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Chaotic Vibration Analysis of the Bottom Rotating Drill String  [PDF]
Qilong Xue,Ruihe Wang,Feng Sun,Zhiyuan Huang
Shock and Vibration , 2014, DOI: 10.1155/2014/429164
Abstract: Drill string vibration is a widely studied topic. This paper developed a real-time measurement system near the drilling bit and extracted the lateral vibration, longitudinal vibration time series of bottom rotating drill string. In order to reconstruct the phase space, we estimated the delay time with mutual information and calculated the embedding dimension through Cao’s method. Finally, the chaotic characterization of the system is analyzed by calculating the correlation dimension and the largest Lyapunov exponent. The results show that such system can exhibit positive finite-time Lyapunov exponents and a clear convergence toward the correlation dimension, which is a strong indicator for the chaotic behavior of the system. It is expected that the new dynamics found in this paper could be of potential implication to the control methods of the drill string vibration. 1. Introduction In oil and gas drilling engineering, the well is created by drilling a hole 5 to 50 inches (127.0?mm to 914.4?mm) in diameter into the earth with a drilling rig that rotates a drill string with a bit attached. In the process, severe drill string vibration is a major contributor to downhole tool failure. It may also cause hole damage and increase the need for more frequent rig repair. Typically, the drilling string vibration can be divided into three types or modes: lateral, longitudinal, and torsional. The destructive nature of each type of vibration is different. Lateral and longitudinal vibrations of the drill string have been undertaken extensive research since it proposed from mid-1960s, The main reason that caused the fatigue failure of the bottomhole assembly (BHA) [2] was considered to be the vibration of the drill string. Many studies of the drill string focused on the determination of natural frequencies [3, 4], bending stress calculation [5, 6], stability analysis [7], lateral displacement prediction [8], and so forth. Spanos et al. [9] established the finite element model of drill string lateral vibration and analyzed nonlinear random vibration. Chunjie and Tie [10] obtained the natural frequency of drill string longitudinal vibration from a finite element model. Vibrations of all three types (lateral, longitudinal, and torsional) may occur during rotary drilling and are coupled. Single vibration model cannot well describe the dynamics of BHA; furthermore, to establish a precise bottom hole kinetic theory model is difficult to achieve because of the underground complex situation. Additionally, the process of drill bit break rocks is a nonlinear process which is
Seismic Prediction While Drilling (SPWD): Looking Ahead of the Drill Bit by Application of Phased Array Technology
Katrin Jaksch,Rüdiger Giese,,Matthias Kopf,Andreas Jurczyk
Scientific Drilling , 2010, DOI: 10.2204/iodp.sd.9.08.2010
Abstract: Geophysical exploration is indispensable for planning deep drilling. Usually 2D- or 3D-seismics investigations are applied and, depending on the resulting geologic model for the underground, the drill site and drilling path are determined. In recent years the focus of exploration has shifted towards small-scale geological structures such as local layers and faults. Depending on the source frequencies and the target depth, 2D- or 3D-seismics from surface cannot always resolve such structures in particular at larger depths. In general, signal frequencies of about 30–70 Hz are typical for surface seismic methods. The deeper and smaller the sought-after structures are, the worse will be the resolution. Therefore, borehole seismic measurements like Vertical Seismic Profile (VSP) or Seismic While Drilling (SWD) have been developed (Fig. 1). For the VSP method geophones are normally integrated in the borehole, while the seismicsource generates seismic waves at the surface. The SWD method uses the drill bit as the seismic source. Hence, the quality of the seismic signals is highly dependent on the drilled rock and the type of drill bit, but even well-suited rock conditions and adequate drilling may not provide sufficient data quality.
Studying Rock Breaking Properties and Penetration Rate Improving Mechanisms for Hybrid Drill Bit in Hard Formation

- , 2017,
Abstract: PDC-牙轮复合钻头是一种综合了PDC钻头与牙轮钻头结构特点和工作原理的新型钻头,能更高效地钻进硬地层。但由于对其破岩机理认识不足,使得PDC-牙轮复合钻头的研发具有盲目性,推广受限。基于弹塑性力学和岩石破碎学,采用Drucker-Prager准则描述岩石本构关系,塑形应变作为破岩判据,通过有限元法建立全尺寸复合钻头和PDC钻头动态破岩的非线性动力学模型,分析了复合钻头作用下硬地层岩石的破坏机制,对比了硬地层中两种钻头的动态破岩过程。结果表明:复合钻头钻井能满足井壁稳定性的要求,然而一旦井壁失稳,井壁岩石将大块脱落;以拉应力破岩为主是复合钻头在硬地层中大幅提高机械钻速的原因之一;硬地层中复合钻头扭转振动低于PDC钻头,破岩效率更高;由于牙轮滚动的多边形效应,复合钻头沿钻进方向对岩石的冲击较PDC钻头更大,能更快钻进硬地层。
A hybrid drill bit combines the structural features and working principles of PDC drill bit and cone drill bit, being able to drill hard formation more efficiently. But its research and development is blind and its promotion is limited due to lack of knowledge about its rock breaking mechanisms. Based on elastoplastic mechanics and rock breaking theory, 3D non-linear dynamic simulation models of dynamic rock breaking with full-gauge hybrid drill bit and PDC bit are established with the finite element method. The constitutive relation of rock is described by Drucker-Prager criteria and the plastic strain is used as the criterion for describing the rock breaking. The failure mechanisms for rock breaking in hard formation with the hybrid drill bit are studied. The dynamic rock breaking with hybrid drill bit in hard formation are compared with that of PDC drill bit. The comparison results show that the well drilled by hybrid drill bit can satisfy the borehole wall stability requirements but that the sidewall rock may fall off. This partly explains the reasons why the use of hybrid drill bit significantly enhances the penetration rate in hard formation and why the rock is broken mainly by tensile stress. The torsional vibration of hybrid drill bit is lower than that of PDC drill bit and the rock breaking efficiency is higher in hard formation. The impact of hybrid drill bit on rock is greater than that of PDC drill bit due to the polygon effect of cone drill bit during scrolling; therefore the hybrid drill bit can drill rock faster than PDC drill bit in hard formation
Field test of the drill-bit vibration signal detection using portable seismometers

YANG Wei,GE Hong-kui,NING Jing,LIN Jian-min,

地球物理学进展 , 2007,
Abstract: It is a important way to explore the undrilled formations by recording the drill-bit vibration signal while drilling,namely SWD.SWD is helpful to eliminate the geological uncertainty and potential hazard.By analyzing the signal characteristic of the drill-bit vibration and performance difference of traditional multi-channel geophones instrument and the portable digital seismometers,we proposed a new way to detect the seismic signal while drilling.In it the advanced portable seismometers are used as transducers in a array.Seismometers with high sensitivity will record the vibration signal continuously while drilling.The preliminary field experiment shows this SWD scenario is feasible.The signal to noise ratio(S/N) obtained by seismometers is higher than geophones.This new approach can be operated easily by drilling engineers and opens a new way to the SWD technique.
Paolo Macini
Rudarsko-Geolo?ko-Naftni Zbornik , 1996,
Abstract: This paper underlines the importance of the correct drill bit application in horizontal wells. Afler the analysis of the peculiarities of horizontal wells and drainholes drilling techniques, advantages and disadvantages of the application of both roller cone and fixed cutters drill bits have been discussed. Also, a review of the potential specific featuries useful for a correct drill bit selection in horizontal small diameter holes has been highlighted. Drill bits for these special applications, whose importance is quickly increasing nowadays, should be characterised by a design capable to deliver a good penetration rate low WOB, and, at the same time, be able to withstand high RPM without premature cutting structure failure and undergauge. Formation properties will also determine the cutting structure type and the eventual specific features for additional gauge and shoulder protection.
Elastic Bending Deformation of the Drill Strings in Channels of Curve Wells  [PDF]
Nabil Wanas Musa
Modern Mechanical Engineering (MME) , 2017, DOI: 10.4236/mme.2017.71001
The problem about identification of elastic bending deformation of a drill string in a curve wells based on the theory of flexible curved rods and the direct inverse problems of drill string bending in the channels of curvilinear bore-holes is stated. The problem is solved which determines the resistance forces and moments during performing ascending-descending operations in curvilinear bore-holes with trajectories of the second order curve shapes. The sensitivity of the resistance forces relative to geometric parameters of the bore-hole axial line trajectories is analyzed.
Design and Exploitation Problems of Drill String in Directional Drilling
Bednarz Stanislaw
Acta Montanistica Slovaca , 2004,
Abstract: Drill string design for directional drilling requires accounting for a number of factors. First, types and expected values of loads should be determined. Then, elements of the drill string should be so selected as to enable realization of the plan at specified loads. Some of additional factors, e. g. purchase, exploitation cost, geological conditions in the bore-hole, washing of the bore-hole, stability, trajectory, rig parameters, accuracy of gauges, pumps parameters remain in conflict. Drill pipes are made of rolled pipes, upset and welded with tool joints to 9,5 m long; the shorter ones can be made of hot forged rods. Exploitation requirements, being a result of practical experience supported by theoretical and laboratory analyses should be a part of syllabuses of technical staff educational programs. Apart from designing the string, it is also vital to lower the risk of a drilling failure. The significance of these aspects seems to be unquestionable.
Features of drill string vibration signal and multiples imaging

地球物理学进展 , 2010,
Abstract: Drill string is the medium connecting the formation and ground. Its vibration stimulated by the rotary bit contains a lot of useful information. It is possible to get the drill tools’ working condition and information of the formation that is drilled and will be drilled by analyzing the drill-bit vibration propagating in the drill string. Because different units of drill string have different cross section areas, the drill-bit vibration signal is reflected on the interface of changing cross section areas. By processing the drill string vibration signal with one-side deconvolved autocorrelation method, drill string image and drill string wave velocity are obtained. They match with the theoretical result very well. This provides a valid basis for the future drill string vibration logging and seismic while drilling (SWD) technology.
Pictorial interlude: Caught up in a ‘whirl’
M Kuehnast, S Andronikou
South African Journal of Surgery , 2012,
Abstract: A patient with the ‘whirl sign’ on computed tomography is 25.3 times as likely as a patient without the sign to have small-bowel obstruction (SBO) necessitating surgery. The ‘whirl sign’ therefore has an important role in the assessment of patients with clinical and radiological signs of SBO.
Conditions d'apparition et formes de rebond d'un outil de forage tric ne Conditions of Appearance and Forms of Lift-Off Dynamics (Bit Bouncing) for a Roller Cone Drill Bit  [cached]
Putot C.,Mabile C.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1999030
Abstract: Le mode de vibration longitudinal du train de tiges peut, dans certaines conditions de forage, dégénérer en rebond avec séparation périodique à l'interface outil tric ne, roche; il va de soi que ce comportement doit être évité. En présence de roches compactes, on a coutume d'associer le rebond à la présence d'un motif à l'interface roche-outil, dit motif trilobé en raison de sa symétrie ternaire. Il se matérialise par une ondulation périodique, sensiblement sinuso dale, du front d'abattage. En roches tendres , l'allure du phénomène de vibration longitudinale est plus chaotique et fait l'objet d'investigations spécifiques liant dynamique et expulsion de copeaux (programme Cutclean). En roches dures , l'expérience prouve que le motif est repris à chaque passage d'outil par érosion différenciée des ondulations, sans qu'il y ait nécessairement décollement. Il s'ensuit une rotation d'ensemble du motif d'interface, de l'ordre de quelques degrés par tour, liée au décalage de phase entre effort de coupe et ondulation. Le phénomène de rebond se manifeste préférentiellement lorsqu'il y a accord entre la fréquence de défilement des c nes - tributaire de la vitesse de rotation - et une fréquence propre du système de forage. Mais le phénomène peut également se manifester loin des résonances prévues par l'analyse linéaire. L'interprétation présentée dans cet article, issue du domaine d'étude de l'usinage des métaux, est une étude de type formulation linéarisée. Le critère de stabilité définit, pour un système donné, l'effort limite comme produit d'un terme caractéristique de la formation par la raideur dynamique du mode de réponse de la structure. Ce terme est analogue au coefficient d'Archard dans une loi d'usure. Le coefficient de proportionnalité entre effort normal et profondeur de passe n'a d'ailleurs (la confusion est fréquente) aucun lien avec le module d'élasticité, mais davantage avec la caractéristique de cohésion de la roche. Ainsi, et conformément à l'intuition, le rebond se manifestera préférentiellement avec une roche très résistante et une structure souple pour la fréquence envisagée. Des considérations d'efficacité de coupe, liées à la compatibilité plus ou moins grande de la géométrie du c ne et de la courbure de l'interface du motif trilobé, sont dégagées et cadrent parfaitement avec une dissymétrie observée sur les enregistrements (Trafor) du couple entre maxima et minima ; les phases de décollement et de reprise de contact en cas de rebond sont également compatibles avec les extrema de poids sur outil. The longitudinal vibration mode of the drill s
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