基于实验与案例分析的盖层封盖能力对煤层气保存的影响（英文）
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摘要
盖层的封盖能力对煤层气藏的保存起着至关重要的作用。为研究盖层的封盖能力,本文采集了五种不同岩性的盖层岩样(包括:新近系黏土岩、古近系红层、二叠系砂岩、二叠系泥岩和二叠系粉砂岩),综合采用显微结构观测、孔隙结构测量和扩散性能测定相结合的实验方法开展相关研究。研究结果表明:泥岩、粉砂岩由于其所具有的结构致密、孔隙率低、孔径分布以微孔和小孔为主以及孔喉比高等特征,是煤层气保存较为理想的盖层;甲烷在泥岩和粉砂岩中的扩散系数约为砂岩的6倍、粘土岩和红层的90倍。为进一步对煤层气通过盖层的逸散情况进行评价,本文构建了一维的煤层气扩散模型。建模分析结果显示:在相同盖层厚度条件下,泥岩、粉砂岩对煤层气的封盖能力是黏土岩和红层的近100倍、砂岩的近17倍。因此当煤层的盖层由黏土岩、红层或砂岩组成时,其下部煤层所遭受的瓦斯逸散作用将更为强烈。许疃煤矿Ⅲ3采区的开采实践验证了上述结论,许疃煤矿的开采实践表明:与二叠系岩层(泥岩、砂岩、粉砂岩)相比古近系红层下方煤层的煤层气含量出现显著降低。
Caprocks play an important role in the trapping of coalbed methane(CBM) reservoirs. To study the sealing capacities of caprocks, five samples with different lithologies of Neogene clayrock, Paleogene redbeds, Permian sandstone, Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation, pore structure measurement and diffusion properties determination. Results indicate that with denser structures, lower porosities, much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks; the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds. To further estimate the CBM escape through caprocks, a one-dimensional CBM diffusion model is derived. Modeling calculation result demonstrates that under the same thickness, the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds, and nearly 17 times higher than sandstone, which indicates that the coal seam below caprocks like clayrock, redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone. Such conclusion is verified by the case study fromⅢ3 District, Xutuan Colliery, where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone, siltstone and sandstone.
Caprocks play an important role in the trapping of coalbed methane(CBM) reservoirs. To study the sealing capacities of caprocks, five samples with different lithologies of Neogene clayrock, Paleogene redbeds, Permian sandstone, Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation, pore structure measurement and diffusion properties determination. Results indicate that with denser structures, lower porosities, much more developed micropores/transition pores and higher pore/throat ratios,mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks; the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds. To further estimate the CBM escape through caprocks, a one-dimensional CBM diffusion model is derived. Modeling calculation result demonstrates that under the same thickness, the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds, and nearly 17 times higher than sandstone, which indicates that the coal seam below caprocks like clayrock, redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone. Such conclusion is verified by the case study fromⅢ3 District, Xutuan Colliery, where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone, siltstone and sandstone.
引文
[1] TAO Ming-xin, SHI Bao-guang, LI Jin-ying, WANG Wan-chun, LI Xiao-bin, GAO Bo. Secondary biological coalbed gas in the Xinji area, Anhui province, China:Evidence from the geochemical features and secondary changes[J]. International Journal of Coal Geology, 2007,71(2):358-370.
[2] JIN Kan, CHENG Yuan-ping, WANG Wei, LIU Hai-bo, LIU Zheng-dong, ZHANG Hao. Evaluation of the remote lower protective seam mining for coal mine gas control:A typical case study from the Zhuxianzhuang Coal Mine, Huaibei Coalfield, China[J]. Journal of Natural Gas Science and Engineering, 2016, 33:44-55.
[3] SIDDIQUI F I, PATHAN A G, UNVER B, ERTUNC G.Sustainable lignite resource planning at Thar coalfield,Pakistan[J]. Journal of Central South University, 2018, 25(5):1165-1172.
[4] WANG Shao-feng, LI Xi-bing, WANG De-ming. Mininginduced void distribution and application in the hydrothermal investigation and control of an underground coal fire:A case study[J]. Process Safety and Environmental Protection, 2016,102:734-756.
[5] ZHANG Guang-chao, HE Fu-lian, LAI Yong-hui, JIA Hong-guo. Ground stability of underground gateroad with 1km burial depth:A case study from Xingdong coal mine,China[J]. Journal of Central South University, 2018, 25(6):1386-1398.
[6] ZHANG Hong, CUI Yong-jun, TAO Ming-xin, PENG Ge-lin,JIN Xiang-lan, LI Gui-hong. Evolution of the CBM reservoir-forming dynamic system with mixed secondary biogenic and thermogenic gases in the Huainan Coalfield,China[J]. Chinese Science Bulletin, 2005, 50(1):30-39.
[7] JIN Kan, CHENG Yuan-ping, WANG Liang, DONG Jun,GUO Pin-kun, AN Feng-hua, JIANG Li-min. The effect of sedimentary redbeds on coalbed methane occurrence in the Xutuan and Zhaoji Coal Mines, Huaibei Coalfield, China[J].International Journal of Coal Geology, 2015, 137:111-123.
[8] LEUNG D Y C, CARAMANNA G, MAROTO-VALER M M. An overview of current status of carbon dioxide capture and storage technologies[J]. Renewable and Sustainable Energy Reviews, 2014, 39:426-443.
[9] WU Yu-dong, JU Yi-wen, HOU Quan-lin, HU Sheng-biao,PAN Jie-nan, FAN Jun-jia. Comparison of coalbed gas generation between Huaibei-Huainan coalfields and Qinshui coal basin based on the tectono-thermal modeling[J].Science China Earth Sciences, 2011, 54(7):1069-1077.
[10] BAO Yuan, WEI Chong-tao, NEUPANE B. Generation and accumulation characteristics of mixed coalbed methane controlled by tectonic evolution in Liulin CBM field, eastern Ordos Basin, China[J]. Journal of Natural Gas Science and Engineering, 2016, 28:262-270.
[11] MCINTOSH J C, WARWICK P D, MARTINI A M,OSBORN S G. Coupled hydrology and biogeochemistry of Paleocene-Eocene coal beds, northern Gulf of Mexico[J].Geological Society of America Bulletin, 2010, 122(7, 8):1248-1264.
[12] QIN Yong, TANG Xiu-yi, YE Jian-ping, JIAO Si-hong.Characteristics and origins of stable carbon isotope in coalbed methane of China[J]. Journal of China University of Mining and Technology, 2000, 29(2):113-119.(in Chinese)
[13] KEDZIOR S, KOTARBA M J, PEKALA Z. Geology, spatial distribution of methane content and origin of coalbed gases in Upper Carboniferous(Upper Mississippian and Pennsylvanian)strata in the south-eastern part of the Upper Silesian Coal Basin, Poland[J]. International Journal of Coal Geology, 2013, 105:24-35.
[14] SAGHAFI A, PINETOWN K. The role of interseam strata in the retention of CO_2 and CH4 in a coal seam gas system[C]//10th International Conference on Greenhouse Gas Control Technologies. Amsterdam, Netherlands, 2011, 4:3117-3124. DOI:10.1016/j.egypro.2011.02.225.
[15] SU Xian-bo, LIN Xiao-ying, ZHAO Meng-jun, SONG Yan,LIU Shao-bo. The upper Paleozoic coalbed methane system in the Qinshui basin, China[J]. AAPG Bulletin, 2005, 89(1):81-100.
[16] MENG Yan-jun, TANG Da-zhen, XU Hao, LI Chen, LI Ling,MENG Shang-zhi. Geological controls and coalbed methane production potential evaluation:A case study in Liulin area,eastern Ordos Basin, China[J]. Journal of Natural Gas Science and Engineering, 2014, 21:95-111.
[17] PALMER I D, METCALFE R S, YEE D, RURI R. Coalbed methane reservoir valuation and exploitation[M]. Xuzhou:China University of Mining and Technology Press, 1996.(in Chinese)
[18] DU Shang, SHAN Xuan-long, YI Jian, LI Ji-yan. Controlling factors of high-quality volcanic reservoirs of Yingcheng Formation in the Songnan gas field[J]. Journal of Central South University, 2018, 25(4):892-902.
[19] ZHAO Zi-long, ZHAO Jing-zhou, REN Hai-jiao, LI Jun,WU Wei-tao. Characterization and formation mechanisms of fractures and their significance to hydrocarbon accumulation:A case study of Lower Ordovician mid-assemblage Formations in central Ordos Basin, China[J]. Journal of Central South University, 2018, 25(11):2766-2784.
[20] CHENG Yuan-ping, WANG Hai-feng, WANG Liang, ZHOU Hong-xing, LIU Hong-yong, LIU Hai-bo, WU Dong-mei, LI Wei. Theories and engineering applications on coal mine gas control[M]. Xuzhou:China University of Mining and Technology Press, 2010.(in Chinese)
[21] SAGHAFI A, JAVANMARD H, ROBERTS D. Parametersaffecting coal seam gas escape through floor and roof strata[C]//Proceeding of the 10th Underground Coal Operators Conference. University of Wollongong and the Australian Institute of Mining and Metallurgy. 2010:210-216.
[22] ZHANG Pei-he, JIN Xiu-liang, LIU Yu-hui, WANG Zheng-xi, LIU Na-na. Synthetical analysis on geological factors ccontrolling coalbed methane[J]. Procedia Earth and Planetary Science, 2011, 3:144-153.
[23] BAO Yuan, WEI Chong-tao, WANG Chao-yong, WANG Guo-chang, LI Qing-guang. Geochemical characteristics and generation process of mixed biogenic and thermogenic coalbed methane in Luling coalfield, China[J]. Energy&Fuels, 2014, 28(7):4392-4401.
[24] HONG Feng, SONG Yan, CHEN Zhen-hong, ZHAO Meng-jun, LIU Shao-bo, QIN Sheng-fei, FU Guo-you. Study on process and model of CBM dissipating[J]. ChineseScience Bulletin, 2005, 50(1):134-139.
[25] LIU Guang-di, ZHAO Zhong-ying, SUN Ming-liang, LI Jian,HU Guo-yi, WANG Xiao-bo. New insights into natural gas diffusion coefficient in rocks[J]. Petroleum Exploration and Development, 2012, 39(5):597-604.
[26] SAGHAFI A. Potential for ECBM and CO_2 storage in mixed gas Australian coals[J]. International Journal of Coal Geology,2010, 82(3,4):240-251.
[27] NELSON J S, SIMMONS E C. Diffusion of methane and ethane through the reservoir cap rock:Implications for the timing and duration of catagenesis[J]. AAPG Bulletin, 1995,79(7):1064-1073.
[28] HUANG Zhi-long, HAO Shi-sheng. Study on sealing of gas concentration and diffusion in overlying gas reservoirs[J].Acta Petrolei Sinica, 1996, 17(4):36-41.(in Chinese)
[2] JIN Kan, CHENG Yuan-ping, WANG Wei, LIU Hai-bo, LIU Zheng-dong, ZHANG Hao. Evaluation of the remote lower protective seam mining for coal mine gas control:A typical case study from the Zhuxianzhuang Coal Mine, Huaibei Coalfield, China[J]. Journal of Natural Gas Science and Engineering, 2016, 33:44-55.
[3] SIDDIQUI F I, PATHAN A G, UNVER B, ERTUNC G.Sustainable lignite resource planning at Thar coalfield,Pakistan[J]. Journal of Central South University, 2018, 25(5):1165-1172.
[4] WANG Shao-feng, LI Xi-bing, WANG De-ming. Mininginduced void distribution and application in the hydrothermal investigation and control of an underground coal fire:A case study[J]. Process Safety and Environmental Protection, 2016,102:734-756.
[5] ZHANG Guang-chao, HE Fu-lian, LAI Yong-hui, JIA Hong-guo. Ground stability of underground gateroad with 1km burial depth:A case study from Xingdong coal mine,China[J]. Journal of Central South University, 2018, 25(6):1386-1398.
[6] ZHANG Hong, CUI Yong-jun, TAO Ming-xin, PENG Ge-lin,JIN Xiang-lan, LI Gui-hong. Evolution of the CBM reservoir-forming dynamic system with mixed secondary biogenic and thermogenic gases in the Huainan Coalfield,China[J]. Chinese Science Bulletin, 2005, 50(1):30-39.
[7] JIN Kan, CHENG Yuan-ping, WANG Liang, DONG Jun,GUO Pin-kun, AN Feng-hua, JIANG Li-min. The effect of sedimentary redbeds on coalbed methane occurrence in the Xutuan and Zhaoji Coal Mines, Huaibei Coalfield, China[J].International Journal of Coal Geology, 2015, 137:111-123.
[8] LEUNG D Y C, CARAMANNA G, MAROTO-VALER M M. An overview of current status of carbon dioxide capture and storage technologies[J]. Renewable and Sustainable Energy Reviews, 2014, 39:426-443.
[9] WU Yu-dong, JU Yi-wen, HOU Quan-lin, HU Sheng-biao,PAN Jie-nan, FAN Jun-jia. Comparison of coalbed gas generation between Huaibei-Huainan coalfields and Qinshui coal basin based on the tectono-thermal modeling[J].Science China Earth Sciences, 2011, 54(7):1069-1077.
[10] BAO Yuan, WEI Chong-tao, NEUPANE B. Generation and accumulation characteristics of mixed coalbed methane controlled by tectonic evolution in Liulin CBM field, eastern Ordos Basin, China[J]. Journal of Natural Gas Science and Engineering, 2016, 28:262-270.
[11] MCINTOSH J C, WARWICK P D, MARTINI A M,OSBORN S G. Coupled hydrology and biogeochemistry of Paleocene-Eocene coal beds, northern Gulf of Mexico[J].Geological Society of America Bulletin, 2010, 122(7, 8):1248-1264.
[12] QIN Yong, TANG Xiu-yi, YE Jian-ping, JIAO Si-hong.Characteristics and origins of stable carbon isotope in coalbed methane of China[J]. Journal of China University of Mining and Technology, 2000, 29(2):113-119.(in Chinese)
[13] KEDZIOR S, KOTARBA M J, PEKALA Z. Geology, spatial distribution of methane content and origin of coalbed gases in Upper Carboniferous(Upper Mississippian and Pennsylvanian)strata in the south-eastern part of the Upper Silesian Coal Basin, Poland[J]. International Journal of Coal Geology, 2013, 105:24-35.
[14] SAGHAFI A, PINETOWN K. The role of interseam strata in the retention of CO_2 and CH4 in a coal seam gas system[C]//10th International Conference on Greenhouse Gas Control Technologies. Amsterdam, Netherlands, 2011, 4:3117-3124. DOI:10.1016/j.egypro.2011.02.225.
[15] SU Xian-bo, LIN Xiao-ying, ZHAO Meng-jun, SONG Yan,LIU Shao-bo. The upper Paleozoic coalbed methane system in the Qinshui basin, China[J]. AAPG Bulletin, 2005, 89(1):81-100.
[16] MENG Yan-jun, TANG Da-zhen, XU Hao, LI Chen, LI Ling,MENG Shang-zhi. Geological controls and coalbed methane production potential evaluation:A case study in Liulin area,eastern Ordos Basin, China[J]. Journal of Natural Gas Science and Engineering, 2014, 21:95-111.
[17] PALMER I D, METCALFE R S, YEE D, RURI R. Coalbed methane reservoir valuation and exploitation[M]. Xuzhou:China University of Mining and Technology Press, 1996.(in Chinese)
[18] DU Shang, SHAN Xuan-long, YI Jian, LI Ji-yan. Controlling factors of high-quality volcanic reservoirs of Yingcheng Formation in the Songnan gas field[J]. Journal of Central South University, 2018, 25(4):892-902.
[19] ZHAO Zi-long, ZHAO Jing-zhou, REN Hai-jiao, LI Jun,WU Wei-tao. Characterization and formation mechanisms of fractures and their significance to hydrocarbon accumulation:A case study of Lower Ordovician mid-assemblage Formations in central Ordos Basin, China[J]. Journal of Central South University, 2018, 25(11):2766-2784.
[20] CHENG Yuan-ping, WANG Hai-feng, WANG Liang, ZHOU Hong-xing, LIU Hong-yong, LIU Hai-bo, WU Dong-mei, LI Wei. Theories and engineering applications on coal mine gas control[M]. Xuzhou:China University of Mining and Technology Press, 2010.(in Chinese)
[21] SAGHAFI A, JAVANMARD H, ROBERTS D. Parametersaffecting coal seam gas escape through floor and roof strata[C]//Proceeding of the 10th Underground Coal Operators Conference. University of Wollongong and the Australian Institute of Mining and Metallurgy. 2010:210-216.
[22] ZHANG Pei-he, JIN Xiu-liang, LIU Yu-hui, WANG Zheng-xi, LIU Na-na. Synthetical analysis on geological factors ccontrolling coalbed methane[J]. Procedia Earth and Planetary Science, 2011, 3:144-153.
[23] BAO Yuan, WEI Chong-tao, WANG Chao-yong, WANG Guo-chang, LI Qing-guang. Geochemical characteristics and generation process of mixed biogenic and thermogenic coalbed methane in Luling coalfield, China[J]. Energy&Fuels, 2014, 28(7):4392-4401.
[24] HONG Feng, SONG Yan, CHEN Zhen-hong, ZHAO Meng-jun, LIU Shao-bo, QIN Sheng-fei, FU Guo-you. Study on process and model of CBM dissipating[J]. ChineseScience Bulletin, 2005, 50(1):134-139.
[25] LIU Guang-di, ZHAO Zhong-ying, SUN Ming-liang, LI Jian,HU Guo-yi, WANG Xiao-bo. New insights into natural gas diffusion coefficient in rocks[J]. Petroleum Exploration and Development, 2012, 39(5):597-604.
[26] SAGHAFI A. Potential for ECBM and CO_2 storage in mixed gas Australian coals[J]. International Journal of Coal Geology,2010, 82(3,4):240-251.
[27] NELSON J S, SIMMONS E C. Diffusion of methane and ethane through the reservoir cap rock:Implications for the timing and duration of catagenesis[J]. AAPG Bulletin, 1995,79(7):1064-1073.
[28] HUANG Zhi-long, HAO Shi-sheng. Study on sealing of gas concentration and diffusion in overlying gas reservoirs[J].Acta Petrolei Sinica, 1996, 17(4):36-41.(in Chinese)