各向异性地层中斜井井壁失稳机理
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摘要
深部层理性地层井壁稳定性必须考虑地层物理力学性质的各向异性,然而目前井壁稳定设计方面仍粗略地将其近似为各向同性体,使得预测的维持井壁稳定的坍塌压力和破裂压力不能满足安全钻井的需要。笔者在研究层理地层岩石力学特性的基础上,获得了一种考虑地层方向特性的井壁围岩应力分布公式,分析了横观各向同性地层的井壁应力分布特征,建立了新的斜井地层井壁稳定分析模型。研究结果表明,岩石的弹性模量、地应力和地层倾斜度的变化对井壁围岩的应力分布和坍塌、破裂压力均会产生影响,克服了常规各向同性井壁稳定分析模型不能准确预测层理性地层斜井井壁稳定的难题。因此在钻井施工设计当中,须根据地层特性选择合适的分析模型,以更好地指导现场实践。
Borehole stability in deep laminar formations is in connection with anisotropy of formation mechanical behaviors,but formations are roughly identified as an approximately isotropic body in the current borehole stability design,which makes the predicted fracture pressure and collapse pressure for maintaining borehole stability incapable of meeting the need of drilling safety.Based on the investigation of bedding rock mechanics of formations,a formula was deduced for the stress distribution of borehole surrounding rocks,which takes directional characteristics of formation into consideration,and built up a new analytical model for borehole stability of a deviated well by means of examining borehole stress distributions of transversely isotropic formations.The result showed that variations in rock elastic modulus,crustal stress and inclination of formations may all have an impact on stress distributions,fracture pressure and collapse pressure of borehole surrounding rocks,and this model solves the problem that conventional analytical models for borehole stability of isotropic formations can not exactly forecast the borehole stability of a deviated well in laminar formations.Therefore,it is necessary to choose a proper analytical model according to formation characteristics in designing drilling constructions so as to guide field practice more effectively.
Borehole stability in deep laminar formations is in connection with anisotropy of formation mechanical behaviors,but formations are roughly identified as an approximately isotropic body in the current borehole stability design,which makes the predicted fracture pressure and collapse pressure for maintaining borehole stability incapable of meeting the need of drilling safety.Based on the investigation of bedding rock mechanics of formations,a formula was deduced for the stress distribution of borehole surrounding rocks,which takes directional characteristics of formation into consideration,and built up a new analytical model for borehole stability of a deviated well by means of examining borehole stress distributions of transversely isotropic formations.The result showed that variations in rock elastic modulus,crustal stress and inclination of formations may all have an impact on stress distributions,fracture pressure and collapse pressure of borehole surrounding rocks,and this model solves the problem that conventional analytical models for borehole stability of isotropic formations can not exactly forecast the borehole stability of a deviated well in laminar formations.Therefore,it is necessary to choose a proper analytical model according to formation characteristics in designing drilling constructions so as to guide field practice more effectively.
引文
[1]金衍,陈勉.井壁稳定力学[M].北京:科学出版社,2012:12-20.Jin Yan,Chen Mian.Mechanics of wellbore stability[M].Bei-jing:Science Press,2012:12-20.
[2]陈勉,金衍,张广清.石油工程岩石力学[M].北京:科学出版社,2008:25-26.Chen Mian,Jin Yan,Zhang Guangqing.Rock mechanics for pe-troleum engineering[M].Beijing:Science Press,2008:25-26.
[3]Westergaard H M.Plastic state of stress around a deep well[J].Jour-nal of the Boston Society of Civil Engineers,1940,27:387-391.
[4]金衍,陈勉,张旭东.钻前井壁稳定预测方法的研究[J].石油学报,2001,22(3):96-99.Jin Yan,Chen Mian,Zhang Xudong.Study on prediction forborehole stability before drilling[J].Acta Petrolei Sinica,2001,22(3):96-99.
[5]Labenski F,Reid P,Santos H.Drilling fluids approaches for con-trol of wellbore instability in fractured formations[R].SPE/IADC85304,2003.
[6]Helstrup O A,Chen Zhixi,Rahman S S.Time-dependent wellbore in-stability and ballooning in naturally fractured formations[J].Journalof Petroleum Science and Engineering,2004,43(1/2):113-128.
[7]金衍,陈勉.利用地震记录钻前预测井壁稳定性研究[J].石油学报,2004,25(1):89-92.Jin Yan,Chen Mian.Prediction of borehole stability by seismicrecords[J].Acta Petrolei Sinica,2004,25(1):89-92.
[8]黄荣樽,陈勉,邓金根,等.泥页岩井壁稳定力学与化学的耦合研究[J].钻井液与完井液,1995,12(3):15-21.Huang Rongzun,Chen Mian,Deng Jingen,et al.Study on shalestability of wellbore by mechanics coupling with chemistry meth-od[J].Drilling Fluids&Completion Fluids,1995,12(3):15-21.
[9]金衍,陈勉.水敏性泥页岩地层临界坍塌时间的确定方法[J].石油钻探技术,2004,32(2):12-14.Jin Yan,Chen Mian.A method for determining the critical timeof wellbore instability at water-sensitive shale formations[J].Pe-troleum Drilling Techniques,2004,32(2):12-14.
[10]陈新,杨强,何满潮,等.考虑深部岩体各向异性强度的井壁稳定分析[J].岩石力学与工程学报,2005,24(16):2882-2888.Chen Xin,Yang Qiang,He Manchao,et al.Stability analysis ofwellbore based on anisotropic strength criterion for deep jointedrock mass[J].Chinese Journal of Rock Mechanics and Engineer-ing,2005,24(16):2882-2888.
[11]Lekhnitskii S G.Theory of elasticity of an anisotropic elastic body[M].Translated by Fern P.San Francisco:Holden-Day lnc,1963.
[12]Amadei B.In situ stress measurements in anisotropic rock[J].International Journal of Rock Mechanics and Mining Science&Geomechanics Abstracts,1984,21(6):327-338.
[13]Amadei B.Importance of anisotropy when estimating and meas-uring in situ stresses in rock[J].International Journal of RockMechanics and Mining Science&Geomechanics Abstracts,1996,33(3):293-325.
[14]Ong S H.Borehole stability[D].Oklahoma:University of Okla-homa,1997.
[16]金衍,张旭东,陈勉.天然裂缝地层中垂直井水力裂缝起裂压力模型研究[J].石油学报,2005,26(6):113-114.Jin Yan,Zhang Xudong,Chen Mian.Initiation pressure modelsfor hydraulic fracturing of vertical wells in naturally fracturedformation[J].Acta Petrolei Sinica,2005,26(6):113-114.
[17]陈勉,周健,金衍,等.随机裂缝性储层压裂特征实验研究[J].石油学报,2008,29(3):431-434.Chen Mian,Zhou Jian,Jin Yan,et al.Experimental study on frac-turing features in naturally fractured reservoir[J].Acta PetroleiSinica,2008,29(3):431-434.
[18]周健,陈勉,金衍,等.裂缝性储层水力裂缝扩展机理试验研究[J].石油学报,2007,28(5):109-113.Zhou Jian,Chen Mian,Jin Yan,et al.Experimental study onpropagation mechanism of hydraulic fracture in naturally frac-tured reservoir[J].Acta Petrolei Sinica,2007,28(5):109-113.
[19]金衍,齐自立,陈勉,等.水平井试油过程裂缝性储层失稳机理[J].石油学报,2011,32(2):295-298.Jin Yan,Qi Zili,Chen Mian,et al.A mechanism study on thefractured reservoir instability during well testing of horizontalwells[J].Acta Petrolei Sinica,2011,32(2):295-298.
[20]Lu Y H,Chen M,Jin Y,et al.A mechanical model of boreholestability for weak plane formation under porous flow[J].Petrole-um Science&Technology,2012,30:1629-1638.
[2]陈勉,金衍,张广清.石油工程岩石力学[M].北京:科学出版社,2008:25-26.Chen Mian,Jin Yan,Zhang Guangqing.Rock mechanics for pe-troleum engineering[M].Beijing:Science Press,2008:25-26.
[3]Westergaard H M.Plastic state of stress around a deep well[J].Jour-nal of the Boston Society of Civil Engineers,1940,27:387-391.
[4]金衍,陈勉,张旭东.钻前井壁稳定预测方法的研究[J].石油学报,2001,22(3):96-99.Jin Yan,Chen Mian,Zhang Xudong.Study on prediction forborehole stability before drilling[J].Acta Petrolei Sinica,2001,22(3):96-99.
[5]Labenski F,Reid P,Santos H.Drilling fluids approaches for con-trol of wellbore instability in fractured formations[R].SPE/IADC85304,2003.
[6]Helstrup O A,Chen Zhixi,Rahman S S.Time-dependent wellbore in-stability and ballooning in naturally fractured formations[J].Journalof Petroleum Science and Engineering,2004,43(1/2):113-128.
[7]金衍,陈勉.利用地震记录钻前预测井壁稳定性研究[J].石油学报,2004,25(1):89-92.Jin Yan,Chen Mian.Prediction of borehole stability by seismicrecords[J].Acta Petrolei Sinica,2004,25(1):89-92.
[8]黄荣樽,陈勉,邓金根,等.泥页岩井壁稳定力学与化学的耦合研究[J].钻井液与完井液,1995,12(3):15-21.Huang Rongzun,Chen Mian,Deng Jingen,et al.Study on shalestability of wellbore by mechanics coupling with chemistry meth-od[J].Drilling Fluids&Completion Fluids,1995,12(3):15-21.
[9]金衍,陈勉.水敏性泥页岩地层临界坍塌时间的确定方法[J].石油钻探技术,2004,32(2):12-14.Jin Yan,Chen Mian.A method for determining the critical timeof wellbore instability at water-sensitive shale formations[J].Pe-troleum Drilling Techniques,2004,32(2):12-14.
[10]陈新,杨强,何满潮,等.考虑深部岩体各向异性强度的井壁稳定分析[J].岩石力学与工程学报,2005,24(16):2882-2888.Chen Xin,Yang Qiang,He Manchao,et al.Stability analysis ofwellbore based on anisotropic strength criterion for deep jointedrock mass[J].Chinese Journal of Rock Mechanics and Engineer-ing,2005,24(16):2882-2888.
[11]Lekhnitskii S G.Theory of elasticity of an anisotropic elastic body[M].Translated by Fern P.San Francisco:Holden-Day lnc,1963.
[12]Amadei B.In situ stress measurements in anisotropic rock[J].International Journal of Rock Mechanics and Mining Science&Geomechanics Abstracts,1984,21(6):327-338.
[13]Amadei B.Importance of anisotropy when estimating and meas-uring in situ stresses in rock[J].International Journal of RockMechanics and Mining Science&Geomechanics Abstracts,1996,33(3):293-325.
[14]Ong S H.Borehole stability[D].Oklahoma:University of Okla-homa,1997.
[16]金衍,张旭东,陈勉.天然裂缝地层中垂直井水力裂缝起裂压力模型研究[J].石油学报,2005,26(6):113-114.Jin Yan,Zhang Xudong,Chen Mian.Initiation pressure modelsfor hydraulic fracturing of vertical wells in naturally fracturedformation[J].Acta Petrolei Sinica,2005,26(6):113-114.
[17]陈勉,周健,金衍,等.随机裂缝性储层压裂特征实验研究[J].石油学报,2008,29(3):431-434.Chen Mian,Zhou Jian,Jin Yan,et al.Experimental study on frac-turing features in naturally fractured reservoir[J].Acta PetroleiSinica,2008,29(3):431-434.
[18]周健,陈勉,金衍,等.裂缝性储层水力裂缝扩展机理试验研究[J].石油学报,2007,28(5):109-113.Zhou Jian,Chen Mian,Jin Yan,et al.Experimental study onpropagation mechanism of hydraulic fracture in naturally frac-tured reservoir[J].Acta Petrolei Sinica,2007,28(5):109-113.
[19]金衍,齐自立,陈勉,等.水平井试油过程裂缝性储层失稳机理[J].石油学报,2011,32(2):295-298.Jin Yan,Qi Zili,Chen Mian,et al.A mechanism study on thefractured reservoir instability during well testing of horizontalwells[J].Acta Petrolei Sinica,2011,32(2):295-298.
[20]Lu Y H,Chen M,Jin Y,et al.A mechanical model of boreholestability for weak plane formation under porous flow[J].Petrole-um Science&Technology,2012,30:1629-1638.
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