基于盐岩损伤机理的深部巨厚盐层钻井液密度设计方法
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摘要
为防止钻井过程中盐层蠕变发生塑性变形而导致卡钻等事故,传统的方法是建立蠕变本构方程及用实验确定蠕变参数,但是得到的控制盐层蠕变的钻井液密度不能很好地反映实际钻井情况。因而提出一种控制近井筒盐岩不产生扩容损伤变形的新方法,并利用该方法设计了深部巨厚盐层钻井液密度。通过室内试验分析了盐岩损伤变形过程中的声发射信号,确定了盐岩的扩容损伤边界。对于深部盐岩钻井工程中的井壁稳定性问题,根据八面体剪应力准则,井壁盐岩的应力状态控制在扩容损伤边界以内,设计了深部盐层安全钻井液密度窗口。与实际钻井对比分析表明,用该方法设计的钻井液密度窗口能够保证盐层安全钻井,且方法简单而有效,便于现场应用。
In order to prevent stick accidents caused from plastic deformation of salt-bed creep during drilling,the density of drilling fluids in salt formation is commonly calculated using the established constitutive equation and the parameters obtained from experiments,which cannot meet the real requirement of drilling fluid.A new approach for controlling the dilatancy damage and deformation at the nearside of borehole was presented and used to calculate the density of drilling fluid for deep big-thickness salt formation.The acoustic emission signal generated from salt rock damage and deformation was analyzed in laboratory to determine the dilatancy border in the damaged salt-formation.The borehole of deep salt formation is stable only when the octahedral shear stress is below the dilatancy boundary.A comparison of the density of drilling fluid designed by the new method with that of the real drilling indicates that the density window for designing drilling fluids can be simply and effectively applied in the course of drilling in the big-thickness salt formations.
In order to prevent stick accidents caused from plastic deformation of salt-bed creep during drilling,the density of drilling fluids in salt formation is commonly calculated using the established constitutive equation and the parameters obtained from experiments,which cannot meet the real requirement of drilling fluid.A new approach for controlling the dilatancy damage and deformation at the nearside of borehole was presented and used to calculate the density of drilling fluid for deep big-thickness salt formation.The acoustic emission signal generated from salt rock damage and deformation was analyzed in laboratory to determine the dilatancy border in the damaged salt-formation.The borehole of deep salt formation is stable only when the octahedral shear stress is below the dilatancy boundary.A comparison of the density of drilling fluid designed by the new method with that of the real drilling indicates that the density window for designing drilling fluids can be simply and effectively applied in the course of drilling in the big-thickness salt formations.
引文
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[3]宋胜利,王海涛,马海涛,等.中原油田盐岩蠕变规律研究及套管损坏预防措施[J].石油学报,2005,26(2):119-121.Song Shengli,Wang Haitao,Ma Haitao,et al.Creeping regularityof salt bed and measures for avoiding casing damage in ZhongyuanOilfield[J].Acta Petrolei Sinica,2005,26(2):119-121.
[4]金衍,陈勉,柳贡慧.盐膏岩地层的井眼缩径变形分析[J].石油大学学报,自然科学版,1999,23(2):37-39.Jin Yan,Chen Mian,Liu Gonghui.Application of flac in boreholeshrinkage in formation of plaster stone and salt stone[J].Journalof the University of Petroleum,China:Edition of Natural Science,1999,23(2):37-39.
[5]邓金根.控制油井盐层段流变缩径的泥浆密度的计算方法[J].岩石力学与工程学报,1997,16(6):522-528.Deng Jingen.Calculation method of mud density to control bore-hole closure rate[J].Chinese Journal of Rock Mechanics and Engi-neering,1997,16(6):522-528.
[6]曾义金.钻井液密度对盐膏层蠕变影响的三维分析[J].石油钻采工艺,2001,23(6):1-3.Zeng Yijin.Three-dimesional analysis on how mud weight affectsthe gypsum-salt bed creep[J].Oil Drilling&Production Technol-ogy,2001,23(6):1-3.
[7]刘力强,马胜利,马瑾,等.三轴压缩下不同构造花岗岩的微破裂时空分布特征及其地震学意义[J].科学通报,1999,44(11):1194-1198.Liu Liqiang,Ma Shengli,Ma Jin,et al.Effect of rock structure onstatistic charateristics of acoustic emission[J].Chinese ScienceBulletin,1999,44(11):1194-1198.
[8]周维垣,杨强.岩石力学数值计算方法[M].北京:中国电力出版社,2005:84-86.Zhou Weiheng,Yang Qiang.Numerical calculation method of rock me-chanics[M].Beijing:China Electric Power Publishing,2005:84-86.
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