Please use this identifier to cite or link to this item: http://repository.kpi.kharkov.ua/handle/KhPI-Press/27265
Title: Incipient regimes of drill bit whirlings on uneven bottoms of deep bore-holes
Other Titles: Зародження режимів кружляння бурового долота на шорсткуватому дні глибокої свердловини
Authors: Gulyayev, Valery Ivanovych
Vashchilina, Olena Valeriyivna
Glazunov, Sergiy Mykolajovych
Keywords: deep drilling; drill bits; nonholonomic dynamics; forward and backward whirls; глибоке буріння; долото; неголономна динаміка; прямі та зворотні кружляння
Issue Date: 2016
Publisher: NTU "KhPI"
Citation: Gulyayev V. I. Incipient regimes of drill bit whirlings on uneven bottoms of deep bore-holes / V. I. Gulyayev, O. V. Vashchilina, S. M. Glazunov // Bulletin of National Technical University "KhPI" : coll. of sci. papers. Ser. : Dynamics and Strength of Machines = Вісник Нац. техн. ун-ту "ХПІ" : зб. наук. пр. Сер. : Динаміка і міцність машин. – Kharkiv : NTU "KhPI", 2016. – № 46 (1218). – P. 81-84.
Abstract: This paper studies the problem of whirl vibrations of rotating drill string bit under conditions of its contact interaction with the borehole bottom surface. The destructive effects of whirl vibrations of drill bits and drill strings have long been recognized. The backward whirling is believed to randomly happen to some degree in 40 % of all wells. It is shown that the situation is essentially associated with enlargement of the compressive thrust force and its approaching to the Eulerian critical value. Then, the bending stiffness of the drill string reduces, it hogs and the diamond impregnations existing in the bit surface penetrate into the rock medium. As this takes place, the bit axis tilts and nutates. It should be particularly emphasized that at this stage, the bit is under action of the vertical force (weight on bit) which essentially exceeds all other forces. It presses the bit to the hole bottom (not to the hole wall) and the bit loses its ability to slide on the bore-hole bottom and begins to roll on its surface, lagging behind or outstripping the drill string rotation. As a result, the point of the bit contact with the reference surface (the instantaneous centre of velocities) may describe extremely complicated trajectories with loops and cuspidal points and to change the motion directions. As examples, whirling of spherical bit is considered.
This paper studies the problem of whirl vibrations of rotating drill string bit under conditions of its contact interaction with the borehole bottom surface. The destructive effects of whirl vibrations of drill bits and drill strings have long been recognized. The backward whirling is believed to randomly happen to some degree in 40 % of all wells. It is shown that the situation is essentially associated with enlargement of the compressive thrust force and its approaching to the Eulerian critical value. Then, the bending stiffness of the drill string reduces, it hogs and the diamond impregnations existing in the bit surface penetrate into the rock medium. As this takes place, the bit axis tilts and nutates. It should be particularly emphasized that at this stage, the bit is under action of the vertical force (weight on bit) which essentially exceeds all other forces. It presses the bit to the hole bottom (not to the hole wall) and the bit loses its ability to slide on the bore-hole bottom and begins to roll on its surface, lagging behind or outstripping the drill string rotation. As a result, the point of the bit contact with the reference surface (the instantaneous centre of velocities) may describe extremely complicated trajectories with loops and cuspidal points and to change the motion directions. As examples, whirling of spherical bit is considered.
DOI: http://dx.doi.org/10.20998/2078-9130.2016.46.88055
URI: http://repository.kpi.kharkov.ua/handle/KhPI-Press/27265
Appears in Collections:Вісник № 46

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