煤样吸附/解吸滞后效应定量分析

Quantitative analysis of methane adsorption/desorption hysteresis effect on coal sample

针对普遍存在的煤样吸附/解吸滞后现象,总结了其滞后机理,分析了现有定量评价体系及存在的问题,提出了基于曲线相似理论的解吸滞后程度表征方法,在历史试验数据的基础上进行了影响因素的相关性分析,揭示了滞后效应对煤层气开发的影响作用。结果表明:宏观的甲烷解吸过程实质上是一个包含解吸-运移2个阶段的综合过程,滞后机理主要反映在解吸受阻和气体运移受阻2个方面;基于Fréchet距离表征的曲线相似度理论可以用来表征解吸滞后程度;随着温度升高,解吸滞后程度呈下降趋势或先降后升趋势;含水煤样滞后程度明显高于干燥煤样,但与含水率无明显关系;块样、柱样的滞后程度高于粉样,粉样的滞后程度与粒径关系不显著。

According to the adsorption/desorption hysteresis phenomenon of the coal samples generally existed,the paper summarized the hysteresis mechanism and analyzed the available quantitative evaluation system and the existed problems. A method was provided to state the desorption hysteresis degree based on the curve similar theory. Based on historical experiment data, a correlation analysis on the influ- ence factors was conducted and the hysteresis effect affected to the coalbed methane development was revealed. The results showed that a macro methane desorption process essentially was a comprehensive process with the desorption and migration two stages and the hysteresis mechanism mainly could reflect the aspects of the desorption resistance and the gas migration resistance. Based on the Frrchet distance features, the curve similarity theory could be applied to state the desorption hysteresis degree. With the temperature increased, the desorp- tion hysteresis degree would be in a decreased tendency or in a first deceasing and then increasing tendency. The hysteresis degree of the water bearing coal samples would be obviously higher than the dry coal samples, but there would be no obvious relationship with the water bearing rate. The hysteresis degree of the lump coal sample and pillar coal sample would be higher than the powder coal sample and the hysteresis degree of the powder coal sample would have no obvious relationship to the coal particle size.