深层页岩在高水平应力差作用下压裂裂缝形态实验研究
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摘要
针对高水平地应力差下的深层页岩开展真三轴水力压裂物模实验,分析其裂缝形态和影响因素。实验结果表明:高水平地应力差下水力裂缝沿垂直最小主应力方向起裂并扩展成横切缝,受层理和天然裂缝的影响会发生穿透、沟通或转向行为,深层页岩裂缝形态可以分为4种:单一横切缝、伴随层理开启的多横切缝网,转向缝网和受天然裂缝影响的复杂缝网;水平地应力差的增大会增加水力裂缝的穿透能力;起裂压力越大,裂缝形态越复杂;先注入高黏度压裂液可以形成水平主缝,之后注入低黏度压裂液造分支缝,可以有效提升深层页岩改造体积。该实验结果可以为深层页岩压裂方案设计提供参考。
A series of hydraulic experiments are conducted to investigate the morphology of fractures in deep shale under high difference of horizontal in-situ stresses using a triaxial fracturing system. The results indicate that the hydraulic fractures always crack in the direction perpendicular to the minor principal stress,and extend,penetrate,connect or deflect when encounter the bedding planes and natural fractures. The fracture morphology have four categories:simple fracture,fractures with bedding planes opening,fractures with deflection and complex fractures affected by natural fractures. The increasing of horizontal stress difference leads to a higher penetrating ability of fractures. The higher the initial pressure,the more complex the fracture morphology. Stimulated reservoir volume can be improved by injecting the high viscosity fracturing fluid to generate the main fractures and by injecting the low viscosity fluid to open the branching fractures.
A series of hydraulic experiments are conducted to investigate the morphology of fractures in deep shale under high difference of horizontal in-situ stresses using a triaxial fracturing system. The results indicate that the hydraulic fractures always crack in the direction perpendicular to the minor principal stress,and extend,penetrate,connect or deflect when encounter the bedding planes and natural fractures. The fracture morphology have four categories:simple fracture,fractures with bedding planes opening,fractures with deflection and complex fractures affected by natural fractures. The increasing of horizontal stress difference leads to a higher penetrating ability of fractures. The higher the initial pressure,the more complex the fracture morphology. Stimulated reservoir volume can be improved by injecting the high viscosity fracturing fluid to generate the main fractures and by injecting the low viscosity fluid to open the branching fractures.
引文
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[19]陈勉,庞飞,金衍.大尺寸真三轴水力压裂模拟与分析[J].岩石力学与工程学报,2000,19(增1):868–872.(CHEN Mian,PANG Fei,JIN Yan.Experiments and analysis on hydraulic fracturing by a large-size triaxial simulator[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(Supp.1):868–872.(in Chinese))
[20]侯冰,陈勉,李志猛,等.页岩储集层水力裂缝网络扩展规模评价方法[J].石油勘探与开发,2014,41(6):833–838.(HOU Bing,CHEN Mian,LI Zhimeng,et al.Propagation area evaluation of hydraulic fracture networks in shale gas reservoirs[J].Petroleum Exploration and Development,2014,41(6):833–838.(in Chinese))
[2]王鹏,纪友亮,潘仁芳,等.页岩脆性的综合评价方法——以四川盆地W区下志留统龙马溪组为例[J].天然气工业,2013,33(12):48–53.(WANG Peng,JI Youliang,PAN Renfang,et al.A comprehensive evaluation methodology of shale brittleness:A case study from the Lower Silurian Longmaxi Fm in Block W,Sichuan Basin[J].Natural Gas Industry,2013,33(12):48–53.(in Chinese))
[3]HU B,DIAO C,LI D D.An experimental investigation of geomechanical properties of deep tight gas reservoirs[J].Journal of Natural Gas Science and Engineering,2017,47:22–33.
[4]WARPINSKI N R,TEUFEL L W.Influence of geologic discontinuities on hydraulic fracture propagation[J].Journal of Petroleum Technology(United States),1984,39(2):209–220.
[5]BLANTON T L.An experimental study of interaction between hydraulically induced and pre-existing fractures[C]//Proceedings of SPE Unconventional Gas Recovery Symposium.Pittsburgh,Pennsylvania:Society of Petroleum Engineers,1982,https://doi.org/10.2118/10847-MS.
[6]ZHOU J,CHEN M,JIN Y,et al.Analysis of fracture propagation behavior and fracture geometry using a tri-axial fracturing system in naturally fractured reservoirs[J].International Journal of Rock Mechanics and Mining Sciences,2008,45(7):1 143–1 152.
[7]程万,金衍,陈勉,等.三维空间中非连续面对水力压裂影响的试验研究[J].岩土工程学报,2015,37(3):559–563.(CHENG Wan,JIN Yan,CHEN Mian,et al.Experimental investigation on influence of discontinuities on hydraulic fracture propagation in three-dimensional space[J].Chinese Journal of Geotechnical Engineering,2015,37(3):559–563.(in Chinese))
[8]侯冰,程万,陈勉,等.裂缝性页岩储层水力裂缝非平面扩展实验[J].天然气工业,2014,34(12):81–86.(HOU Bing,CHENG Wan,CHEN Mian,et al.Experiments on the non-planar extension of hydraulic fractures in fractured shale gas reservoirs[J].Natural Gas Industry,2014,34(12):81–86.(in Chinese))
[9]衡帅,杨春和,曾义金,等.页岩水力压裂裂缝形态的试验研究[J].岩土工程学报,2014,36(7):1 243–1 251.(HENG Shuai,YANG Chunhe,ZENG Yijin,et al.Experimental study on hydraulic fracture geometry of shale[J].Chinese Journal of Geotechnical Engineering,2014,36(7):1 243–1 251.(in Chinese))
[10]侯冰,谭鹏,陈勉,等.致密灰岩储层压裂裂缝扩展形态试验研究[J].岩土工程学报,2016,38(2):219–225.(HOU Bing,TAN Peng,CHEN Mian,et al.Experimental investigation on propagation geometry of hydraulic fracture in compact limestone reservoirs[J].Chinese Journal of Geotechnical Engineering,2016,38(2):219–225.(in Chinese))
[11]BLAIR S C,THORPE R K,HEUZE F E,et al.Laboratory observations of the effect of geological discontinuities on hydrofracture propagation[C]//Proceedings of the 30th US Symposium on Rock Mechanics.Morgantown,West Virginia:ARMA,1989:443–450.
[12]POTLURI N K,ZHU D,HILL A D.The effect of natural fractures on hydraulic fracture propagation[M].Sheveningen,The Netherlands:Society of Petroleum Engineers,2005:189–194.
[13]程万,金衍,陈勉,等.三维空间中水力裂缝穿透天然裂缝的判别准则[J].石油勘探与开发,2014,41(3):371–376.(CHENG Wan,JIN Yan,CHEN Mian,et al.A criterion for identifying hydraulic fractures crossing natural fractures in 3D space[J].Petroleum Exploration and Development,2014,41(3):371–376.(in Chinese))
[14]陈勉.页岩气储层水力裂缝转向扩展机制[J].中国石油大学学报:自然科学版,2013,37(5):88–94.(CHEN Mian.Re-orientation and propagation of hydraulic fractures in shale gas reservoir[J].Journal of China University of Petroleum,2013,37(5):88–94.(in Chinese))
[15]侯冰,陈勉,张保卫,等.裂缝性页岩储层多级水力裂缝扩展规律研究[J].岩土工程学报,2015,37(6):1 041–1 046.(HOU Bing,CHEN Mian,ZHANG Baowei,et al.Propagation of multiple hydraulic fractures in fractured shale reservoir[J].Chinese Journal of Geotechnical Engineering,2015,37(6):1 041–1 046.(in Chinese))
[16]赵金洲,任岚,胡永全.页岩储层压裂缝成网延伸的受控因素分析[J].西南石油大学学报:自然科学版,2013,35(1):1–9.(ZHAO Jinzhou,REN Lan,HU Yongquan.Controlling factors of hydraulic fractures extending into network in shale formations[J].Journal of Southwest Petroleum University:Science and Technology,2013,35(1):1–9.(in Chinese))
[17]MAYERHOFER M J,LOLON E P,YOUNGBLOOD J E,et al.Integration of microseismic fracture mapping results with numerical fracture network production modeling in the barnett shale[C]//Proceedings of SPE Annual Technical Conference and Exhibition.San Antonio,Texas,USA:Society of Petroleum Engineers,2006:24–27.
[18]RICKMAN R,MULLEN M,PETER E,et al.A practical use of shale petrophysics for simulation design optimization:all shale plays are not clones of the Barnett shale[C]//Proceedings of SPE Annual Technical Conference and Exhibition.Denver,Colorado,USA:Society of Petroleum Engineers,2008:21–24.
[19]陈勉,庞飞,金衍.大尺寸真三轴水力压裂模拟与分析[J].岩石力学与工程学报,2000,19(增1):868–872.(CHEN Mian,PANG Fei,JIN Yan.Experiments and analysis on hydraulic fracturing by a large-size triaxial simulator[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(Supp.1):868–872.(in Chinese))
[20]侯冰,陈勉,李志猛,等.页岩储集层水力裂缝网络扩展规模评价方法[J].石油勘探与开发,2014,41(6):833–838.(HOU Bing,CHEN Mian,LI Zhimeng,et al.Propagation area evaluation of hydraulic fracture networks in shale gas reservoirs[J].Petroleum Exploration and Development,2014,41(6):833–838.(in Chinese))