二氧化碳驱替煤层甲烷过程竞争吸附的耦合数值模拟  

Coupling Numerical Simulation of Competitive Adsorption in the Process of Carbon Dioxide Displacement of Coalbed Methane

作　　者：贺志宏 张文豪 康建宏[2,3] 吴佳俊 王庭嵘 HE Zhihong;ZHANG Wenhao;KANG Jianhong;WU Jiajun;WANG Tingrong(Xishan Coal Electricity(Group)Co.,Ltd.,Taiyuan,Shanxi 030053,China;School of Safety Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Jiaozuo,Henan 454003,China)

机构地区：[1]西山煤电(集团)有限责任公司,山西太原030053 [2]中国矿业大学安全工程学院,江苏徐州市221116 [3]河南省瓦斯地质与瓦斯治理重点实验室,河南焦作市454003

出　　处：《矿业研究与开发》2023年第4期133-138,共6页Mining Research and Development

基　　金：国家自然科学基金面上项目(51974304);河南省瓦斯地质与瓦斯治理重点实验室—省部共建国家重点实验室培育基地开放基金项目(WS2020A05)。

摘　　要：研究二氧化碳驱替煤层甲烷的竞争吸附特性,对注二氧化碳提高煤层气采收率具有重要意义。基于达西渗流、菲克扩散和扩展朗格缪尔方程,建立了甲烷与二氧化碳在煤层中运移与置换解吸的耦合数学模型,数值模拟了不同二氧化碳注气压力以及注抽钻孔布置对提高煤层气采收率的影响。研究结果表明:在二氧化碳驱替甲烷的过程中,注气钻孔附近的煤层中会出现“甲烷富集区”,且随着注气时间的增加,“甲烷富集区”逐渐向排气钻孔移动,最终煤层中甲烷浓度分布趋于稳定,煤层中平均甲烷浓度约为原始甲烷浓度的56.5%;排气钻孔甲烷流量先衰减然后快速增大到峰值,再缓慢减小趋于一个稳定值;注抽钻孔间距对排气钻孔处甲烷浓度稳定后的流量没有影响,但对甲烷的流量峰值以及峰值出现的时间有显著影响。The study on the competitive adsorption characteristics in carbon dioxide displacement of coalbed methane is of great significance for improving coalbed methane recovery by carbon dioxide injection(CO2-ECBM).Based on Darcy seepage,Fick diffusion and extended Langmuir equation,a multi-field coupling mathematical model of migration,displacement and desorption of methane and carbon dioxide in coal seam was established.The effects of different carbon dioxide gas injection pressure and the arrangement of injection and extraction boreholes on improving coalbed methane recovery were numerically simulated.The results show that in the process of carbon dioxide displacing methane,a"methane enrichment area"will appear in the coal seam near the gas injection borehole,and with the increase of gas injection time,the"methane enrichment area"will gradually move to the exhaust borehole until the methane concentration distribution in the coal seam is stable,and the average methane concentration in the coal seam is 56.5%of the original methane concentration.The methane flow rate in the exhaust borehole first decreases,then increases rapidly to a peak,and then decreases slowly to a stable value.In addition,the distance between injection and extraction boreholes has no effect on the methane flow after the methane concentration at the exhaust borehole is stable,but has an obvious effect on the peak value of methane flow and the time of peak value.

关 键 词：竞争吸附 多场耦合 二氧化碳 煤层气 数值模拟 

分 类 号：TD845[矿业工程—煤矿开采] TD984[矿业工程—矿山开采]