2种方法优选确定易县紫荆关最大水平主应力量值
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摘要
钻杆式水压致裂原地应力测试系统的柔性严重影响最大水平主应力的计算精度,如何提高深孔水压致裂测试精度是这一领域的热点和难点。为准确确定河北易县紫荆关断裂附近孔深达600 m的ZJGTEST-ZK 10钻孔原地应力状态,采用现场测试曲线和室内抗拉强度试验共同对研究区最大水平主应力量值进行比选确定。利用钻孔所揭露岩芯开展巴西圆盘劈裂、空心岩柱液压致裂以及双圆环直接拉伸3种室内试验确定该区域花岗岩的抗拉强度,测定值范围为6.42～9.35 MPa。现场水压致裂测试抗拉强度均值为8.01 MPa,与室内试验结果具有可比性。研究结果确定了该区最大水平主应力为17.70～35.38 MPa,最小水平主应力为10.36～19.38 MPa,垂直主应力为5.82～15.49MPa,地应力状态有利于逆断层活动,应力场状态稳定且最大水平主应力方向为北东向,范围为NE40°～56°。通过测试结果的对比分析,当测试段深度大于440 m时,测试系统柔性的影响作用明显,基于室内试验测定岩石抗拉强度而计算的最大水平主应力量值明显大于基于重张压力计算值,且更能反映区域真实地应力状态。
The compliance of a drilling-rod hydraulic fracturing test system has severe impacts on the calculation precision of the maximum horizontal principal stresses. How to improve the accuracy of deep hole hydraulic fracturing test has always been a hot topic and tough task in this field. In order to determine the in-situ stress state in a borehole of ZJGTEST-ZK 10 of 600 m deep,close to the Zijingguan fault in the Yi County,Hebei Province,Brazilian disk tests,hollow cylinder hydro-fracturing test,and concentric annular core tension test were conducted so as to determine the tensile strength of rock cores,and the tensile strength of granite cores ranges from 6.42 MPa to 9.35 MPa. The average tensile strength determined by the in-situ hydraulic fracturing test was 8.01 MPa,which was consistent with those determined by the above three laboratory tests. Based on the ten successful in-situ hydraulic fracturing tests and three laboratory tests,final determined maximum horizontal principal stresses range from 17.70 MPa to 35.38 MPa,the measured minimum horizontal principal stresses range from 10.36 MPa to 19.38 MPa,and the estimated vertical principal stresses range from 5.82 MPa to 15.49 MPa,the orientation of the maximum horizontal principal stress is NE,and ranges from NE40° to NE56°. The stress state is stable,and favorable for thrust faulting. By comparing the maximum horizontal principal stress magnitudes based on different tensile strengths and reopening pressures,the maximum horizontal principal stresses based on tensile strengths are markedly greater than those based on reopening pressures due to the negative impacts from the test system compliance when the test interval is deeper than 440 m. For the deeper test intervals,the maximum horizontal principal stresses based on tensile strengths indicate true in-situ stress state.
The compliance of a drilling-rod hydraulic fracturing test system has severe impacts on the calculation precision of the maximum horizontal principal stresses. How to improve the accuracy of deep hole hydraulic fracturing test has always been a hot topic and tough task in this field. In order to determine the in-situ stress state in a borehole of ZJGTEST-ZK 10 of 600 m deep,close to the Zijingguan fault in the Yi County,Hebei Province,Brazilian disk tests,hollow cylinder hydro-fracturing test,and concentric annular core tension test were conducted so as to determine the tensile strength of rock cores,and the tensile strength of granite cores ranges from 6.42 MPa to 9.35 MPa. The average tensile strength determined by the in-situ hydraulic fracturing test was 8.01 MPa,which was consistent with those determined by the above three laboratory tests. Based on the ten successful in-situ hydraulic fracturing tests and three laboratory tests,final determined maximum horizontal principal stresses range from 17.70 MPa to 35.38 MPa,the measured minimum horizontal principal stresses range from 10.36 MPa to 19.38 MPa,and the estimated vertical principal stresses range from 5.82 MPa to 15.49 MPa,the orientation of the maximum horizontal principal stress is NE,and ranges from NE40° to NE56°. The stress state is stable,and favorable for thrust faulting. By comparing the maximum horizontal principal stress magnitudes based on different tensile strengths and reopening pressures,the maximum horizontal principal stresses based on tensile strengths are markedly greater than those based on reopening pressures due to the negative impacts from the test system compliance when the test interval is deeper than 440 m. For the deeper test intervals,the maximum horizontal principal stresses based on tensile strengths indicate true in-situ stress state.
引文
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[18]LI D,WONG L N Y.The Brazilian disc test for rock mechanics applications:review and new insights[J].Rock Mechanics and Rock Engineering,2013,46(2):269-287.
[19]王成虎,王仁涛,王春权.多直径岩芯液压致裂岩石抗拉强度快速试验机研发[J].岩石力学与工程学报,2017,36(增1):3 321-3 331.(WANG Chenghu,WANG Rentao,WANG Chunquan.Research and development of rapid testing machine for hydraulic fracturing rock with multi-diameter core[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(Supp.1):3 321-3 331.(in Chinese))
[20]王成虎,邢博瑞,江英豪,等.水压致裂原位应力测量的特征值参数的计算机辅助确定[J].工程地质学报,2016,24(增l):1 347-1 354.(WANG Chenghu,XING Borui,JIANG Yinghao,et al.Computer assisted determination of eigenvalue parameters in situ stress measurement of hydraulic fracturing[J].Journal of Engineering Geology,2016,24(Supp.l):1 347-1 354.(in Chinese))
[21]LUONG M P.Direct tensile and direct shear strengths of Fontainebleau sandstone[C]//The 29th US Symposium on Rock Mechanics(USRMS).[S.l.]:American Rock Mechanics Association,1988:237-246.
[22]黄禄渊,杨树新,崔效锋,等.华北地区实测应力特征与断层稳定性分析[J].Rock and Soil Mechanics,2013,34(增1):204-213.(HUANG Luyuan,YANG Shuxin,CUI Xiaofeng,et al.Analysis of measured stress characteristics and fault stability in North China[J].Rock and Soil Mechanics,2013,34(Supp.1):204-213.(in Chinese))
[23]HAIMSON B C.The effect of lithology,inhomogeneity,topography,and faults,on in situ stress measurements by hydraulic fracturing,and the importance of correct data interpretation and independent evidence in support of results[C]//International Symposium on In-Situ Rock Stress.[S.l.]:International Society for Rock Mechanics,2010:11-14.
[24]HUDSON J A.A critical examination of indirect tensile strength tests for brittle rocks[Ph.D.Thesis][D].Minnesota:University of Minnesota,1970.
[25]AMADEI B,STEPHANSSON O.Rock stress and its measurement[M].London:Chapman and Hall,1997:121-178.
[2]ZANG A,STEPHASSON O.Stress field of the earth's crust[M].London:Springer,2010:141-145.
[3]王成虎.地应力主要测试和估算方法回顾与展望[J].地质论评,2014,60(5):971-996.(WANG Chenghu.Review and prospect of main test and estimation methods of geostress[J].Geological Review,2014,60(5):971-996.(in Chinese))
[4]ITO T,EVANS K,KAWAI K,et al.Hydraulic fracture reopening pressure and the estimation of maximum horizontal stress[J].International Journal of Rock Mechanics and Mining Sciences,1999,36(6):811-826.
[5]ITO T,IGARASHI A,KATO H,et al.Crucial effect of system compliance on the maximum stress estimation in the hydrofracturing method:Theoretical considerations and field-test verification[J].Earth Planets and Space,2006,58(8):963-971.
[6]王成虎,宋成科,邢博瑞.水压致裂应力测量系统柔性分析及其对深孔测量的影响[J].现代地质,2012,26(4):808-816.(WANGChenghu,SONG Chengke,XIN Borui.Flexible analysis of hydraulic fracturing stress measurement system and its effect on deep hole measurement[J].Geoscience,2012,26(4):808-816.(in Chinese))
[7]COVIELLO A,LAGIOIA R,NOVA R.On the measurement of the tensile strength of soft rocks[J].Rock Mechanics and Rock Engineering,2005,38(4):251-273.
[8]PERRAS M A,DIEDERICHS M S.A review of the tensile strength of rock:concepts and testing[J].Geotechnical and Geological Engineering,2014,32(2):525-546.
[9]ITO T,SATOH T,KATO H.Deep rock stress measurement by hydraulic fracturing method taking account of system compliance effect[C]//Proceedings of the 5th International Symposium On In-situ Rock Stress.Beijing:[s.n.],2010:25-27.
[10]HAIMSON B C,ZHAO Z.Effect of borehole size and pressurization rate on hydraulic fracturing breakdown pressure[C]//Rock Mechanics as A Multidisciplinary Science.Roegiers:[s.n.],1991:191-199.
[11]CUISIAT F D,HAIMSON B C.Scale effects in rock mass stress measurements[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1992,29(2):99-117.
[12]YAMASHITA F,MIZOGUCHI K,FUKUYAMA E,et al.Reexamination of the present stress state of the Atera fault system,central Japan,based on the calibrated crustal stress data of hydraulic fracturing tests obtained by measuring the tensile strength of rocks[J].Journal of Geophysical Research:Solid Earth,2010,115(B4):409-423.
[13]CHANG C,JO Y,OH Y,et al.Hydraulic fracturing in situ stress estimations in a potential geothermal site,Seokmo Island,South Korea[J].Rock Mechanics and Rock Engineering,2014,47(5):1 793-1 808.
[14]鞠紫云.紫荆关断裂在太行山北段的特征及其发生发展过程的推论[J].地质通报,1983,(1):61-71.(JU Ziyun.The characteristics of zijingguan fault in the northern section of taihang mountains and the corollary to its occurrence and development[J].Geological Bulletin,1983,(1):61-71.(in Chinese))
[15]朴允羲.华北紫荆关深断裂影象解译[J].石油试验地质,1985,7(2):136-140.(PU Yunxi.Interpretation of deep fault images in bauhinia of north China[J].Petroleum Experimental Geology,1985,7(2):136-140.(in Chinese))
[16]LEE M Y,HAIMSON B C.Statistical evaluation of hydraulic fracturing stress measurement parameters[J].International Journal of Rock Mechanics and Mining Sciences and eomechanics Abstracts,1989,26(6):447-456.
[17]HUDSON J A,HARDY M P,FAIRHURST C.The failure of rock beams:Part II-Experimental studies[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1973,10(1):69-82.
[18]LI D,WONG L N Y.The Brazilian disc test for rock mechanics applications:review and new insights[J].Rock Mechanics and Rock Engineering,2013,46(2):269-287.
[19]王成虎,王仁涛,王春权.多直径岩芯液压致裂岩石抗拉强度快速试验机研发[J].岩石力学与工程学报,2017,36(增1):3 321-3 331.(WANG Chenghu,WANG Rentao,WANG Chunquan.Research and development of rapid testing machine for hydraulic fracturing rock with multi-diameter core[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(Supp.1):3 321-3 331.(in Chinese))
[20]王成虎,邢博瑞,江英豪,等.水压致裂原位应力测量的特征值参数的计算机辅助确定[J].工程地质学报,2016,24(增l):1 347-1 354.(WANG Chenghu,XING Borui,JIANG Yinghao,et al.Computer assisted determination of eigenvalue parameters in situ stress measurement of hydraulic fracturing[J].Journal of Engineering Geology,2016,24(Supp.l):1 347-1 354.(in Chinese))
[21]LUONG M P.Direct tensile and direct shear strengths of Fontainebleau sandstone[C]//The 29th US Symposium on Rock Mechanics(USRMS).[S.l.]:American Rock Mechanics Association,1988:237-246.
[22]黄禄渊,杨树新,崔效锋,等.华北地区实测应力特征与断层稳定性分析[J].Rock and Soil Mechanics,2013,34(增1):204-213.(HUANG Luyuan,YANG Shuxin,CUI Xiaofeng,et al.Analysis of measured stress characteristics and fault stability in North China[J].Rock and Soil Mechanics,2013,34(Supp.1):204-213.(in Chinese))
[23]HAIMSON B C.The effect of lithology,inhomogeneity,topography,and faults,on in situ stress measurements by hydraulic fracturing,and the importance of correct data interpretation and independent evidence in support of results[C]//International Symposium on In-Situ Rock Stress.[S.l.]:International Society for Rock Mechanics,2010:11-14.
[24]HUDSON J A.A critical examination of indirect tensile strength tests for brittle rocks[Ph.D.Thesis][D].Minnesota:University of Minnesota,1970.
[25]AMADEI B,STEPHANSSON O.Rock stress and its measurement[M].London:Chapman and Hall,1997:121-178.