考虑天然裂缝成簇分布的压裂液滤失研究
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摘要
对于天然裂缝发育的储层,压裂过程中压裂液的滤失对水力裂缝尺寸、支撑剂分布以及地层污染情况都有着较大影响。目前考虑天然裂缝影响的压裂液滤失模型,都忽略了天然裂缝成簇分布的特征,从而导致模型存在局限性。通过倍增串级方法建立了二维分形离散裂缝网络模型,合理地表征了天然裂缝成簇分布的特征;通过对裂缝孔隙介质网格单元进行剖分,将裂缝网络转化为各向异性的等效连续介质模型;最后建立了基于渗透率张量的裂缝性储层压裂液滤失模型。计算结果表明:天然裂缝发育带的走向在宏观上决定了压裂液的滤失方向和压力波的传播方向;压裂液会沿着长裂缝进行滤失,建议压裂施工时应提前对水力裂缝壁面的天然裂缝进行封堵;压裂液黏度对滤失速度也有一定的影响。
The fracturing fluid leak-off in the reservoirs with developed natural fractures had a comparatively great influence on hydraulic fracture structure,proppant distribution and formation contamination.However,the current mathematical model for fracturing fluid leak-off considering natural fractures almost ignored or simplified the clustered distributed natural fractures,which limited the applications of these models.So firstly,by the multiplicative cascade method,we established a two-dimensional fractal discrete fracture networks model which reasonably showed the clustered distribution of natural fractures.Then,the established fracture networks were transformed into homogeneous anisotropic equivalent continuum media through subdividing the fractured porous domain into small elements.Ultimately,a mathematical model of fracturing fluid leak-off in fractured reservoir was established based on the permeability tensor.The results showed that the the strike of fracture rich zone determined the direction of fracturing fluid leak-off and pressure propagation.As the fracturing fluid tended to filtrate along long fractures,it was suggested to seal the natural fractures near hydraulic fractures before fracturing treatments.Moreover,fracturing fluid viscosity had certain influence on leak-off velocity.
The fracturing fluid leak-off in the reservoirs with developed natural fractures had a comparatively great influence on hydraulic fracture structure,proppant distribution and formation contamination.However,the current mathematical model for fracturing fluid leak-off considering natural fractures almost ignored or simplified the clustered distributed natural fractures,which limited the applications of these models.So firstly,by the multiplicative cascade method,we established a two-dimensional fractal discrete fracture networks model which reasonably showed the clustered distribution of natural fractures.Then,the established fracture networks were transformed into homogeneous anisotropic equivalent continuum media through subdividing the fractured porous domain into small elements.Ultimately,a mathematical model of fracturing fluid leak-off in fractured reservoir was established based on the permeability tensor.The results showed that the the strike of fracture rich zone determined the direction of fracturing fluid leak-off and pressure propagation.As the fracturing fluid tended to filtrate along long fractures,it was suggested to seal the natural fractures near hydraulic fractures before fracturing treatments.Moreover,fracturing fluid viscosity had certain influence on leak-off velocity.
引文
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[3]Nagel N B,Sanchez-Nagel M A,Zhang F,et al.Coupled numerical evaluations of the geomechanical interactions between a hydraulic fracture stimulation and a natural fracture system in shale formations[J].Rock Mechanics and Rock Engineering,2013,46(3):581-609.
[4]夏富国,郭建春,刘立宏,等.天然裂缝压裂液滤失模型[J].油气地质与采收率,2013,20(4):105-110.
[5]李勇明,刘鹏,赵金洲,等.基于有限元裂缝网络的压裂液滤失模拟[J].石油天然气学报,2014,36(9):132-136.
[6]Guo Jianchun,Liu Yuxuan.Opening of natural fracture and its effect on leak off behavior in fractured gas reservoirs[J].Journal of Natural Gas Science and Engineering,2014,18:324-328.
[7]赵立强,任登峰,罗志锋,等.天然裂缝性储层压裂液滤失研究[J].西南石油大学学报(自然科学版),2014,36(4):142-148.
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[13]Anthony Raphael Lamb,Gerard Gorman,Olivier R Gosselin,et al.Coupled deformation and fluid flow in fractured porous media using dual permeability and explicitly defined fracture geometry[C]//paper SPE-131725-MS presented at the SPE EU-ROPEC/EAGE Annual Conference and Exhibition,14-17 June2010,Barcelona,Spain.
[14]卢波,葛修润,朱冬林,等.节理岩体表征单元体的分形几何研究[J].岩石力学与工程学报,2005,24(8):1355-1361.
[15]朱冬林.节理岩体的REV及变形与强度数值估算[D].武汉:中国科学院武汉岩土力学研究所,2003.
[16]庞作会.基于节理网络模型的岩体REV数值估算与无网格伽辽金法(EFGM)[J].岩石力学与工程学报,1999,18(3),195-120.
[2]Barree R D,Mukherjee H.Determination of pressure dependent leakoff and its effect on fracture geometry[C]//paper SPE-36424-MS presented at the SPE Annual Technical Conference and Exhibition,6-9 October 1996,Denver,Colorado,USA.
[3]Nagel N B,Sanchez-Nagel M A,Zhang F,et al.Coupled numerical evaluations of the geomechanical interactions between a hydraulic fracture stimulation and a natural fracture system in shale formations[J].Rock Mechanics and Rock Engineering,2013,46(3):581-609.
[4]夏富国,郭建春,刘立宏,等.天然裂缝压裂液滤失模型[J].油气地质与采收率,2013,20(4):105-110.
[5]李勇明,刘鹏,赵金洲,等.基于有限元裂缝网络的压裂液滤失模拟[J].石油天然气学报,2014,36(9):132-136.
[6]Guo Jianchun,Liu Yuxuan.Opening of natural fracture and its effect on leak off behavior in fractured gas reservoirs[J].Journal of Natural Gas Science and Engineering,2014,18:324-328.
[7]赵立强,任登峰,罗志锋,等.天然裂缝性储层压裂液滤失研究[J].西南石油大学学报(自然科学版),2014,36(4):142-148.
[8]Villaescusa E.Statistical modelling of rock jointing[C]//presented at the Proceedings of the Conference on Probabilistic Methods in Geotechnical Engineering,10-12 February 1993,Canberra,Australia.
[9]Odling N E.Network properties of a two-dimensional natural fracture pattern[J].Pure&Applied Geophysics,1992,138(1):95-114.
[10]Darcel C,Bour O,Davy P,de Dreuzy J R.Connectivity properties of two-dimensional fracture networks with stochastic fractal correlation[J].Water Resources Research,2003,39(10):1272.
[11]Schertzer D,Lovejoy S.Physical modeling and analysis of rain and clouds by anisotropic scaling multiplicative processes[J].Journal of Geophysical Research,1987,92(D8):9693-9714.
[12]Bour O,Davy P,Darcel C,et al.A statistical scaling model for fracture network geometry,with validation on a multiscale mapping of a joint network(Hornelen Basin,Norway)[J].Journal of Geophysical Research Solid Earth,2002,107(B6):ETG 4-1-ETG 4-12.
[13]Anthony Raphael Lamb,Gerard Gorman,Olivier R Gosselin,et al.Coupled deformation and fluid flow in fractured porous media using dual permeability and explicitly defined fracture geometry[C]//paper SPE-131725-MS presented at the SPE EU-ROPEC/EAGE Annual Conference and Exhibition,14-17 June2010,Barcelona,Spain.
[14]卢波,葛修润,朱冬林,等.节理岩体表征单元体的分形几何研究[J].岩石力学与工程学报,2005,24(8):1355-1361.
[15]朱冬林.节理岩体的REV及变形与强度数值估算[D].武汉:中国科学院武汉岩土力学研究所,2003.
[16]庞作会.基于节理网络模型的岩体REV数值估算与无网格伽辽金法(EFGM)[J].岩石力学与工程学报,1999,18(3),195-120.