Stick-slip Vibration Research Articles

Fluid–solid coupling simulation of a new hydraulic self-adaptive PDC cutter for improving well-drilling efficiency in complex formations

A new type of hydraulic self-adaptive polycrystalline-diamond-compact (PDC) cutter (SAPC) is designed for controlling cutting depth of the PDC bit flexibly and reducing the harm of stick–slip vibration to drilling operation. The fluid–solid coupling movement of SAPC under different well-drilling conditions are simulated and analyzed. The results show that the up-going time of SAPC can be increased by reducing the diameter of the thin connecting pipe, increasing the diameter of the SAPC liquid-cavity, increasing the height of the cavity, increasing the liquid viscosity and increasing the initial spring force/decreasing the elasticity coefficient. Among them, reducing the diameter of thin connecting pipeline and increasing cavity diameter are the most sensitive. The up-going time can also be increased by the way of changing liquid viscosity without changing the structure of SAPC. Increasing the initial spring force and decreasing the elasticity coefficient can also increase the up-going time of the SAPC, however, the response window to the linkage force is reduced. The double-pipeline embedded SAPC can effectively reduce the volume and installation difficulty. The reasonable thin pipeline diameter is 0.2–0.5 mm, and the thick pipeline diameter is more than 2 mm, and the cavity diameter is more than 18 mm. Based on the results of the numerical simulation study, the up-going time of the SAPC is designed over 1.25 s, which meets the performance requirements of the hydraulic SAPC using in complex reservoir drilling, such as carbonate-sandstone reservoir.

Formation Mechanism of Metro Rail Corrugation Based on Wheel–Rail Stick–Slip Behaviors

Field investigation shows that most corrugations occur on the inner rail surface of curved tracks with a radius of less than 700 m. In order to explore the formation mechanism of metro corrugation, the relationship between wheel–rail stick–slip characteristics and rail corrugation is studied by combining single wheelset curving and a rigid–flexible coupling model. The numerical results illustrate that the lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the small radius curve eventually leads to the generation of inner rail corrugation, and the lateral torsional stick–slip vibration of outer rail–outer wheel of the driven wheelset may also occur, but the intensity is weak and the probability is low. The lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the large radius curve is also easy to cause inner rail corrugation, but the degree of inner rail corrugation is lower than that on the small radius curve; the outer rail on the large radius curve is still not easy to produce corrugation. The formation mechanism of rail corrugation on the straight track is different from that on the curve track, which is mainly related to the wheel–rail longitudinal torsional stick–slip vibration.

Design and Hardware in-the-Loop Validation of an Effective Super-Twisting Controller for Stick-Slip Suppression in Drill-String Systems

Abstract This paper presents a novel controller for drill string systems based on a super-twisting sliding mode theory. The aim is to eliminate the stick-slip vibration and maintain a constant drill string velocity at the desired reference value. The proposed controller inherently attenuates the torsional vibration while ensuring the stability and high efficiency of the drill string. A discontinuous lumped-parameter torsional model of vertical drill strings based on four components (rotary table, drill pipes, drill collars, and drill bit) is considered. The Karnopp friction model is adopted to simulate the nonlinear bit-rock interaction phenomena. In order to provide a more accurate evaluation, the proposed drill string controller is implemented with the induction motor, a variable frequency drive, and a gearbox to closely mirror the real environment of oil well drill strings. The increasing demand for prototyping and testing high-power plants in realistic and safe environments has led to the advancement of new types of experimental investigations without hurting the real system or building a small-scale prototype for testing. The dynamic performance of the proposed controller has been investigated with matlab software and in a novel hardware-in-the-loop (HIL) testing platform. A power plant is modeled and implemented in the real-time simulator OPAL-RT 5600, whereas the controllers are implemented in the dSPACE 1103 control board. The results obtained through simulatiosn and HIL testing demonstrate the feasibility and high performance of the proposed controller.

Stick-slip investigation of dual drilling and reaming bottom hole assembly

Drillstring vibration is known to cause failures of drilling equipment, including the drill bit. In particular, stick-slip vibration has been known for causing premature failure of the drill bit, hence resulting in reducing the rate of penetration. With dual reaming while drilling, cutting forces are acting on the drillstring due to the simultaneous contact of the reamer and the drill bit. Field studies have shown dramatic changes in the dynamics of the bottom hole assembly due to the dual cutting actions. This paper investigates the dynamics of bottom hole assembly for dual reaming and drilling operation, with emphasis on stick-slip vibrations due to the reamer and the bit contact with the formation. A coupled vibration model representing the drillstring was created to simulate the stick-slip vibrations caused by the bit and reamer interactions using the finite element approach. The numerical analysis showed an elevated stick-slip vibration due to the dual-action of the reamer and the bit. Sensitivity analysis indicated that the cutter aggressiveness for the bit and the reamer are the most significant parameters affecting stick-slip behavior.

Friction-induced vibration of a slider-on-rotating-disc system considering uniform and non-uniform friction characteristics with bi-stability

The friction-induced vibration of a novel slider-on-rotating-disc system is studied by a combination of numerical analysis on the theoretical model and experimental investigation on the test rig. In this system, the rotation of an L-shaped component couples with the friction-induced stick–slip vibration in the tangential direction and produces a state-dependent normal force. The numerical results of the dynamic responses by employing the Coulomb friction model and the friction model with Stribeck effect are both in good agreement with the experimental results, therefore the credibility of the numerical analysis on the theoretical dynamic model is validated. The bi-stability phenomenon, i.e., there is coexistence of a stable pure sliding response and a stable stick–slip limit cycle in a certain parameter range, is not only revealed in the numerical analysis but also observed experimentally. Moreover, a novel approach to constitute a non-uniform friction interface on the disc surface is explored for its efficacy in suppressing the friction-induced stick–slip vibration of the system also by both numerical analysis and experimental testing, namely, the disc surface is divided into sectors assigned with different friction properties. Both the numerical and experimental results show that the non-uniform friction interface of the disc with appropriate friction properties of these sectors can be an effective approach to diminish the range of the operating parameters where the stick–slip vibration occurs and thereby reduce the possibility of occurrence of stick–slip vibration in the system.

A capsule-structured triboelectric energy harvester with stick-slip vibration and vibro-impact

Despite great progress made in triboelectric energy harvesting, most investigations are purely about experiments and/or manufacturing. There is a serious lack of in-depth theoretical studies of the underlying vibration and its effects on power yield. In this paper, a novel triboelectric energy harvester is presented and its non-smooth structural dynamics and electrical performance are studied. This first theoretical study of a capsule-structured triboelectric energy harvester includes a mathematical model coupling the structural dynamics and electric dynamics, which integrates in-plane sliding mode and contact-separation mode. The influences of friction properties on sliding surfaces, electrostatic force, initial slider position, excitation level and harvester dimensions, are investigated. The performance of this harvester is not limited by its frequency bandwidth, whose average power increases from 10.3 μW at 3 Hz to 69.4 μW at 14 Hz. Impact/chatter events are found to improve power yield, for example, there is a dramatic increase of 20 μW at 6 Hz due to impact induced by a slight increase of excitation amplitude. Additionally, the internal capsule length plays a subtle role and a length beyond a certain value causes a sharp fall of power yield. These findings enable innovative designs and provide fabrication guidelines of triboelectric energy harvesters.

Eliminating Stick-Slip Vibrations in Drill-Strings with a Dual-Loop Control Strategy Optimised by the CRO-SL Algorithm

Friction-induced stick-slip vibrations are one of the major causes for down-hole drill-string failures. Consequently, several nonlinear models and control approaches have been proposed to solve this problem. This work proposes a dual-loop control strategy. The inner loop damps the vibration of the system, eliminating the limit cycle due to nonlinear friction. The outer loop achieves the desired velocity with a fast time response. The optimal tuning of the control parameters is carried out with a multi-method ensemble meta-heuristic, the Coral Reefs Optimisation algorithm with Substrate Layer (CRO-SL). It is an evolutionary-type algorithm that combines different search strategies within a single population, obtaining a robust, high-performance algorithm to tackle hard optimisation problems. An application example based on a real nonlinear dynamics model of a drill-string illustrates that the controller optimised by the CRO-SL achieves excellent performance in terms of stick-slip vibrations cancellation, fast time response, robustness to system parameter uncertainties and chattering phenomenon prevention.

Analysis of stability and stick-slip motion of a friction-induced vibrating system with dwell-time effect

In this paper, the authors investigate the stability and stick-slip motion of a friction-induced vibrating system placed on a belt moving at constant velocity using two-state model with consideration of dwell-time effect. The two-state model can be considered as an extension of the LuGre model because it can capture both Stribeck and dwell-time effects in the case of near-zero relative motion velocity between two surfaces. The previously known Stribeck effect is that the friction force decreases as the relative velocity increases in the near-zero range, while the dwell-time effect exhibits that the friction force increases as two surfaces are kept in contact for a certain time. With new effect of dwell-time, properties of stick-slip motion are explored in detail, including the equilibrium point position, the stability of the equilibrium point, Hopf bifurcation, characteristics of velocity and the change of friction force in different cases of belt velocity. The obtained result indicates that the influence of dwell-time on system responses is significant in the near-zero velocity range. Using the Routh-Hurwitz criterion, the authors show that there is a positive shift in the direction of increase of belt velocity for the stable zone of the equilibrium position compared with the stable zone obtained from the LuGre model. The formulations of the limit cycle and phases of motion in stick-slip vibration of the system are demonstrated by numerical simulations.

Hybrid Backstepping Sliding Mode Controller for Stick–slip Vibrations Mitigation in Rotary Drilling Systems

The main objective of this paper is to suppress the stick–slip vibrations in the drilling system so that the drill bit can follow the desired nominal angular velocity of the Top Drive in an optimal time. Hence to protect drilling equipment from hazards and increase drilling performances by decreasing the non-productive time (NPT). Three control systems have been proposed to achieve this objective, a sliding controller is firstly designed and then a backstepping approach is discussed secondly. Furthermore, a hybridization of sliding mode control with a backstepping approach has been proposed on the so-called hybrid backstepping sliding mode controller. The latter has not been proposed before in the literature for rotary drilling systems. Moreover, two torsion models of the system have been discussed for different degrees of freedom. Based on the comparison between controllers’ responses, the effectiveness and the robustness of the hybrid controller have been demonstrated and highlighted, whose fast response can protect the drilling equipment from hazards that may be caused by the slip phase of the vibrations. Hence, it is recommended to implement the proposed controller in smart rotary drilling systems for petroleum industry.

An ADRC-based Stick-slip Vibration Control Method for Drill String

For complex deep wells, the drill string stick-slip vibration is a intensive destructiveness torsional vibration caused by twisting vibration and down hole drag. This phenomenon can be explained that the bit is motionless for some time, and when the torque on drill string is large enough, the bit suddenly rotate at a high-speed. The stick-slip vibration has become a major problem to be solved urgently in the exploration and exploitation of deep and ultra-deep wells. In drilling operations, the stick-slip will occur in drilling for more than half of the time. Usually, the stick-slip vibration leads to the decrease of penetration rate and the increase of completion cycle. In serious cases, it leads to drill string fracture, bit failure, and even serious downhole accidents. In this thesis, the drill string torsion model is established, the drill string stick-slip vibration mechanical model is proposed, the equation of stick-slip vibration motion is analyzed and the general laws of drill string stick-slip vibration are acquired. In order to effectively suppress stick-slip vibration, an auto-disturbance rejection control (ADRC) method is adopted. Result of experiment shows that the soft-torque control method can make the actual speed of motor changed according to the torque, so as to decrease the motor torque fluctuations, eliminate stick-slip vibration and achieve the drill string soft-torque control.

Review on Stick-slip Vibration’s Mechanism Analysis and Its Control Strategy in Deep Drilling with Drag Bits

The stick-slip Vibration is one of the major causes for drilling quality reduction, shorter drilling tool lifespan, drilling efficiency decrease, it also affect the drilling cost and completion period seriously. The complex situations in the process of drilling result in the slow progress in this aspect, they rarely break through. The recent advances are outlined in stick-slip vibration of the drill string in three areas: theoretical analysis, experiment research and control strategy. The main research direction, methods and existing problem in the progress are introduced, which will provide reference and guidance for further research.

Nonlinear Vibration of a Time-Space Coupled Drill String System Based on the Surface Morphology of Rock

In this paper, the nonlinear vibration of a time-space coupled axial and torsional drill string system is investigated. Considering the surface morphology of rock, top drive system and mud, the drill string system is discretized by finite element method. The dynamic equations of the fully discrete drill string system based on rock surface morphology (SM) is established. Based on the surface morphology and strength of rock, the concept of rock surface state matrix is proposed. The stability and time domain response of the system are obtained by numerical simulation and compared with the multiple regeneration (MR) model. The results show that stick slip vibration and bit reversal are more likely to occur when drilling system cuts unhomogeneous rock, and stick slip vibration is the main reason to cause the drill bit impact rock. The stable driving torsional speed is lower than that of calculated by conventional models. In the calculation process, the volume conservation accuracy of the SM model is higher than that of the MR model. Moreover, the numerical convergence and efficiency of SM model are higher than that of MR model.

Investigation of the mitigation effect of an anti-stall tool on stick-slip vibrations of drill strings

ABSTRACT The anti-stall tool (AST) is a downhole tool used to mitigate stick-slip vibrations during drilling. It has the ability to adjust the cutting depth of the drill bit and is characterized by an axial spring and a screw pair. In this paper, the dynamic characteristics and working mechanism of the AST are studied by modeling and parametric analysis. Based on the lumped-mass model, torsional dynamic models of the drill string without and with the AST are built and simulated. The simulation results of the drill string model indicate that there is an upper limit on the weight on bit (WOB) (148 kN) and a lower limit on the rotary table speed (84 RPM) to avoid stick-slip vibration, and that a stick-slip vibration cycle can be divided into five phases. The simulation results of the model with the AST indicate that the AST can mitigate the stick-slip vibration and stabilize the bit angular velocity effectively for a large range of WOBs (120–200 kN) and rotary table speeds (40–120 RPM). The AST spring strength and helical angle have important influences on AST performance. Reasonable values for these two parameters should be determined to ensure AST effectiveness while avoiding other adverse effects. This work can provide guidance for AST applications and improve drilling efficiency and safety.

Stick-slip vibration in water-lubricated bearing-shaft system simulated in persistent homology-based machine learning model

Stick-slip vibration images of water-lubricated rubber stern bearing are collected by using machine vision technology. Then these images are analyzed by the methods of persistent homology-based machine learning (PHML). During this analysis, the corresponding barcode is obtained by calculating the homology of the simplicial complex of the vibration images, and the topological characteristics of the vibration images are obtained based on the barcode images, then the support vector machine (SVM) learning is used to study the topological features, and finally the classification and identification of the stick-slip vibration of water-lubricated rubber stern tube bearing are completed. The results have shown that the length of the longest 1D Betti number is closely related to vibration value. Based on these data, it is possible to use the warning beep effectively, create an intelligent description of the beep process, and provide a new idea for simulating stick-slip vibration in the stern bearing.

Decentralized Overlapping Control Design with Application to Rotary Drilling System

The main objective of this paper is the development of overlapping decomposition strategy for controller design of rotary drilling systems based on the state feedback technique. The lamped model of the system has been considered, Graph-based representation has been used to rearrange the states of the model, and then a new model has been decomposed into subsystems after analyzing the interconnection terms. The expansion–contraction principle, combined with Lyapunov theory, is used to investigate the global stability of the decomposed system so that controllability of the designed controller is guaranteed and its robustness is improved. Moreover, the designed strategy has been validated with high-frequency mode stick-slip vibrations data measured in an operational rotary drilling system of an exploration well drilled in an Algerian hydrocarbon field.

Experimental Study on Axial Impact Mitigating Stick-Slip Vibration with a PDC Bit

Stick-slip vibration reduces the drilling rate of penetration, causes early wear of bits, and threatens the safety of downhole tools. Therefore, it is necessary to study suppression methods of stick-slip vibration to achieve efficient and safe drilling. Field tests show that the use of downhole axial impactors is helpful to mitigate stick-slip vibration and improve rock-breaking efficiency. However, there are many deficiencies in the study of how axial impact load affects stick-slip vibration of a PDC bit. In this paper, based on the two-degrees-of-freedom spring-mass-damper model and similarity theory, a laboratory experiment device for suppressing stick-slip vibration of a PDC bit under axial impact load has been developed, and systematic experimental research has been carried out. The results show that the axial impact force can suppress the stick-slip vibration by reducing the amplitude of weight on bit and torque fluctuations and by increasing the main frequency of torque. The amplitude of impact force affects the choice of the optimal back-rake angle. The impact frequency is negatively correlated with the fluctuation amplitude of the rotary speed. When the impact frequency is greater than 100 Hz, the fluctuation amplitude of the rotary speed will not decrease.

Research on Weight-on-bit Self-adjusting Dual-diameter PDC Bit Design and Effect Evaluation Utilizing Stress-Releasing Effect of Rock at Bottomhole

Rock-breaking efficiency is not so satisfied using the conventional PDC bit, especially in the hard, soft–hard interbedded, and strong abrasive formations in ultra-deep wells. A method is proposed to make full use of stress-releasing effect at bottomhole, thereby improving the rock-breaking efficiency, and a supporting weight-on-bit (WOB) self-adjusting dual-diameter PDC bit (WSDB) has been invented. The WSDB can dynamically adjust the depth-of-cut control characteristics, which could improve the rate of penetration (ROP) while mitigating the stick–slip vibration caused by the rapid change of depth of cut. The stress field of the rock at the bottomhole is calculated with a numerical method, and the working mechanism of the bit is analyzed. The application effect of the WSDB is evaluated through laboratory tests preliminarily. The results show that the stress concentration area on the shoulder of the reaming bit is decreased obviously and a larger stress unloading area emerges in the intersection between reaming and pilot bit. Thus, mechanical specific energy (MSE) can be greatly reduced when the reaming bit drills into this section. Indoor tests show that the maximum ROP of WSDB can be reached up to 70% higher compared to the conventional PDC bit, and higher ROP could be obtained with a relatively lower bit torque. With drilling parameters greater than the critical revolution and WOB, the reduction in MSE can be reached up to 36% during the rock-breaking process. Making further efforts into the optimization of bit structure to reduce the vibration intensity is expected to achieve more improved bit performance.

Mitigation of Stick-Slip Vibrations in Drilling Systems With Tuned Top Boundary Parameters

Abstract Aiming at preventing stick-slip oscillations in drilling systems for oil and gas explorations, a reduced-order model is proposed to capture the nonlinear torsional dynamics of drilling operations. In this model, the drill string structure is simplified as a single-degree-of-freedom (DOF) system suffering from dry frictions at the drill bit, while the electromechanical boundary generated by the top drive system is modeled as another tunable DOF used for stick-slip suppression. To simplify and parameterize the problems, a normalized 2DOF system with negative damping and tunable parameters is deduced via nondimensionalization and linearization. Based on this system, stability criteria are obtained analytically in the five-dimensional parametric space. Stable regions and the optimized boundary parameters are found analytically. The results suggest that the system can be stabilized by an optimally tuned boundary when and only when the magnitude of the negative damping is no greater than 2. It also reveals that the stability deteriorates if the inertia on the top is huge and nonadjustable, which is the commonest scenario for commercial drilling rigs nowadays. Finally, applications of the tuned boundary in a typical drilling system for stick-slip mitigation are conducted and verified numerically. The results indicate that the control performance can be potentially enhanced by three to five times, via an additional virtual negative inertia generated by the top drive motor. This research provides an alternative approach to fully optimize the top boundary for curing stick-slip vibrations in drilling systems.

Fractional-order controllers for stick-slip vibration mitigation in oil well drill-strings

Drillstring–borehole interaction can produce severely damaging vibrations. An example is stick–slip vibration, which negatively affects drilling performance, tool integrity and completion time, and costs. Attempts to mitigate stick–slip vibration typically use passive means and/or change the operation parameters, such as weight on bit and rotational speed. Automating the latter approach, by means of feedback control, holds the promise of quicker and more effective mitigation. The present work presents three separate fractional-order controllers for mitigating drillstring slip–stick vibrations. For the sake of illustration, the drillstring is represented by a torsional vibration lumped parameter model with four degrees of freedom, including parameter uncertainty. The robustness of these fractional-order controllers is compared with traditional proportional-integral-derivative controllers under variation of the weight on bit and the drill bit’s desired rotary speed. The results confirm the proposed controllers effectiveness and feasibility, with rapid time response and less overshoot than conventional proportional-integral-derivative controllers.

Nonlinear integrated dynamic analysis of drill strings under stick-slip vibration

Stick-slip torsional vibration raising from bit-formation contact is a catastrophic dynamic phenomenon occurring in deep-water oil and gas drilling systems. The torsional vibrations can result in premature fatigue failure of drilling equipment and reduce drilling efficiency. Thus, studying the dynamics of the system is a vital key to identify the roots of the vibration and establish appropriate mitigation and remediation methods. In this paper, an efficient approach for finite element (FE) modeling of stick-slip vibrations of the full drill strings was proposed. The model was developed based on a rate-dependent formulation of bit-rock interaction, in which the cutting process was integrated through the frictional contact. The nonlinear effects of the large rotations and the geometrically nonlinear axial-torsional coupling were taken into account. The effect of energy dissipation due to the presence of drill mud along the drill pipes and drill collars was incorporated through Rayleigh viscous damping. Modal analysis was conducted to determine the natural frequencies and the mode shapes of the drill string. Furthermore, a five degree-of-freedom lumped parameter model was developed. The performance of the developed models was verified through comparisons with example stick-slip results from a field test. The study showed that the self-excited torsional vibrations may also occur at fundamental frequencies lower than the first natural torsional frequency of the drill string, depending on operational parameters. The conducted research work resulted in a robust and practical integrated FE model to simulate the entire drill string system dynamics under torsional vibrations.