times, and the increasing trend in the sensitive stage is more sensitive.