Abstract: Based on the mechanism of coalbed methane recovery by CO2 injection, starting from the experiments simulation studies and production practice, the influence factors of coalbed methane recovery by CO2 injection was analyzed. The study found that the main influence factors were as followings: the conditions of coal quality, water, injection pressure and rate of CO2.The gas injection process was affected by the different types, contents and distribution characteristics of the minerals in the coal and the water in the coal seam. Without external water supply in the state of free water, the higher content of carbonate mineral in coal was, the higher coalbed methane recovery was. The higher the gas injection pressure was, the better coalbed methane seepage channel output was. In a certain time, the methane stripping ratio increased with the increase rate of CO2 injection. By using analytic hierarchy process on the sensitivity analysis of the different factors, the results showed that the weighting coefficient of coal quality conditions was 0.55. Coal quality condition played a main role in the process of gas injection.

Key words: Coal bed methane, CO2 injection, Recovery, Influence factors, Mineral species

摘要： 基于煤储层注CO2 提高煤层气采收率的机理, 从实验模拟研究和现场出发, 总结和分析了注CO2 过程的影响因素。通过研究发现, 影响因素主要有煤质条件、 水和CO2 的注入压力及注入速率。煤质条件中的矿物、煤层中的水因其种类、 含量及分布特点不同而影响注气过程, 在煤中无外来水源补给的自由水状态下, 煤中碳酸盐矿物含量越高, 煤层气采收率越高; 注气压力越大, 煤层气产出的渗流通道越好, 在一定时间内甲烷脱附率随着CO2注入速率的增加而增大。通过层次分析法对各影响因素进行敏感性分析发现, 煤质条件的权重系数为0. 5 5, 在注气过程中起主要作用。

关键词: 煤层气, 注CO2, 采收率, 影响因素, 矿物种类