摘要
煤矿开采逐渐走向深部,深部煤岩体表现为复杂的孔隙结构及低渗透特性,因此正确认识气体与水在煤岩等低渗岩土介质中的渗透规律、表征煤岩孔裂隙结构网络对于深部开采具有重要意义。核磁共振在研究煤岩孔隙结构和渗流路径方面具有快速无损的特征。为研究深部煤体在氮气驱水与渗流过程中的流体运移和分布,以及深部煤体原始状态与各级围压状态下的煤体内部孔隙的分布情况,对平煤十二矿己15-31030工作面圆柱形煤样试件分别进行了称重、烘干、饱水,在不同驱替压力下对试件进行了氮气驱水与渗流状态下的核磁共振CPMG序列测试和核磁共振(Nuclear Magnetic Resonance,NMR)成像检测,对饱水试样进行了变围压状态下的核磁共振CPMG序列测试。得到了煤样的横向弛豫时间T 2谱、一维频率编码和NMR成像图,并进行了结果分析。分析结果表明,煤体随着围压的增加,其孔隙率并不是单调变化,而是先增加再减小最后趋向于不变,其吸附孔数量变化规律趋近孔隙率的改变;氮气驱水能驱掉运移孔中的水分,对于渗透孔及以下级别孔隙中的总含水量影响不大;通过核磁共振CPMG序列计算得到煤体孔隙率演化图形。NMR成像结果表明,深部煤体大多无散布大孔隙,且小孔隙分布较均匀。
The coal mining gradually goes deeper,and the deep coal-rock exhibits complex pore structure and low permeability characteristics.For this reason,it is of significance to characterize the transportation constitutive of methane and pore water in the low-permeability coal rock and the pore fracture network.NMR has fast and non-destructive characteristics in studying the pore structure and seepage path of coal-rock.In order to study the fluid migration and distribution of deep coal in the process of nitrogen flooding and seepage,and understand the distribution of pores in the state of deep coal and the coal under confining pressure,the cylindrical coal sample at the working face No.31030 of the Ji-15 coal seam in Pingdingshan Coal Mine No.12,Henan Province,China,was collected and subjected to a NMR CPMG sequence test and a MRI(Magnetic Resonance Imaging)test under the conditions of weighing,drying,saturated water,nitrogen flooding and seepage under different flooding pressures.The transverse relaxation T 2 spectrum,one-dimensional frequency code and NMR imaging of coal samples were obtained.Also,the saturated sample was subjected to a nuclear magnetic resonance CPMG sequence test under confined pressure,and analyzed the results.The results show that the porosity of the coal does not change monotonously with the increase of confining pressure,but increases and then decreases and finally tends to remain unchanged.The variation of the number of adsorption pores approaches the change of porosity.Nitrogen flooding can drive out the water in the transport pores,which has little effect on the total water content below the percolation level.The porosity evolution of coal was calculated by using NMR CPMG sequence.The MRI shows that the coal sample is different from other rock masses,with no large pores scattered,and the distribution of small and medium pores is relatively uniform.
作者
邓淋升
周宏伟
薛东杰
孙晓彤
刘泽霖
DENG Linsheng;ZHOU Hongwei;XUE Dongjie;SUN Xiaotong;LIU Zelin(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 100083,China;State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology,Beijing 100083,China;State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400030,China;Key Laboratory of Safety and High-efficiency Coal Mining,Anhui University of Science and Technology,Huainan 232001,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2019年第S01期133-141,共9页
Journal of China Coal Society
基金
国家重点研发计划资助项目(2016YFC0600704)
国家自然科学基金青年基金资助项目(51504257)
中国矿业大学(北京)越琦学者基金资助项目(2018B051616)。
关键词
核磁共振
氮气驱水
T2谱
孔隙结构
气液两相渗流
围压
nuclear magnetic resonance
N2 flooding
T2
pore structure
N2-H2O percolation
confining pressure
