岩体水力劈裂非稳定渗流影响机制初探
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摘要
水力劈裂是石油开采、土石坝安全控制、原位地应力测试、隧洞突涌水防治等中的常见突出问题。首先,构建一维非稳定渗流模型,推导其解析解,并将水力劈裂关键因素水压力、水力梯度随时间的变化规律与有限元模拟结果进行对比,从而证明该理论解的正确性。其次,非稳定渗流结果与稳定渗流对比表明,在非稳定渗流状态下水压突增时刻,靠进水口处水力梯度最大,而趋于稳定状态时,水力梯度逐渐减小并最终达到稳定。同时,渗透性越小,高水力梯度作用时间越长,岩体发生水力劈裂的危险性越大。因此,采用非稳定渗流研究岩体水力劈裂作用机制是十分必要的。
Hydraulic fracturing is a frequent problem in petroleum extraction,dam safety monitoring,in-situ geostress testing,tunnel-groundwater inrush prevention,etc.Firstly,a one-dimensional model considering unsteady seepage is established and its analytical solutions are derived.Comparing the calculated key factors(water pressure and hydraulic gradient) of hydraulic fracturing with the simulated result by finite element method,accuracy of these theoretical solutions is proved.Secondly,in terms of comparison with the result only considering steady status,it is presented that hydraulic gradient gets maximum as soon as water pressure increases in unsteady process.By contrast,hydraulic gradient gradually decreases and tends to be stable when reaching steady seepage status.Finally,the effect of rock permeability on hydraulic fracturing is also studied.The probability that hydraulic fracturing happens grows higher while the permeability is lower.In summary,it is essential to consider unsteady seepage status in mechanism study of hydraulic fracturing.
Hydraulic fracturing is a frequent problem in petroleum extraction,dam safety monitoring,in-situ geostress testing,tunnel-groundwater inrush prevention,etc.Firstly,a one-dimensional model considering unsteady seepage is established and its analytical solutions are derived.Comparing the calculated key factors(water pressure and hydraulic gradient) of hydraulic fracturing with the simulated result by finite element method,accuracy of these theoretical solutions is proved.Secondly,in terms of comparison with the result only considering steady status,it is presented that hydraulic gradient gets maximum as soon as water pressure increases in unsteady process.By contrast,hydraulic gradient gradually decreases and tends to be stable when reaching steady seepage status.Finally,the effect of rock permeability on hydraulic fracturing is also studied.The probability that hydraulic fracturing happens grows higher while the permeability is lower.In summary,it is essential to consider unsteady seepage status in mechanism study of hydraulic fracturing.
引文
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[13]黄润秋,王贤能,陈龙生.深埋隧道涌水过程的水力劈裂作用分析[J].岩石力学与工程学报,2000,19(5):573-576.(HUANGRunqiu,WANG Xianneng,CHEN Longsheng.Study on the effect ofhydraulic fracturing during water gushing in deep tunnel[J].ChineseJournal of Rock Mechanics and Engineering,2000,19(5):573-576.(in Chinese))
[14]李宗利,任青文.自然营造力作用下岩体混凝土水力劈裂分析与探讨[J].岩土力学,2008,29(8):2121-2125.(LI Zongli,RENQingwen.Analysis and discussion on rock and concrete materialhydraulic fracturing under natural power[J].Rock and Soil Mechanics,2008,29(8):2 121-2 125.(in Chinese))
[15]李宗利,张宏朝,任青文,等.岩石裂纹水力劈裂分析与临界水压计算[J].岩土力学,2005,26(8):1216-1220.(LI Zongli,ZHANGHongchao,REN Qingwen,et al.Analysis of hydraulic fracturing andcalculation of critical internal water pressure of rock fracture[J].Rockand Soil Mechanics,2005,26(8):1 216-1 220.(in Chinese))
[2]葛洪魁,林英松,王顺昌.水力压裂地应力测量有关技术问题的讨论[J].石油钻采工艺,1998,20(6):53-62.(GE Hongkui,LINYingsong,WANG Shunchang.Discussion of technical problems onhydraulic fracturing geostress measurements[J].Oil Drilling andProduction Technology,1998,20(6):53-62.(in Chinese))
[3]MORGENSTERN V,MORGENSTERN N R,VAUGHAN P R.Some observation on allowable grouting pressures[C]//Proceedings ofGrouts and Drill Conference.London:Institute of Civil Engineering,1963:36-42.
[4]WONG H Y,FARMER I W.Hydro-fracture mechanisms in rockduring pressure grouting[J].Rock Mechanics and Rock Engineering,1973,5(1):21-41.
[5]陈愈炯.土坝坝体的防渗灌浆[J].水利水电技术,1980,(2):1-7.(CHEN Yujiong.Grouting seepage control of dam[J].Water Resourcesand Hydropower Technologies,1980,(2):1-7.(in Chinese))
[6]JULIAN B R,FOULGER G R,MONASTERO F C,et al.Imaginghydraulic fractures in a geothermal reservoir[J].Geophysical ResearchLetters,2010,37(7):1-5.
[7]HUBBERT M K,WILLIS D G.Mechanics of hydraulic fracturing[J].Petroleum Transactions AIME,1957,210(1):153-168.
[8]NOBARI E S,LEE K L,DUNCAN J M.Hydraulic fracturing inzoned earth and rockfill dams[R].Berkley,California:University ofCalifornia,1973.
[9]丁金栗,孙亚平.水力劈裂试验中击实土厚壁筒应力分析[J].水利学报,1987,(3):16-22.(DING Jinli,SUN Yaping.Analysis ofstress of thick wall cylinder of compacted soil in hydraulic fracturingexperiment[J].Journal of Hydraulic Engineering,1987,(3):16-22.(in Chinese))
[10]阳友奎,肖长富,吴刚,等.不同地应力状态下水力压裂的破裂模式[J].重庆大学学报:自然科学版,1993,16(3):30-35.(YANGYoukui,XIAO Changfu,WU Gang,et al.Hydrofracturing breakdownmodes under different in-situ stress states[J].Journal of ChongqingUniversity:Natural Science,1993,16(3):30-35.(in Chinese))
[11]詹美礼,岑建.岩体水力劈裂机制圆筒模型试验及解析理论研究[J].岩石力学与工程学报,2007,26(6):1173-1181.(ZHANMeili,CEN Jian.Experimental and analytical study of hydraulicfracturing of cylinder sample[J].Chinese Journal of Rock Mechanicsand Engineering,2007,26(6):1 173-1 181.(in Chinese))
[12]阳友奎,肖长富,邱贤德,等.水力压裂裂缝形态与缝内压力分布[J].重庆大学学报:自然科学版,1995,19(3):20-26.(YANG Youkui,XIAO Changfu,QIU Xiande,et al.Fracture geometry and pressuredistribution in fracture for hydrofracturing[J].Journal of ChongqingUniversity:Natural Science,1995,19(3):20-26.(in Chinese))
[13]黄润秋,王贤能,陈龙生.深埋隧道涌水过程的水力劈裂作用分析[J].岩石力学与工程学报,2000,19(5):573-576.(HUANGRunqiu,WANG Xianneng,CHEN Longsheng.Study on the effect ofhydraulic fracturing during water gushing in deep tunnel[J].ChineseJournal of Rock Mechanics and Engineering,2000,19(5):573-576.(in Chinese))
[14]李宗利,任青文.自然营造力作用下岩体混凝土水力劈裂分析与探讨[J].岩土力学,2008,29(8):2121-2125.(LI Zongli,RENQingwen.Analysis and discussion on rock and concrete materialhydraulic fracturing under natural power[J].Rock and Soil Mechanics,2008,29(8):2 121-2 125.(in Chinese))
[15]李宗利,张宏朝,任青文,等.岩石裂纹水力劈裂分析与临界水压计算[J].岩土力学,2005,26(8):1216-1220.(LI Zongli,ZHANGHongchao,REN Qingwen,et al.Analysis of hydraulic fracturing andcalculation of critical internal water pressure of rock fracture[J].Rockand Soil Mechanics,2005,26(8):1 216-1 220.(in Chinese))
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