煤层注N_2促排瓦斯时效性实验研究

Experimental Research on Timeliness of Promoting Gas Drainage by N_2 Injection in Coal Bed

为了研究煤层注弱吸附性气体强化瓦斯排放的过程和效果,利用自行搭建的煤层注气驱替实验装置,进行了注N_2驱替CH_4实验.实验结果表明:注N_2驱替煤层CH_4具有时效特性,排出CH_4体积分数逐渐衰减,流量先升后降.注气压力对驱替CH_4效果显著,注气压力越高,驱出CH_4体积分数衰减越快,驱出气体流量越大,增流效应越明显;相同时间内,注气压力越高,累计驱出CH_4体积越大,促排效果越明显.结合实验过程中二元气体物理状态变化规律,认为注N_2促排煤层CH_4机理有:气体的置换作用、气流的携载作用和气流的稀释扩散作用等.

In order to make clearly the process and features of gas emission by injecting N” N= displacement coal seam CH4 tests were performed by using coal bed gas injection displacement experiment device. The results show that N= displacement coal bed CH4 is a time-dependent process with a gradual decay of drained CH4 concentration,and CH4 flow increases at first and then decreases. Gas injection pressure has significant impact on the displacement effect, the higher the injection pressure,the faster the drained CH4 concentration decay,the larger injection gas flow, the more significant the flow rate increases. During the same time, the higher gas injection displacement pressure is, the larger the drained CH4 volume. According to the theoretical analysis, the mechanisms of injecting ^ displacement coal bed CH4 include the gas displacement, the air carrying and the dilution and diffusion of gas flow.