考虑动态裂隙压缩系数条件下煤层渗透率敏感性研究

Study of Sensibility to Coalbed Permeability in Consideration of Compressibility Coefficient of Dynamic Crevices

针对应力敏感性煤层裂隙特性，基于P＆M模型并引入裂缝压缩系数方程，求得考虑孔隙压缩系数变化下的渗透率的应力敏感性公式。计算表明：在考虑了孔隙压缩系数动态变化情况下，所推导的渗透率敏感性公式较忽略孔隙压缩系数变化的P＆M模型具有更好的拟合度，特别是在排采后期这种差异性更加明显。其引起的相对偏差随着压力衰减程度的增加而递增．故不能忽略裂隙体积压缩系数变化对渗透率的影响。该方程在煤层气井动态分析、制订合理的增产措施和生产制度时具有一定的指导意义。

In the light of the characteristics of stress-sensitive coal seam crevices, based on the P＆M model and the introduction of fracture compress- ibility equation, permeability sensitivity formula is obtained in consideration of variation of pore compressibility coefficient. Calculations show that： in consideration of dynamic changes of the compressibility factor, the herein deduced permeability sensitivity formula have a better fitting degree than the P＆M model that neglected the pore compressibility variation, especially the differences are more obvious in the late stage of gas recovery with wa- ter drainage. The caused relative deviation rises with the increase in the degree of pressure attenuation. Therefore it cannot ignore the influence of fracture volume compressibility variation on the permeability. The equation has certain significance in the performance analysis of CBM wells and de- velopment of reasonable stimulation measures and production systems.