中煤阶煤层气井排采阶段划分及渗透率变化
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摘要
煤层渗透率动态变化规律是煤层气开发所面临的重点问题之一。根据无因次产气率划分煤层气井排采阶段,结合等温吸附实验下煤层气的解吸过程确定排采阶段分界点位置。通过物质能量动态平衡理论建立中煤阶煤储层渗透率评价模型,从渗透率变化趋势、主导机制、产能动态等方面,阐释了中煤阶煤层气井不同排采阶段煤储层渗透率动态变化特征与控制机理。结果表明,排采过程中,煤储层绝对渗透率发生"先降低—后回返—再上升"的动态变化。排水阶段水相有效渗透率迅速下降,气相有效渗透率为0。储层压力降低至临界解吸压力后进入产气阶段,气相有效渗透率迅速增加,水相有效渗透率缓慢降低。产气量衰减阶段绝对渗透率开始下降,在滑脱效应影响下,气相有效渗透率仍然保持缓慢上升,水相有效渗透率降低。
Understanding the dynamic changing patterns of the permeability of coal seams is one of the key issues in coalbed methane development. In this study, we divided the drainage and production stages of coalbed methane wells according to the non-dimensionalized gas production rate. By combining these figures with the coalbed methane desorption process identified in isothermal adsorption experiments, we further determined the interfacial location between the drainage and production stages.A model for evaluating the permeability of medium-rank coal reservoirs was also developed using the dynamic balance theory of material and energy. Finally, the dynamic characteristics and control mechanisms of coal reservoir permeability in different drainage and production stages of medium-rank coalbed methane wells were explained from multiple perspectives, including the trend of permeability variation, the dominant mechanism, and the productivity dynamics. The results show that the absolute permeability of the coal reservoir experiences a dynamic change of "first decreasing, then reverting, and finally increasing" during the drainage and production processes. A rapid reduction in the effective permeability of water phase and a zero effective permeability of gas phase are observed during the drainage stage. The reservoir enters the gas production stage once the reservoir pressure drops to the critical desorption pressure. During this stage, the effective permeability of gas phase increases rapidly while the effective permeability of the water phase drops slowly. The absolute permeability begins to decrease during the gas production reduction phase. Influenced by the slippage effect, the effective permeability of the gas phase continues to increase slowly while the effective permeability of water phase reduces.
Understanding the dynamic changing patterns of the permeability of coal seams is one of the key issues in coalbed methane development. In this study, we divided the drainage and production stages of coalbed methane wells according to the non-dimensionalized gas production rate. By combining these figures with the coalbed methane desorption process identified in isothermal adsorption experiments, we further determined the interfacial location between the drainage and production stages.A model for evaluating the permeability of medium-rank coal reservoirs was also developed using the dynamic balance theory of material and energy. Finally, the dynamic characteristics and control mechanisms of coal reservoir permeability in different drainage and production stages of medium-rank coalbed methane wells were explained from multiple perspectives, including the trend of permeability variation, the dominant mechanism, and the productivity dynamics. The results show that the absolute permeability of the coal reservoir experiences a dynamic change of "first decreasing, then reverting, and finally increasing" during the drainage and production processes. A rapid reduction in the effective permeability of water phase and a zero effective permeability of gas phase are observed during the drainage stage. The reservoir enters the gas production stage once the reservoir pressure drops to the critical desorption pressure. During this stage, the effective permeability of gas phase increases rapidly while the effective permeability of the water phase drops slowly. The absolute permeability begins to decrease during the gas production reduction phase. Influenced by the slippage effect, the effective permeability of the gas phase continues to increase slowly while the effective permeability of water phase reduces.
引文
[1] TAO Shu, TANG Dazhen, XU Hao, et al. Factors controlling high-yield coalbed methane vertical wells in the Fanzhuang Block, Southern Qinshui Basin[J]. International Journal of Coal Geology, 2014, 134-135:38-45. doi:10.1016/j.coal.2014.10.002
[2] TIAN Lin, CAO Yunxing, CHAI Xuezhou, et al. Best practices for the determination of low-pressure/permeabi-lity coalbed methane reservoirs, Yuwu Coal Mine, Luan mining area, China[J]. Fuel, 2015, 160:100-107. doi:10.1016/j.fuel.2015.07.082
[3]周军平,鲜学福,姜永东,等.考虑有效应力和煤基质收缩效应的渗透率模型[J].西南石油大学学报(自然科学版),2009, 31(1):4-8. doi:10.3863/j.issn.1674-5086.2009.01.002ZHOU Junping, XIAN Xuefu, JIANG Yongdong, et al.A permeability model considering the effective stress and coal matrix shrinking effect[J]. Journal of Southwest Petroleum University(Science&Technology Edition), 2009,31(1):4-8. doi:10.3863/j.issn.1674-5086.2009.c01.002
[4] CONNELL L,LU Meng, PAN Zhejun. An analytical coal permeability model for tri-axial strain and stress conditions[J]. International Journal of Coal Geology,2010, 84(2):103-114. doi:10.1016/j.coal.2010.08.011
[5] HARPALANIS, CHEN G. Influence of gas production induced volumetric strain on permeability of coal[J]. Geotechnical&Geological Engineering, 1997,15(4):303-325.
[6] PALMER I. Permeability changes in coal:Analytical modeling[J]. International Journal of Coal Geology, 2009,77(1):119-126. doi:10.1016/j.coal.2008.09.006
[7]徐宏杰,桑树勋,易同生,等.黔西地区煤层埋深与地应力对其渗透性控制机制[J].地球科学——中国地质大学学报,2014,39(11):1607-1616. doi:10.3799/dqkx.2014.143XU Hongjie, SANG Shuxun, YI Tongsheng, et al. Control mechanism of buried depth and in-situ stress for coal reservoir permeability in western Guizhou[J]. Earth Science:Journal of China University of Geosciences, 2014,39(11):1607-1616. doi:10.3799/dqkx.2014.143
[8] FU Xuehai,QIN Yong,WANG G G X,et al. Evaluation ofcoal structure and permeability with the aid of geophysical logging technology[J], Fuel, 2009, 88(11):2278-2285.doi:10.1016/j.fuel.2009.05.018
[9] CHEN Yaxi, LIU Dameng, YAO Yanbin, et al. Dynamic permeability change during coalbed methane production and its controlling factors[J]. Journal of Natural Gas Science and Engineering, 2015,25:335-346. doi:10.1016/j.jngse.2015.05.018
[10]张培河.基于生产数据分析的沁水南部煤层渗透性研究[J].天然气地球科学,2010,21(3):503-507.ZHANG Peihe. Study of permeability of coal seam based on data well production in south Qinshui Basin[J]. Natural Gas Geoscience, 2010, 21(3):503-507.
[11]莫日和,张芬娜,綦耀光,等.煤层气井有杆泵内煤粉沉积的影响因素分析[J].西南石油大学学报(自然科学版),2016, 38(5):143-150. doi:10.11885/j.issn.1674-5086.2014.10.31.05MO Rihe,ZHANG Fenna,QI Yaoguang,et al. Movement of pulverized coal in sucker rod pump in coalbed methane well[J]. Journal of Soutlhwest Petroleum University(Science&Technology Edition), 2016, 38(5):143-150. doi:10.11885/j.issn. 1674-5086.2014.10.31.05
[12]孟召平,张纪星,刘贺,等.考虑应力敏感性的煤层气井产能模型及应用分析[J].煤炭学报,2014, 39(4):593-599. doi:10.13225/j.cnki.jccs.2013.1780MENG Zhaoping,ZHANG Jixing,LIU He, et al.Productivity model of CBM wells considering the stress sensitivity and its application analysis[J]. Journal of China Coal Society, 2014, 39(4):593-599. doi:10.13225/j.cnki.jccs.2013.1780
[13]汤达祯,赵俊龙,许浩,等.中-高煤阶煤层气系统物质能量动态平衡机制[J].煤炭学报,2016, 41(1):40-48.doi:10. 13225/j.cnki.jccs.2015.9009TANG Dazhen, ZHAO Junlong, XU Hao, et al. Material and energy dynamic balance mechanism in middle-high rank coalbed methane(CBM)systems[J]. Journal of China Coal Society, 2016,40(1):40-48. doi:10. 13225/j.cnki.jccs.2015.9009
[14] WANG Gang, QIN Yong, XIE Yiwei, et al. The division and geologic controlling factors of a vertical superimposed coalbed methane system in the northern Gujiao blocks,China[J]. Journal of Natural Gas Science and Engineering,2015,24:379-389. doi:10.1016/j.jngse.2015.04.005
[15] XIA Peng, ZENG Fangui, SONG Xiaoxia. Parameters controlling high-yield coalbed methane vertical wells in the B3 area, Xishan coal field, Shanxi, China[J]. Energy Exploration&Exploitation, 2016, 34(5):711-734. doi:10.1177/0144598716656066
[16]逄建东,汪雷,臧晓琳,等.古交地区煤层气地质条件及资源潜力分析[J].科学技术与工程,2015,15(33):155-160, 165. doi:10.3969/j.issn.1671-1815.-2015.33.027PANG Jiandong,WANG Lei, ZANG Xiaolin, et al. The geological conditions and resource potential analysis of coal bed gas in Gujiao area[J]. Science Technology and Engineering,2015,15(33):155-160,165. doi:10.3969/j.-issn.1671-1815.2015.33.027
[17]倪小明,苏现波,张小东.煤层气开发地质学[M].北京:化学工业出版社,2010.
[18]秦义,李仰民,白建梅,等.沁水盆地南部高煤阶煤层气井排采工艺研究与实践[J].天然气工业,2011,31(11):22-25. doi:10.3787/j.issn.1000-0976.2011.11.006QIN Yi,LI Yangmin,BAI Jianmei,et al. Technologies in the CBM drainage and production of wells in the southern Qinshui basin with high-rank coal beds[J]. Natural Gas Industry, 2011, 31(11):22-25. doi:10.3787/j.issn.1000-0976.2011.11.006
[19]孟艳军,汤达祯,李治平,等.高煤阶煤层气井不同排采阶段渗透率动态变化特征与控制机理[J].油气地质与采收率,2015, 22(2):66-71. doi:10.3969/j.issn.1009-9603.2015.02.012MENG Yanjun, TANG Dazhen, LI Zhiping, et al. Dynamic variation characteristics and mechanism of permeability in high-rank CBM wells at different drainage and production stages[J]. Petroluem Geology and Recovery Efficiency, 2015, 22(2):66-71. doi:10.3969/j.issn.1009-9603.2015.02.012
[20]张政,秦勇,WANG Guoxiong,等.基于等温吸附实验的煤层气解吸阶段数值描述[J].中国科学:地球科学,2013,43(8):1352-1358.ZHANG Zheng, QIN Yong, WANG Guoxiong, et al. Numerical description of coalbed methane desorption stages based on isothermal adsorption experiment[J]. Science China Earth Sciences, 2013, 43(8):1352-1358.
[21] MENG Yanjun, TANG Dazhen, XU Hao, et al. Division of coalbed methane desorption stages and its significance[J]. Petroleum Exploration and Development, 2014,41(5):671-677. doi:10.1016/S1876-3804(14)60080-X
[22] MA Feiying, WANG Yongqing, LI Haitao, et al. Staged coalbed methane desorption and the contribution of each stage to productivity[J]. Chemistry and Technology of Fuels and Oils, 2014, 50(5):448-448. doi:10.1007/s10553-014-0531-3
[23] PALMER I. Permeability changes in coal:analytical modeling[J]. International Journal of Coal Geology, 2009,77(1):119-126. doi:10.1016/j.coal.2008.09.006
[24] ALEXIS D A,KARPYN Z T,ERTEKIN T,et al. Fracture permeability and relative permeability of coal and theirdependence on stress conditions[J]. Journal of Unconventional Oil and Gas Resources, 2015, 10:1-10. doi:10.-1016/j.juogr.2015.02.001
[25] HAM Y, KANTZAS A. Measurement of relative permeability of coal:Approaches and limitations[C]. SPE114994,2008. doi:10.2118/114994-MS
[26]崔玉峰,王贵文,孙艳慧,等.低孔低渗储层物性下限确定方法及其适用性[J].西南石油大学学报(自然科学版),2016, 38(6):35-48. doi:10.11885/j.issn.167450-86.2015.02.04.05CUI Yufeng,WANG Guiwen, SUN Yanhuit et al. Methods of cutoff determination and applicability analysis in low porosity and low permeability reservoir[J]. Journal of Southwest Petroleum University(Science&Technology Edition), 2016,38(6):35-48. doi:10.11885/j.issn. 1674-5-086.2015.02.04.05
[27] SEIDLE J P, JEANSONNE M W, ERICKSON D J. Application of matchstick geometry to stress dependent permeability in coals[C]. SPE24361,1992. doi:10.2118/24361-MS
[28] SHI Jiquan, DURUCAN S. A model for changes in coalbed permeability during primary and enhanced methane recovery[C]. SPE 87230,2005. doi:10.2118/87230-PA
[29] XU Hao, TANG Dazhen, TANG Shuheng, et al. A dynamic prediction model for gas-water effective permeability based on coalbed methane production data[J]. International Journal of Coal Geology, 2014, 121(1):44-52. doi:10.1016/j.coal.2013.11.008
[30]孟召平,田永东,李国富.煤层气开发地质学理论与方法[M].北京:科学出版社,2010.
[31] BALAN H O, GUMRAH F. Assessment of shrinkage-swelling influences in coal seams using rankdependent physical coal properties[J]. International Journal of Coal Geology,2009,77(1):203-213. doi:10.1016/j.coal.2008.09.014
[32]胡素明,李相方.考虑煤自调节效应的煤层气藏物质平衡方程[J].天然气勘探与开发,2010,33(1):38-41.doi:10.3969/j.issn.1673-3177.2010.01.009HU Suming, LI Xiangfang. Material balance equation of coalbed methane reservoir with consideration of self-adjustment effect of coal[J]. Natural Gas Exploration and Development, 2010, 33(1):38-41. doi:10.3969/j.issn.-1673-3177.2010.01.009
[2] TIAN Lin, CAO Yunxing, CHAI Xuezhou, et al. Best practices for the determination of low-pressure/permeabi-lity coalbed methane reservoirs, Yuwu Coal Mine, Luan mining area, China[J]. Fuel, 2015, 160:100-107. doi:10.1016/j.fuel.2015.07.082
[3]周军平,鲜学福,姜永东,等.考虑有效应力和煤基质收缩效应的渗透率模型[J].西南石油大学学报(自然科学版),2009, 31(1):4-8. doi:10.3863/j.issn.1674-5086.2009.01.002ZHOU Junping, XIAN Xuefu, JIANG Yongdong, et al.A permeability model considering the effective stress and coal matrix shrinking effect[J]. Journal of Southwest Petroleum University(Science&Technology Edition), 2009,31(1):4-8. doi:10.3863/j.issn.1674-5086.2009.c01.002
[4] CONNELL L,LU Meng, PAN Zhejun. An analytical coal permeability model for tri-axial strain and stress conditions[J]. International Journal of Coal Geology,2010, 84(2):103-114. doi:10.1016/j.coal.2010.08.011
[5] HARPALANIS, CHEN G. Influence of gas production induced volumetric strain on permeability of coal[J]. Geotechnical&Geological Engineering, 1997,15(4):303-325.
[6] PALMER I. Permeability changes in coal:Analytical modeling[J]. International Journal of Coal Geology, 2009,77(1):119-126. doi:10.1016/j.coal.2008.09.006
[7]徐宏杰,桑树勋,易同生,等.黔西地区煤层埋深与地应力对其渗透性控制机制[J].地球科学——中国地质大学学报,2014,39(11):1607-1616. doi:10.3799/dqkx.2014.143XU Hongjie, SANG Shuxun, YI Tongsheng, et al. Control mechanism of buried depth and in-situ stress for coal reservoir permeability in western Guizhou[J]. Earth Science:Journal of China University of Geosciences, 2014,39(11):1607-1616. doi:10.3799/dqkx.2014.143
[8] FU Xuehai,QIN Yong,WANG G G X,et al. Evaluation ofcoal structure and permeability with the aid of geophysical logging technology[J], Fuel, 2009, 88(11):2278-2285.doi:10.1016/j.fuel.2009.05.018
[9] CHEN Yaxi, LIU Dameng, YAO Yanbin, et al. Dynamic permeability change during coalbed methane production and its controlling factors[J]. Journal of Natural Gas Science and Engineering, 2015,25:335-346. doi:10.1016/j.jngse.2015.05.018
[10]张培河.基于生产数据分析的沁水南部煤层渗透性研究[J].天然气地球科学,2010,21(3):503-507.ZHANG Peihe. Study of permeability of coal seam based on data well production in south Qinshui Basin[J]. Natural Gas Geoscience, 2010, 21(3):503-507.
[11]莫日和,张芬娜,綦耀光,等.煤层气井有杆泵内煤粉沉积的影响因素分析[J].西南石油大学学报(自然科学版),2016, 38(5):143-150. doi:10.11885/j.issn.1674-5086.2014.10.31.05MO Rihe,ZHANG Fenna,QI Yaoguang,et al. Movement of pulverized coal in sucker rod pump in coalbed methane well[J]. Journal of Soutlhwest Petroleum University(Science&Technology Edition), 2016, 38(5):143-150. doi:10.11885/j.issn. 1674-5086.2014.10.31.05
[12]孟召平,张纪星,刘贺,等.考虑应力敏感性的煤层气井产能模型及应用分析[J].煤炭学报,2014, 39(4):593-599. doi:10.13225/j.cnki.jccs.2013.1780MENG Zhaoping,ZHANG Jixing,LIU He, et al.Productivity model of CBM wells considering the stress sensitivity and its application analysis[J]. Journal of China Coal Society, 2014, 39(4):593-599. doi:10.13225/j.cnki.jccs.2013.1780
[13]汤达祯,赵俊龙,许浩,等.中-高煤阶煤层气系统物质能量动态平衡机制[J].煤炭学报,2016, 41(1):40-48.doi:10. 13225/j.cnki.jccs.2015.9009TANG Dazhen, ZHAO Junlong, XU Hao, et al. Material and energy dynamic balance mechanism in middle-high rank coalbed methane(CBM)systems[J]. Journal of China Coal Society, 2016,40(1):40-48. doi:10. 13225/j.cnki.jccs.2015.9009
[14] WANG Gang, QIN Yong, XIE Yiwei, et al. The division and geologic controlling factors of a vertical superimposed coalbed methane system in the northern Gujiao blocks,China[J]. Journal of Natural Gas Science and Engineering,2015,24:379-389. doi:10.1016/j.jngse.2015.04.005
[15] XIA Peng, ZENG Fangui, SONG Xiaoxia. Parameters controlling high-yield coalbed methane vertical wells in the B3 area, Xishan coal field, Shanxi, China[J]. Energy Exploration&Exploitation, 2016, 34(5):711-734. doi:10.1177/0144598716656066
[16]逄建东,汪雷,臧晓琳,等.古交地区煤层气地质条件及资源潜力分析[J].科学技术与工程,2015,15(33):155-160, 165. doi:10.3969/j.issn.1671-1815.-2015.33.027PANG Jiandong,WANG Lei, ZANG Xiaolin, et al. The geological conditions and resource potential analysis of coal bed gas in Gujiao area[J]. Science Technology and Engineering,2015,15(33):155-160,165. doi:10.3969/j.-issn.1671-1815.2015.33.027
[17]倪小明,苏现波,张小东.煤层气开发地质学[M].北京:化学工业出版社,2010.
[18]秦义,李仰民,白建梅,等.沁水盆地南部高煤阶煤层气井排采工艺研究与实践[J].天然气工业,2011,31(11):22-25. doi:10.3787/j.issn.1000-0976.2011.11.006QIN Yi,LI Yangmin,BAI Jianmei,et al. Technologies in the CBM drainage and production of wells in the southern Qinshui basin with high-rank coal beds[J]. Natural Gas Industry, 2011, 31(11):22-25. doi:10.3787/j.issn.1000-0976.2011.11.006
[19]孟艳军,汤达祯,李治平,等.高煤阶煤层气井不同排采阶段渗透率动态变化特征与控制机理[J].油气地质与采收率,2015, 22(2):66-71. doi:10.3969/j.issn.1009-9603.2015.02.012MENG Yanjun, TANG Dazhen, LI Zhiping, et al. Dynamic variation characteristics and mechanism of permeability in high-rank CBM wells at different drainage and production stages[J]. Petroluem Geology and Recovery Efficiency, 2015, 22(2):66-71. doi:10.3969/j.issn.1009-9603.2015.02.012
[20]张政,秦勇,WANG Guoxiong,等.基于等温吸附实验的煤层气解吸阶段数值描述[J].中国科学:地球科学,2013,43(8):1352-1358.ZHANG Zheng, QIN Yong, WANG Guoxiong, et al. Numerical description of coalbed methane desorption stages based on isothermal adsorption experiment[J]. Science China Earth Sciences, 2013, 43(8):1352-1358.
[21] MENG Yanjun, TANG Dazhen, XU Hao, et al. Division of coalbed methane desorption stages and its significance[J]. Petroleum Exploration and Development, 2014,41(5):671-677. doi:10.1016/S1876-3804(14)60080-X
[22] MA Feiying, WANG Yongqing, LI Haitao, et al. Staged coalbed methane desorption and the contribution of each stage to productivity[J]. Chemistry and Technology of Fuels and Oils, 2014, 50(5):448-448. doi:10.1007/s10553-014-0531-3
[23] PALMER I. Permeability changes in coal:analytical modeling[J]. International Journal of Coal Geology, 2009,77(1):119-126. doi:10.1016/j.coal.2008.09.006
[24] ALEXIS D A,KARPYN Z T,ERTEKIN T,et al. Fracture permeability and relative permeability of coal and theirdependence on stress conditions[J]. Journal of Unconventional Oil and Gas Resources, 2015, 10:1-10. doi:10.-1016/j.juogr.2015.02.001
[25] HAM Y, KANTZAS A. Measurement of relative permeability of coal:Approaches and limitations[C]. SPE114994,2008. doi:10.2118/114994-MS
[26]崔玉峰,王贵文,孙艳慧,等.低孔低渗储层物性下限确定方法及其适用性[J].西南石油大学学报(自然科学版),2016, 38(6):35-48. doi:10.11885/j.issn.167450-86.2015.02.04.05CUI Yufeng,WANG Guiwen, SUN Yanhuit et al. Methods of cutoff determination and applicability analysis in low porosity and low permeability reservoir[J]. Journal of Southwest Petroleum University(Science&Technology Edition), 2016,38(6):35-48. doi:10.11885/j.issn. 1674-5-086.2015.02.04.05
[27] SEIDLE J P, JEANSONNE M W, ERICKSON D J. Application of matchstick geometry to stress dependent permeability in coals[C]. SPE24361,1992. doi:10.2118/24361-MS
[28] SHI Jiquan, DURUCAN S. A model for changes in coalbed permeability during primary and enhanced methane recovery[C]. SPE 87230,2005. doi:10.2118/87230-PA
[29] XU Hao, TANG Dazhen, TANG Shuheng, et al. A dynamic prediction model for gas-water effective permeability based on coalbed methane production data[J]. International Journal of Coal Geology, 2014, 121(1):44-52. doi:10.1016/j.coal.2013.11.008
[30]孟召平,田永东,李国富.煤层气开发地质学理论与方法[M].北京:科学出版社,2010.
[31] BALAN H O, GUMRAH F. Assessment of shrinkage-swelling influences in coal seams using rankdependent physical coal properties[J]. International Journal of Coal Geology,2009,77(1):203-213. doi:10.1016/j.coal.2008.09.014
[32]胡素明,李相方.考虑煤自调节效应的煤层气藏物质平衡方程[J].天然气勘探与开发,2010,33(1):38-41.doi:10.3969/j.issn.1673-3177.2010.01.009HU Suming, LI Xiangfang. Material balance equation of coalbed methane reservoir with consideration of self-adjustment effect of coal[J]. Natural Gas Exploration and Development, 2010, 33(1):38-41. doi:10.3969/j.issn.-1673-3177.2010.01.009