页岩气储层迂曲微裂缝二维重构及多点起裂分析
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摘要
在复杂的地质条件下,页岩气储层中的天然裂缝往往呈现迂曲状几何形态,为了研究迂曲微裂缝在水力压裂过程中的起裂位置,根据描述真实裂缝几何形态的相关参数,利用自主开发的MATLAB程序,实现了对不同长度、孔隙度、迂曲度和方位角的裂缝的二维重构,借助COMSOL Multiphisics中"自由和多孔介质流动模块"以及"多孔弹性模块"建立了裂缝—基质耦合渗流模型及岩石基质应力—应变模型,对不同迂曲度、方位角以及带天然裂缝的迂曲裂缝周围应力及起裂位置进行分析。结果表明,压裂液流速在迂曲微裂缝中呈现波动下降,其压力平缓下降且压力梯度沿裂缝长度方向逐渐减小;迂曲微裂缝会在裂缝曲率较大的位置出现多个起裂点,且起裂位置数量和区域大小随裂缝迂曲度的增大而增加,而裂缝方位角的变化对起裂位置影响较小;在主裂缝中流体压力作用下,未胶结的天然裂缝两端出现破裂,更有利于页岩气储层中复杂缝网的形成。
In order to study the initiation points of tortuous micro-fractures which normally exist in shale gas reservoir,the MATLAB program was used to reconstruct micro-fractures of different lengths,porosity,tortuosity and azimuth,based on the parameters describing the geometry of the real fractures.The fracture-matrix coupled seepage model and a rock matrix stress-strain model were established by the module of"Free and Porous Media Flow"and"Pore Elasticity"in COMSOL Multiphisics to analyze stress distribution and fracture initiation positions with different tortuosity,azimuths,and micro-fractures with natural fractures.The results show that the fracturing fluid flow velocity decreases in the tortuous micro-fractures with fluctuation,its pressure decreases gently and the pressure gradient decreases with the length of the tortuous micro-fracture.The tortuous micro-fractures initiate at multiply points where the fracture curvature is large,and the number and area of crack initiation sites increase with the increase of the crack curvature.The azimuth angle has little effect on the initiation points.For the natural fractures,initiations occur at both tips of the unconsolidated natural cracks and the cement in the cemented natural cracks will first break under the pressure of the main fractures.
In order to study the initiation points of tortuous micro-fractures which normally exist in shale gas reservoir,the MATLAB program was used to reconstruct micro-fractures of different lengths,porosity,tortuosity and azimuth,based on the parameters describing the geometry of the real fractures.The fracture-matrix coupled seepage model and a rock matrix stress-strain model were established by the module of"Free and Porous Media Flow"and"Pore Elasticity"in COMSOL Multiphisics to analyze stress distribution and fracture initiation positions with different tortuosity,azimuths,and micro-fractures with natural fractures.The results show that the fracturing fluid flow velocity decreases in the tortuous micro-fractures with fluctuation,its pressure decreases gently and the pressure gradient decreases with the length of the tortuous micro-fracture.The tortuous micro-fractures initiate at multiply points where the fracture curvature is large,and the number and area of crack initiation sites increase with the increase of the crack curvature.The azimuth angle has little effect on the initiation points.For the natural fractures,initiations occur at both tips of the unconsolidated natural cracks and the cement in the cemented natural cracks will first break under the pressure of the main fractures.
引文
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[14]Qu Guanzheng,Qu Zhanqing,Hazlett R D,et al.Geometrical description and permeability calculation about shale tensile micro-fractures[J].Petroleum Exploration and Development,2016,43(1):115-152.曲冠政,曲占庆,Hazlett R D,等.页岩拉张型微裂缝几何特征描述及渗透率计算[J].石油勘探与开发,2016,43(1):115-152.
[15]Long Pengyu,Zhang Jinchuan,Tang Xuan,et al.Feature of muddy shale fissure and its effect for shale gas exploration and development[J].Natural Gas Geoscience,2011,22(3):525-532.龙鹏宇,张金川,唐玄,等.泥页岩裂缝发育特征及其对页岩气勘探和开发的影响[J].天然气地球科学,2011,22(3):525-532.
[16]Song Dangyu,He Kaikai,Ji Xiaofeng,et al.Fine characterization of pore and fractures in coal based on a CT scan[J].Natural Gas Industry,2018,38(3):41-49.宋党育,何凯凯,吉小峰,等.基于CT扫描的煤中孔裂隙精细描述[J].天然气工业,2018,38(3):41-49.
[17]Bars M L,Worster M G.Interfacial conditions between a pureuid and a porous medium:Implications for binary alloy solidification[J].Journal of Fluid Mechanics,2006,550:149-173.
[18]Wang H F.Theory of Linear Poroelasticity With Application to Geomechanics and Hydrogeology[M].USA:Princeton University Press,2000:56-62.
[19]Qu Zhanqing,Li Xiaolong,Li Jianxiong,et al.Crack morphology of multiple radial well fracturing based on extended finite element method[J].Journal of China University of Petroleum:Edition of Natural Science,2018,42(1):73-81.曲占庆,李小龙,李建雄,等.基于扩展有限元法的多径向井压裂裂缝形态[J].中国石油大学学报:自然科学版,2018,42(1):73-81.
[20]Cheng Yuanfang,Chang Xin,Sun Yuanwei,et al.Research on fracture network propagation pattern of shale reservoir based on fracture mechanics[J].Natural Gas Geoscience,2014,25(4):603-611.程远方,常鑫,孙元伟,等.基于断裂力学的页岩储层缝网延伸形态研究[J].天然气地球科学,2014,25(4):603-611.
[21]Zhang Liang,Yao Leihua,Wang Yingdong.3Dgeological modeling method based on COMSOL Multiphysics[J].Coal Geology&Exploration,2014,42(6):14-19.张亮,姚磊华,王迎东.基于COMSOL Multiphysics的三维地质建模方法[J].煤田地质与勘探,2014,42(6):14-19.
[22]Wang Rui,Shen Zhenzhong,Chen Xiaobing.Full coupled analysis of seepage-stress fields for high arch dam based on COM-SOL Multiphysics[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(supplement 2):3197-3204.王瑞,沈振中,陈孝兵.基于COMSOL Multiphysics的高拱坝渗流-应力全耦合分析[J].岩石力学与工程学报,2013,32(增刊2):3197-3204.
[23]Fei Kang,Liu Hanlong,Kong Gangqiang.Implementation of a thermo-bounding surface model in COMSOL[J].Rock and Soil Mechanics,2017,38(6):1819-1826.费康,刘汉龙,孔纲强.热力耦合边界面模型在COMSOL中的开发应用[J].岩石力学,2017,38(6):1819-1826.
[24]Wei Bo,Chen Junbin,Xie Qing,et al.Simulation of hydraulic fracturing crack propagating of horizontal shale well based on extended finite element method[J].Journal of Xi’an Shiyou University:Natural Science Edition,2016,31(2):70-81.魏波,陈军斌,谢青,等.基于扩展有限元的页岩水平井压裂裂缝扩展模拟[J].西安石油大学学报:自然科学版,2016,31(2):70-81.
[25]Abass H H,Van Domelen M L,EI Rabaa W M.Experimental observations of hydraulic fracture propagation through coal blocks[C]∥SPE Eastern Regianal Meeting,Ohio,USA:Society of Petroleum Engineers,2015:239-252.
[26]Takashi A,Shunsuke Y,Isao K,et al.Consideration on shape of hydraulic fracture based on laboratory experiment[C]∥Abu Dhabi International Petroleum Exhibition and Conference,Abu Dhabi:Society of Petroleum Engineers,2015:1-8.
[27]Hisanao O,Shivam A,John T F,et al.Effect of small scale heterogeneity on the growth of hydraulic fractures[C]∥SPEHydraulic Fracturing Technology Confernece and Exhibition,Texas:Society of Petroleum Engineers,2017:1-22.
[2]Economides M J,Martin T.Modern Fracturing-Enhancing Natural Gas Production[M].Houston,TX:Energy Tribune Publishing Inc.,2007:3-5.
[3]Zheng Junwei,Sun Deqiang,Li Xiaoyan,et al.Advance in exploration and exploitation technologies of shale gas[J].Natural Gas Geoscience,2011,22(3):511-516.郑军卫,孙德强,李小燕,等.页岩气勘探开发技术进展[J].天然气地球科学,2011,22(3):511-516.
[4]Warpinski N R,Mayerhofer M J,Vincent M C,et al.Stimulating unconventional reservoirs:Maximizing network growth while optimizing fracture conductivity[C]∥SPE Unconventional Reservoir Conference,Colorado:Society of Petroleum Engineers,2008:1-19.
[5]Weng Dingwei,Lei Qun,Xu Yun,et al.Network fracturing techniques and its application in the field[J].Acta Petrolei Sinica,2011,32(2):280-284.翁定为,雷群,胥云,等.缝网压裂技术及其现场应用[J].石油学报,2011,32(2):280-284.
[6]Feng Yanjun,Kang Hongpu.Hydraulic fracturing initiation and propagation[J].Chinese Journal of Rock Mechanics and Engineering,2013,3(S2):3169-3179.冯彦军,康红普.水力压裂起裂与扩展分析[J].岩石力学与工程学报,2013,3(增刊2):3169-3179.
[7]Li Zhaomin,Cai Wenbin,Zhang Qi,et al.Study on the initiation and propagation laws of the fractures in horizontal well fracturing[J].Journal of Xi’an Shiyou University:Natural Science Edition,2008,23(5):46-48,52.李兆敏,蔡文斌,张琪,等.水平井压裂裂缝起裂及裂缝延伸规律研究[J].西安石油大学学报:自然科学版,2008,23(5):46-48,52.
[8]Guo Tiankui,Zhang Shicheng,Liu Weilai,et al.Initiation pressure of multi-stage fracking for perforated horizontal wells of shale gas reservoirs[J].Natural Gas Industry,2013,33(12):87-93.郭天魁,张士诚,刘卫来,等.页岩储层射孔水平井分段压裂的起裂压力[J].天然气工业,2013,33(12):87-93.
[9]Hossian M M,Rahman M K,Rahman S S.A comprehensive monograph for hydraulic fracture initiation from deviated wellbore under arbitrary stress regimes[C]∥SPE Asia Pacific Oil and Gas Conference and Exhibition,Jakarta:Society of Petroleum Engineers,1999:1-11.
[10]Hossian M M,Rahman M K,Rahman S S.Hydraulic fracture initiation and propagation:Roles of wellbore trajectory,perforation and stress regimes[J].Journal of Petroleum Science and Engineering,2000,27(3/4):129-149.
[11]Wang Lei,Yang Chunhe,Guo Yintong,et al.Investigation on fracture initiation modes of horizontal wells based on laboratory hydraulic fracturing test[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(supplement 2):3624-3632.王磊,杨春和,郭印同,等.基于室内水力压裂试验的水平井起裂模式研究[J].岩石力学与工程学报,2015,34(增刊2):3624-3632.
[12]Guo Yintong,Yang Chunhe,Jia Changgui,et al.Research on hydraulic fracturing physical simulation of shale and fracture characterization method[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(1):52-59.郭印同,杨春和,贾长贵,等.页岩水力压裂物理模拟与裂缝表征方法研究[J].岩石力学与工程学报,2014,33(1):52-59.
[13]Jiang Hu,Liu Shujie,He Baosheng,et al.Experiments of the oriented perforating impact on the multi-fracture pattern of hydraulic fracturing treatment[J].Natural Gas Industry,2014,34(2):66-70.姜浒,刘书杰,何保生,等.定向射孔对水力压裂多裂缝形态的影响实验[J].天然气工业,2014,34(2):66-70.
[14]Qu Guanzheng,Qu Zhanqing,Hazlett R D,et al.Geometrical description and permeability calculation about shale tensile micro-fractures[J].Petroleum Exploration and Development,2016,43(1):115-152.曲冠政,曲占庆,Hazlett R D,等.页岩拉张型微裂缝几何特征描述及渗透率计算[J].石油勘探与开发,2016,43(1):115-152.
[15]Long Pengyu,Zhang Jinchuan,Tang Xuan,et al.Feature of muddy shale fissure and its effect for shale gas exploration and development[J].Natural Gas Geoscience,2011,22(3):525-532.龙鹏宇,张金川,唐玄,等.泥页岩裂缝发育特征及其对页岩气勘探和开发的影响[J].天然气地球科学,2011,22(3):525-532.
[16]Song Dangyu,He Kaikai,Ji Xiaofeng,et al.Fine characterization of pore and fractures in coal based on a CT scan[J].Natural Gas Industry,2018,38(3):41-49.宋党育,何凯凯,吉小峰,等.基于CT扫描的煤中孔裂隙精细描述[J].天然气工业,2018,38(3):41-49.
[17]Bars M L,Worster M G.Interfacial conditions between a pureuid and a porous medium:Implications for binary alloy solidification[J].Journal of Fluid Mechanics,2006,550:149-173.
[18]Wang H F.Theory of Linear Poroelasticity With Application to Geomechanics and Hydrogeology[M].USA:Princeton University Press,2000:56-62.
[19]Qu Zhanqing,Li Xiaolong,Li Jianxiong,et al.Crack morphology of multiple radial well fracturing based on extended finite element method[J].Journal of China University of Petroleum:Edition of Natural Science,2018,42(1):73-81.曲占庆,李小龙,李建雄,等.基于扩展有限元法的多径向井压裂裂缝形态[J].中国石油大学学报:自然科学版,2018,42(1):73-81.
[20]Cheng Yuanfang,Chang Xin,Sun Yuanwei,et al.Research on fracture network propagation pattern of shale reservoir based on fracture mechanics[J].Natural Gas Geoscience,2014,25(4):603-611.程远方,常鑫,孙元伟,等.基于断裂力学的页岩储层缝网延伸形态研究[J].天然气地球科学,2014,25(4):603-611.
[21]Zhang Liang,Yao Leihua,Wang Yingdong.3Dgeological modeling method based on COMSOL Multiphysics[J].Coal Geology&Exploration,2014,42(6):14-19.张亮,姚磊华,王迎东.基于COMSOL Multiphysics的三维地质建模方法[J].煤田地质与勘探,2014,42(6):14-19.
[22]Wang Rui,Shen Zhenzhong,Chen Xiaobing.Full coupled analysis of seepage-stress fields for high arch dam based on COM-SOL Multiphysics[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(supplement 2):3197-3204.王瑞,沈振中,陈孝兵.基于COMSOL Multiphysics的高拱坝渗流-应力全耦合分析[J].岩石力学与工程学报,2013,32(增刊2):3197-3204.
[23]Fei Kang,Liu Hanlong,Kong Gangqiang.Implementation of a thermo-bounding surface model in COMSOL[J].Rock and Soil Mechanics,2017,38(6):1819-1826.费康,刘汉龙,孔纲强.热力耦合边界面模型在COMSOL中的开发应用[J].岩石力学,2017,38(6):1819-1826.
[24]Wei Bo,Chen Junbin,Xie Qing,et al.Simulation of hydraulic fracturing crack propagating of horizontal shale well based on extended finite element method[J].Journal of Xi’an Shiyou University:Natural Science Edition,2016,31(2):70-81.魏波,陈军斌,谢青,等.基于扩展有限元的页岩水平井压裂裂缝扩展模拟[J].西安石油大学学报:自然科学版,2016,31(2):70-81.
[25]Abass H H,Van Domelen M L,EI Rabaa W M.Experimental observations of hydraulic fracture propagation through coal blocks[C]∥SPE Eastern Regianal Meeting,Ohio,USA:Society of Petroleum Engineers,2015:239-252.
[26]Takashi A,Shunsuke Y,Isao K,et al.Consideration on shape of hydraulic fracture based on laboratory experiment[C]∥Abu Dhabi International Petroleum Exhibition and Conference,Abu Dhabi:Society of Petroleum Engineers,2015:1-8.
[27]Hisanao O,Shivam A,John T F,et al.Effect of small scale heterogeneity on the growth of hydraulic fractures[C]∥SPEHydraulic Fracturing Technology Confernece and Exhibition,Texas:Society of Petroleum Engineers,2017:1-22.
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