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Influence of friction on buckling of a drill string in the circular channel of a bore hole

Petroleum Science 2016年第4期13卷 698-711页

作者： Valery Gulyayev natalya shlyun Department of Mathematics National Transport UniversityKiev Ukraine

Enhancement of technology and techniques for drilling deep directed oil and gas bore hole is one of the most important problems of the current petroleum *** infrequently, the drilling of these bore holes is attended by occurrence of extraordinary situations associated with technical accidents. Among these is the Eulerian loss of stability of a drill string in the channel of a curvilinear bore hole. Methods of computer simulation should play a dominant role in prediction of these states. In this paper, a new statement of the problem of critical buckling of the drill strings in 3D curvilinear bore holes is proposed. It is based on combined use of the theory of curvilinear elastic rods, Eulerian theory of stability, theory of channel surfaces, and methods of classical mechanics of systems with nonlinear constraints. It is noted that the stated problem is singularly perturbed and its solutions have the shapes of localized harmonic wavelets. The calculation results showed that the friction effects lead to essential redistribution of internal axial forces, as well as changing the eigenmode shapes and sites of their localization. These features make the buckling phenomena less predictable and raise the role of computer simulation of these effects.

关键词： Directed bore hole Drill string Critical states Singular perturbation Friction forces Harmonic wavelet

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Critical Buckling of Drill Strings in Cylindrical Cavities of Inclined Bore-Holes

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Journal of Mechanics Engineering and Automation 2016年第1期6卷 25-38页

作者： Nabil Musa Valery Gulyayev Nataliya shlyun Hasan Aldabas Department of Mechanical Engineering Philadelphia University Amman Jordan Department of Mathematics National Transport University Suvorov str. 1 Kiev 01010 Ukraine

Notwithstanding the fact that the problem of drill string buckling （Eulerian instability） inside the cylindrical cavity of an inclined bore-hole attracts attention of many specialists, it is far from completion. This peculiarity can be explained by the complexity of its mathematic model which is described by singularly perturbed equations. Their solutions （eigen modes） have the shapes of boundary effects or buckles （harmonic wavelets） localized in zones of the bore-hole that are not specified in advance. Therefore, the problem should be stated in the domain of entire length of the drill string or in some separated part including an expected zone of its buckling. In the paper, a mathematic model for computer analysis of incipient buckling of a drill string in cylindrical channel of an inclined bore-hole is elaborated. The constitutive equation is deduced with allowance made for action of gravity, contact, and friction forces. Computer simulation of the drill string buckling is performed for different values of the bore-hole inclination angle, its length, friction coefficient, and clearance. The eigen values （critical loads） are found and modes of stability loss are constructed. The numerical results for the case when the inclination angle equals friction angle coincide with ones obtained analytically.

关键词： Deep drilling inclined bore-holes drill strings stability singularly perturbed problem.

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龙爪稷愈伤组织的诱导和植株再生

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山东大学学报（自然科学版） 1995年第3期30卷 331-335页

作者：何向远滕世云山东大学生物系山东济南

龙爪稷幼胚在含２，４－Ｄ３ｍｇ／ＬＭｓ培养基上，可诱导出愈伤组织，经继代培养后，在含ＩＡＡ和椰子乳的分化培养基上可以再生植株；继代时间不同的组织成苗途径不同．再生苗在试管内可结实，种子发育正常可以萌发．

关键词：龙爪稷愈伤组织再生植株器官发生体细胞胚发

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