吸附–解吸状态下煤层气运移机制
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摘要
带吸附作用的煤层气运移规律一直是煤层气地质学界关注的焦点问题之一。为研究吸附–解吸状态下的煤层气运移机制,推导了气体吸附–解吸方程并分析了多孔介质扩散–渗流理论,开展了煤层气运移实验并对实验结果进行了分析。研究结果发现:煤体孔隙结构对煤层气运移具有"容阻效应","容储""阻降"二重特性并存构成了煤基质的基本功能;气体运移过程中煤体对CO_2和CH_4吸附能力的差异体现在吸附响应时间、吸附速率增长率、吸附平衡时间和最大吸附体积等4项指标;煤层气运移过程中扩散和渗流两种方式并存,当裂隙及大孔内气体压力较中–微孔隙系统气体压力高时,气体运移速率以渗流为主,否则以扩散为主。
The migration law of coalbed methane(CBM) with adsorption has always been the focus of attention in the field of coalbed methane geology. In order to study the mechanism of CBM migration under adsorption-desorption state, the deduction of gas adsorption-desorption equation and theoretical analysis of gas diffusion-seepage in porous media were carried out, and new viewpoints were put forward by means of experimental analysis of CBM migration. The results identified that:(1) for the CBM migration, pore structure of coal body has the storage-resistance effect, the dual functions of gas storage and gas pressure drop form the basic feature of coal matrix,(2) adsorption reaction time, adsorption rate, growth rate, adsorption equilibrium time and the maximum adsorption capacity are 4 key indexes of the different gases,(3) diffusion and seepage coexist in the process of CBM migration. When the gas pressure in fracture and macropore is higher than that in medium-micropore system,the gas migration velocity is dominated by seepage, otherwise diffusion is dominant.
The migration law of coalbed methane(CBM) with adsorption has always been the focus of attention in the field of coalbed methane geology. In order to study the mechanism of CBM migration under adsorption-desorption state, the deduction of gas adsorption-desorption equation and theoretical analysis of gas diffusion-seepage in porous media were carried out, and new viewpoints were put forward by means of experimental analysis of CBM migration. The results identified that:(1) for the CBM migration, pore structure of coal body has the storage-resistance effect, the dual functions of gas storage and gas pressure drop form the basic feature of coal matrix,(2) adsorption reaction time, adsorption rate, growth rate, adsorption equilibrium time and the maximum adsorption capacity are 4 key indexes of the different gases,(3) diffusion and seepage coexist in the process of CBM migration. When the gas pressure in fracture and macropore is higher than that in medium-micropore system,the gas migration velocity is dominated by seepage, otherwise diffusion is dominant.
引文
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[15]KING G R.Numerical simulation of the simultaneous flow of methane and water through dual porosity coal seams during the degasification process[D].Pennsylvania:The Pennsylvania State University,1985.
[16]BOYER C M.Methane modeling-predicting the inflow of methane gas into coal mines[R].Final Report,DOE Contract Number DE-AC22-80PC30123,1982.
[17]张东明，齐消寒，宋润权，等.采动裂隙煤岩体应力与瓦斯流动的耦合机理[J].煤炭学报，2015,40(4):774-780.ZHANG Dongming,QI Xiaohan,SONG Runquan,et al.Coupling mechanism of rock mass stress and gas flow in coal mining fissures[J].Journal of China Coal Society,2015,40(4):774-780.
[18]尹光志，黄启翔，张东明，等.地应力场中含瓦斯煤岩变形破坏过程中瓦斯渗透特性的试验研究[J].岩石力学与工程学报，2010,29(2):336-343.YIN Guangzhi,HUANG Qixiang,ZHANG Dongming,et al.Test study of gas seepage characteristics of gas-bearing coal specimen during process of deformation and failure in geo-stress field[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(2):336-343.
[19]姜德义，袁曦，陈结，等.吸附气体对突出煤渗流特性的影响[J].煤炭学报，2015,40(9):2091-2096.JIANG Deyi,YUAN Xi,CHEN Jie,et al.Effect of adsorptional gases on permeability of outburst coal[J].Journal of China Coal Society,2015,40(9):2091-2096.
[20]周动，王辰，冯增朝，等.煤吸附解吸甲烷细观结构变形试验研究[J].煤炭学报，2016,41(9):2238-2245.ZHOU Dong,WANG Chen,FENG Zengchao,et al.Experiment on the deformation of the meso-structure of coal during the methane adsorption and desorption[J].Journal of China Coal Society,2016,41(9):2238-2245.
[21]侯泉林，雒毅，韩雨贞，等.煤的变形产气机理探讨[J].地质通报，2014,33(5):715-722.HOU Quanlin,LUO Yi,HAN Yuzhen,et al.Gas production mechanism in the process of coal tectonic deformation[J].Geological Bulletin of China,2014,33(5):715-722.
[2]BARRER R M.Diffusion in and through solid[M].Cambridge:Cambridge University Press,1951.
[3]孟召平，刘珊珊，王保玉，等.不同煤体结构煤的吸附性能及其孔隙结构特征[J].煤炭学报，2015,40(8):1865-1870.MENG Zhaoping,LIU Shanshan,WANG Baoyu,et al.Adsorption capacity and its pore structure of coals with different coal body structure[J].Journal of China Coal Society,2015,40(8):1865-1870.
[4]MASTALERZ M,DROBNIAK A,STRAPOC D,et al.Variations in pore characteristics in high volatile bituminous coals:Implications for coalbed gas content[J].International Journal of Coal Geology,2008,76:205-216.
[5]SWANSON S,MASTALERZ M D,ENGLE M,et al.Pore characteristics of Wilcox Group Coal,U.S.Gulf Coast Region:Implications for the occurrence of coalbed gas[J].International Journal of Coal Geology,2015,139:80-94.
[6]马东民，李来新，李小平，等.大佛寺井田4号煤CH4与CO2吸附解吸实验比较[J].煤炭学报，2014,39(9):1938-1944.MA Dongmin,LI Laixin,LI Xiaoping,et al.Contrastive experiment of adsorption-desorption between CH4 and CO2 in coal seam 4 of Dafosi coal mine[J].Journal of China Coal Society,2014,39(9):1938-1944.
[7]刘永茜，张浪，李浩荡，等．含水率对煤层气渗流的影响[J].煤炭学报，2014,39(9):1840-1844.LIU Yongqian,ZHANG Lang,LI Haodang,et al.Effect of moisture content on CBM seepage[J].Journal of China Coal Society,2014,39(9):1840-1844．
[8]SKOCZYLAS N,DUTKA B,SOBCZYK J.Mechanical and gaseous properties of coal briquettes in terms of outburst risk[J].Fuel,2014,134:45-52.
[9]琚宜文，林红，李小诗，等.煤岩构造变形与动力变质作用[J].地学前缘，2009,16(1):158-166.JU Yiwen,LIN Hong,LI Xiaoshi,et al.Tectonic deformation and dynamic metamorphism of coal[J].Earth Science Frontiers,2009,16(1):158-166.
[10]姜波，琚宜文.构造煤结构及其储层物性特征[J].天然气工业，2004,24(5):27-29.JIANG Bo,JU Yiwen.Tectonic coal structure and its petrophysical features[J].Natural Gas Industry,2004,24(5):27-29.
[11]秦跃平，王健，郑赟，等.煤粒瓦斯变压吸附数学模型及数值解算[J].煤炭学报，2017,42(4):923-928.QIN Yueping,WANG Jian,ZHENG Yun,et al.Coal particle gas adsorption mathematical model and numerical solution under variable pressures[J].Journal of China Coal Society,2017,42(4):923-928.
[12]张志刚，程波.含瓦斯煤体非线性渗流模型[J].中国矿业大学学报，2015,44(3):453-459.ZHANG Zhigang,CHENG Bo.Study of a nonlinear seepage model of coal containing gas[J].Journal of China University of Mining&Technology,2015,44(3):453-459.
[13]魏建平，王洪磊，王登科，等.考虑渗流-扩散的煤层瓦斯流动修正模型[J].中国矿业大学学报，2016,45(5):873-878.WEI Jianping,WANG Honglei,WANG Dengke,et al.An improved model of gas flow in coal based on the effect of penetration and diffusion[J].Journal of China University of Mining&Technology,2016,45(5):873-878.
[14]刘永茜，张玉贵，张浪.煤层瓦斯运移机制的关键参数表征[J].岩石力学与工程学报，2017,36(5):1145-1151.LIU Yongqian,ZHANG Yugui,ZHANG Lang.Key parameters for gas migration mechanism in coal seam[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(5):1145-1151.
[15]KING G R.Numerical simulation of the simultaneous flow of methane and water through dual porosity coal seams during the degasification process[D].Pennsylvania:The Pennsylvania State University,1985.
[16]BOYER C M.Methane modeling-predicting the inflow of methane gas into coal mines[R].Final Report,DOE Contract Number DE-AC22-80PC30123,1982.
[17]张东明，齐消寒，宋润权，等.采动裂隙煤岩体应力与瓦斯流动的耦合机理[J].煤炭学报，2015,40(4):774-780.ZHANG Dongming,QI Xiaohan,SONG Runquan,et al.Coupling mechanism of rock mass stress and gas flow in coal mining fissures[J].Journal of China Coal Society,2015,40(4):774-780.
[18]尹光志，黄启翔，张东明，等.地应力场中含瓦斯煤岩变形破坏过程中瓦斯渗透特性的试验研究[J].岩石力学与工程学报，2010,29(2):336-343.YIN Guangzhi,HUANG Qixiang,ZHANG Dongming,et al.Test study of gas seepage characteristics of gas-bearing coal specimen during process of deformation and failure in geo-stress field[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(2):336-343.
[19]姜德义，袁曦，陈结，等.吸附气体对突出煤渗流特性的影响[J].煤炭学报，2015,40(9):2091-2096.JIANG Deyi,YUAN Xi,CHEN Jie,et al.Effect of adsorptional gases on permeability of outburst coal[J].Journal of China Coal Society,2015,40(9):2091-2096.
[20]周动，王辰，冯增朝，等.煤吸附解吸甲烷细观结构变形试验研究[J].煤炭学报，2016,41(9):2238-2245.ZHOU Dong,WANG Chen,FENG Zengchao,et al.Experiment on the deformation of the meso-structure of coal during the methane adsorption and desorption[J].Journal of China Coal Society,2016,41(9):2238-2245.
[21]侯泉林，雒毅，韩雨贞，等.煤的变形产气机理探讨[J].地质通报，2014,33(5):715-722.HOU Quanlin,LUO Yi,HAN Yuzhen,et al.Gas production mechanism in the process of coal tectonic deformation[J].Geological Bulletin of China,2014,33(5):715-722.
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