煤基质收缩效应和有效应力对煤层渗透率影响的新数学模型

在煤层气开发过程中,由于受到煤基质收缩效应和有效应力作用的影响,煤层渗透率将随煤储层压力的下降而变化。基于Bangham固体变形理论和有效应力应变理论,建立了煤基质收缩效应和有效应力耦合作用影响下煤层渗透率的数学模型。分析结果表明,自煤层气开始生产起,随着煤储层压力的降低,煤层渗透率变化将可能出现3种情况。经过对已有的现场试验结果与模型结论的对比,证明了该模型与现场实际相符。

A New Mathematical Model for Influence of Shrinkage Effect and Effective Stress of Coal Matrix on Infiltration Rate of Coal Seam

In the exploration process of coal-bed gas,the infiltration rate of a coal seam will change with the decrease of the seam gas pressure due to the influence of the shrinkage effect and effective stress of coal matrix. Based on Bangham solid deformation theory and the strain theory of the effective stress,a mathematical model for the infiltration rate of the coal seam under the influence of the shrinkage effect of coal matrix and the coupling action if the effective stress was set up. The analysis results showed that since the beginning of coal-bed gas production and with the decrease of the seam gas pressure,three changes of the seam filtration rate might take place. The contrast of the existing site test results with the model conclusions proved that the model tallied with the practice.