Understanding and Eliminating Drill String Twist-Offs by the Collection of High Frequency Dynamics Data

2011 ◽  
Author(s):  
Constantijn Raap ◽  
Andrew David Craig ◽  
Daniel Perez Garcia
Keyword(s):  
High Frequency ◽  
Drill String

scholarly journals Stick-slip and Torsional Friction Factors in Inclined Wellbores

2018 ◽  
Vol 148 ◽  
pp. 16002 ◽  
Author(s):  
Ulf Jakob F. Aarsnes ◽  
Roman J. Shor
Keyword(s):  
High Frequency ◽  
String Model ◽  
Drill String ◽  
Distributed Model ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Rock Interaction ◽  
Interaction Field ◽  
Friction Factors ◽  
Start Ups

Stick slip is usually considered a phenomenon of bit-rock interaction, but is also often observed in the field with the bit off bottom. In this paper we present a distributed model of a drill string with an along-string Coulomb stiction to investigate the effect of borehole inclination and borehole friction on the incidence of stick-slip. This model is validated with high frequency surface and downhole data and then used to estimate static and dynamic friction. A derivation of the torsional drill string model is shown and includes the along-string Coulomb stiction of the borehole acting on the string and the ‘velocity weakening’ between static and dynamic friction. The relative effects of these two frictions is investigated and the resulting drillstring behavior is presented. To isolate the effect of the along-string friction from the bit-rock interaction, field data from rotational start-ups after a connection (with bit off bottom) is considered. This high frequency surface and downhole data is then used to validate the surface and downhole behavior predicted by the model. The model is shown to have a good match with the surface and downhole behavior of two deviated wellbores for depths ranging from 1500 to 3000 meters. In particular, the model replicates the amplitude and period of the oscillations, in both the topside torque and the downhole RPM, as caused by the along-string stick slip. It is further shown that by using the surface behavior of the drill-string during rotational startup, an estimate of the static and dynamic friction factors along the wellbore can be obtained, even during stick-slip oscillations, if axial tension in the drillstring is considered. This presents a possible method to estimate friction factors in the field when off-bottom stick slip is encountered, and points in the direction of avoiding stick slip through the design of an appropriate torsional start-up procedure without the need of an explicit friction test.

scholarly journals Effects of axial impact load on the dynamics of an oilwell drillstring

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983687
Author(s):  
Liping Tang ◽  
Xiaohua Zhu ◽  
Hongzhi Lin
Keyword(s):  
Sensitivity Analysis ◽  
High Frequency ◽  
Impact Load ◽  
Drill String ◽  
Impact Loads ◽  
Harmonic Force ◽  
Cross Sectional ◽  
Axial Impact ◽  
Energy Conservation Method ◽  
The Impact

This article studies the dynamics of oilwell drillstring under large and small axial impact loads. For the case of large impact load, the drillstring is regarded as a continuous bar under the impact load of a falling mass, and the energy conservation method is implemented. A sensitivity analysis is conducted to investigate the effect of cross-sectional area of the drill string on the impact stress. Results show that the design of drillstring with different cross-sectional areas is not a suitable method. In order to understand the effect of high-frequency small axial impact (applied from percussion tools or downhole generators) on the drillstring vibration, a mechanical model in which the drillstring is regarded as a 2-degree-of-freedom system under a harmonic force is developed. Sensitivity analysis on the effects of impact generator placement and impact frequency on drillstring dynamics are conducted. Results show that the impact generator should be installed near the drill bit and that high frequency is recommended to be used.

Energy transfer through parametric excitation to reduce self-excited drill string vibrations

2021 ◽  
pp. 107754632110310
Author(s):  
Vincent Kulke ◽  
Georg-Peter Ostermeyer
Keyword(s):  
Energy Transfer ◽  
Parametric Excitation ◽  
High Frequency ◽  
Drill String ◽  
Alternative Methods ◽  
Installation Space ◽  
Energy Output ◽  
Torsional Oscillations ◽  
Bottom Hole ◽  
Bottom Hole Assembly

Drilling a wellbore can result in several types of vibration that lead to inefficient drilling and premature failure of drill string components. These vibrations are subdivided based on their operating direction into lateral, torsional, and axial vibrations. Especially in hard and dense formations, high-frequency torsional oscillations are found in the bottom-hole assembly (BHA). These critical vibrations are induced by a self-excitation mechanism caused by the bit–rock interaction. Self-excitation mechanisms are regenerative effects, mode coupling, or a velocity-dependent torque characteristic at the drill bit. To increase drilling performance and reduce tool failure due to high-frequency torsional oscillations, the critical vibration amplitudes localized at the bottom-hole assembly need to be minimized. Increasing the damping of self-excited systems to affect the energy output during vibration is a common approach to mitigate self-excited vibrations. In drilling systems, the achievable damping is naturally limited by the small installation space due to the drilled borehole diameter. Therefore, alternative methods to influence vibrations are necessary. Applying parametric excitation in self-excited systems can result in a parametric anti-resonance and therefore in an energy transfer within different modes of the structure. This allows, among other benefits, improved utilization of the structural damping. In this article, the influence of additional stiffness–based parametric excitation on self-excited torsional vibration in downhole drilling systems is investigated. For this purpose, a finite element model of a drill string is reduced using the component mode synthesis and analyzed with the goal to mitigate torsional vibrations. The multiple degree of freedom drill string model is investigated regarding the additional energy transfer due to the parametric excitation. Robustness of various parameters, especially with regard to the positioning within the bottom-hole assembly, is analyzed and discussed. Additionally, the problem of multiple unstable self-excited modes due to the nonlinear velocity-dependent torque characteristic in drilling systems is addressed.

Small High Frequency Powerful Vibrator and its Application to Underwater Sound Generator

2013 ◽  
Author(s):  
Shinichi Takagawa
Keyword(s):  
High Frequency ◽  
Short Pulse ◽  
Drill String ◽  
Seismic Survey ◽  
Outer Diameter ◽  
Underwater Sound ◽  
Thrust Bearings ◽  
Powerful High Frequency ◽  
Sound Pulses ◽  
Sound Generator

The author has developed a small and powerful high frequency cam-type vibrator using roller thrust bearings with uneven races. The diameter of the vibrator is nearly the same as the outer diameter of the thrust bearing, and it is very small compared with other vibrators. This vibrator can be installed at the bottom end of a drill string as a high frequency vibro-hammering gear. Although the amplitude of the axial displacement is fixed, combination of two vibrators of this type can make the amplitude variable by superimposition. This variable superimposition can also be used as an On-Off switch of the vibration. The underwater sound used for seismic survey is usually a short pulse with a duration of several to several tens of milliseconds. The vibrator described in this paper is capable of generating such short sound pulses owing to the variable superimposition. Present sound generators for seismic survey are usually big and heavy and generate sound pulses with a wide frequency spectrum, centered around 100Hz. The cam-type vibrator described in this research is much smaller and lighter than present systems, making the deployment near the seafloor easy for even at great depths, which in return leads to more detailed results in stratum surveys. The emitted sound is a pure tone whose frequency can be anywhere between 100 and 1000Hz. The author has tried to develop this type of sound generator under the support of JOGMEC (Japan Oil, Gas and Metals National Corporation). In this paper, the principle of the vibration, the design of the sound generator and the result of the experiment shall be discussed.

scholarly journals The effect of high-frequency torsional impacts on the dynamic response of a drill string in a stick state

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401982857
Author(s):  
Liping Tang ◽  
Wei He ◽  
Xiaohua Zhu
Keyword(s):  
Dynamic Response ◽  
High Frequency ◽  
Impact Load ◽  
Drill String ◽  
Superposition Method ◽  
Drill Bit ◽  
Stick Slip ◽  
Mode Superposition Method ◽  
Study Results ◽  
The Impact

Stick–slip vibration is common in the oil well drilling process and is detrimental to down-hole equipment and drilling efficiency. In recent years, a new type of drilling technology, torsional impact drilling, has been developed to mitigate the stick–slip phenomena, particularly in the drilling of deep or abrasive formations. With this drilling technique, high-frequency torsional impacts are generated and applied to the drill bit, providing the drill bit with auxiliary energy. By mitigating or suppressing the stick–slip vibration, part of the energy wasted as a result of vibration can be regained. However, the effect of these impact loads on the dynamic response of a drill string in a stick state is unknown. In order to address this issue, a continuous system model of a drill string that includes torsional impact load was constructed. In the model, a Fourier series approach was used for the impact load, and the mechanical model was resolved with the mode superposition method. Case studies were done to understand the drill string dynamics, with and without the impact. The case study results demonstrate that high-frequency torsional impacts have little influence on the dynamic response of a drill string in a stick state.

scholarly journals Signal Transmission Capability Improvement of a Telemetry Drill String Using the Reflected Signal at the Transmission Line Termination

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jia Jia ◽  
Yinao Su ◽  
Yue Shen ◽  
Gaixing Hu ◽  
Lingtan Zhang ◽  
...  
Keyword(s):  
Transmission Line ◽  
High Frequency ◽  
Signal Transmission ◽  
Drill Pipe ◽  
Drill String ◽  
Transmission Characteristic ◽  
Electromagnetic Parameters ◽  
Drill Pipes ◽  
Reflected Signal ◽  
Transmission Capability

A telemetry drill string system consists of a string of wired drill pipes, and high-frequency signals pass the adjacent drill pipes through inductive couplers. Such a system is used to upload downhole information at high data transmission rates for measurements while drilling (MWD). Since the signal energy attenuates greatly in the system, many repeaters must be provided to ensure signal transmission. A reduction in the signal transmission in a telemetry drill string can extend the relay distance and improve the reliability of the transmission system. In this study, the transmission characteristic of the rod of the wired drill pipe is studied using transmission line theory, and the transmission characteristic of the inductive coupler is studied using high-frequency circuit theory. Using impedance matching between the transmission line of the rod and the inductive coupler, external impedance compensation elements, including a capacitor and a resistor, are recommended, and the electromagnetic parameters of the wired drill pipe are determined. Based on the determined electromagnetic parameters, certain changes in the external impedance compensation capacitance and resistance can lead to impedance mismatch between the transmission line and the inductive coupler. This will generate a reflected signal at the transmission line, and the vector superposes with the transmitted signal. The terminal reflection coefficient of the transmission line is controlled by increasing the compensation resistance value to enhance the signal amplitude, which can compensate the transmission loss when passing through the inductive coupler to a certain extent. Thus, the signal transmission capability of the telemetry drill string can be improved, allowing for long-distance signal transmission or drastically extending the relay distance, while maintaining a certain channel bandwidth.

Rock–bit interaction effects on high-frequency stick-slip vibration severity in rotary drilling systems

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chafiaa Mendil ◽  
Madjid Kidouche ◽  
Mohamed Zinelabidine Doghmane ◽  
Samir Benammar ◽  
Kong Fah Tee
Keyword(s):  
High Frequency ◽  
Drill String ◽  
System Stability ◽  
Practical Implementation ◽  
Rotary Drilling ◽  
Stick Slip ◽  
Content Type ◽  
Drilling System ◽  
Rock Bit ◽  
Slip Phenomenon

PurposeThe drill string vibrations can create harmful effects on drilling performance because they generate the stick-slip phenomenon which reduces the quality of drilling and decreases the penetration rate and may affect the robustness of the designed controller. For this reason, it is necessary to carefully test the different rock-bit contact models and analyze their influences on system stability in order to mitigate the vibrations. The purpose of this paper is to investigate the effects of rock-bit interaction on high-frequency stick-slip vibration severity in rotary drilling systems.Design/methodology/approachThe main objective of this study is an overview of the influence of the rock-bit interaction models on the bit dynamics. A total of three models have been considered, and the drilling parameters have been varied in order to study the reliability of the models. Moreover, a comparison between these models has allowed the determination of the most reliable function for stick-slip phenomenon.FindingsThe torsional model with three degrees of freedom has been considered in order to highlight the effectiveness of the comparative study. Based on the obtained results, it has been concluded that the rock-bit interaction model has big influences on the response of the rotary drilling system. Therefore, it is recommended to consider the results of this study in order to design and implement a robust control system to mitigate harmful vibrations; the practical implementation of this model can be advantageous in designing a smart rotary drilling system.Originality/valueMany rock-bit functions have been proposed in the literature, but no study has been dedicated to compare them; this is the main contribution of this study. Moreover, a case study of harmonic torsional vibrations analysis has been carried out in well-A, which is located in an Algerian hydrocarbons field, the indices of vibrations detection are given with their preventions.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

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