摘要
基于煤层注水对提高煤层气采收率、防治瓦斯灾害的重要性,研究了低渗煤体在自渗吸过程中的微观渗流特征.采用核磁共振(NMR)技术监测煤样在自渗吸实验中的T2谱与一维频谱,得到了煤体在不同时刻、不同位置的一维水信号分布情况.结合孔隙结构,通过核磁法从微观角度分析吸水量和含水量的时间与空间演化规律.结果表明:在快速上升阶段与缓慢上升阶段的前期,吸附孔对煤样自渗吸起主导作用,最先达到饱和状态;随着时间的增加,中孔和大孔-微裂隙对自渗吸的贡献作用逐渐显著.孔隙吸水能力与孔径呈负相关,吸水量与孔径分布频率呈正相关.水进入煤样后,很小一部分水沿毛细管阻力较小的连通路径向前推进并率先到达出口,形成优势通道;而大部分水沿横向向同一水平面扩散,当此水平面内的孔隙接近饱和后,再向上部运移.
The micro-seepage characteristics of low-permeability coals in spontaneous imbibition were studied based on the importance of coal seam water injection to improve the recovery rate of coalbed methane and prevent gas disaster.The T2 spectrum and one-dimensional spectrum of coal samples were monitored during spontaneous imbibition experiment by using nuclear magnetic resonance(NMR)technology,which can obtain the one-dimensional water signal distribution of coals at different times and positions.Combining with the pore structure,the time and space evolution rules of water absorption and water content were analyzed by NMR method from microscopic view.The results show that in the rapid rising stage and the prior period of slow rising stage,the adsorption pores play a leading role in spontaneous imbibition of coal samples and reach the saturation state first.With the increase of time,the contribution of mesopore and macropore-microcracks to spontaneous imbibition becomes significant gradually.Water absorbing capacity of pore is negatively correlated with pore size and the volume of water absorption is positively correlated with the frequency of pore size distribution.After water enters the coal samples,a small part of water advances along the connected path with low capillary resistance and reaches the outlet first,forming the dominant channel.However,most of the water diffuses laterally to the same horizontal plane.When the pores in this horizontal plane approach saturation state,they migrate upward.
作者
孙晓彤
周宏伟
薛东杰
刘泽霖
安露
王雷
车俊
SUN Xiaotong;ZHOU Hongwei;XUE Dongjie;LIU Zelin;AN Lu;WANG Lei;CHE Jun(School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;School of Energy and Mining Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology(Beijing),Beijing 100083,China;State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400030,China)
出处
《中国矿业大学学报》
CSCD
北大核心
2021年第4期804-812,共9页
Journal of China University of Mining & Technology
基金
国家重点研发计划项目(2016YFC0600704)
煤矿灾害动力学与控制国家重点实验室开放项目(2011DA105287-FW201604)
中国矿业大学(北京)越崎学者基金项目(2017A03)。
关键词
低渗
NMR
自渗吸
渗流
孔径分布
low-permeability
NMR
spontaneous imbibition
seepage
pore size distribution
