温度冲击作用下煤的渗透率变化规律与增透机制
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摘要
为了研究温度冲击条件下的煤体渗透性变化规律及增透机制,利用恒温箱和液氮对原煤煤样进行了两种条件下的温度冲击试验,分析了煤样在温度冲击前后的渗透率变化情况和微观裂隙发育情况,探讨了温度冲击过程中的声发射信号分布规律。试验结果表明:在经过冷冲击处理和热-冷冲击处理后,煤体的渗透率平均增幅分别为48.68%和469.24%,热-冷冲击处理过程中煤样的声发射能量峰值是冷冲击处理过程中煤样的声发射能量峰值的3.6倍,相比冷冲击处理,热-冷处理所产生的微裂纹数量更多,裂隙呈树枝状发育,增透效果更好;煤体性质的各向异性和温度冲击所产生的超过煤体抗拉强度的热应力是主要的增透机制。
To study the change law of permeability of coal under the condition of temperature impact and the mechanism of increasing permeability, the temperature impact test of two kinds of conditions of coal samples were carried out using thermostat and liquid nitrogen, the permeability variation of coal samples before and after temperature shock and the development of micro fracture were analyzed, and the distribution of acoustic emission signal in the process of temperature shock was also discussed. The experimental results indicate that after the cold shock treatment and hot-cold shock treatment,an average increase of permeability of coal were 48. 68% and 469. 24% respectively,the AE energy peak during hot-cold impact process is 3. 6 times of that during the cold shock process. Compared with cold shock treatment, the hot-cold impact process produces more number of crack, the fractures show a dendritic development, and the effect of increasing permeability is better. The thermal stress exceeding the tensile strength of coal produced by the anisotropy and thermal shock properties of coal is the main mechanism of increasing permeability.
To study the change law of permeability of coal under the condition of temperature impact and the mechanism of increasing permeability, the temperature impact test of two kinds of conditions of coal samples were carried out using thermostat and liquid nitrogen, the permeability variation of coal samples before and after temperature shock and the development of micro fracture were analyzed, and the distribution of acoustic emission signal in the process of temperature shock was also discussed. The experimental results indicate that after the cold shock treatment and hot-cold shock treatment,an average increase of permeability of coal were 48. 68% and 469. 24% respectively,the AE energy peak during hot-cold impact process is 3. 6 times of that during the cold shock process. Compared with cold shock treatment, the hot-cold impact process produces more number of crack, the fractures show a dendritic development, and the effect of increasing permeability is better. The thermal stress exceeding the tensile strength of coal produced by the anisotropy and thermal shock properties of coal is the main mechanism of increasing permeability.
引文
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[23]黄中伟,位江巍,李根生,等.液氮冻结对岩石抗拉及抗压强度影响试验研究[J].岩土力学,2016,37(3):694-700.HUANG Zhongwei,WEI Jiangwei,LI Gensheng,et al.An experimental study of tensile and compressive strength of rocks under cryogenic nitrogen freezing[J].Rock and Soil Mechanics,2016,37(3):694-700.
[24]王登科.含瓦斯煤岩本构模型与失稳规律研究[D].重庆:重庆大学,2009.
[25]康健.岩石热破裂的研究及应用[M].大连:大连理工大学出版社,2008.
[26]袁振明,马羽宽,何泽云.声发射技术及其应用[M].北京:机械工业出版社,1985.
[2]CHENG Yuanping,WANG Liang,LIU Hongyong,et al.Definition,theory,methods,and applications of the safe and efficient simultaneous extraction of coal and gas[J].International Journal of Coal Science&Technology,2015,2(1):52-65.
[3]叶建平,史保生,张春才.中国煤储层渗透性及其主要影响因素[J].煤炭学报,1999,24(2):118-122.YE Jianping,SHI Baosheng,ZHANG Chuncai.Coal reservoir permeability and its controlled factors in China[J].Journal of China Coal Society,1999,24(2):118-122.
[4]BENNION D B,THOMAS F B,BIETZ R F.Low permeability gas reservoirs:Problems,opportunities and solutions for drilling,completion,stimulation and production[J].SPE 35577,1996:117-131.
[5]BRYANT J,HAGGSTROM J.An environmental solution to help re-duce freshwater demands and minimize chemical use[J].SPE153867,2012:1-10.
[6]HOLTSCLAW J,LOVELESS D,SAINI R,et al.Environmentally focused crosslinked-gel system results in high retained proppantpack conductivity[J].SPE 146832,2011:2803-2815.
[7]MCDANIEL B W,GRUNDMANN S R,KENDRICK W D,et al.Field applications of cryogenic nitrogen as a hydraulic fracturing fluid[J].Journal of Petroleum Technology,1998,50(3):38-39.
[8]张亮,罗炯,崔国栋,等.低温气体辅助煤层气压裂中的冷冲击机理[J].地球科学,2016,41(4):664-674.ZHANG Liang,LUO Jiong,CUI Guodong,et al.Mechanisms of cold shock during coalbed frcaturingassisted with cryogenic gases[J].Earth Science,2016,41(4):664-674.
[9]杨新乐,任常在,张永利,等.低渗透煤层气注热开采热-流-固耦合数学模型及数值模拟[J].煤炭学报,2013,38(6):1044-1049.YANG Xinle,REN Changzai,ZHANG Yongli,et al.Numerical simulation of the coupled thermal-fluid-solid mathematical models during extracting methane in low-permeability coal bed by heat injection[J].Journal of China Coal Society,2013,38(6):1044-1049.
[10]杨新乐,张永利.热采煤层气藏过程煤层气运移规律的数值模拟[J].中国矿业大学学报,2011,40(1):89-94.YANG Xinle,ZHANG Yongli.Process of coal bed methane gas migration regularity numerical simulation with heat injection[J].Journal of China University of Mining and Technology,2011,40(1):89-94.
[11]杨新乐,张永利.气固耦合作用下温度对煤瓦斯渗透率影响规律的实验研究[J].地质力学学报[J].2008,14(4):374-380.YANG Xinle,ZHANG Yongli.Experimental study of effect of temperature on coal gas permeability under gas-solid coupling[J].Journal of Geomechanics,2008,14(4):374-380.
[12]杨新乐,张永利,李成全,等.考虑温度影响下煤层气解吸渗流规律试验研究[J].岩土工程学报,2008,30(12):1811-1814.YANG Xinle,ZHANG Yongli,LI Chengquan,et al.Experimental study of desorption and seepage rules of coal-bed gas considering temperature conditions[J].Chinese Journal of Geotechnical Engineering,2008,30(12):1811-1814.
[13]HEARD H C.Thermal expansion and inferred permeability of climax quartz monzonite to 300℃and 27.6 MPa[J].International Journal of Rock Mechanics&Mining Science&Geomechanics Abstracts 1980,17(5):289-296.
[14]SOMERTON W H,GUPTA V S.Role of fluxing agents in thermal alteration of sandstone[J].Journal of Petroleum Technology,1965,17(5):585-588.
[15]任韶然,范志坤,张亮,等.液氮对煤岩的冷冲击作用机制及试验研究[J].岩石力学与工程学报,2013,32(S2):3790-3794.REN Shaoran,FAN Zhikun,ZHANG Liang,et al.Mechanisms and experimental study of thermal-shock effect on coal-rock using liquid nitrogen[J].Chinese Journal of Rock Mechanics and Engineer-ing,2013,32(S2):3790-3794.
[16]MUTLUTURK M,ALTINDAG R,TORK G.A decay function model for the integrity loss of rock when subjected to recurrent cycles of freezing-thawing and heating-cooling[J].International Journal of Rock Mechanics&Mining Sciences,2004,41(2):237-244.
[17]韦江雄,余其俊,李铁锋,等.冷热循环负荷作用下混凝土微观形貌分析[J].混凝土,2007(1):19-22.WEI Jiangxiong,YU Qijun,LI Tiefeng,et al.Microscopic analysis on hardened Portland cement concrete under thermal cycles[J].Concrete,2007(1):19-22.
[18]蔡承政,李根生,黄中伟,等.液氮冻结条件下岩石孔隙结构损伤试验研究[J].岩土力学,2014,35(4):965-971.CAI Chengzheng,LI Gensheng,HUANG Zhongwei,et al.Experiment study of rock porous structure damage under cryogenic nitrogen freezing[J].Rock and Soil Mechanics,2014,35(4):965-971.
[19]CHA Minsu,YIN Xiaolong,KNEAFSEY Timothy,et al.Cryogenic fracturing for reservoir stimulation-laboratory studies[J].Journal of Petroleum Science and Engineering,2014,124(12):436-450.
[20]张春会,李伟龙,王锡朝,等.液氮溶浸煤致裂的机理研究[J].河北科技大学学报,2015,36(4):425-430.ZHANG Chunhui,LI Weilong,WANG Xichao,et al.Research of fracturing mechanism of coal subjected to liquid nitrogen cooling[J].Journal of Hebei University of Science and Technology,2015,36(4):425-430.
[21]李和万,王来贵,牛富民,等.冷热交替作用致煤样裂隙结构损伤试验[J].安全与环境学报,2016,16(1):40-43.LI Hewan,WANG Laigui,NIU Fumin,et al.Experimental study on the structure crack damage of the coal samples via the abrupt temperature-changing cycles[J].Journal of Safety and Environment,2016,16(1):40-43.
[22]李和万,王来贵,牛富民,等.液氮对不同温度煤裂隙冻融扩展作用研究[J].中国安全科学学报,2015,25(10):121-126.LI Hewan,WANG Laigui,NIU Fumin,et al.Study on effect of freeze-thaw cycle with liquid nitrogen on crack extension of coal at different initial temperatures[J].China Safety Science Journal,2015,25(10):121-126.
[23]黄中伟,位江巍,李根生,等.液氮冻结对岩石抗拉及抗压强度影响试验研究[J].岩土力学,2016,37(3):694-700.HUANG Zhongwei,WEI Jiangwei,LI Gensheng,et al.An experimental study of tensile and compressive strength of rocks under cryogenic nitrogen freezing[J].Rock and Soil Mechanics,2016,37(3):694-700.
[24]王登科.含瓦斯煤岩本构模型与失稳规律研究[D].重庆:重庆大学,2009.
[25]康健.岩石热破裂的研究及应用[M].大连:大连理工大学出版社,2008.
[26]袁振明,马羽宽,何泽云.声发射技术及其应用[M].北京:机械工业出版社,1985.