煤层气吸附-解吸机理再认识
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摘要
煤层气是以吸附成藏的非常规气藏,其圈闭机理与以游离气成藏的常规气藏不同。本文分析了游离气与吸附气的圈闭机理,研究认为煤层气的吸附并不存在临界解吸现象,生产过程中的临界解吸是煤层气-水关系以及毛管压力导致的,并提出了一种水动力学封闭形式。研究认为煤层裂缝-割理系统被水饱和,溶解态煤层气会以浓度差扩散的方式慢速散失,但是游离气和吸附气可以被水动力学圈闭在煤层的基质中。根据水动力学封闭机理,煤层气的吸附是平衡的,不存在欠饱和状态,而排采过程中会出现临界解吸现象,表现出欠饱和赋存的状态,是毛管压力作用的结果。
Coalbed methane is an unconventional gas reservoir in a sorption state, of which the trapping mechanism is totally different from the conventional gas reservoir in a free state. The trapping mechanism of free gas and sorption gas is analyzed in this paper. It is investigated that the undersaturated state can hardly occur in coalbed methane sorption process and the critical description results from the gas-water relationship and the capillary pressure. Meanwhile, a new hydraulic trapping mechanism is reported. The research indicates that the cleat-fracture system of coal seam is saturated with water and the methane leakage occurs in the solution state. However, the free gas and sorption gas can be trapped in the coal matrix. With reference to the hydraulic trapping mechanism, gas sorption is an equilibrium process without any undersaturated state and the methane production experiences the critical desorption process, showing the undersaturated storage state.
Coalbed methane is an unconventional gas reservoir in a sorption state, of which the trapping mechanism is totally different from the conventional gas reservoir in a free state. The trapping mechanism of free gas and sorption gas is analyzed in this paper. It is investigated that the undersaturated state can hardly occur in coalbed methane sorption process and the critical description results from the gas-water relationship and the capillary pressure. Meanwhile, a new hydraulic trapping mechanism is reported. The research indicates that the cleat-fracture system of coal seam is saturated with water and the methane leakage occurs in the solution state. However, the free gas and sorption gas can be trapped in the coal matrix. With reference to the hydraulic trapping mechanism, gas sorption is an equilibrium process without any undersaturated state and the methane production experiences the critical desorption process, showing the undersaturated storage state.
引文
[1] 菅笑飞,唐书恒,刘人和,等.柳林地区煤层气储层特征与产能动态预测[J].新疆石油地质,2015,36(3):326-329.
[2] Pan,Z.,& Wood,D.A.(2015).Coalbed methane (CBM) exploration,reservoir characterisation,production,and modelling:a collection of published research (2009—2015).Journal of Natural Gas Science & Engineering,26,1472-1484.
[3] Moore T A.Coalbed methane:a review.International Journal of Coal Geology,2012,101:36-81.
[4] 洪峰,宋岩,赵孟军,等.沁水盆地盖层对煤层气富集的影响[J].天然气工业,2005,25(12):34-36+14.
[5] King G R.Material-balance techniques for coal-seam and devonian shale gas reservoirs with limited water influx.SPE Reservoir Engineering,1993,8(1):67-72.
[6] Ziarani A S,Aguilera R,Clarkson C R.Investigating the effect of sorption time on coalbed methane recovery through numerical simulation.Fuel,2011,90(7):2428-2444.
[7] Carapezza M L,Ranaldi M,Gattuso A,et al.The sealing capacity of the cap rock above the Torre Alfina geothermal reservoir (Central Italy) revealed by soil CO 2,flux investigations[J].Journal of Volcanology & Geothermal Research,2015,291(291):25-34.
[8] Barth J A C,Nowak M E,Zimmer M,et al.Monitoring of cap-rock integrity during CCS from field data at the Ketzin pilot site (Germany):Evidence from gas composition and stable carbon isotopes[J].International Journal of Greenhouse Gas Control,2015,43:133-140.
[9] Jin Z,Yuan Y,Sun D,et al.Models for dynamic evaluation of mudstone/shale cap rocks and their applications in the Lower Paleozoic sequences,Sichuan Basin,SW China[J].Marine & Petroleum Geology,2014,49(49):121-128.
[10] Schl?mer S,Krooss B M.Experimental characterisation of the hydrocarbon sealing efficiency of cap rocks[J].Marine & Petroleum Geology,1997,14(5):565-580.
[11] 朱苏阳,李传亮,杜志敏,等.也谈煤层气的液相吸附[J].新疆石油地质,2015,36(5):101-104.
[12] 李传亮,彭朝阳,朱苏阳.煤层气其实是吸附气[J].岩性油气藏,2013,25(2):112-115.
[13] 朱苏阳,李传亮,杜志敏,等.煤层气的复合解吸模式研究[J].中国矿业大学学报,2016,45(2):316-324.
[14] 李志军,李新宁,梁辉,王瑞英.吐哈和三塘湖盆地水文地质条件对低煤阶煤层气的影响[J].新疆石油地质,2013,34(2):158-161.
[15] 宋洪庆,朱维耀,王一兵,等.煤层气低速非达西渗流解析模型及分析[J].中国矿业大学学报,2013,42(1)93-99.
[16] Van Voast W A.Geochemical signature of formation waters associated with coalbed methane.AAPG Bulletin,2003,87(4):667-676.
[17] Su X,Feng Y,Chen J,Pan J.The characteristics and origins of cleat in coal from Western North China.International Journal of Coal Geology,2001,47(1):51-62.
[18] Huang L,Zhang L,Shao Q,et al.Simulations of binary mixture adsorption of carbon dioxide and methane in carbon nanotubes:temperature,pressure,and pore size effects[J].The Journal of Physical Chemistry C,2007,111(32):11912-11920.
[19] Schlegel M E,Zhou Z,McIntosh J C,et al.Constraining the timing of microbial methane generation in an organic-rich shale using noble gases,Illinois Basin,USA[J].Chemical Geology,2011,287(1):27-40.
[20] Gentzis T,Schoderbek D,Pollock S.Evaluating the coalbed methane potential of the Gething coals in NE British Columbia,Canada:An example from the Highhat area,Peace River coalfield[J].International journal of coal geology,2006,68(3):135-150.
[2] Pan,Z.,& Wood,D.A.(2015).Coalbed methane (CBM) exploration,reservoir characterisation,production,and modelling:a collection of published research (2009—2015).Journal of Natural Gas Science & Engineering,26,1472-1484.
[3] Moore T A.Coalbed methane:a review.International Journal of Coal Geology,2012,101:36-81.
[4] 洪峰,宋岩,赵孟军,等.沁水盆地盖层对煤层气富集的影响[J].天然气工业,2005,25(12):34-36+14.
[5] King G R.Material-balance techniques for coal-seam and devonian shale gas reservoirs with limited water influx.SPE Reservoir Engineering,1993,8(1):67-72.
[6] Ziarani A S,Aguilera R,Clarkson C R.Investigating the effect of sorption time on coalbed methane recovery through numerical simulation.Fuel,2011,90(7):2428-2444.
[7] Carapezza M L,Ranaldi M,Gattuso A,et al.The sealing capacity of the cap rock above the Torre Alfina geothermal reservoir (Central Italy) revealed by soil CO 2,flux investigations[J].Journal of Volcanology & Geothermal Research,2015,291(291):25-34.
[8] Barth J A C,Nowak M E,Zimmer M,et al.Monitoring of cap-rock integrity during CCS from field data at the Ketzin pilot site (Germany):Evidence from gas composition and stable carbon isotopes[J].International Journal of Greenhouse Gas Control,2015,43:133-140.
[9] Jin Z,Yuan Y,Sun D,et al.Models for dynamic evaluation of mudstone/shale cap rocks and their applications in the Lower Paleozoic sequences,Sichuan Basin,SW China[J].Marine & Petroleum Geology,2014,49(49):121-128.
[10] Schl?mer S,Krooss B M.Experimental characterisation of the hydrocarbon sealing efficiency of cap rocks[J].Marine & Petroleum Geology,1997,14(5):565-580.
[11] 朱苏阳,李传亮,杜志敏,等.也谈煤层气的液相吸附[J].新疆石油地质,2015,36(5):101-104.
[12] 李传亮,彭朝阳,朱苏阳.煤层气其实是吸附气[J].岩性油气藏,2013,25(2):112-115.
[13] 朱苏阳,李传亮,杜志敏,等.煤层气的复合解吸模式研究[J].中国矿业大学学报,2016,45(2):316-324.
[14] 李志军,李新宁,梁辉,王瑞英.吐哈和三塘湖盆地水文地质条件对低煤阶煤层气的影响[J].新疆石油地质,2013,34(2):158-161.
[15] 宋洪庆,朱维耀,王一兵,等.煤层气低速非达西渗流解析模型及分析[J].中国矿业大学学报,2013,42(1)93-99.
[16] Van Voast W A.Geochemical signature of formation waters associated with coalbed methane.AAPG Bulletin,2003,87(4):667-676.
[17] Su X,Feng Y,Chen J,Pan J.The characteristics and origins of cleat in coal from Western North China.International Journal of Coal Geology,2001,47(1):51-62.
[18] Huang L,Zhang L,Shao Q,et al.Simulations of binary mixture adsorption of carbon dioxide and methane in carbon nanotubes:temperature,pressure,and pore size effects[J].The Journal of Physical Chemistry C,2007,111(32):11912-11920.
[19] Schlegel M E,Zhou Z,McIntosh J C,et al.Constraining the timing of microbial methane generation in an organic-rich shale using noble gases,Illinois Basin,USA[J].Chemical Geology,2011,287(1):27-40.
[20] Gentzis T,Schoderbek D,Pollock S.Evaluating the coalbed methane potential of the Gething coals in NE British Columbia,Canada:An example from the Highhat area,Peace River coalfield[J].International journal of coal geology,2006,68(3):135-150.
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