等压扩散和高压注入条件下CO_2对煤中CH_4置换效应

Replacement effect of carbon dioxide to methane in coal under isobaric diffusion and high pressure injection conditions

为了揭示注气压力对置换煤层瓦斯效应的影响,开展了等压扩散和高压注气2种条件下CO_2对煤中CH_4置换试验研究。试验结果表明:在置换源气体充入量相等的条件下等压扩散试验中CO_2对煤中CH_4的置换量大于高压注气试验的置换量,且等压扩散条件下CO_2置换CH_4效率维持在0.44 cm^3/cm^3左右,而高压注气条件下CO2置换CH_4效率却随注入量的增加而持续增加,但其增加率逐渐衰减。等压扩散条件下吸附平衡后系统总压略有下降,降幅一般为8%左右;高压注气条件下吸附平衡后系统总压呈持续上升规律,最大增幅为60%。研究成果对该项技术工程应用的启示是:井下煤层注气置换/驱替煤层瓦斯时,不一定要追求高的注气压力,采用低压注气也可收到良好的促排瓦斯效果,又能大幅度提高注气的安全可靠性。

In order to reveal the influence of gas injection pressure on replacement effect of coal seam methane,the experi-mental study on replacement of methane in coal by carbon dioxide under two types of conditions including isobaric diffusion and high pressure gas injection was carried out. The results showed that under the same injection amount of replacement source gas,the replacement amount of carbon dioxide to methane in coal under isobaric diffusion condition was higher than that under high pressure gas injection condition. The replacement efficiency under isobaric diffusion condition remained sta-ble at about 0. 44 cm3 / cm3 ,while the replacement efficiency under high pressure gas injection condition continuously in-creased with the increase of injection amount,but the increasing rate decreased gradually. The system total pressure after ad-sorption equilibrium under isobaric diffusion condition decreased slightly,with the decreasing amplitude of about 8%,while the system total pressure after adsorption equilibrium under high pressure gas injection condition increased continuously,with the maximum increasing amplitude of 60% . The enlightenment of the results on the engineering application of this technology is that the replacement / displacement of coal seam methane by gas injection for underground coal seam does not have to pur-sue the high gas injection pressure,the application of low pressure gas injection can also receive a good gas drainage effect and can significantly improve the safety and reliability of gas injection.