煤层注N_2促排瓦斯时效性实验研究

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.

Experimental Research on Timeliness of Promoting Gas Drainage by N2 Injection in Coal Bed

In order to make clearly the process and features of gas emission by injecting N₂， N₂ displacement coal seam CH₄ tests were performed by using coal bed gas injection displacement experiment device. The results show that N₂ 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 N₂ displacement coal bed CH₄ include the gas displacement， the air carrying and the dilution and diffusion of gas flow.