页岩气体积压裂井筒组合体力学新模型研究
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摘要
在四川威远-长宁国家级页岩气示范区,部分井次在储层改造过程中出现了井筒完整性失效问题,严重影响了页岩气的开发效果。准确分析页岩气井施工过程中井筒组合体的应力变化规律对提高页岩气井筒完整性具有重要意义。传统建模方法忽略了固井之前井筒组合体的应力变化。针对上述问题,根据分步有限元的模拟思想,通过相应推导,建立了考虑水泥环初始应力应变的井筒组合体数值模型,可以模拟钻井、固井以及压裂过程中井筒组合体应力分布;采用场变量、生死单元等数值模拟技术建立了页岩气井井筒组合体解析模型,模型同时考虑了页岩弹性模量各向异性特征、水泥环初始应力应变,比常规模型更符合现场实际。研究结果表明:解析模型与分步有限元数值模型的计算结果很接近;储层初始弹性模量各向异性对井筒组合体应力的影响较小,在研究过程中可以忽略。研究结果可为页岩气井体积压裂过程中井筒的完整性分析提供理论指导。
In the Weiyuan-Changning shale gas demonstration area in Sichuan,wellbore integrity failures of some wells were observed during the reservoir stimulation,which seriously hindered the development of shale gas.Accurate analysis on the stress of the wellbore assembly during the construction of shale gas wells is of great significance for improving the wellbore integrity. The traditional modeling method did not consider the stress variation of the wellbore assembly before cementing. To address the problem,according to the simulation idea of distributed finite element,the numerical simulation of the wellbore assembly considering the initial stress and strain of the cement sheath is established by derivation,which can simulate the stress distribution of the wellbore assembly during drilling,cementing and fracturing. Numerical simulation techniques like field model and birth-death element are used to establish an analytical model of shale gas wellbore assembly. The anisotropy of shale elastic modulus and the initial stress and strain of cement sheath are also considered in the model,which is more in line with the actual situation than the conventional model. The results show that the analytical model is very close to the numerical results of the fractional step finite element model. The initial elastic modulus anisotropy of the reservoir has little effect on the stress of the wellbore assembly and can be neglected. The study can provide theoretical guidance for the analysis of wellbore integrity problems in the shale gas stimulated reservoir volume fracturing.
In the Weiyuan-Changning shale gas demonstration area in Sichuan,wellbore integrity failures of some wells were observed during the reservoir stimulation,which seriously hindered the development of shale gas.Accurate analysis on the stress of the wellbore assembly during the construction of shale gas wells is of great significance for improving the wellbore integrity. The traditional modeling method did not consider the stress variation of the wellbore assembly before cementing. To address the problem,according to the simulation idea of distributed finite element,the numerical simulation of the wellbore assembly considering the initial stress and strain of the cement sheath is established by derivation,which can simulate the stress distribution of the wellbore assembly during drilling,cementing and fracturing. Numerical simulation techniques like field model and birth-death element are used to establish an analytical model of shale gas wellbore assembly. The anisotropy of shale elastic modulus and the initial stress and strain of cement sheath are also considered in the model,which is more in line with the actual situation than the conventional model. The results show that the analytical model is very close to the numerical results of the fractional step finite element model. The initial elastic modulus anisotropy of the reservoir has little effect on the stress of the wellbore assembly and can be neglected. The study can provide theoretical guidance for the analysis of wellbore integrity problems in the shale gas stimulated reservoir volume fracturing.
引文
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[11]殷有泉,蔡永恩,陈朝伟,等.非均匀地应力场中套管载荷的理论解[J].石油学报,2006,27(4):133-138.YIN Y Q,CAI Y E,CHEN Z W,et al.Theoretical solution of casing loading in non-uniform ground stress field[J].Acta Petrolei Sinica,2006,27(4):133-138.
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[15]房军,徐龙兴.非均匀地应力作用下套管和水泥环表面受力特性分析[J].石油大学学报(自然科学版),1997,21(1):46-48.FANG J,XU L X.Analysis of surface loading on casing and cement sheath under nonuniform geologic stress[J].Journal of the University of Petoleum,China(E-dition of Natural Science),1997,21(1):46-48.
[16]PATTILLO P D,KRISTIANSEN T G.Analysis of horizontal casing integrity in the Valhall field[R].SPE78204-MS,2002.
[17]GRAY K,PODNOS E,BECKER E.Finite element studies of near-wellbore region during cementing operations:part I[J].SPE Drilling and Completion,2007,24(1):127-136.
[18]KRIS R,BOSMA M,GASTEBLED O.Improve the economics of oil and gas wells by reducing the risk of cement failure[R].SPE 74497-MS,2002.
[19]MUELLER D T,EID R N.Characterization of the early-time mechanical behavior of well cements employed in surface casing operations[R].SPE 98632-MS,2006.
[20]SAINT-MARC J,ANDRE G,AXEL-PIERRE B.Initial state of stress:the key to achieving long-term cement-sheath integrity[R].SPE 116651-MS,2008.
[21]范明涛,柳贡慧,李军,等.页岩气井温压耦合下固井质量对套管应力的影响[J].石油机械,2016,44(8):1-5.FAN M T,LIU G H,LI J,et al.Effect of cementing quality on casing stress of shale gas well under heat-mechanical coupling[J].China Petroleum Machinery,2016,44(8):1-5.
[22]范明涛,李军,柳贡慧,等.页岩气水平井体积压裂过程中套损机理研究[J].石油机械,2018,46(4):82-87.FAN M T,LI J,LIU G H,et al.Study on casing damage mechanism in volume fracturing of shale gas horizontal well[J].China Petroleum Machinery,2018,46(4):82-87.
[23]隋阳,刘建伟,郭旭东,等.体积压裂技术在红台低含油饱和度致密砂岩油藏的应用[J].石油钻采工艺,2017,39(3):349-355.SUI Y,LIU J W,GUO X D,et al.Application of volumetric fracturing technology in Hongtai tight sandstone oil reservoir of low oil saturation[J].Oil Drilling&Production Technology,2017,39(3):349-355.
[24]董文涛,申瑞臣,乔磊,等.体积压裂多因素耦合套变机理研究[J].钻采工艺,2017,40(6):35-37.DONG W T,SHEN R C,QIAO L,et al.Research on casing deformation by coupled multiple factors during volumetric fracturing in shale gas wells[J].Drilling&Production Technology,2017,40(6):35-37.
[25]蔡美峰,何满潮,刘东燕.岩石力学与工程[M].北京:科学出版社,2002.CAI M F,HE M C,LIU D Y.Rock mechanics and engineering[M].Beijing:Science Press,2002.
[2]陈作,薛承瑾,蒋廷学,等.页岩气井体积压裂技术在我国的应用建议[J].天然气工业,2010,30(10):30-32.CHEN Z,XUE C J,JIANG T X,et al.Proposals for the application of fracturing by stimulated reservoir volume(SRV)in shale gas wells in China[J].Natural Gas Industry,2010,30(10):30-32.
[3]JACOT R H,BAZAN L W,BRUCE M R.Technology integration:a methodology to enhance production and maximize economics in horizontal marcellus shale wells[R].SPE 135262-MS,2010.
[4]薛承瑾.页岩气压裂技术现状及发展建议[J].石油钻探技术,2011,39(3):24-29.XUE C J.Technical advance and development proposals of shale gas fracturing[J].Petroleum Drilling Techniques,2011,39(3):24-29.
[5]戴强.页岩气井完井改造期间生产套管损坏原因初探[J].钻采工艺,2015,38(3):22-25.DAI Q.Analysis of production casing damage reasons during testing and completion of shale gas well[J].Drilling and Production Technology,2015,38(3):22-25.
[6]田中兰,石林,乔磊.页岩气水平井井筒完整性问题及对策[J].天然气工业,2015,35(9):70-76.TIAN Z L,SHI L,QIAO L.Research of and countermeasure for wellbore integrity of shale gas horizontal well[J].Natural Gas Industry,2015,35(9):70-76.
[7]ZINKHAM R E,GOODWIN R J.Burst resistance of pipe cemented into the earth[J].Journal of Petroleum Technology,1962,14(9):1033-1040.
[8]龚伟安.试论套管挤压理论中的几个问题(一)---关于两种挤压理论的本质区别兼论圆管弹塑性失稳问题[J].石油钻采机械通讯,1979(5):27-34.GONG W A.Discussion on several problems on casing collapse theory(I)-on the essential difference between the two collapse theories and the elastoplastic instability of the circular tube[J].Oil Field Machinery,1979(5):27-34.
[9]THIERCELIN M J,DARGAUD B,BARET J F,et al.Cement design based on cement mechanical response[J].SPE Drilling and Completion,1998,13(4):266-273.
[10]李军,陈勉,柳贡慧,等.套管、水泥环及井壁围岩组合体的弹塑性分析[J].石油学报,2005,26(6):99-103.LI J,CHEN M,LIU G H,et al.Elastic-plastic analysis of casing-concrete sheath-rock combination[J].Acta Petrolei Sinica,2005,26(6):99-103.
[11]殷有泉,蔡永恩,陈朝伟,等.非均匀地应力场中套管载荷的理论解[J].石油学报,2006,27(4):133-138.YIN Y Q,CAI Y E,CHEN Z W,et al.Theoretical solution of casing loading in non-uniform ground stress field[J].Acta Petrolei Sinica,2006,27(4):133-138.
[12]陈朝伟,蔡永恩.套管-地层系统套管载荷的弹塑性理论分析[J].石油勘探与开发,2009,36(2):242-246.CHEN Z W,CAI Y E.Study on casing load in a casing-stratum system by elastoplastic theory[J].Petroleum Exploration and Development,2009,36(2):242-246.
[13]SHAHRI M,SCHUBERT J J,AMANI M.Detecting and modeling cement failure in high-pressure/hightemperature(HP/HT)wells,using finite element method(FEM)[R].IPTC-10961-MS,2005.
[14]练章华,何明烛.岩石、水泥环、套管互作用的粘弹塑性有限元力学模型[J].西南石油学院学报(自然科学版),1994,16(2):97-103.LIAN Z H,HE M Z.Viscoelastic-plastic finite element mechanics models of interaction of rock,cement ring and casing[J].Journal of Southwestern Petroleum Institute(Edition of Natural Science),1994,16(2):97-103.
[15]房军,徐龙兴.非均匀地应力作用下套管和水泥环表面受力特性分析[J].石油大学学报(自然科学版),1997,21(1):46-48.FANG J,XU L X.Analysis of surface loading on casing and cement sheath under nonuniform geologic stress[J].Journal of the University of Petoleum,China(E-dition of Natural Science),1997,21(1):46-48.
[16]PATTILLO P D,KRISTIANSEN T G.Analysis of horizontal casing integrity in the Valhall field[R].SPE78204-MS,2002.
[17]GRAY K,PODNOS E,BECKER E.Finite element studies of near-wellbore region during cementing operations:part I[J].SPE Drilling and Completion,2007,24(1):127-136.
[18]KRIS R,BOSMA M,GASTEBLED O.Improve the economics of oil and gas wells by reducing the risk of cement failure[R].SPE 74497-MS,2002.
[19]MUELLER D T,EID R N.Characterization of the early-time mechanical behavior of well cements employed in surface casing operations[R].SPE 98632-MS,2006.
[20]SAINT-MARC J,ANDRE G,AXEL-PIERRE B.Initial state of stress:the key to achieving long-term cement-sheath integrity[R].SPE 116651-MS,2008.
[21]范明涛,柳贡慧,李军,等.页岩气井温压耦合下固井质量对套管应力的影响[J].石油机械,2016,44(8):1-5.FAN M T,LIU G H,LI J,et al.Effect of cementing quality on casing stress of shale gas well under heat-mechanical coupling[J].China Petroleum Machinery,2016,44(8):1-5.
[22]范明涛,李军,柳贡慧,等.页岩气水平井体积压裂过程中套损机理研究[J].石油机械,2018,46(4):82-87.FAN M T,LI J,LIU G H,et al.Study on casing damage mechanism in volume fracturing of shale gas horizontal well[J].China Petroleum Machinery,2018,46(4):82-87.
[23]隋阳,刘建伟,郭旭东,等.体积压裂技术在红台低含油饱和度致密砂岩油藏的应用[J].石油钻采工艺,2017,39(3):349-355.SUI Y,LIU J W,GUO X D,et al.Application of volumetric fracturing technology in Hongtai tight sandstone oil reservoir of low oil saturation[J].Oil Drilling&Production Technology,2017,39(3):349-355.
[24]董文涛,申瑞臣,乔磊,等.体积压裂多因素耦合套变机理研究[J].钻采工艺,2017,40(6):35-37.DONG W T,SHEN R C,QIAO L,et al.Research on casing deformation by coupled multiple factors during volumetric fracturing in shale gas wells[J].Drilling&Production Technology,2017,40(6):35-37.
[25]蔡美峰,何满潮,刘东燕.岩石力学与工程[M].北京:科学出版社,2002.CAI M F,HE M C,LIU D Y.Rock mechanics and engineering[M].Beijing:Science Press,2002.