Experimental study on characteristics of replacement and displacement of CH4 at different CO2 injection temperatures
BAI Gang,JIANG Yanhang,ZHOU Xihua,LAN Anchang,WANG Jiren
注气温度是煤层注气促抽瓦斯的关键技术参数,为研究CO2注入温度不同对CH4驱替量的影响规律,采用自主研发的CO2置换驱替CH4试验系统,开展CO2注入温度为40、50和60 ℃的置换驱替CH4试验,研究CO2置换驱替CH4过程中煤层温度、气体浓度、驱替效率、CO2封存量与CH4解吸量等变化规律。结果表明:注气温度是影响CH4解吸量与CO2封存量的关键因素,提高注气温度可以能够驱替出更多的CH4并储存更多的CO2;CO2注入温度越高,CO2突破时间越短,突破时间分别为107、73.8和57.5min,出口CO2体积浓度达到99.99%所需时间越短,相同注气时间内解吸CH4体积量和CO2封存量越多;注气温度由40℃升至60℃时,煤层CH4累计解吸量分别为6.43、6.57和6.71 cm3/g,CH4产出率提高了2.1%~4.3%,煤层累计封存CO2解吸量分别为17.39、17.99和17.41cm3/g;注气驱替CH4过程中煤层吸附CO2起占主要地位,随着注气时间的增加,煤层温度升高,可分为缓慢升温、急剧升温和缓慢降温阶段,且缓慢升温阶段随着CO2注入温度升高而明显“滞后”,表现为“逐渐驱替”效应,煤层温度最高变化量分别为10.5、11.4和11.3℃;运移速率随CO2注入温度的升高而增大,分别为0.006 53、0.007 81和0.008 86 cm/s,运移速率提高了19.6%~35.7%;相同注气温度下,驱替效率随注气时间增加逐渐增大,且注气温度越高,相同注气时间内驱替效果越明显,试验结束分别为88.49%、90.93%和91.7%,驱替效率可提高2.44%~3.21%。
The gas injection temperature is the key technical parameter in the field of enhanced coalbed methane drainage engineering by gas injection. In order to study the influence of different CO2 injection temperature on CH4 displacement,the self-developed CO2 replacement-displacement CH4 experimental system was used to carry out displacement CH4 experiments at 40,50 and 60 ℃ for CO2 injection temperature,to study the changing rules of coal seam temperature,gas concentration,displacement efficiency,CO2 storage volume and CH4 desorption volume in the process of CO2 replacement-displacement CH4. The results show that gas injection temperature is a key factor affecting the amount of CH4 desorption and CO2 storage. Increasing the gas injection temperature can displace more CH4 and store more CO2. The higher the CO2 injection temperature,the shorter the breakthrough time of CO2(107,73.8 and 57.5min,respectively),the shorter the time required for the outlet CO2 concentration to reach 99.99%,and the larger the volume of CH4 desorption and the CO2storage in the same gas injection time. When the temperature of injection rises from 40℃ to 60℃,the cumulative amount of CH4 desorption in coal seam is 6.43,6.57 and 6.71cm3/g,respectively,and the CH4 production rate increases by 2.1%~4.3%. The cumulative volume of CO2 storage in coal seam is 17.39,17.99 and 17.41cm3/g,respectively. In the process of gas injection displacement for CH4,CO2 adsorption in coal seams plays a major role. With the increase of gas injection time,the temperature of coal seams increases,which can be divided into stages of slow temperature increase,rapid temperature increase,and slow temperature decrease. And the slow temperature decrease stage is obviously "lagged" with the increase of CO2 injection temperature,which shows the effect of "gradual displacement",and the maximum change of coal seam temperature is 10.5,11.4 and 11.3℃.The migration rate increased with the increase of CO2 injection temperature(0.006 53 cm/s,0.007 81 cm/s and 0.008 86 cm/s,respectively),and the migration rate increased by 19.6%-35.7%.Under the same injection temperature,the displacement efficiency gradually increases with the increase of gas injection time,and the higher the injection temperature,the more obvious the displacement effect is in the same gas injection time,which are 88.49%,90.93% and 91.7% at the end of the experiment,respectively,and the displacement efficiency can be increased by 2.44%~3.21%.
CO2-ECBM; gas injection temperature; breakthrough time; displacement efficiency; migration rate
0 引言
1 样品与试验
1.1 煤样采集和处理
1.2 CO2驱替CH4试验装置
1.3 试验步骤
2 试验结果与讨论
2.1 气体浓度与突破时间
2.2 CH4解吸量与CO2封存量
2.3 驱替过程中热效应分析
2.4 运移速率与驱替效率
3 结论
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会