煤储层纳米孔隙结构及其瓦斯扩散特征
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摘要
研究煤复杂发育的孔隙结构对揭示煤层气体赋存机理及扩散运移规律有重要意义.为了研究煤的纳米孔隙结构,利用SEM、液氮吸附、小角X射线研究了不同煤阶煤的纳米孔隙在形式和分布上的非均匀性.实验煤样煤基质中的孔呈多峰分布,且孔径范围主要集中在2~10nm.煤样低温液氮吸附实验测得煤样的吸附量为3.676cm3/g,煤样的比表面积为1.416m2/g.以最可几孔径作为研究对象,在实验压力范围内,吸附压力越大,最可几孔径变大的越多;瓦斯气体在纳米级孔隙结构中的扩散模式以过渡型扩散为主,微孔更发达的煤样中,扩散更接近Knudsen型扩散,中孔更发达的煤样中,扩散更接近Fick型扩散;Knudsen数与温度呈负相关关系,温度高于250K后,Knudsen数趋于稳定,与压强呈正相关关系,压强越大,扩散越容易.
In order to study the characteristics of nanometer pore structure of coal,the heterogeneous structures of nano pores of different rank coals were investigated by using SEM,liquid nitrogen adsorption and small angle X ray.It is found that the mesopore shows the multimodal division,mainly concentrated in the 2-10 aperture and nm.The adsorption capacity of coal low-temperature nitrogen adsorption experiments of coal samples is 3.676 cm3/g,and coal sample surface area is 1.416 m2/g.By analyzing the most probable aperture,the range of experimental pressure can be found out,and the most probable pore size will be increased with the adsorbent pressure.Gas diffusion model in most nanoscale pore structure model prefers coals mainly concentrated on transitional diffusion.In more developed microporous coal samples(anthracite),the diffusion type is closer to the Knudsen diffusion.In much less developed coal samples,the main diffusion type is closer to Fick diffusion.The Knudsen number is negatively related to temperature,and Knudsen number tends to be stable when the temperature is higher than250 K,which is positively correlated with the pressure.The diffusion will be easier with the increase of pressure.
In order to study the characteristics of nanometer pore structure of coal,the heterogeneous structures of nano pores of different rank coals were investigated by using SEM,liquid nitrogen adsorption and small angle X ray.It is found that the mesopore shows the multimodal division,mainly concentrated in the 2-10 aperture and nm.The adsorption capacity of coal low-temperature nitrogen adsorption experiments of coal samples is 3.676 cm3/g,and coal sample surface area is 1.416 m2/g.By analyzing the most probable aperture,the range of experimental pressure can be found out,and the most probable pore size will be increased with the adsorbent pressure.Gas diffusion model in most nanoscale pore structure model prefers coals mainly concentrated on transitional diffusion.In more developed microporous coal samples(anthracite),the diffusion type is closer to the Knudsen diffusion.In much less developed coal samples,the main diffusion type is closer to Fick diffusion.The Knudsen number is negatively related to temperature,and Knudsen number tends to be stable when the temperature is higher than250 K,which is positively correlated with the pressure.The diffusion will be easier with the increase of pressure.
引文
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Liu,Y.,Wilcox,J.,2012.Molecular Simulation of CO2Adsorption in Micro-and Mesoporous Carbons with Surface Heterogeneity.International Journal of Coal Geology,104:83-95.
Lu,J.,Shao,L.Y.,Yang,M,F.,et al.,2017.Depositional Model for Peat Swamp and Coal Facies Evolution Using Sedimentology,Coal Macerals,Geochemistry and Sequence Stratigraphy.Journal of Earth Science,28(6):1163-1177.
Nie,B.S.,Duan,S.M.,1998.The Adsorption Essence of Gas on Coal Surface.Journal of Taiyuan University of Technology,29(4):417-421(in Chinese with English abstract).
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Nie,B.S.,Liu,X.F.,Yuan,S.F.,et al.,2016.Sorption Charateristics of Methane among Various Rank Coals:Impact of Moisture.Adsorption,22(3):315-325.
Wang,P.F.,Jiang,Z.X.,Li,Z.,et al.,2017.Micro-Nano Pore Structure Characteristics in the Lower Cambrian Niutitang Shale,Northeast Chongqing.Earth Science,42(7):1147-1156(in Chinese with English abstract).https://doi.org/10.3799/dqkx.2017.093
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Zhang,H.,2001.Genetical Type of Proes in Coal Reservoir and its Research Significance.Journal of China Coal Society,26(1):40-44(in Chinese with English abstract).
陈萍,唐修义,2001.低温氮吸附法与煤中微孔隙特征的研究.煤炭学报,26(5):552-556.
何学秋,聂百胜,2001.孔隙气体在煤层中扩散的机理.中国矿业大学学报,30(1):1-4.
聂百胜,段三明,1998.煤吸附瓦斯的本质.太原理工大学学报,29(4):417-421.
聂百胜,柳先锋,郭建华,等,2015.水分对煤体瓦斯解吸扩散的影响.中国矿业大学学报,44(5):781-787.
王朋飞,姜振学,李卓,等,2017.渝东北下寒武统牛蹄塘组页岩微纳米孔隙结构特征.地球科学,42(7):1147-1156.
杨永飞,王晨晨,姚军,等,2016.页岩基质微观孔隙结构分析新方法.地球科学,41(6):1067-1073.
张慧,2001.煤孔隙的成因类型及其研究.煤炭学报,26(1):40-44.
Chen,P.,Tang,X.Y.,2001.The Research on the Adsorption of Nitrogen in Low Temperature and Micro-Pore Properties in Coal.Journal of China Coal Society,26(5):552-556(in Chinese with English abstract).
He,X.Q.,Nie,B.S.,2001.Diffusion Mechanism of Porous Gases in Coal Seams.Journal of China University of Mining&Technology,30(1):1-4(in Chinese with English abstract).
Kang,Y.L.,Huang,F.S.,You,L.J.,et al.,2016.Impact of Fracturing Fluid on Multiscale Mass Transport in Coalbed Methane Reservoirs.International Journal of Coal Geology,154-155:123-135.
Lastoskie,C.,Gubbins,K.E.,Quirke,N.,1993.Pore Size Heterogeneity and the Carbon Slit Pore:A Density Functional Theory Model.Langmuir,9(10):2693-2702.
Li,H.Y.,Ogawa,Y.,Shimada,S.,2003.Mechanism of Methane Flow through Sheared Coals and Its Role on Methane Recovery.Fuel,82(10):1271-1279.
Li,Z.,2013.A Program for SAXS Data Processing and Analysis.Chinese Physics C,37(10):112-117.
Li,Z.,Wu,Z.,Mo,G.,et al.,2014.Small Angle X-Ray Scattering Station at Beijing Synchrotron Radiation Facility.Instrumentation Science and Technology,42(2):128-141.
Liu,Y.,Wilcox,J.,2012.Molecular Simulation of CO2Adsorption in Micro-and Mesoporous Carbons with Surface Heterogeneity.International Journal of Coal Geology,104:83-95.
Lu,J.,Shao,L.Y.,Yang,M,F.,et al.,2017.Depositional Model for Peat Swamp and Coal Facies Evolution Using Sedimentology,Coal Macerals,Geochemistry and Sequence Stratigraphy.Journal of Earth Science,28(6):1163-1177.
Nie,B.S.,Duan,S.M.,1998.The Adsorption Essence of Gas on Coal Surface.Journal of Taiyuan University of Technology,29(4):417-421(in Chinese with English abstract).
Nie,B.S.,Liu,X.F.,Guo,J.H.,et al.,2015.Effect of Moisture on Gas Desorption and Diffusion in Coal Mass.Journal ofChinaUniversityof Mining&Technology,44(5):781-787(in Chinese with English abstract).
Nie,B.S.,Liu,X.F.,Yuan,S.F.,et al.,2016.Sorption Charateristics of Methane among Various Rank Coals:Impact of Moisture.Adsorption,22(3):315-325.
Wang,P.F.,Jiang,Z.X.,Li,Z.,et al.,2017.Micro-Nano Pore Structure Characteristics in the Lower Cambrian Niutitang Shale,Northeast Chongqing.Earth Science,42(7):1147-1156(in Chinese with English abstract).https://doi.org/10.3799/dqkx.2017.093
Yang,Y.F.,Wang,C.C.,Yao,J.,et al.,2016.A New Method for Microscopic Pore Structure Analysis in Shale Matrix.Earth Science,41(6):1067-1073(in Chinese with English abstract).https://doi.org/10.3799/dqkx.2016.088
Zhang,H.,2001.Genetical Type of Proes in Coal Reservoir and its Research Significance.Journal of China Coal Society,26(1):40-44(in Chinese with English abstract).
陈萍,唐修义,2001.低温氮吸附法与煤中微孔隙特征的研究.煤炭学报,26(5):552-556.
何学秋,聂百胜,2001.孔隙气体在煤层中扩散的机理.中国矿业大学学报,30(1):1-4.
聂百胜,段三明,1998.煤吸附瓦斯的本质.太原理工大学学报,29(4):417-421.
聂百胜,柳先锋,郭建华,等,2015.水分对煤体瓦斯解吸扩散的影响.中国矿业大学学报,44(5):781-787.
王朋飞,姜振学,李卓,等,2017.渝东北下寒武统牛蹄塘组页岩微纳米孔隙结构特征.地球科学,42(7):1147-1156.
杨永飞,王晨晨,姚军,等,2016.页岩基质微观孔隙结构分析新方法.地球科学,41(6):1067-1073.
张慧,2001.煤孔隙的成因类型及其研究.煤炭学报,26(1):40-44.