高煤阶煤孔隙结构及分形特征
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摘要
高煤阶煤与中低煤阶煤在孔隙结构特征方面存在明显差异,分形理论为定量描述高煤阶煤储层孔隙特征提供了有效手段。基于扫描电镜、压汞实验和孔渗测试,以华北地区最大镜质体反射率(Ro,max)在1.9%~2.95%之间的9个煤样为研究对象,采用分段回归的方法对各样品进行不同孔径段分形维数计算,并讨论了孔隙结构分形维数与孔隙体积百分比、Ro,max、孔隙度和渗透率的关系。结果表明,高煤阶煤微小孔发育,半封闭孔含量较高,孔隙连通性一般,且孔隙结构具有明显的分段分形特征,同一煤样的超大孔(孔隙半径r>5μm)、大孔(0.5μm孔分形维数均随Ro,max增加而增加,随对应孔隙体积百分比增加而减小;孔隙度或渗透率与超大孔、大孔和中孔、微小孔分形维数分别呈二次相关、线性正相关、负相关;各分形区间分形维数分布的偏度和峰度与孔隙度或渗透率分别呈高度正相关和负相关,这为高煤阶煤孔隙度、渗透率提供了理想的线性方程(y=ax+b)预测模型。
Significant differences exist in pore structures between high rank coals and medium-low rank coals,and the principle of fractal geometry is an effective tool for quantitatively describing pore characteristics of high rank coal reservoirs. The experiments comprising scanning electron microscopy,mercury intrusion,porosity and permeability testing were performed on nine coal samples( Ro,maxfrom 1. 9% to 2. 95%) from North China. The pore fractal dimensions of samples were calculated using the subsection regression method and the relationships between the pore fractal dimension and different parameters including pore volume percent,coal degree of metamorphism,porosity and permeability were discussed. The results show that coal samples are characterized by abundant micro-ascopores,relatively high semi-closed pore content,general pore connectivity and clearly piecewise fractal dimensions. For each sample,fractal dimensions of supermacropore( pore radius r > 5 μm),macropore( 0. 5 μm < r < 5 μm),mesopore( 0. 05 μm < r < 0. 5 μm) and micro-ascopore( r < 0. 05 μm) decrease in turn. In addition,fractal dimensions of these pores except micro-ascopores increase with the increasing Ro,maxand decreasing pore volume percent for all samples. The correlations between coal porosity( or permeabil-ity) and fractal dimensions of supermacropore,macropore and mesopore,micro-ascopore present as quadratic,linearly positive and linearly negative curves,respectively. The skewness and kurtosis of fractal dimension distribution for each sample are positively and negatively associated with porosity or permeability respectively.Meanwhile,based on skewness and kurtosis,the prediction models of linear equations( y = ax + b) can be used to predict porosity and permeability of high rank coals.
Significant differences exist in pore structures between high rank coals and medium-low rank coals,and the principle of fractal geometry is an effective tool for quantitatively describing pore characteristics of high rank coal reservoirs. The experiments comprising scanning electron microscopy,mercury intrusion,porosity and permeability testing were performed on nine coal samples( Ro,maxfrom 1. 9% to 2. 95%) from North China. The pore fractal dimensions of samples were calculated using the subsection regression method and the relationships between the pore fractal dimension and different parameters including pore volume percent,coal degree of metamorphism,porosity and permeability were discussed. The results show that coal samples are characterized by abundant micro-ascopores,relatively high semi-closed pore content,general pore connectivity and clearly piecewise fractal dimensions. For each sample,fractal dimensions of supermacropore( pore radius r > 5 μm),macropore( 0. 5 μm < r < 5 μm),mesopore( 0. 05 μm < r < 0. 5 μm) and micro-ascopore( r < 0. 05 μm) decrease in turn. In addition,fractal dimensions of these pores except micro-ascopores increase with the increasing Ro,maxand decreasing pore volume percent for all samples. The correlations between coal porosity( or permeabil-ity) and fractal dimensions of supermacropore,macropore and mesopore,micro-ascopore present as quadratic,linearly positive and linearly negative curves,respectively. The skewness and kurtosis of fractal dimension distribution for each sample are positively and negatively associated with porosity or permeability respectively.Meanwhile,based on skewness and kurtosis,the prediction models of linear equations( y = ax + b) can be used to predict porosity and permeability of high rank coals.
引文
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[16]傅雪海,秦勇,张万红,等.基于煤层气运移的煤孔隙分形分类及自然分类研究[J].科学通报,2005,50(增刊):51-55.
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[18]LIU Pengcheng,YUAN Zhe,LI Kewen.An improved capillary pressure model using fractal geometry for coal rock[J].Journal of Petroleum Science and Engineering,2016,145:473-481.
[19]姚艳斌,刘大锰.煤储层精细定量表征与综合评价模型[M].北京:地质出版社,2013:45-59.
[20]张松航,唐书恒,汤达祯,等.鄂尔多斯盆地东缘煤储层渗流孔隙分形特征[J].中国矿业大学学报,2009,38(5):713-718.
[21]安士凯,桑树勋,李仰民,等.沁水盆地南部高煤级煤储层孔隙分形特征[J].中国煤炭地质,2011,23(2):17-21.
[22]尹志军,盛国君,王春光.基于压汞法的煤岩各段孔隙的分形特征[J].金属矿山,2011,40(9):54-57.
[23]贾慧敏.高煤阶煤岩孔隙结构分形特征研究[J].石油化工高等学校学报,2016,29(1):53-56.
[24]李留仁,赵艳艳,李忠兴,等.多孔介质微观孔隙结构分形特征及分形系数的意义[J].石油大学学报(自然科学版),2004,28(3):105-107.
[25]邵震杰,陈家良,秦勇.能源地质学[M].徐州:中国矿业大学出版社,2004:148-149.
[26]李五忠,田文广,陈刚,等.不同煤阶煤层气选区评价参数的研究与应用[J].天然气工业,2010,30(6):45-47.
[27]文慧俭,闫林,姜福聪,等.低孔低渗储层孔隙结构分形特征[J].大庆石油学院学报,2007,31(1):15-18.
[28]霍多特.煤与瓦斯突出[M].宋世钊,王友安,译.北京:中国工业出版社,1966:27-30.
[29]许启鲁,黄文辉,唐书恒,等.深部中-高煤级煤储层孔隙结构与吸附性[J].现代地质,2016,30(2):413-419.
[30]赵爱红,廖毅,唐修义.煤的孔隙结构分形定量研究[J].煤炭学报,1998,23(4):439-442.
[31]苏现波,林晓英.煤层气地质学[M].北京:煤炭工业出版社,2008:106-108.
[32]傅雪海,秦勇,韦重韬.煤层气地质学[M].徐州:中国矿业大学出版社,2007:46-47,135-139.
[33]申卫兵,张保平.不同煤阶煤岩力学参数测试[J].岩石力学与工程学报,2000,19(增刊):860-862.
[34]SUUBERG E M,DEEVI S C,YUN Y.Elastic behaviour of coals studied by mercury porosimetry[J].Fuel,1995,74(10):1522-1530.
[35]刘大锰,姚艳斌,蔡益栋,等.华北石炭—二叠系煤的孔渗特征及主控因素[J].现代地质,2010,24(6):1198-1203.
[36]李俊乾,刘大锰,姚艳斌,等.基于主地质参数的煤层气有利开发区优选及应用[J].现代地质,2014,28(3):653-658.
[2]MOORE Tim A.Coalbed methane:A review[J].International Journal of Coal Geology,2012,101:36-81.
[3]侯海海.柴达木盆地北缘侏罗系煤储层物性特征与综合评价[D].北京:中国矿业大学(北京),2015.
[4]GILMAN A,BECKIE R.Flow of coal-bed methane to a gallery[J].Transport in Porous Media,2000,41:1-16.
[5]LI Song,TANG Dazhen,XU Hao,et al.The pore-fracture system properties of coalbed methane reservoirs in the Panguan Syncline,Guizhou,China[J].Geoscience Frontiers,2012,3(6):853-862.
[6]唐相路,姜振学,李卓,等.渝东南地区龙马溪组高演化页岩微纳米孔隙非均质性及主控因素[J].现代地质,2016,30(1):163-171.
[7]ZHANG Songhang,TANG Shuheng,TANG Dazhen,et al.Determining fractal dimensions of coal pores by FHH model:Problems and effects[J].Journal of Natural Gas Science and Engineering,2014,21:929-939.
[8]ZHOU Sandong,LIU Dameng,CAI Yidong,et al.Fractal characterization of pore-fracture in low-rank coals using a low-field NMR relaxation method[J].Fuel,2016,181:218-226.
[9]于艳梅,胡耀青,梁卫国,等.应用CT技术研究瘦煤在不同温度下孔隙变化特征[J].地球物理学报,2012,55(2):637-644.
[10]PAN Jienan,NIU Qinghe,WANG Kai,et al.The closed pores of tectonically deformed coal studied by small-angle X-ray scattering and liquid nitrogen adsorption[J].Microporous and Mesoporous Materials,2016,224:245-252.
[11]PRINZ D,PYCKHOUT-HINTZEN W,LITTKE R.Development of the meso-and macroporous structure of coals with rank as analysed with small angle neutron scattering and adsorption experiments[J].Fuel,2004,83(4/5):547-556.
[12]LI Wei,LIU Hongfu,SONG Xiaoxia.Multifractal analysis of Hg pore size distributions of tectonically deformed coals[J].International Journal of Coal Geology,2015,144/145:138-152.
[13]贺承祖,华明琪.储层孔隙结构的分形几何描述[J].石油与天然气地质,1998,19(1):15-23.
[14]贺伟,钟孚勋,贺承祖,等.储层岩石孔隙的分形结构研究和应用[J].天然气工业,2000,20(2):67-70.
[15]马新仿,张士诚,郎兆新.用分段回归方法计算孔隙结构的分形维数[J].石油大学学报(自然科学版),2004,28(6):54-56.
[16]傅雪海,秦勇,张万红,等.基于煤层气运移的煤孔隙分形分类及自然分类研究[J].科学通报,2005,50(增刊):51-55.
[17]MAHAMUD Manuel María,NOVO Marta F.The use of fractal analysis in the textural characterization of coals[J].Fuel,2008,87(2):222-231.
[18]LIU Pengcheng,YUAN Zhe,LI Kewen.An improved capillary pressure model using fractal geometry for coal rock[J].Journal of Petroleum Science and Engineering,2016,145:473-481.
[19]姚艳斌,刘大锰.煤储层精细定量表征与综合评价模型[M].北京:地质出版社,2013:45-59.
[20]张松航,唐书恒,汤达祯,等.鄂尔多斯盆地东缘煤储层渗流孔隙分形特征[J].中国矿业大学学报,2009,38(5):713-718.
[21]安士凯,桑树勋,李仰民,等.沁水盆地南部高煤级煤储层孔隙分形特征[J].中国煤炭地质,2011,23(2):17-21.
[22]尹志军,盛国君,王春光.基于压汞法的煤岩各段孔隙的分形特征[J].金属矿山,2011,40(9):54-57.
[23]贾慧敏.高煤阶煤岩孔隙结构分形特征研究[J].石油化工高等学校学报,2016,29(1):53-56.
[24]李留仁,赵艳艳,李忠兴,等.多孔介质微观孔隙结构分形特征及分形系数的意义[J].石油大学学报(自然科学版),2004,28(3):105-107.
[25]邵震杰,陈家良,秦勇.能源地质学[M].徐州:中国矿业大学出版社,2004:148-149.
[26]李五忠,田文广,陈刚,等.不同煤阶煤层气选区评价参数的研究与应用[J].天然气工业,2010,30(6):45-47.
[27]文慧俭,闫林,姜福聪,等.低孔低渗储层孔隙结构分形特征[J].大庆石油学院学报,2007,31(1):15-18.
[28]霍多特.煤与瓦斯突出[M].宋世钊,王友安,译.北京:中国工业出版社,1966:27-30.
[29]许启鲁,黄文辉,唐书恒,等.深部中-高煤级煤储层孔隙结构与吸附性[J].现代地质,2016,30(2):413-419.
[30]赵爱红,廖毅,唐修义.煤的孔隙结构分形定量研究[J].煤炭学报,1998,23(4):439-442.
[31]苏现波,林晓英.煤层气地质学[M].北京:煤炭工业出版社,2008:106-108.
[32]傅雪海,秦勇,韦重韬.煤层气地质学[M].徐州:中国矿业大学出版社,2007:46-47,135-139.
[33]申卫兵,张保平.不同煤阶煤岩力学参数测试[J].岩石力学与工程学报,2000,19(增刊):860-862.
[34]SUUBERG E M,DEEVI S C,YUN Y.Elastic behaviour of coals studied by mercury porosimetry[J].Fuel,1995,74(10):1522-1530.
[35]刘大锰,姚艳斌,蔡益栋,等.华北石炭—二叠系煤的孔渗特征及主控因素[J].现代地质,2010,24(6):1198-1203.
[36]李俊乾,刘大锰,姚艳斌,等.基于主地质参数的煤层气有利开发区优选及应用[J].现代地质,2014,28(3):653-658.