CO2置换增产煤层气室内实验研究

摘要

Since the ECBM technology can not only improve the recovery of coalbed methane but also achieve the goal of reducing greenhouse effect by storage of CO2, study of the production rate and the influencing factors of CH4displacement by CO2 has become a very hot point for researchers. In this paper, the effect of pressure injection on the displacement performance of CO2was studied by displacing CH4with CO2under different pressure injection conditions but at the same confining pressure. The results demonstrated that with the increase of pressure injection, the coalbed adsorption capacity of CO2and CH4increased and so was the total adsorption capacity of the mixture. Because CO2was superior to CH4in the incentive competition of coal surface adsorption, the desorption capacity of CH4increased with the increase of pressure. Productivity rate and displacement ratio of CH4appeared to decrease with the increase of pressure and consequently were negatively correlated with pressure, indicating that within a certain range, lower injection pressure could result in a higher CH4productivity and better displacement effect than those with a higher injection pressure.%注入二氧化碳开采煤层气技术(ECBM)既可以提高煤层气采收率,又可以封存二氧化碳,减少温室效应,因此对CO2置换CH4采出率和影响因素的研究已成为当下热点.文章通过在同一围压下,不同注入压力条件下注CO2置换CH4试验,研究注入压力对CO2置换效果的影响.研究表明:随着注入压力的增加,煤层对CO2和CH4的吸附量增加,混合气体总吸附量也随之增大;由于CO2气体在煤表面吸附位的激励竞争上优于CH4,使得CH4的解吸量随着压力升高而增大;随着压力的增加,CH4的产出率和置换比都呈下降趋势,压力与两者的关系呈负相关,表明在一定范围内,低注入压力状态下的CH4产出率更好,低压状态下的置换效果更好.