预防套管变形的许用压裂注入压力计算方法
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摘要
注入压力是页岩气储层改造设计中的关键参数之一,较高的注入压力有利于打开地层、顺利注入压裂液和支撑剂、尽快取得较大的储层改造体积,但如果注入压力过大则套管变形的风险也会明显增加。为此,以一个工程项目为实例,提出了在保障套管完整性前提下的注入压力安全窗口上限即最大安全注入压力值的数值计算格式,并以四川盆地威远区块某页岩气井为例进行了验证计算。研究内容包括:(1)建立区块尺度的初始精细地应力场的三维有限元模型;(2)建立引入地层刚度非对称特性的初级子模型,以此来模拟裂缝分布的非对称属性;(3)建立包含套管、水泥环和地层材料属性的二级子模型;(4)利用子模型计算不同的注入载荷压裂引起的套管变形,判断得到满足套管变形安全要求的最大许用压裂注入压力。实例井的计算结果表明,当注入压力为80 MPa时,固井质量差、裂缝分布不对称的时候,得到的套管上最大位移点的水平位移值、垂直位移值明显小于90 MPa时的变形量,依据P110套管钢材的屈服极限判断此时的套管变形为弹性应变,该注入压力是安全的。结论认为,采用该计算方法得到的结果与工程实际吻合度高,具有合理的精度和准确性。
Injection pressure is one of the key parameters used in the design of shale gas reservoir stimulation. Higher injection pressure helps to initiate fractures, inject fracturing fluid and proppant smoothly and maximize the stimulated reservoir volume as soon as possible. If the injection pressure is too high, however, the risk of casing deformation is increased significantly. In this paper, the numerical calculation format of the injection pressure safety window while ensuring casing integrity(i.e., maximum safety injection pressure) was proposed based on an example of an actual engineering project. Then, it was verified based on the actual situation of one shale gas well in Weiyuan. The numerical calculation format is as follows. First, a 3D finite element model of initial fine geostress field is established in the scale of block. Second, a primary submodel for introducing the asymmetric characteristics of reservoir stiffness to simulate the asymmetry of fracture distribution. Third, a secondary submodel containing the attributes of casing, cement sheath and reservoir material properties. Fourth, submodels are used to calculate the casing deformation generated by different injection loads and estimate the maximum allowable fracturing injection pressure(pj) while the safety requirement of casing deformation is satisfied. The calculation result of the case well shows that when the cementing quality is poor and fractures are distributed asymmetrically, the lateral and vertical displacements at the maximum displacement point of the casing under the injection pressure of 80 MPa are obviously lower than those under 90 MPa. According to the yield limit criterion of P-110 casing steel, the casing deformation in this case is elastic strain, so the injection pressure of 80 MPa is safe. In conclusion, this method has rational precision and accuracy, for its numerical result is consistent with the actual engineering phenomenon.
Injection pressure is one of the key parameters used in the design of shale gas reservoir stimulation. Higher injection pressure helps to initiate fractures, inject fracturing fluid and proppant smoothly and maximize the stimulated reservoir volume as soon as possible. If the injection pressure is too high, however, the risk of casing deformation is increased significantly. In this paper, the numerical calculation format of the injection pressure safety window while ensuring casing integrity(i.e., maximum safety injection pressure) was proposed based on an example of an actual engineering project. Then, it was verified based on the actual situation of one shale gas well in Weiyuan. The numerical calculation format is as follows. First, a 3D finite element model of initial fine geostress field is established in the scale of block. Second, a primary submodel for introducing the asymmetric characteristics of reservoir stiffness to simulate the asymmetry of fracture distribution. Third, a secondary submodel containing the attributes of casing, cement sheath and reservoir material properties. Fourth, submodels are used to calculate the casing deformation generated by different injection loads and estimate the maximum allowable fracturing injection pressure(pj) while the safety requirement of casing deformation is satisfied. The calculation result of the case well shows that when the cementing quality is poor and fractures are distributed asymmetrically, the lateral and vertical displacements at the maximum displacement point of the casing under the injection pressure of 80 MPa are obviously lower than those under 90 MPa. According to the yield limit criterion of P-110 casing steel, the casing deformation in this case is elastic strain, so the injection pressure of 80 MPa is safe. In conclusion, this method has rational precision and accuracy, for its numerical result is consistent with the actual engineering phenomenon.
引文
[1]高德利.油气井管柱力学与工程[M].东营:中国石油大学出版社,2006.Gao Deli.Down-hole tubular mechanics and its applications[M].Dongying:China University of Petroleum Press,2006.
[2]Gao Deli&Gao Baokui.A method for calculating tubing behavior in HPHT wells[J].Journal of Petroleum Science and Engineering,2004,41(1/3):183-188.
[3]高德利,张武辇,李文勇.南海西江大位移井钻完井工艺分析研究[J].石油钻采工艺,2004,26(3):1-6.Gao Deli,Zhang Wunian&Li Wenyong.Analysis study on drilling and completion techniques for Xijiang in South China Sea[J].Oil Drilling&Production Technology,2004,26(3):1-6.
[4]高德利.复杂结构静优化设计与钻完井控制技术[M].东营:中国石油大学出版社,2011.Gao Deli.Optimized design and control techniques for drilling completion of complex-structure wells[M].Dongying:China University of Petroleum Press,2011.
[5]张效羽,徐秉业,赵国珍.模糊识别及预测在役套管的变形损坏[J].天然气工业,1999,19(2):72-74.Zhang Xiaoyu,Xu Bingye&Zhao Guozhen.Fuzzy diagnosis and prediction of on-stream casing damage[J].Natural Gas Industry,1999,19(2):72-74.
[6]张效羽.套管有限元计算的若干问题分析[J].天然气工业,2001,21(1):62-65.Zhang Xiaoyu.Analysis of some problems in casing calculation by finite element method[J].Natural Gas Industry,2001,21(1):62-65.
[7]练章华,韩建增,董事尔,唐波,董范,李渊.基于数值模拟的复杂地层套管破坏机理研究[J].天然气工业,2002,22(1):48-51.Lian Zhanghua,Han Jianzeng,Dong Shi'er,Tang Bo,Dong Fan&Li Yuan.Research on the casing failure mechanism of complex formation by numerical simulation[J].Natural Gas Industry,2002,22(1):48-51.
[8]韩建增,李中华,于百勤,练章华,施太和.几何缺陷对套管抗挤强度影响的有限元分析[J].天然气工业,2004,24(5):71-72.Han Jianzeng,Li Zhonghua,Yu Baiqin,Lian Zhanghua&Shi Taihe.Finite element analysis about effect of geometric imperfection on casing collapse resistance[J].Natural Gas Industry,2004,24(5):71-72.
[9]沈新普.页岩气储层压裂引起的套管完整性数值评价[C]//第21届全国结构工程学术会议论文集.沈阳,2012.Shen Xinpu.Numerical estimation on casing integrity in hydraulic fracturing of shale gas formation[C]//Papers Collection of the21st National Academic Conference on Structural Engineering.Shenyang,Liaoning,2012.
[10]董文涛,申思远,付利.体积压裂套管失效分析[J].石化技术,2016,23(11):156-157.Dong Wentao,Shen Siyuan&Fu Li.Analysis of casing failure in SRV fracturing[J].Petrochemical Industry Technology,2016,23(11):156-157.
[11]刘奎,王宴滨,高德利,李星君,张勇.页岩气水平井压裂对井筒完整性的影响[J].石油学报,2016,37(3):406-414.Liu Kui,Wang Yanbin,Gao Deli,Li Xingjun&Zhang Yong.Effects of hydraulic fracturing on horizontal wellbore for shale gas[J].Acta Petrolei Sinica,2016,37(3):406-414.
[12]李军,李玉梅,张德龙,杨宏伟,孙世斌.页岩气井分段压裂套损影响因素分析[J].断块油气田,2017,24(3):387-390.Li Jun,Li Yumei,Zhang Delong,Yang Hongwei&Sun Shibin.Analysis of casing damage for staged fracturing in shale gas well[J].Fault-Block Oil and Gas Field,2017,24(3):387-390.
[13]陈作,曾义金.深层页岩气分段压裂技术现状及发展建议[J].石油钻探技术,2016,44(1):6-11.Chen Zuo&Zeng Yijin.Present situations and prospects of multi-stage fracturing technology for deep shale gas development[J].Petroleum Drilling Techniques,2016,44(1):6-11.
[14]高利军,柳占立,乔磊,庄茁,杨恒林.页岩气水力压裂中套损机理及其数值模拟研究[J].石油机械,2017,45(1):75-80.Gao Lijun,Liu Zhanli,Qiao Lei,Zhuang Zhuo&Yang Henglin.Mechanism analysis and numerical simulation of casing failure in hydraulic fracturing of shale gas formation[J].China Petroleum Machinery,2017,45(1):75-80.
[15]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,2015,41(3):22-25.Dai Qiang.Analysis of production casing damage reasons during testing and completion of shale gas well[J].Drilling&Production Technology,2015,41(3):22-25.
[16]杨恒林,乔磊,田中兰.页岩气储层工程地质力学一体化技术进展与探讨[J].石油钻探技术,2017,45(2):25-31.Yang Henglin,Qiao Lei&Tian Zhonglan.Advance in shale gas reservoir engineering and geomechanics integration technology and relevant discussions[J].Petroleum Drilling Techniques,2017,45(2):25-31.
[17]郝美美.页岩气井油层套管受力分析及应力分布计算研究[D].重庆:重庆科技学院,2016.Hao Meimei.Analysis of shale gas well's casing and stress distribution calculation[D].Chongqing:Chongqing College of Science and Technology,2016.
[18]于浩,练章华,林铁军.页岩气压裂过程套管失效机理有限元分析[J].石油机械,2014,42(8):84-88.Yu Hao,Lian Zhanghua&Lin Tiejun.Finite element analysis of failure mechanism of casing during shale gas fracturing[J].China Petroleum Machinery,2014,42(8):84-88.
[19]付丽霞,朱伟,薛改珍.套管错断的原因、实例及解决的办法[J].国外油田工程,2002,18(9):35-42.Fu Lixia,Zhu Wei&Xue Gaizhen.Casing failure's sake,example,and solutions[J].Foreign Oilfield Engineering,2002,18(9):35-42.
[20]张卫东,杨勇,路智勇,刘新华,张艳增,王瑞和,等.延缓断层处套管损坏的方法[J].断块油气田,2012,19(6):800-802.Zhang Weidong,Yang Yong,Lu Zhiyong,Liu Xinhua,Zhang Yanzeng,Wang Ruihe,et al.Method of delaying casing damage at the fault[J].Fault-Block Oil and Gas Field,2012,19(6):800-802.
[21]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 Zhonglan,Shi Lin&Qiao Lei.Research of and countermeasure for wellbore integrity of shale gas horizontal well[J].Natural Gas Industry,2015,35(9):70-76.
[22]陈朝伟,石林,项德贵.长宁-威远页岩气示范区套管变形机理及对策[J].天然气工业,2016,36(11):70-75.Chen Zhaowei,Shi Lin&Xiang Degui.Mechanism of casing deformation in the Changning-Weiyuan national shale gas project demonstration area and countermeasures[J].Natural Gas Industry,2016,36(11):70-75.
[23]沈新普,金生吉.油层压裂模拟的损伤力学方法及数值应用实例[J].沈阳工业大学学报,2014,36(3):341-346.Shen Xinpu&Jin Shengji.Numerical method and application example of stimulation damage mechanics for fracture of reservoir formation[J].Journal of Shenyang University of Technology,2014,36(3):341-346.
[2]Gao Deli&Gao Baokui.A method for calculating tubing behavior in HPHT wells[J].Journal of Petroleum Science and Engineering,2004,41(1/3):183-188.
[3]高德利,张武辇,李文勇.南海西江大位移井钻完井工艺分析研究[J].石油钻采工艺,2004,26(3):1-6.Gao Deli,Zhang Wunian&Li Wenyong.Analysis study on drilling and completion techniques for Xijiang in South China Sea[J].Oil Drilling&Production Technology,2004,26(3):1-6.
[4]高德利.复杂结构静优化设计与钻完井控制技术[M].东营:中国石油大学出版社,2011.Gao Deli.Optimized design and control techniques for drilling completion of complex-structure wells[M].Dongying:China University of Petroleum Press,2011.
[5]张效羽,徐秉业,赵国珍.模糊识别及预测在役套管的变形损坏[J].天然气工业,1999,19(2):72-74.Zhang Xiaoyu,Xu Bingye&Zhao Guozhen.Fuzzy diagnosis and prediction of on-stream casing damage[J].Natural Gas Industry,1999,19(2):72-74.
[6]张效羽.套管有限元计算的若干问题分析[J].天然气工业,2001,21(1):62-65.Zhang Xiaoyu.Analysis of some problems in casing calculation by finite element method[J].Natural Gas Industry,2001,21(1):62-65.
[7]练章华,韩建增,董事尔,唐波,董范,李渊.基于数值模拟的复杂地层套管破坏机理研究[J].天然气工业,2002,22(1):48-51.Lian Zhanghua,Han Jianzeng,Dong Shi'er,Tang Bo,Dong Fan&Li Yuan.Research on the casing failure mechanism of complex formation by numerical simulation[J].Natural Gas Industry,2002,22(1):48-51.
[8]韩建增,李中华,于百勤,练章华,施太和.几何缺陷对套管抗挤强度影响的有限元分析[J].天然气工业,2004,24(5):71-72.Han Jianzeng,Li Zhonghua,Yu Baiqin,Lian Zhanghua&Shi Taihe.Finite element analysis about effect of geometric imperfection on casing collapse resistance[J].Natural Gas Industry,2004,24(5):71-72.
[9]沈新普.页岩气储层压裂引起的套管完整性数值评价[C]//第21届全国结构工程学术会议论文集.沈阳,2012.Shen Xinpu.Numerical estimation on casing integrity in hydraulic fracturing of shale gas formation[C]//Papers Collection of the21st National Academic Conference on Structural Engineering.Shenyang,Liaoning,2012.
[10]董文涛,申思远,付利.体积压裂套管失效分析[J].石化技术,2016,23(11):156-157.Dong Wentao,Shen Siyuan&Fu Li.Analysis of casing failure in SRV fracturing[J].Petrochemical Industry Technology,2016,23(11):156-157.
[11]刘奎,王宴滨,高德利,李星君,张勇.页岩气水平井压裂对井筒完整性的影响[J].石油学报,2016,37(3):406-414.Liu Kui,Wang Yanbin,Gao Deli,Li Xingjun&Zhang Yong.Effects of hydraulic fracturing on horizontal wellbore for shale gas[J].Acta Petrolei Sinica,2016,37(3):406-414.
[12]李军,李玉梅,张德龙,杨宏伟,孙世斌.页岩气井分段压裂套损影响因素分析[J].断块油气田,2017,24(3):387-390.Li Jun,Li Yumei,Zhang Delong,Yang Hongwei&Sun Shibin.Analysis of casing damage for staged fracturing in shale gas well[J].Fault-Block Oil and Gas Field,2017,24(3):387-390.
[13]陈作,曾义金.深层页岩气分段压裂技术现状及发展建议[J].石油钻探技术,2016,44(1):6-11.Chen Zuo&Zeng Yijin.Present situations and prospects of multi-stage fracturing technology for deep shale gas development[J].Petroleum Drilling Techniques,2016,44(1):6-11.
[14]高利军,柳占立,乔磊,庄茁,杨恒林.页岩气水力压裂中套损机理及其数值模拟研究[J].石油机械,2017,45(1):75-80.Gao Lijun,Liu Zhanli,Qiao Lei,Zhuang Zhuo&Yang Henglin.Mechanism analysis and numerical simulation of casing failure in hydraulic fracturing of shale gas formation[J].China Petroleum Machinery,2017,45(1):75-80.
[15]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,2015,41(3):22-25.Dai Qiang.Analysis of production casing damage reasons during testing and completion of shale gas well[J].Drilling&Production Technology,2015,41(3):22-25.
[16]杨恒林,乔磊,田中兰.页岩气储层工程地质力学一体化技术进展与探讨[J].石油钻探技术,2017,45(2):25-31.Yang Henglin,Qiao Lei&Tian Zhonglan.Advance in shale gas reservoir engineering and geomechanics integration technology and relevant discussions[J].Petroleum Drilling Techniques,2017,45(2):25-31.
[17]郝美美.页岩气井油层套管受力分析及应力分布计算研究[D].重庆:重庆科技学院,2016.Hao Meimei.Analysis of shale gas well's casing and stress distribution calculation[D].Chongqing:Chongqing College of Science and Technology,2016.
[18]于浩,练章华,林铁军.页岩气压裂过程套管失效机理有限元分析[J].石油机械,2014,42(8):84-88.Yu Hao,Lian Zhanghua&Lin Tiejun.Finite element analysis of failure mechanism of casing during shale gas fracturing[J].China Petroleum Machinery,2014,42(8):84-88.
[19]付丽霞,朱伟,薛改珍.套管错断的原因、实例及解决的办法[J].国外油田工程,2002,18(9):35-42.Fu Lixia,Zhu Wei&Xue Gaizhen.Casing failure's sake,example,and solutions[J].Foreign Oilfield Engineering,2002,18(9):35-42.
[20]张卫东,杨勇,路智勇,刘新华,张艳增,王瑞和,等.延缓断层处套管损坏的方法[J].断块油气田,2012,19(6):800-802.Zhang Weidong,Yang Yong,Lu Zhiyong,Liu Xinhua,Zhang Yanzeng,Wang Ruihe,et al.Method of delaying casing damage at the fault[J].Fault-Block Oil and Gas Field,2012,19(6):800-802.
[21]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 Zhonglan,Shi Lin&Qiao Lei.Research of and countermeasure for wellbore integrity of shale gas horizontal well[J].Natural Gas Industry,2015,35(9):70-76.
[22]陈朝伟,石林,项德贵.长宁-威远页岩气示范区套管变形机理及对策[J].天然气工业,2016,36(11):70-75.Chen Zhaowei,Shi Lin&Xiang Degui.Mechanism of casing deformation in the Changning-Weiyuan national shale gas project demonstration area and countermeasures[J].Natural Gas Industry,2016,36(11):70-75.
[23]沈新普,金生吉.油层压裂模拟的损伤力学方法及数值应用实例[J].沈阳工业大学学报,2014,36(3):341-346.Shen Xinpu&Jin Shengji.Numerical method and application example of stimulation damage mechanics for fracture of reservoir formation[J].Journal of Shenyang University of Technology,2014,36(3):341-346.