高能复合射孔爆生气体作用下预存裂缝起裂扩展研究
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摘要
在高能复合射孔压裂过程中,受爆生气体流动速度、裂缝表面粗糙度、裂缝周围渗透性等因素的影响,裂缝内压力梯度随时间而变化。气体压力分布影响裂缝尖端应力强度,因而不能用传统的破裂压力来判断裂缝起裂扩展。通过设定与时间相关的气体压力分布函数,推导高地应力约束条件下预存裂缝尖端应力强度,得到了井壁岩层起裂扩展条件,该条件可以反映裂缝内爆生气体压力梯度随时间变化的特性。从相应的算例分析,井眼内气体升压越缓,起裂压力和止裂压力越低,且使止裂时间越推后,能得到较长的岩层裂缝长度。图4表1参10
In a high energy combined perforation,the pressure gradient of detonation gas along cracks varies with time due to the influences of flow velocity,crack surface roughness and media permeability.Since the pressure gradient affects stress strength of crack top,it is unsuitable to judge crack initiation by the traditional breakdown pressure.A function describing gas pressure distribution along the crack is proposed to derive the corresponding stress strength of crack top,and then the conditions of crack initiation in borehole rocks are concluded.The conditions reflect that gas pressure gradient varies with time.The example analysis reveals that slower borehole pressurization gives rise to lower crack initiation and arrest pressure,greater extension of crack arrest time,and longer cracks in the formation.
In a high energy combined perforation,the pressure gradient of detonation gas along cracks varies with time due to the influences of flow velocity,crack surface roughness and media permeability.Since the pressure gradient affects stress strength of crack top,it is unsuitable to judge crack initiation by the traditional breakdown pressure.A function describing gas pressure distribution along the crack is proposed to derive the corresponding stress strength of crack top,and then the conditions of crack initiation in borehole rocks are concluded.The conditions reflect that gas pressure gradient varies with time.The example analysis reveals that slower borehole pressurization gives rise to lower crack initiation and arrest pressure,greater extension of crack arrest time,and longer cracks in the formation.
引文
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[10]李宁,Swoboda G.爆破荷载的数值模拟与应用[J].岩石力学与工程学报,1994,13:357-364.(LI Ning,Swoboda G.A numerical modelfor blast load and its application[J].Chinese Journal of RockMechanics and Engineering,1994,13:357-364.)
[2]叶显军,张惠生,田国理.液体火药高能气体压裂技术研究和在深层油气藏中的应用[J].石油勘探与开发,2000,27(3):67-69.(YE Xian-jun,ZHANG Hui-sheng,TIAN Guo-li.The highenergy gas fracturing technique of liquid explosive and itsapplication in deep-seated oil and gas reservoir[J].PetroleumExploration and Development,2000,27(3):67-69.)
[3]毕研斌,石红萍.油井压裂效果分析方法[J].石油勘探与开发,1998,25(4):72-75.(BI Yan-bin,SHI Hong-ping.Analyticalapproach of fracturing effectiveness in oil wells[J].PetroleumExploration and Development,1998,25(4):72-75.)
[4]李传亮.射孔完井条件的岩石破裂压力计算公式[J].石油钻采工艺,2002,24(2):37-38.(LI Chuan-liang.Calculation formula ofrock fracture pressure in perforation well completion[J].Petroleum Drilling and Production,2002,24(2):37-38.)
[5]曹言光,刘长松,林平,等.应用断裂力学理论建立油气井压裂时岩石破裂压力计算模型[J].西安石油学院学报(自然科学版),2003,18(4):36-39.(CAO Yan-guang,LIU Chang-song,LINPing,et al.Establishing the models for calculating the fracturingpressure of formation rock during oil/gas wells fracturing byusing fracture mechanics theory[J].Journal of Xi’an PetroleumInstitute(Natural Science Edition),2003,18(4):36-39.)
[6]阿特金森B K.岩石断裂力学[M].尹祥础,修济刚(译).北京:地震出版社,1992.(Atkinson B K.Fracture mechanics of rock[M].YIN Xiang-chu,XIU Ji-gang(Trans.).Beijing:Seismological Press,1992.)
[7]刘建中,王秀娟,孙玉玲,等.人工压裂形成多裂缝的可能性研究[J].石油勘探与开发,2002,29(3):103-106.(LIU Jian-zhong,WANG Xiu-juan,SUN Yu-ling,et al.Possibility study on multi-fracture creation during artificial hydraulic fracturing[J].PetroleumExploration and Development,2002,29(3):103-106.)
[8]赵永胜,王秀娟,兰玉波,等.关于压裂裂缝形态模型的讨论[J].石油勘探与开发,2001,28(6):97-98.(ZHAO Yong-sheng,WANG Xiu-juan,LAN Yu-bo,et al.Discussion on the model ofinduced fracture geometry[J].Petroleum Exploration andDevelopment,2001,28(6):97-98.)
[9]Nilson R H,Proffer W J,Duff R E.Modeling of gas-driven fracturesinduced by propellant combustion within a borehole[J].Int.J.Rock.Mech.Min.Sci.&Geomech.,1985,22(1):3-19.
[10]李宁,Swoboda G.爆破荷载的数值模拟与应用[J].岩石力学与工程学报,1994,13:357-364.(LI Ning,Swoboda G.A numerical modelfor blast load and its application[J].Chinese Journal of RockMechanics and Engineering,1994,13:357-364.)
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