CO₂ geo-sequestration in unminable coal seams is one promising method to mitigate greenhouse gas emissions and would be a means of cleaner production. At the same time, the injected CO₂ can enhance coalbed methane recovery and offsets the economic cost for CO₂ transportation and injection. However, this technology is still at its primary stage and so far, no large scale of field CO₂ injection has been implemented. One of the main difficulties encountered in this process is the permeability reduction induced by CO₂ injection and as a result, the injection rate is sharply dropped in the later period. In this paper, detailed laboratory experiments are conducted to investigate the permeability reduction effects during CO₂ injections. The dynamic permeability reduction effects are measured with the continuous CO₂ injection under different confining pressure conditions. Permeability reduction effects of 13%-77% are obtained with respect to the CO₂ exposure time in different testings. In low permeability scenario, the permeability reduction effects are severer. Specifically, when the absolute permeability is 1mD, 0.42mD, 0.18mD and 0.03mD, the permeability reduction is 13%, 36%, 48% and 77%, respectively. Compared with the coal triaxial adsorption tests, it is suggested that the permeability equilibrium is not equal to the adsorption equilibrium. The triaxial adsorption equilibrium process takes much longer time than that of permeability equilibrium process. Based on the testing results, a novel dynamic permeability model is proposed to illustrate the permeability evolutions. The existence of weak internal surface influences the matrix strain and the permeability. This model is also validated by other’s experimental results and can be used for explaining coal seam permeability reduction effects of CO₂ injection in coal seams.

不可开采煤层中的CO ₂固存是减轻温室气体排放的一种有前途的方法，并且将成为清洁生产的一种手段。同时，注入的CO ₂可以提高煤层气的采收率并抵消CO ₂运输和注入的经济成本。但是，该技术仍处于初级阶段，到目前为止，尚未实现大规模的现场CO ₂注入。在此过程中遇到的主要困难之一是由CO ₂引起的渗透率降低因此，注入速率在随后的时期急剧下降。在本文中，进行了详细的实验室实验以研究注入CO ₂期间渗透率降低的影响。动态渗透率降低效果是通过在不同围压条件下连续注入CO ₂来测量的。相对于CO ₂获得了13％-77％的渗透率降低效果在不同测试中的曝光时间。在低渗透率的情况下，渗透率降低的影响更为严重。具体地，当绝对磁导率是1mD，0.42mD，0.18mD和0.03mD时，磁导率降低分别是13％，36％，48％和77％。与煤三轴吸附试验相比，建议渗透率平衡不等于吸附平衡。三轴吸附平衡过程比渗透率平衡过程需要更长的时间。根据测试结果，提出了一种新型的动态渗透率模型来说明渗透率的变化。内表面薄弱的存在会影响基体应变和渗透率。₂在煤层中注入。