气体钻井井底低温对岩石破碎的影响机制
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摘要
首先分析井底钻头喷嘴的Joule-Thomson效应,其次,建立急剧冷却条件下井底岩石的温度场分布模型,并以此建立井底岩石动态热应力分布模型,对气体钻井井底热冲击应力进行深入剖析。此外,通过引入井底岩石裂纹尖端应力强度因子,对钻头载荷和热应力共同作用下的井底岩石裂纹扩展失稳进行分析,对砂岩岩样进行液氮冷却试验,并对其进行声波实时测量。结果表明:在热应力的作用下岩石裂纹的抗扩展阻力存在极小值,气体钻井岩屑粒度较小;随着温度的降低,波速在岩石中呈线性衰减,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。
Low temperature at the outlet of drilling bit nozzles can be induced due to Joule-Thomson effect during well drilling using gases as drilling fluid. In this study,a numerical simulation model for analyzing the temperature distribution around the bottom of the hole was established based on the Joule-Thomson cooling effect,and then the induced thermal shock stress was calculated according to the temperature distribution. The expansion and instability of rock cracks were analyzed in terms of a stress intensity factor at the cracking tips of rock. Experiments were conducted using liquid nitrogen for cooling of rock samples in order to verify the thermal cracking models,and a real-time acoustic technique was used to measure the cracking effect. The results show that,under the thermal stress,a minimal cracking resistance of anti-propagation exists,and cuttings with small sizes were obtained during gas drilling. It appears that the wave velocity decreases at low temperatures,and the first wave amplitude has a dramatic delay,which illustrate that the cooling can have an important impact on the internal structure of rocks.
Low temperature at the outlet of drilling bit nozzles can be induced due to Joule-Thomson effect during well drilling using gases as drilling fluid. In this study,a numerical simulation model for analyzing the temperature distribution around the bottom of the hole was established based on the Joule-Thomson cooling effect,and then the induced thermal shock stress was calculated according to the temperature distribution. The expansion and instability of rock cracks were analyzed in terms of a stress intensity factor at the cracking tips of rock. Experiments were conducted using liquid nitrogen for cooling of rock samples in order to verify the thermal cracking models,and a real-time acoustic technique was used to measure the cracking effect. The results show that,under the thermal stress,a minimal cracking resistance of anti-propagation exists,and cuttings with small sizes were obtained during gas drilling. It appears that the wave velocity decreases at low temperatures,and the first wave amplitude has a dramatic delay,which illustrate that the cooling can have an important impact on the internal structure of rocks.
引文
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[21]王龙甫.弹性力学[M].2版.北京:科学出版社,1979.
[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.
[2]CHEN G,CHEN X.The application of air and air/foam drilling technology in Tabnak gas field,Southern Iran[R].SPE 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[R].SPE94081,2005
[5]GUO B,MISKA S,LEE R.Volume requirements for directional air drilling[R].SPE 27510,1994.
[6]ZHU H,MENG Y.Influence of relevant parameters on hole cleaning and pipe string erosion in air drilling[R].SPE 126515,2010.
[7]LI J,LIU G H,GUO B Y.Pilot test shows promising technology for gas drilling[J].Journal Petroleum Technology,2012,64(7):32-37.
[8]YANG S J,LIU G H,LI J.The characteristics of recycling gas drilling technology[J].Petroleum Science,2012,9(9):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[R].SPE 31656,1985.
[15]MURRAY A S,CUNNINGHAM R A.Effect of mud column pressure on drilling rate[J].Transaction of American Institute of Mining,Metallurgical,and Petroleum Engineer,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 Institute of Mining,Metallurgical,and Petroleum Engineer,1959,216:9-17.
[17]LI Y G,QIAN F Y,LO P Y.Application of water-base mud in deep well drilling[R].SPE 10562,1982.
[18]SHEFFIELD J S,SITZMAN J J.Air drilling practices in the midcontinent and rocky mountain areas[R].SPE13490,1985.
[19]仉洪云,高德利,郭柏云.气体钻井井底岩石热应力分析[J].中国石油大学学报(自然科学版),2013,37(1):70-74.ZHANG Hongyun,GAO Deli,GUO Boyun.Downhole rock thermal stress analysis in gas drilling[J].Journal of China University of Petroleum(Edition of Natural Science),2013,37(1):70-74.
[20]陶文铨.传热学[M].西安:西北工业大学出版社,2006.
[21]王龙甫.弹性力学[M].2版.北京:科学出版社,1979.
[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.