盖层封闭CO_2气与CH_4气的差异性分析

Difference of CO_2 and CH_4 sealing by caprock

在盖层封闭天然气机理及影响因素分析的基础上,对盖层对CO_2气和CH_4气封闭的差异性进行了研究。结果认为:盖层对CH_4气的毛细管封闭作用强于其对CH_2气的毛细管封闭作用;CO_2气的扩散作用强于CH_4气的扩散作用,但二者的扩散方向有所不同,CH_4气的扩散方向总是由地下至地表,而CO_2气只有在近地表或地下深处扩散方向是向上的,在二者之间扩散方向应是向下扩散的;CO_2气对盖层微渗漏空间的愈合能力比CH_4气对盖层微渗漏空间的愈合能力差。

Based on analysis of the mechanism and affecting factors of sealing natural gas by caprock, the difference of sealing CO2 and CH4 gas by caprock is studied. It is thought that the capillary sealing effect of caprock on CH4 gas is stronger than that of CO2 gas; the diffusion effect of CO2 is stronger than that of CH4, but showing different directions. CH4 always diffuses upward, while CO2 only shows upward diffusion at near surface or in deep formation, and diffuses downward in between; CO2 gas has poorer healed ability to micro leaking caprock than CH4 .