基于传导、对流不同加热模式的油页岩孔隙结构变化的对比研究
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摘要
原位热解开采是未来油页岩开发的主流趋势,其原位加热方式主要分为传导和对流2种加热模式。在油页岩原位热解开采过程中,孔隙是油气渗流的主要通道,孔隙结构的连通特征直接影响和控制着热解油气的产出过程。为此,利用马弗炉和蒸汽锅炉对φ8 mm×25 mm的圆柱体油页岩试件分别实施传导和对流加热,最高加热温度均为550℃,并基于显微CT和3D数字岩芯重建技术对加热前后油页岩孔隙的大小、分布以及变化规律进行综合研究,分析不同加热模式对于油页岩的孔隙结构影响的差异及机制。研究表明:油页岩经传导加热后孔隙率为原始孔隙率的2.90倍,而经蒸汽对流加热后孔隙率为原始孔隙率的3.51倍。可见,与传导加热相比,对流加热使油页岩受热均匀,换热面积更大,使油页岩中固体有机质热解更充分,促使油页岩中的孔隙快速向四周拓展连通成大规模的孔隙连通团。另一方面,蒸汽对流加热能迅速携带走附着在孔隙壁上和滞留在"死端"孔隙中的残留页岩油,提高了孔隙间连通性,有效增大了孔隙直径,形成比传导加热连通性更好的孔隙结构,同时蒸汽携带油气一起产出,提高了油气的回收率。因此,对流加热为油页岩原位热解开采的首选加热模式,研究结果为实现大规模油页岩原位注蒸汽开发提供了有利技术支撑。
In-situ pyrolysis is the mainstream trend of oil shale exploitation in the future. The in-situ heating methods are mainly divided into conduction and convection heating modes. In the process of in-situ pyrolysis of oil shale,the pores are the main channel for oil and gas seepage. The connection characteristics of the pore structure affect and control directly the production process of pyrolytic oil and gas. Therefore,in this paper,the cylindrical oil shale samples of φ 8 mm×25 mm are heated through conduction and convection with muffle furnace and steam boiler respectively. The maximum heating temperature is 550 ℃. With the micro-CT and 3 D digital core reconstruction technology,the size,distribution and evolution of pores of oil shale before and after heating were studied comprehensively,and the differences of different heating modes on pore structure of oil shale were analyzed. The results show that the porosity is 2.90 times of the original porosity after the conduction heating. However,after the steam convection heating,the porosity is 3.51 times of the original porosity. The convection heating heats the oil shale evenly and the area of heat exchange is larger,so that the pyrolysis of the solid organic matter in the oil shale is more thoroughly,prompting the pores in the oil shale to expand rapidly and to connect into the large-scale connected pore groups. In addition,the convection heating steam quickly carries away the shale oil that adheres to the pore wall and remains in the dead-end of pores,which improves the connectivity between the pores and increases the pore diameter effectively and forms a better connected pore structure than in the conduction heating. The steam carries away oil and gas together simultaneously,which increases the recovery ratio of oil and gas. Therefore,convection heating is the preferred heating mode for in-situ pyrolysis of oil shale.
In-situ pyrolysis is the mainstream trend of oil shale exploitation in the future. The in-situ heating methods are mainly divided into conduction and convection heating modes. In the process of in-situ pyrolysis of oil shale,the pores are the main channel for oil and gas seepage. The connection characteristics of the pore structure affect and control directly the production process of pyrolytic oil and gas. Therefore,in this paper,the cylindrical oil shale samples of φ 8 mm×25 mm are heated through conduction and convection with muffle furnace and steam boiler respectively. The maximum heating temperature is 550 ℃. With the micro-CT and 3 D digital core reconstruction technology,the size,distribution and evolution of pores of oil shale before and after heating were studied comprehensively,and the differences of different heating modes on pore structure of oil shale were analyzed. The results show that the porosity is 2.90 times of the original porosity after the conduction heating. However,after the steam convection heating,the porosity is 3.51 times of the original porosity. The convection heating heats the oil shale evenly and the area of heat exchange is larger,so that the pyrolysis of the solid organic matter in the oil shale is more thoroughly,prompting the pores in the oil shale to expand rapidly and to connect into the large-scale connected pore groups. In addition,the convection heating steam quickly carries away the shale oil that adheres to the pore wall and remains in the dead-end of pores,which improves the connectivity between the pores and increases the pore diameter effectively and forms a better connected pore structure than in the conduction heating. The steam carries away oil and gas together simultaneously,which increases the recovery ratio of oil and gas. Therefore,convection heating is the preferred heating mode for in-situ pyrolysis of oil shale.
引文
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[18]KANGZ, YANGD, ZHAOY, etal.Thermalcrackingand corresponding permeability of Fushun oil shale[J]. Oil Shale,2011,28(2):273–283.
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[24]YANIK J,YüKSEL M,SA?LAM M,et al. Characterization of the oil fractions of shale oil obtained by pyrolysis and supercritical water extraction[J]. Fuel,1995,74(1):46–50.
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[26]SUN Y,HEL,KANG S,et al. Pore evolution of oil shale during sub-critical water extraction[J]. Energies,2018,11(4):842.
[27]赵林.过热蒸汽对流加热油页岩原位开采基础实验研究[硕士学位论文][D].太原:太原理工大学,2015.(ZHAO Lin. Experimental studyonin-situminingbasedoverheatsteamconvectionheatingoil shale[M. S. Thesis][D]. Taiyuan:Taiyuan University of Technology,2015.(in Chinese))
[28]YU Y,LIANG W,HU Y,et al. Study of micro-pores development in leancoalwithtemperature[J].InternationalJournalofRock Mechanics and Mining Sciences,2012,51(4):91–96.
[29]SU X G,DU X J,YUAN H H,et al. Research of the thermal stability ofstructureofresinanchoringmaterialbasedon3DCT[J].International Journal of Adhesion and Adhesives,2016,68:161–168.
[30]ZHAO J,YANG D,KANG Z,et al. A micro-CT study of changes in theinternalstructureofDaqingandYan'anoilshalesathigh temperatures[J]. Oil Shale,2012,29(4):357.
[31]NI X,MIAO J,LV R,et al. Quantitative 3D spatial characterization and flow simulation of coal macropores based onμCT technology[J].Fuel,2017,200:199–207.
[32]康志勤,王玮,赵阳升,等.基于显微CT技术的不同温度下油页岩孔隙结构三维逾渗规律研究[J].岩石力学与工程学报,2014,33(9):1 837–1 842.(KANG Zhiqin,WEI Wei,ZHAO Yangsheng,etal.Three-dimensionalpercolationmechanisminoilshaleunder different temperatures based on micro-CT[J]. Chinese Journal of Rock MechanicsandEngineering, 2014, 33(9):1837–1842.(in Chinese))
[2]DYNI J R. Geology and resources of some world oil-shale deposits[J].Oil Shale,2003,20(3):193–252.
[3]钱家麟,王剑秋,李术元.世界油页岩资源利用和发展趋势[J].吉林大学学报,2006,36(6):877–887.(QIAN Jialin,WANG Jianqiu,LIShuyuan.Worldoilshaleutilizationanditsfuture[J].Journalof Jilin University,2006,36(6):877–887.(in Chinese))
[4]刘招君,董清水,叶松青,等.中国油页岩资源现状[J].吉林大学学报,2006,36(6):869–876.(LIUZhaojun,DONGQingshui,YE Songqing,et al. The situation of oil shale resources in China[J].Journal of Jilin University,2006,36(6):869–876.(in Chinese))
[5]SUN Y,BAI F,LIU B,et al. Characterization of the oil shale products derived via topochemical reaction method[J]. Fuel,2014,115(1):338–346.
[6]DYNI J R. Geology and resources of some world oil-shale deposits[J].Oil Shale,2003,20(3):193–252.
[7]SOONE J,DOILOV S. Sustainable utilization of oil shale resources andcomparisonofcontemporarytechnologiesusedforoilshale processing[J]. Oil Shale,2003,20(3):311–323.
[8]钱家麟,尹亮,王剑秋,等.油页岩:石油的补充能源[M].北京:中国石化出版社,2008:137–139.(QIAN Jialin,YIN Liang,WANGJianqiu,etal.Oilshale-supplementaryenergyofpetroleum[M].Beijing:China Petrochemical Press,2008:137–139.(in Chinese))
[9]AL-QODAHZ,SHAWAQFEHAT,LAFIWK.Adsorptionof pesticides from aqueous solutions using oil shale ash[J]. Desalination,2007,208(1):294–305.
[10]ADAMR.BRANDT.Convertingoilshaletoliquidfuelswiththe AlbertaTaciukProcessor:energyinputsandgreenhousegas emissions[J]. Energy and Fuels,2015,23(12):6 253–6 258.
[11]刘德勋,王红岩,郑德温,等.世界油页岩原位开采技术进展[J].天然气工业,2009,(5):128–132.(LIU Dexun,WANG Hongyan,ZHENG Dewen,et al. World progress of oil shale in-situ exploitation methods[J]. Natural Gas Industry,2009,(5):128–132.(in Chinese))
[12]HARFI K E,MOKHLISSE A,CHAN?A M B,et al. Pyrolysis of the Moroccan(Tarfaya)oilshalesundermicrowaveirradiation[J].Fuel,2000,79(7):733–742.
[13]冯雪威,陈晨,陈大勇.油页岩原位开采技术研究新进展[J].中国矿业,2011,20(6):84–87.(FENG Xuewei,CHENG Chen,CHEN Dayong.Newdevelopmentofoilshalein-situtechnology[J].China Mining Magazine,2011,20(6):84–87.(in Chinese))
[14]FAN Y,DURLOFSKY L J,TCHELEPI H A. Numerical simulation of the in-situ upgrading of oil shale[J]. SPE Journal,2009,15(2):368–381.
[15]HARFI K E,MOKHLISSE A,CHAN?A M B,et al. Pyrolysis of the Moroccan(Tarfaya)oilshalesundermicrowaveirradiation[J].Fuel,2000,79(7):733–742.
[16]赵阳升,冯增朝,杨栋,等.对流加热油页岩开采油气的方法[P].中国:ZL 200510012473,2005–4–20.(ZHAO Yangsheng,FENG Zengchao,YANG Dong,et al. Convection heating oil shale oil and gas extractionmethod[P].China:ZL200510012473,2005–4–20.(in Chinese))
[17]BAI F,SUN Y,LIU Y,et al. Evaluation of the porous structure of Huadian oil shale during pyrolysis using multiple approaches[J]. Fuel,2017,187:1–8.
[18]KANGZ, YANGD, ZHAOY, etal.Thermalcrackingand corresponding permeability of Fushun oil shale[J]. Oil Shale,2011,28(2):273–283.
[19]TIWARI P,DEO M,LIN C L,et al. Characterization of oil shale pore structure before and after pyrolysis by using X-ray micro CT[J]. Fuel,2013,107(9):547–554.
[20]SAIFT,LINQ,BIJELJICB,etal.Microstructuralimagingand characterization of oil shale before and after pyrolysis[J]. Fuel,2017,197:562–574.
[21]RABBANI A,BAYCHEV T G,AYATOLLAHI S,et al. Evolution of pore-scalemorphologyofoilshaleduringpyrolysis:aquantitative analysis[J]. Transport in Porous Media,2017,(4):1–20.
[22]康志勤,吕兆兴,杨栋,等.油页岩原位注蒸汽开发的固–流–热–化学耦合数学模型研究[J].西安石油大学学报:自然科学版,2008,23(4):30–34.(KANG Zhiqin,LüZhaoxing,YANG Dong,et al. The solid-fluid-thermal-chemistry coupling mathematical model foroilshalein-situsteaminjectingdevelopment[J].JournalofXi'an Shiyou University:Natural Science,2008,23(4):30–34.(in Chinese))
[23]NAZZAL J M,WILLIAMS P T. Influence of temperature and steam ontheproductsfromtheflashpyrolysisofJordanoilshale[J].International Journal of Energy Research,2002,26(14):1 207–1 219.
[24]YANIK J,YüKSEL M,SA?LAM M,et al. Characterization of the oil fractions of shale oil obtained by pyrolysis and supercritical water extraction[J]. Fuel,1995,74(1):46–50.
[25]HARFI K E,BENNOUNA C,MOKHLISSE A,et al. Supercritical fluidextractionofMoroccan(Timahdit)oilshalewithwater[J].Journal of Analytical and Applied Pyrolysis,1999,50(2):163–174.
[26]SUN Y,HEL,KANG S,et al. Pore evolution of oil shale during sub-critical water extraction[J]. Energies,2018,11(4):842.
[27]赵林.过热蒸汽对流加热油页岩原位开采基础实验研究[硕士学位论文][D].太原:太原理工大学,2015.(ZHAO Lin. Experimental studyonin-situminingbasedoverheatsteamconvectionheatingoil shale[M. S. Thesis][D]. Taiyuan:Taiyuan University of Technology,2015.(in Chinese))
[28]YU Y,LIANG W,HU Y,et al. Study of micro-pores development in leancoalwithtemperature[J].InternationalJournalofRock Mechanics and Mining Sciences,2012,51(4):91–96.
[29]SU X G,DU X J,YUAN H H,et al. Research of the thermal stability ofstructureofresinanchoringmaterialbasedon3DCT[J].International Journal of Adhesion and Adhesives,2016,68:161–168.
[30]ZHAO J,YANG D,KANG Z,et al. A micro-CT study of changes in theinternalstructureofDaqingandYan'anoilshalesathigh temperatures[J]. Oil Shale,2012,29(4):357.
[31]NI X,MIAO J,LV R,et al. Quantitative 3D spatial characterization and flow simulation of coal macropores based onμCT technology[J].Fuel,2017,200:199–207.
[32]康志勤,王玮,赵阳升,等.基于显微CT技术的不同温度下油页岩孔隙结构三维逾渗规律研究[J].岩石力学与工程学报,2014,33(9):1 837–1 842.(KANG Zhiqin,WEI Wei,ZHAO Yangsheng,etal.Three-dimensionalpercolationmechanisminoilshaleunder different temperatures based on micro-CT[J]. Chinese Journal of Rock MechanicsandEngineering, 2014, 33(9):1837–1842.(in Chinese))