不同注源气体置换-驱替煤层甲烷突破时间的差异性分析

Analysis on the difference of breakthrough time for different injection gases to replace-displace methane in coal seams

煤层注气促抽瓦斯是近年来逐步发展起来的强化抽采技术,注气突破时间是该技术的重要参数之一。突破时间是指注源气体从煤层一端注入到另一端检测出该组分所需的时间,它与注源气体的吸附性、渗透性有着密切的关系。为了研究渗透和吸附对注气突破时间的影响规律,利用含瓦斯煤层注气模拟实验装置,进行了煤层注He,N_2和CO_2置换-驱替CH_4的实验室模拟实验。实验结果表明,不考虑煤对气体吸附性的纯渗流条件下,N_2和CO_2纯渗流突破时间极短,仅为总突破时间的5.93%和0.28%,表明气体吸附性能是引起总突破时间差异的主要因素;另外,随着注源气体吸附性增强,其总突破时间大幅度增加,He,N_2和CO_2的总突破时间分别为0.92,14,246 min。实验结果结合理论模型计算分析得出:注源气体吸附性越强,总突破时间越长,注气初期的置换效应越明显,但随着注源气体的吸附不断趋于饱和,其驱替效应逐渐增强。

Coal gas injection is an intensive extraction technology which is gradually developed in recent years, and the breakthrough time of gas injection is one of the important parameters of the technology. The breakthrough time is the required time of injection gas goes from one end of the coal seam to the other end, and it is closely related to the adsorption and the permeability of the source gas. In order to study the laws of permeability and adsorption on the breakthrough time, the laboratory simulation experiment is carried out with injecting He, N2 and CO2 in coal seams to replace-displace CH4. The results show that thebreakthrough time on pure seepage of N2 and CO2 is very short, only 5.930/00 and 0.28% of the total breakthrough time, which indicates that gas adsorption performance is the main factor that causes the difference of breakthrough time. The breakthrough time increases as the gas adsorption performace of injection gas increases, and the breakthrough time of He, N2 and CO2 is 0.92 min, 14 min and 246 min, respectively. According to the laboratory experiment and theoretical model analysis, it can be concluded that the stronger the adsorption performance of injection gas is, the longer the breakthrough time and the more obvious the replacement effect in the initial stage of gas injection is, but the displacement effect gradually increases as the adsorption of the injection gas tends to be saturated.