CO2注气压力对CH4驱替特性影响实验研究*

为研究CO2驱替CH4过程中注气压力对气体解吸特性的影响，采用自主搭建的驱替实验平台，在0.6，0.8，1.0 MPa不同注气压力下进行驱替实验，研究CO2驱替CH4过程中煤层温度、气体浓度、置换效率和渗透率等变化规律。实验结果表明:提高CO2注气压力可提高CO2置换驱替煤层CH4的效果。随着注气压力增大，CH4累计解吸量增大，CO2突破时间越短，CO2封存量越大，置换效率升高，驱替比下降。注气压力为0.6，0.8，1.0 MPa时，CH4累计解吸量分别为90.2，94.1，97.8 L；CO2封存量分别为19.73，19.92，20.21 mL/g；置换效率由76.9%上升到80.2%再到82.9%，驱替比由3.28下降到3.17再到3.09。注气驱替CH4过程中煤层温度升高，可分为低速升温、高速升温和趋于平缓阶段。煤层温度最高变化量分别为9.4,11.5，12.7 ℃。同一注气压力下，煤层渗透率变化可分为缓慢增长、急剧下降和趋于稳定阶段。

Experimental study on influence of COCO2 injection pressure on CHCO4 displacement characteristics

In order to study the influence of gas injection pressure on the gas desorption characteristics during the process of CO2 displacement for CH4,the displacement experiments were carried out under different gas injection pressures of 0.6 MPa,0.8 MPa and 1.0 MPa by using the self-built displacement test platform,and the variation laws of coal seam temperature,gas concentration,displacement efficiency and permeability during the process of CO2 displacement for CH4.The experimental results showed that increasing the CO2 injection pressure could improve the effect of CO2 displacement for CH4 in the coal seam.With the increase of gas injection pressure,the cumulative desorption amount of CH4 increased,the shorter the CO2 breakthrough time,the larger the CO2 storage amount,the displacement efficiency increased,and the displacement ratio decreased.When the gas injection pressure was 0.6,0.8,1.0 MPa,the cumulative desorption amount of CH4 was 90.2,94.1,97.8 L,respectively,and the CO2 storage amount was 19.73,19.92,20.21 mL/g,respectively.The displacement efficiency increased from 76.9% to 80.2% and then to 82.9%,and the displacement ratio decreased from 3.28 to 3.17 and then to 3.09.The temperature of coal seam in the process of gas injection displacement for CH4 increased,which could be divided into the low speed temperature rise stage,high speed temperature rise stage and tending to be gentle stage.The maximum variation of coal seam temperature was 9.4,11.5,12.7 ℃,respectively.Under the same gas injection pressure,the change of coal seam permeability could be divided into the slow growth stage,sharp decline stage and tending to be stable stage.