超深井筒温度分布及其对围岩力学性质的影响研究
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摘要
钻井液停止循环后井底温度回升,极易发生由于温度升高而造成的井壁岩石延迟破坏。为探究钻井液循环过程中,由于井筒温度变化而造成的井壁失稳问题,首先通过基于非稳态温度分布的数值计算方法,探究时间、工程参数对井筒温度分布的影响;此外,借助高温高压岩石力学试验机,进行不同温度下的细砂岩的强度实验,探究温度变化对岩石强度的影响规律。实验结果表明:钻井液开始循环后,井口附近温度随时间增加呈上升趋势,井底附近呈下降趋势,存在一个与时间有关的临界井深;温度变化主要集中在井筒附近很小的区域,并且在钻井液循环初期温度迅速降低;钻井液的排量、黏度、密度越大,井底附近的井壁温度降低幅度越大,其中,排量改变对井壁温度分布影响最为明显;温度增加使含裂缝岩样的破坏程度加剧,除滑移破坏,伴有断面破坏和端面破坏发生,在裂缝倾角–抗压强度关系中,温度升高对发生滑移的区域影响不明显;温度升高,岩样的抗压强度明显降低,应力–应变曲线变得曲折,存在明显的塑性变形段,破坏过程变得复杂。
After the drilling fluid stops circulating,the bottom hole temperature rises again,which is very easy to cause delayed damage of the wellbore rock caused by the temperature rise. The wellbore instability caused by the change of wellbore temperature during drilling fluid circulation was analyzed. Firstly,the influence of time and engineering parameters on the temperature distribution of wellbore was studied by numerical calculation method based on unsteady temperature distribution. In addition,the strength experiments of fine sandstone at different temperatures were carried out by means of high temperature and high pressure rock mechanics testing machine,and the influence law of temperature change on rock strength was researched. The experimental results show that after drilling fluid circulation,the temperature near the wellhead increases with time,and the temperature near the bottom of the well decreases with time,and there exists a critical well depth related to time. The temperature changes mainly concentrate in a small area near the wellbore,and the temperature decreases rapidly in the initial stage of drilling fluid circulation;the larger the displacement,viscosity and density of drilling fluid,the greater the decrease of wellbore temperature near the bottom hole,and the change of displacement has the most obvious effect on the temperature distribution of wellbore;the temperature increases,which aggravates the damage degree of fractured rock samples and eliminates slip damage. With the occurrence of cross-section failure and end-face failure,in the fracture dip-compressive strength diagram,the influence of temperature rise on the slip area is not obvious;with the increase of temperature,the compressive strength of rock sample decreases obviously,and the stress-strain curve becomes tortuous,there are obvious plastic deformation sections,and the failure process becomes complex.
After the drilling fluid stops circulating,the bottom hole temperature rises again,which is very easy to cause delayed damage of the wellbore rock caused by the temperature rise. The wellbore instability caused by the change of wellbore temperature during drilling fluid circulation was analyzed. Firstly,the influence of time and engineering parameters on the temperature distribution of wellbore was studied by numerical calculation method based on unsteady temperature distribution. In addition,the strength experiments of fine sandstone at different temperatures were carried out by means of high temperature and high pressure rock mechanics testing machine,and the influence law of temperature change on rock strength was researched. The experimental results show that after drilling fluid circulation,the temperature near the wellhead increases with time,and the temperature near the bottom of the well decreases with time,and there exists a critical well depth related to time. The temperature changes mainly concentrate in a small area near the wellbore,and the temperature decreases rapidly in the initial stage of drilling fluid circulation;the larger the displacement,viscosity and density of drilling fluid,the greater the decrease of wellbore temperature near the bottom hole,and the change of displacement has the most obvious effect on the temperature distribution of wellbore;the temperature increases,which aggravates the damage degree of fractured rock samples and eliminates slip damage. With the occurrence of cross-section failure and end-face failure,in the fracture dip-compressive strength diagram,the influence of temperature rise on the slip area is not obvious;with the increase of temperature,the compressive strength of rock sample decreases obviously,and the stress-strain curve becomes tortuous,there are obvious plastic deformation sections,and the failure process becomes complex.
引文
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[17]LIU M,JIN Y,LU Y,et al.Oil-based critical mud weight window analyses in HTHP fractured tight formation[J].Journal of Petroleum Science and Engineering,2015,135:750-764.
[2]李世平.岩石力学简明教程[M].北京:煤炭工业出版社,1996:19-66.(LI Shiping.Concise tutorial of rock mechanics[M].Beijing:China Coal Industry Publishing House,1996:19-66.(in Chinese))
[3]周宏伟,谢和平,左建平.深部高地应力下岩石力学行为研究进展[J].力学进展,2005,35(1):91-97.(ZHOU Hongwei,XIEHeping,ZUO Jianping.Development in researches on mechanical behaviors of rocks under the condition of high ground pressure in the depths[J].Advances in Mechanics,2005,35(1):91-97.(in Chinese))
[4]LAJTAI E Z.Strength of discontinuous rocks in direct shear[J].Geotechnique,1969,19(2):218-233.
[5]谢和平,高峰,鞠杨.深部岩体力学研究与探索[J].岩石力学与工程学报,2015,34(11):2 161-2 179.(XIE Heping,GAO Feng,JU Yang.Research and development of rock mechanics in deep ground engineering[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(11):2 161-2 179.(in Chinese))
[6]陈景涛,冯夏庭.高地应力下岩石的真三轴试验研究[J].岩石力学与工程学报,2006,25(8):1 537-1 543.(CHEN Jingtao,FENGXiating,True triaxial experimental study on rock with high geostress[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(8):1 537-1 543.(in Chinese))
[7]CLEARY M.Effects of depth on rock fracture[C]//Rock at Great Depth.Rotterdam:A.A.Balkema,1989:153-1163.
[8]何满潮,谢和平,彭苏萍,等.深部开采岩体力学研究[J].岩石力学与工程学报,2005,24(16):2 803-2 813.(HE Manchao,XIEHeping,PENG Suping,et al.Study on rock mechanics in deep mining engineering[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(16):2 803-2 813.(in Chinese))
[9]SINGH J.Strength of rocks at depth[C]//Rock at Great Depth.Rotterdam:A.A.Balkema,1989:37-44.
[10]尹土兵,李夕兵,宫凤强,等.温压耦合作用下岩石动态破坏过程和机制研究[J].岩石力学与工程学报,2012,31(增1):2 815-2 816.(Study on dynamic failure process and mechanism of rock subjected to coupling temperature and pressure[J].Journal of Rock and Mechanical Engineering,2012,31(Supplement1):2 815-2 816.(in Chinese))
[11]崔玉海,唐高峰,丁晓芳,等.注水管柱中温度效应的分析与计算[J].石油钻采工艺,2003,25(2):50-54.(CUI Yuhai,TANGGaofeng,DING Xiaofeng,et al.Analysis and calculation of the temperature effect in the water injection string[J].Oil Drilling and Production Technology,2003,25(2):50-54.(in Chinese))
[12]单学军,张士诚,王文雄,等.稠油开采中井筒温度影响因素分析[J].石油勘探与开发,2004,31(3):136-139.(SHAN Xuejun,ZHANG Shicheng,WANG Wenxiong,et al.Layer subdivision in the late high water cut stage in the complex fault block reservoirs,Dongxin Oilfield[J].Petroleum Exploration and Development,2004,31(3):136-139.(in Chinese))
[13]RAMEY H J J.Wellbore heat transmission[J].Journal of Petroleum Technology,1962,14(4):427-435.
[14]SCHOEPPEL R J,BENNETT R E.Numerical simulation of borehole and formation temperature distributions while drilling to total depth[J].Society of Petroleum Engineers.Doi:10.2118/3364-MS
[15]王博.深水钻井环境下的井筒温度压力计算方法研究[硕士学位论文][D].北京:中国石油大学,2007.(WANG Bo.Research on the method of wellbore temperature and pressure calculation during deepwater drilling[M.S.Thesis][D].Beijing:China University of Petroleum,2007.(in Chinese))
[16]高永海,孙宝江,王志远,等.深水钻探井筒温度场的计算与分析[J].中国石油大学学报:自然科学版,2008,32(2):58-62.(GAO Yonghai,SUN Baojiang,WANG Zhiyuan,et al.Calculation and analysis of wellbore temperature field in deep water drilling[J].Journal of China University of Petroleum,2008,32(2):58-62.(in Chinese))
[17]LIU M,JIN Y,LU Y,et al.Oil-based critical mud weight window analyses in HTHP fractured tight formation[J].Journal of Petroleum Science and Engineering,2015,135:750-764.