气体钻井低温破岩机理分析
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摘要
气体钻井有着较高的机械钻速在很大程度上归因于钻头水眼处的焦耳–汤姆森低温效应。这种效应对井底岩石产生了热冲击应力,使得井底岩石的强度降低,进而促进了机械破岩的作用。首先建立了非对称冷却条件下井底岩石的温度场的分布模型,并以此建立了井底岩石三维动态热应力分布模型,对气体钻井井底热冲击应力进行了深入的剖析。其次,通过莫尔–库仑准则,对岩石的黏聚力变化进行了分析,得出随着冷却时间的加长,岩石强度迅速降低,有利于岩石的破坏。最后,为验证理论模型,对砂岩岩样进行液氮冷却试验,并对其进行声波实时测量,声波的首波波幅也有明显的延迟,说明冷却处理对岩心内部结构产生了很大影响。
The factors contributing to high penetration rate of gas drilling are complex. The isentropic flow is generated when gas passes through bit nozzle during gas drilling. This phenomenon will lead to cryogenic effects, and then the resulted thermal shock stress at bottom hole rock will reduce the rock strength, contributing to the role of the rock failure. First, a model for the temperature distribution of bottom hole rock under asymmetric cooling is established. The three-dimensional dynamic thermal shock stress distribution model is established based on the temperature field. Then, the change of the rock cohesion is analyzed by using the Mohr-Coulomb criterion. The results demonstrate that as the temperature decreases, the strength of rock is greatly reduced, resulting in increased ROP. Finally the liquid nitrogen cooling tests and real-time measurements of acoustic waves are conducted to verify the above theory. The first wave amplitude has a dramatic delay, which illustrates that the cooling has an important impact on the internal structure of rock. The mechanism of rock failure under dynamic low temperature in gas drilling is clearly depicted.
The factors contributing to high penetration rate of gas drilling are complex. The isentropic flow is generated when gas passes through bit nozzle during gas drilling. This phenomenon will lead to cryogenic effects, and then the resulted thermal shock stress at bottom hole rock will reduce the rock strength, contributing to the role of the rock failure. First, a model for the temperature distribution of bottom hole rock under asymmetric cooling is established. The three-dimensional dynamic thermal shock stress distribution model is established based on the temperature field. Then, the change of the rock cohesion is analyzed by using the Mohr-Coulomb criterion. The results demonstrate that as the temperature decreases, the strength of rock is greatly reduced, resulting in increased ROP. Finally the liquid nitrogen cooling tests and real-time measurements of acoustic waves are conducted to verify the above theory. The first wave amplitude has a dramatic delay, which illustrates that the cooling has an important impact on the internal structure of rock. The mechanism of rock failure under dynamic low temperature in gas drilling is clearly depicted.
引文
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[2]CHEN G,CHEN X.The application of air and air/foam drilling technology in tabnak gas field,southern iran[C]//Social of Petroleum Engineer 101560,2006.
[3]GAS RESEARCH INSTITUTE.Underbalanced Drilling manual[M].GRI Reference,1997.
[4]GUO B,GHALAMBOR A,XU C.A systematic approach to predicting liquid loading in gas wells[J].SPE Production&Facilities Journal,2006,21:81–88.
[5]GUO B,MISKA S,LEE R.Volume requirements for directional air drilling[C]//Social of Petroleum Engineering27510.1994.
[6]ZHU H,MENG Y.Influence of relevant parameters on hole cleaning and pipe string erosion in air drilling[C]//Social of Petroleum Engineering 126515.2010.
[7]LI J,LIU G H,GUO B Y.Pilot test shows promising technology for gas drilling[J].Journal Petroleum Technology,2012,7:32–37.
[8]YANG S J,LIU G H,LI J.The characteristics of recycling gas drilling technology[J].Petroleum Science,2012,1:59–65.
[9]YANG S J,LIU G H,LI J.Distribution of the sizes of rock cuttings in gas drilling at various depths[J].Computer Modeling in Engineering&Science,2012,89(2):79–96.
[10]LI J,YANG S J,LIU G H.Cutting breakage and transportation mechanism of air drilling[J].International Journal of Oil,Gas and Coal Technology,2013,6(3):259–270.
[11]LI J,YANG S J,LIU G H.Gas flow control method of recycling gas drilling technology[J].International Journal of Oil,Gas and Coal Technology,2013,6(6):645–657.
[12]YANG S J,LIU G H,LI J.Thermal stress on bottom hole rock of gas drilling[J].International Journal of Oil,Gas and Coal Technology,2012,5(4):385–398.
[13]MOORE P L.Five factor that affect drilling rate[J].Oil and Gas Journal,1958,56(40):141–162.
[14]BOURGOYNE A T,MILLHEIM K K,CHENEVERT M E,et al.Applied drilling engineering[C]//Social of Petroleum Engineer 31656.1985.
[15]MURRAY A S,CUNNINGHAM R A.Effect of mud column pressure on drilling rate.transaction of american istitute of mining,metallurgical,and petroleum engineer[J].1955,205:196–204.
[16]CUNNINGHAM R A,FENINK J G.Laboratory study of effect of overburden,formation,and mud column pressure on drilling rate of permeable formations[J].Transaction of American Istitute of Mining,Metallurgical,and Petroleum Engineer,1959,216:9–17.
[17]BLACK A D,GREEN S J.Laboratory simulation of deep well drilling[R].Petroleum Engineer,1978.
[18]SHEFFIELD J S,SITZMAN J J.Air drilling practices in the midcontinent and rocky mountain areas[C]//Social of Pereoleum Engineer 13490.1985.
[19]仉鸿云,高德利,郭伯云.气体钻井井底岩石热应力分析[J].中国石油大学学报(自然科学),2013,34(1):70–74.(ZHANG Hong-yun,GAO De-li,GUO Bo-yun.Downhole rock thermal stress analysis in gas drilling[J].Journal of China University of Petroleum(Science edition),2013,34(1):70–74.(in Chinese))
[20]陶文铨.传热学[M].西安:西北工业大学出版社,2006,12.(TAO Wen-shuan.Heat transfer theory[M].Xi'an:Northwestern Polytechnic University Press,2006.(in Chinese))
[21]王龙甫.弹性力学[M].2版.北京:科学出版社,1979.(WANG Long-fu.Elastic mechanics[M].2nd ed.Beijing:Science Press,1979.(in Chinese))
[22]陈勉,金衍,张广清.石油工程岩石力学[M].北京:科学出版社,2008.(CHEN Mian,JIN Yan,ZHANG Guang-qing.Rock mechanics of petroleum engineering[M].Beijing:Science Press,2008.(in Chinese))