EA050247B1 - BIT SUPPORT UNIT INCLUDING A HIGH-FREQUENCY TORSIONAL VIBRATION DAMPER - Google Patents

Abstract

Systems and methods for damping torsional vibrations of borehole systems are described. These systems include a borehole string, a bit support unit configured to secure and receive a rock breaking device, said breaking device being located at the end of the borehole string and mounted on the bit support unit, and a damping system configured to at least one of the following: be mounted on or within the bit support unit, wherein the damping system comprises at least one damper element located in contact with a portion of the bit support unit.

Description

Cross-reference to related applications

This application claims the benefit of U.S. Patent Application No. 16/568,789, filed September 12, 2019, which is incorporated herein by reference in its entirety.

Prerequisites for the creation of an invention

1. Field of application of the invention.

The present invention generally relates to well operations and systems for damping vibrations of well systems during operation.

2. Description of the prior art.

Wells are drilled into the earth's crust for many purposes, such as carbon dioxide sequestration, geothermal exploration and production, and hydrocarbon exploration and production. In all cases, wellbores are drilled to access or penetrate a material (such as a gas or liquid) contained in a formation (such as a reservoir) beneath the earth's surface. Wellbores may contain various types of tools and devices to perform various tasks and measurements.

During operation, downhole components may be subject to vibration that may affect their performance. For example, severe vibrations in drill strings and bottom hole assemblies (BHAs) may be caused by cutting forces on the bit or mass imbalances in downhole tools such as mud motors. The effects of such vibrations may include, but are not limited to, reduced ROP, reduced measurement quality, and excessive fatigue and wear of downhole components, tools, and/or devices.

Statement of the essence of the invention

The present document describes systems and methods for damping vibrations, such as torsional vibrations, of well systems. The systems include a well system configured to rotate within a wellbore and a damping system implemented on the well system. The damping system includes one or more dampers that are mounted on or in a bit support unit of the well system. The dampers are configured to reduce or eliminate one or more specific modes and, thus, improved well operations and/or greater efficiency can be achieved.

Additionally, systems and methods for damping torsional vibrations of borehole systems are described. Said systems include a borehole string, a bit support unit designed with the possibility of securing and receiving a rock destruction device, wherein said destruction device is located at the end of the borehole string and mounted on the bit support unit, and a damping system designed with at least one of the following:

installations on or in the bit support unit, wherein the damping system comprises at least one damping element located in contact with a section of the bit support unit.

The specified methods include installing a damping system in at least one of the following variants:

on the support unit of the bit or as part of it, located on the well string of the well system, wherein the support unit of the bit has a disintegration device attached to it. The damping system includes at least one damping element located in contact with a section of the support unit of the bit, wherein at least part of the damping element moves relative to the support unit of the bit at a speed that is the sum of periodic changes in speed having an amplitude and an average speed.

Brief description of graphic materials

The subject matter of the invention, which is considered to be the present invention, is particularly pointed out and expressly claimed in the claims at the end of this description. The above and other features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein like elements are designated by like reference numerals, wherein:

Fig. 1 shows an example of a system for performing well operations in which embodiments of the present invention can be used;

Fig. 2 is an illustrative graph of a typical curve of frictional force or torque versus relative velocity or relative rotational speed between two interacting objects;

Fig. 3 shows a hysteresis graph of the dependence of the friction force on the displacement for a positive relative average velocity with additional small changes in velocity;

Fig. 4 shows a graph of the dependence of the friction force, relative velocity, and the product of both on time for a positive relative average velocity with additional small changes in velocity;

Fig. 5 shows a hysteresis graph of the dependence of the friction force on the displacement for a relative average velocity of zero with additional small changes in velocity;

Fig. 6 shows a graph of the dependence of the friction force, relative velocity and the product

- 1 050247 both for a relative mean velocity of zero with additional small velocity changes;

Fig. 7 is a schematic representation of a damping system in accordance with one embodiment of the present invention;

Fig. 8A shows a graph of the tangential acceleration measured at the bit;

Fig. 8B is a graph corresponding to Fig. 8A illustrating the rotation speed;

Fig. 9A is a schematic diagram of a well system showing the shape of the well system as a function of the distance from the bit;

Fig. 9B shows illustrative corresponding forms of torsional vibrations that may be excited during operation of the well system shown in Fig. 9A;

Fig. 10 is a schematic diagram of a damping system in accordance with one embodiment of the present invention;

Fig. 11 is a schematic diagram of a damping system in accordance with one embodiment of the present invention;

Fig. 12 is a schematic illustration of a damping system in accordance with one embodiment of the present invention;

Fig. 13 is a schematic representation of a damping system in accordance with one embodiment of the present invention;

Fig. 14 is a schematic diagram of a damping system in accordance with one embodiment of the present invention;

Fig. 15 is a schematic illustration of a damping system in accordance with one embodiment of the present invention;

Fig. 16 is a schematic diagram of a damping system in accordance with one embodiment of the present invention;

Fig. 17 is a schematic diagram of a damping system in accordance with one embodiment of the present invention;

Fig. 18 is a schematic illustration of a damping system in accordance with one embodiment of the present invention;

Fig. 19 is a schematic diagram of a damping system according to one embodiment of the present invention; and Fig. 20 is a schematic diagram of the dependence of the vibration damping coefficient on the amplitude of local vibration;

Fig. 21 shows a schematic representation of a well tool having a damping system;

Fig. 22 shows a cross-sectional view of the downhole tool shown in Fig. 21;

Fig. 23 is a schematic illustration of a bit support assembly incorporating a damping element in accordance with one embodiment of the present invention;

Fig. 24 is a schematic illustration of a tangential damper element in accordance with one embodiment of the present invention;

Fig. 25 is a schematic illustration of a tangential damper element in accordance with one embodiment of the present invention;

Fig. 26 is an illustrative graph of a typical curve of force or torque versus relative linear velocity or relative rotational velocity between two interacting objects associated with a hydraulic damping element; and Fig. 27 is a schematic illustration of a bit support assembly incorporating a damping element in accordance with one embodiment of the present invention.

Detailed description

In Fig. 1 there is shown a basic diagram of a system for performing well operations. As shown, the system is a drilling system 10, which includes a drill string 20 having a drilling assembly 90, also called a bottom hole assembly (BHA), transported in a wellbore 26 penetrating an earth formation 60. The drilling system 10 includes a conventional drilling rig 11, installed on a platform 12, which supports a rotary table 14, which is rotated by a main drive, such as an electric motor (not shown), at a desired rotation speed. The drill string 20 includes a drilling tubular element 22, such as a drill pipe, extending downwardly from the rotary table 14 into the wellbore 26. A disintegration device 50, such as a bit attached to the end of a BHA 90, disintegrates geological formations while rotating to drill a borehole 26. A drill string 20 is connected to surface equipment such as systems for lifting, rotating and/or pushing, including, but not limited to, a drawworks 30 via a kelly 21, a swivel 28 and a line 29 via a hoist block 23. In some embodiments, the surface equipment may include a top drive (not shown). During drilling operations, the drawworks 30 is controlled to control the load on

- 2 050247 bit, which affects the rate of penetration during drilling. The operation of the winch 30 is well known in this field of technology and is therefore not described in detail in this document.

During drilling operations, a suitable drilling fluid 31 (also called a drilling fluid) from a source or reservoir 32 for drilling fluid is circulated under pressure through the drill string 20 by means of a pump 34 for drilling fluid. The drilling fluid 31 passes into the drill string 20 through a shock absorber 36, a fluid line 38 and a kelly 21. The drilling fluid 31 is released in the bottom hole assembly 51 through an opening in the disintegration device 50. The drilling fluid 31 is circulated up the wellbore through an annular space 27 between the drill string 20 and the wellbore 26 and is returned to the reservoir 32 for drilling fluid through a return line 35. A sensor S1 in the fluid line 38 transmits information about the flow rate of the fluid. The torque sensor S2 on the surface and the sensor S3 associated with the drill string 20 respectively provide information on the torque and the rotation speed of the drill string. In addition, one or more sensors (not shown) associated with the line 29 are used to provide the hook load of the drill string 20 and with respect to other required parameters related to drilling the wellbore 26. The system may further comprise one or more downhole sensors 70 located on the drill string 20 and/or the BHA 90.

In some applications, the disintegration device 50 is rotated solely by rotation of the drill pipe 22. However, in other applications, a drilling motor 55 (e.g., a downhole motor) located in the drilling assembly 90 is used to rotate the disintegration device 50 and/or to superimpose or supplement the rotation of the drill string 20. In any case, the rate of penetration (ROP) of the disintegration device 50 into the earth formation 60 for a given formation and a given drilling assembly is largely dependent on the weight on bit and the rotational speed of the drill bit. In one aspect of the embodiment shown in Fig. 1, the drilling motor 55 is connected to the disintegration device 50 via a drive shaft (not shown) located in the bearing assembly 57. The drilling motor 55 rotates the disintegration device 50 when the drilling fluid 31 passes through the drilling motor 55 under pressure. The bearing assembly 57 supports the radial and axial forces of the disintegration device 50, the fall of the drilling motor thrust and the reaction upward load from the applied weight on the bit. Stabilizers 58, connected to the bearing assembly 57 and/or other suitable positions, act as centralizers for the drilling assembly 90 or its parts.

The surface control unit 40 receives signals from the downhole sensors 70 and devices via the transducer 43, such as a pressure transducer located in the liquid line 38, as well as from the sensors S1, S2, S3, hook load sensors, engine speed sensors, torque sensors and any other sensors used in the system, and processes such signals in accordance with programmed commands provided to the surface control unit 40. The surface control unit 40 displays the desired drilling parameters and other information on the display/monitor 42 for use by an operator at the drilling site to control drilling operations. The surface control unit 40 comprises a computer, a memory device for storing data, computer programs, models and algorithms accessible to a processor on the computer, a recording device such as a magnetic tape drive, a memory unit, etc. for recording data and other peripheral devices. The surface control unit 40 may also comprise simulation models for computer processing of data in accordance with the programmed commands. The control unit responds to user commands entered through a suitable device, such as a keyboard. The ground control unit 40 is configured to activate warning signals 44 when certain unsafe or undesirable operating conditions occur.

The drilling assembly 90 also comprises other sensors and devices or tools for providing various measurements related to the formation surrounding the wellbore and for drilling the wellbore 26 along the desired path. Such devices may comprise a device for measuring the specific resistance of the formation near the drill bit, gamma ray devices for measuring the intensity of the gamma ray logging of the formation and devices for determining the inclination, azimuth and position of the drill string and/or in front of them. The formation resistivity logging device 64, made in accordance with the embodiment described in this document, can be connected in any suitable position, including above the lower deviation initiation subassembly or the guiding mechanism 62, for estimating or determining the resistance of the formation near the disintegration device 50, or in front of it, or in other suitable positions. The inclinometer 74 and the gamma ray logging device 76 can be positioned respectively to determine the inclination of the BHA and the intensity of the gamma ray logging of the formation. Any suitable inclinometer and gamma logging device may be used. In addition, an azimuth device (not shown), such as a magnetometer or a gyroscopic device, may be used to determine the azimuth of the drill string. Such devices are known in the art and are therefore not described in detail herein. In the above-described illustrative configuration, the drilling motor 55 transmits electrical power to the device 50

- 3 050247 disintegration through the shaft, which also allows drilling fluid to pass from the drilling motor 55 to the disintegration device 50. In an alternative embodiment of the drill string 20, the drilling motor 55 can be connected below the resistivity logging device 64 or in any other suitable position.

As shown in Fig. 1, other logging while drilling (LWD) devices (generally designated herein by reference numeral 77), such as devices for measuring formation porosity, permeability, density, rock properties, fluid properties, etc., may be positioned at suitable positions of the drilling assembly 90 to provide information suitable for evaluating the subterranean formation along the wellbore 26. Such devices may include, but are not limited to, temperature measuring tools, pressure measuring tools, borehole diameter measuring tools (e.g., a caliper), acoustic tools, nuclear logging tools, nuclear magnetic resonance tools, and formation testing and sampling tools.

The above-mentioned devices transmit data to the borehole telemetry system 72, which, in turn, transmits the received data up the wellbore to the surface control unit 40. The borehole telemetry system 72 also receives signals and data from the surface control unit 40 and transmits such received signals and data to the corresponding borehole devices. In one aspect, the telemetry system with a mud pulse communication channel can be used to transmit data between the borehole sensors 70 and the devices and surface equipment during drilling operations. The transducer 43, located in the liquid line 38 (for example, the drilling mud feed line), detects pulses in the drilling mud in response to data transmitted by the borehole telemetry system 72. The transducer 43 generates electrical signals in response to changes in the pressure of the well mud and transmits such signals through the conductor 45 to the surface control unit 40. In other aspects, any other suitable telemetry system may be used for two-way data transmission (e.g., downlink and uplink) between the surface and the BHA 90, including, but not limited to, an acoustic telemetry system, an electromagnetic telemetry system, an optical telemetry system, a wired telemetry system that may employ wireless interfaces or repeaters located in the drill string or wellbore. The wired telemetry system may be formed by connecting sections of drill pipes, wherein each section of pipe includes a data transmission line, such as a wire, running along the pipe. The connection for transmitting data between sections of pipe may be made by any suitable method, including, without limitation, solid state electrical or optical connections, inductive, capacitive, resonant coupling, such as electromagnetic resonant coupling methods, or directional coupling. In the case where flexible tubing is used as the drill pipe 22, the data transmission line can be lowered along the side of the flexible tubing.

The drilling system described so far in this document refers to drilling systems that use a drill pipe to transport the drilling assembly 90 into the borehole 26, wherein the weight on bit is controlled from the surface, typically by means of control of a drilling drawworks. However, in a large number of modern drilling systems, especially for drilling highly deviated and horizontal boreholes, coiled tubing strings are used to transport the drilling assembly into the borehole. In such an application, a thruster is sometimes deployed in the drill string to provide the required force on the drill bit. In addition, when using coiled tubing, the tubing is not rotated by a rotary table, but is instead introduced into the borehole by a suitable pump, while a borehole motor, such as a drilling motor 55, rotates the disintegration device 50. In offshore drilling, an offshore drilling rig or vessel is used to support the drilling equipment, including the drill string.

Also with reference to Fig. 1, a resistivity logging tool 64 may be provided, including, for example, a plurality of antennas, including, for example, transmitters 66a or 66b and/or receivers 68a or 68b. The specific resistivity may be one of the formation properties that are of interest when making a drilling decision. Those skilled in the art will understand that other tools for measuring formation properties may be used together with or instead of the resistivity logging tool 64.

Liner-assisted drilling may be a single configuration or operation used to provide a disintegration device, which is becoming increasingly attractive in the oil and gas industry because it has several advantages over conventional drilling. One example of such a configuration is shown and described in joint U.S. Patent No. 9,004,195, entitled Apparatus and Method for Drilling a Wellbore, Installing Casing, and Cementing the Wellbore in a Single Run, which is incorporated herein by reference in its entirety. It is important to note that despite the relatively low rate of penetration during drilling, the time it takes to deliver the liner to the target location is reduced because the liner is single

- 4 050247 simultaneously lowered into the wellbore during drilling of the wellbore. This can be useful when working in swelling formations, where the narrowing of the drilled hole can interfere with subsequent installation of the casing string. In addition, drilling with casing in depleted and unstable reservoirs minimizes the risk of stuck pipe or drill string due to wellbore collapse.

Although Fig. 1 is shown and described with respect to drilling operations, those skilled in the art will appreciate that similar configurations, although using different components, can be used to perform various downhole operations. For example, as is known in the art, wireline, wireline, liner drilling, borehole reaming, coiled tubing, and/or other configurations can be used. In addition, various production configurations can be used to extract and/or inject materials from/into geological formations. Thus, the present disclosure should not be limited to drilling operations, but can be used for any suitable or desired downhole operations.

Significant vibrations in drill strings and bottom hole assemblies during drilling operations may be caused by cutting forces on the bit or by mass imbalances in downhole tools such as drilling motors. Such vibrations may result in a reduction in the rate of penetration during drilling, a reduction in the quality of measurements made by the bottom hole assembly tools, and may lead to wear, fatigue, and/or failure of downhole components. As understood by those skilled in the art, there are various vibrations such as lateral vibrations, axial vibrations, and torsional vibrations. For example, stick-slip motion of the entire drilling system and high-frequency torsional vibrations (HFTV) are types of torsional vibrations. The terms vibration, oscillation, and variation are used with the same broad meaning of repetitive and/or periodic movements or periodic deviations from a mean value such as mean position, mean speed, mean acceleration, mean force, and/or mean torque. In particular, these terms are not limited to harmonic excursions but may include all types of excursions such as, but not limited to, periodic, harmonic and statistical excursions. Torsional vibrations may be excited by self-exciting mechanisms that arise from the interaction of the drill bit or any other cutting structure such as a reamer and the formation. The main difference between stick-slip vibrations and HFCC is the frequency and typical mode shapes: For example, HFCCs have a frequency that is typically higher than 50 Hz compared to stick-slip torsional vibrations, which typically have a frequency below 1 Hz. Moreover, the stick/slip excited mode is typically the first mode of the entire drilling system, while the HFTO mode may be of higher order and is typically localized to smaller portions of the drilling system with relatively high amplitudes at the excitation point, which may be the bit or any other cutting structure (such as a reamer), or any contact between the drilling system and the formation (such as via a stabilizer).

Due to the high frequency of vibrations, HFTO corresponds to high values of acceleration and torque along the BHA. Those skilled in the art will understand that in order to exhibit torsional motions, one component of acceleration, force and torque is always accompanied by two other components of acceleration, force and torque. In this sense, acceleration, force and torque are equivalent in the sense that none of these elements can occur without the other two. High frequency vibration or oscillation loads can adversely affect the efficiency, reliability and/or durability of the electronic and mechanical parts of the BHA. Embodiments proposed herein relate to providing torsional vibration damping on a downhole system to mitigate HFTO. In some embodiments of the present invention, torsional vibration can be activated if a threshold of a measured property, such as torsional vibration amplitude or frequency, is reached in the system.

According to a non-limiting embodiment proposed in the present document, the torsional vibration damping system can be based on friction dampers. For example, according to some embodiments, friction between two parts, such as two interacting objects, in a BHA or a drill string can dissipate energy and reduce the level of torsional vibrations, thereby mitigating potential damage caused by high-frequency vibrations. Preferably, the energy dissipation of the friction damper is at least equal to the input value of the HFTO energy caused by the interaction of the bit and the formation.

The friction dampers described in this document can result in significant energy dissipation and thus damping of torsional vibrations. When two components or interacting objects are in contact with each other and move relative to each other, the frictional force acts in the direction opposite to the speed of relative movement between the contacting surfaces of the components or interacting objects. The frictional force

- 5 050247 leads to energy dissipation.

Although specifically described with respect to friction dampers, the dampers, damper elements and damper systems of the present invention are not limited to friction. Thus, as described below, other damping principles can be implemented using dampers of various configurations. For example, damping can be generated using viscous damping, frictional damping, hydraulic damping, magnetic damping (e.g., eddy current damping), piezoelectric (shunt) damping, etc. The damper element used in the present document can be part of a damper system configured to dissipate energy due to relative movement between at least a portion of the damper element and the well string. That is, the relative movement of the damper element or part thereof allows energy to be dissipated (e.g. HFTO) and thus reduces vibration within or along the wellbore.

Fig. 2 is an illustrative graph 200 of a typical curve of frictional force or torque versus relative speed v (e.g., or relative rotational speed) between two interacting objects. The two interacting objects have a contact surface and a force component F _N perpendicular to the contact surface that is engaged with the two interacting objects. The graph 200 shows the dependence of the frictional force or torque of the two interacting objects on a speed reduction mode, such as a frictional contact or a cutting mode characteristic. At higher relative speeds (v>0) between the two interacting objects, the frictional force or torque has a distinctive value, shown by point 202. A decrease in the relative speed will result in an increase in the frictional force or torque (also called a speed reduction characteristic). The frictional force or torque reaches its maximum when the relative speed is zero. The maximum frictional force is also known as static friction, sticking friction, or adhesion.

In essence, the friction force F_R depends on the normal force, as shown in the equation F_R=μF_N, with the friction coefficient μ. In essence, the friction coefficient μ is a function of the velocity. In this document, the normal force may also change according to the excited vibration in the normal direction. In the case where the relative velocity between two interacting objects is zero (v=0), the static friction force FS refers to the normal force component F _n according to the equation F_S=μ_0F_N with the static friction coefficient μ_0. In the case where the relative velocity between two interacting objects is not zero (v*0), such a friction coefficient is called the dynamic friction coefficient μ. If the relative velocity is further reduced to negative values (i.e. if the relative displacement of the two interacting objects is switched to the opposite), the friction force or torque switches in the opposite direction with a high absolute value corresponding to the step from the positive maximum to the negative minimum value at point 204 on graph 200. Thus, the dependence of the friction force on the velocity shows a change in sign at the point at which the velocity changes sign and is discontinuous at point 204 on graph 200. The velocity reduction characteristic is a well-known effect between interacting objects that are frictionally connected. It is assumed that the velocity reduction characteristics of the contact force or torque are a potential root cause of sticking/slipping. The velocity reduction characteristic can also be achieved by using a dispersion fluid with a higher viscosity at lower relative velocities and a lower viscosity at higher relative velocities. If the dispersed fluid passes through a relatively small channel, the same effect can be achieved in the sense that the flow resistance is relatively high or low at low or high relative velocities, respectively.

With reference to Figs. 8A-8B, Fig. 8A shows the measured swirl acceleration of the well system as a function of time. During the 5-second measurement, as shown in Fig. 8A, an oscillatory swirl acceleration is shown with an average acceleration of approximately 0 g, superimposed on a vibrational swirl acceleration at a relatively low amplitude from approximately 0 s to 3 s and relatively high amplitudes of up to 100 g from approximately 3 s to 5 s. Fig. 8B shows the corresponding rotation speed during the same period of time as in Fig. 8A. In accordance with Fig. 8A, Fig. 8B shows the average speed v_0 (shown by the line v_0 in Fig. 8B), which is relatively constant at a rotation speed of about 190 rpm. The average speed is superimposed by oscillatory vibrations of the rotation speed with relatively low amplitudes from about 0 s to 3 s and relatively high amplitudes from about 3 s to 5 s in accordance with the relatively low and high acceleration amplitudes shown in Fig. 8A. It is noteworthy that the oscillatory rotation speed does not lead to negative values of the rotation speed, not even in the period of time from about 3 s to 5 s, when the amplitudes of the oscillations of the rotation speeds are relatively high.

- 6 050247

With reference to Fig. 2, point 202 illustrates the average speed of the two interacting objects, which corresponds to the average speed v_0 shown in Fig. 8B. In the schematic representation of Fig. 2, the data shown in Fig. 8B correspond to a point with a speed oscillation with a relatively high frequency due to high-frequency torsional oscillations close to the average speed v_0, which changes relatively slowly over time compared to the high-frequency torsional oscillations. Thus, the point illustrating the data shown in Fig. 8B moves back and forth on the positive branch of the curve shown in Fig. 2, only rarely reaching negative speed values or in their absence. Accordingly, the corresponding frictional force or torque oscillations around the positive average frictional force or average frictional torque and are usually substantially positive or only rarely reaching negative values. As discussed further below, point 202 illustrates where the positive average value of the relative velocity corresponds to the static torque, and point 204 illustrates a favorable point for frictional damping. It should be noted that the frictional forces or torque between the drilling system and the borehole wall will not generate additional damping of the high-frequency oscillations in the system. This is because the relative velocity between the contact surfaces of the interacting objects (e.g., the stabilizer and the borehole wall) does not have an average velocity that is so close to zero that HFTO causes a change in the sign of the relative velocity of the two interacting objects. Rather, the relative velocity between the two interacting objects has a high average value at a distance from zero that is large, so that HFTO does not cause a change in the sign of the relative velocity of the two interacting objects (e.g., as illustrated by point 202 in Fig. 2).

It will be understood by those skilled in the art that the reduced characteristic of the contact force or torque with respect to the relative speed, as shown in Fig. 2, results in the application of energy in the system for the oscillatory relative movements of the interacting objects with an average speed v_0, i.e. a high value compared to the speed of the oscillatory movement. In this context, other examples of self-excitation mechanisms, such as the coupling between an axial and a torsional degree of freedom, can lead to a similar characteristic.

The corresponding hysteresis graph is shown in Fig. 3, and the time graph for the friction force and velocity is shown in Fig. 4.

Fig. 3 shows a hysteresis plot of the frictional force F _r , sometimes also referred to as the cutting force in this context, versus the displacement relative to the position, which moves at a positive average velocity with additional small changes in velocity that result in an additional small displacement dx. Accordingly, Fig. 4 shows the frictional force (F _r ), the relative velocity (dx/dT), and their product (labeled 400 in Fig. 4) for a positive average relative velocity with additional small changes in velocity that result in an additional small displacement dx. Those skilled in the art will appreciate that the area between the frictional force and the velocity over time is equal to the dissipated energy (i.e., the area between line 400 and the zero axis), which is negative in the case shown in Fig. 3 and Fig. 4. Thus, in the case shown in Fig. 3 and Fig. 4, energy is transferred into vibration from friction through frictional contact.

Referring again to Fig. 2, point 204 denotes a favorable average speed for friction damping of small speed changes or vibrations in addition to the average speed. For small vibrations of the relative motion between two interacting objects, the cessation at point 204 in Fig. 2 with a change in the sign of the relative speed of the interacting objects also leads to an abrupt change in the friction force or torque. This change in sign leads to hysteresis, which leads to a large amount of dissipated energy. For example, one can compare Fig. 5 and Fig. 6, which are similar graphs to Fig. 3 and Fig. 4, respectively, but illustrate the case of zero average relative speed with additional small speed changes or vibrations. The area below line 600 in Fig. 6, which corresponds to the product F_rdx/dT, is equal to the dissipated energy during one period and, in this case, is positive. Thus, in the case shown in Fig. 5 and Fig. 6, energy is transferred from the high-frequency vibration through the frictional contact to the friction. The effect is comparatively high compared to the case shown in Fig. 3 and Fig. 4, and has the desired sign. It is also seen from a comparison of Figs. 2, 5 and 6 that the dissipated energy depends significantly on the difference between the maximum friction force and the minimum friction force for v=0 (i.e., position 204 in Fig. 2). The higher the difference between the maximum friction force and the minimum friction force for v=0, the higher the dissipated energy. Although speed reduction characteristics such as that shown in Fig. 2 were generated in Figs. 3-4, embodiments of the present invention are not limited to such type of characteristics. The devices and methods described herein will be functional for any type of characteristic, provided that the friction force or torque passes

- 7 050247 there is a stage with a change in sign when the relative velocity between two interacting objects changes.

Friction dampers according to some embodiments of the present invention will now be described. Friction dampers are installed on or in a drilling system, such as the drilling system 10 shown in Fig. 1, and/or a part of the drilling system 10, such as a part of the bottom hole assembly 90. Frictions are part of friction damping systems with two interacting objects, such as a first element and a second element having a frictional contact surface with the first element. Friction damping systems according to the present invention are arranged such that the first element has an average speed that is related to the rotational speed of the drilling system in which it is installed. For example, the first element can have a similar or the same average speed or rotational speed as the drilling system such that small changing oscillations lead to a change in sign or a transition through zero of the relative speed between the first element and the second element in accordance with point 204 in Fig. 2. It should be noted that the friction forces or torque between the drilling system and the borehole wall will not generate additional damping of the high-frequency vibrations in the system. This is due to the fact that the relative speed between the contact surfaces (e.g., the stabilizer and the borehole) does not have a zero average value (e.g., point 202 in Fig. 2). According to the embodiments described in this document, the static friction between the first element and the second element is set high enough to allow the first element to accelerate the second element (during rotation) with an average speed v ₀ with the same value as that of the drilling system. Thus, the additional high-frequency vibrations provide sliding between the first element (e.g., the damping device) and the second element (e.g., the drilling system) with positive or negative speeds in accordance with the vibrations around the position shown in Fig. 2, which is equal to or close to point 204 in Fig. 2. Sliding occurs if the inertial force FI exceeds the static friction force expressed as the coefficient of static friction multiplied by the normal force between the two interacting objects: F_I>μ_0F_N. According to embodiments of the present invention, the normal force F _N (for example, caused by the contact and surface pressure on the contact surface between the two interacting objects) and the coefficient of static friction μ ₀ are adjusted to achieve optimal energy dissipation and optimal amplitude. In addition, the moment of inertia (torsional), contact and ground pressure of the contacting surfaces and the placement of the damper or contact surface relative to the distance from the bit can be optimized.

For example, Fig. 7 schematically shows a damping system 700 in accordance with one embodiment of the present invention. The damping system 700 is part of a well system 702, such as a bottom hole assembly and/or a drilling assembly. The well system 702 includes a string 704 that is rotated to provide drilling operations of the well system 702 to form a wellbore 706 within a formation 708. As described above, the wellbore 706 is typically filled with a drilling fluid, such as a drilling mud. The damping system 700 comprises a first element 710, operatively connected, for example, fixedly connected or made integrally with the well system 702, to ensure that the first element 710 rotates at an average speed, which is associated, for example, similar or the same as the average speed of the well system 702. The first element 710 is in frictional contact with the second element 712. The second element 712 is at least partially mounted with the possibility of movement on the well system 702 with a contact surface 714 located between the first element 710 and the second element 712.

In the case of friction forces, the difference between the minimum and maximum friction force depends positively on the normal force and the coefficient of static friction. The dissipated energy increases with the friction force and the harmonic displacement, but the energy is dissipated only in the sliding phase. In the sticking phase, the relative displacement between the friction interfaces and the dissipated energy are zero. The upper amplitude limit of sticking increases linearly with the normal force and the coefficient of friction in the contact interface. The reason is that the reaction force in the contact interface, J(x )>M_H=F_N μ_Н r, which can be caused by the inertia J of one of the contacting objects if it is accelerated with (x), must be higher than the torque M_H=F_N μ_Н r, which determines the limit between sticking and sliding. The notation used in this document is: F_N represents the normal force, μ_Н represents the effective coefficient of friction, and r represents the effective or average radius of the frictional contact region. In the case of complex frictional contact parts of interacting objects, sticking or sliding may occur simultaneously. In this paper, the contact pressure can be optimized to achieve optimal damping and amplitude.

Similar mechanisms are applicable if the contact force is caused by displacement and a spring element.

- 8 050247 ment. The acceleration (x) of the contact area may be due to the excitation of some type of oscillation and depends on the corresponding oscillation mode, as further discussed below with reference to Fig. 9B. In the case of an attached inertial mass, J the acceleration (x) is equal to the acceleration of the excited oscillation mode and the corresponding oscillation mode in the attachment position, provided that there is a grip in the contact interaction.

It is necessary to regulate the normal force and the friction force in order to ensure the sliding phase in the appropriate or permissible amplitude range. The permissible amplitude range can be defined by an amplitude that lies between zero and load limits, which are, for example, given in industrial specifications for tools and components. The limit can also be given as a percentage of the expected amplitude without a damper. The dissipated energy, which can be compared with the input energy, for example, by forcing or self-excitation, is one quantity for determining the effectiveness of the damper. Another quantity is the provision of equivalent damping of the system, proportional to the ratio of the dissipated energy in one period of harmonic vibration to the potential energy in one period of vibration in the system. This quantity is especially effective in the case of self-excited systems. In the case of self-excited systems, excitation can be approximated by a negative damping coefficient, and both equivalent damping and negative damping can be compared directly. The damping force provided by the damper is nonlinear and strongly depends on the amplitude.

As shown in Fig. 20, the damping is zero in the sticking phase (left end of the graph in Fig. 20), when the relative displacement between the interacting objects is zero. If, as described above, the limit between the sticking phase and the sliding phase is exceeded by the force that is transmitted through the contact interface, a relative sliding displacement occurs, which causes energy dissipation. Then, the damping coefficient provided by the frictional damping increases to a maximum and then decreases to a minimum. The amplitude that will appear depends on the excitation, which can be described by the term negative damping. In this document, the maximum of the provided damping, shown in Fig. 20, should be higher than the negative damping from the self-excitation mechanism. The amplitude that occurs in the so-called limit cycle can be determined by the intersection of the negative damping coefficient and the equivalent damping coefficient provided by the friction damper.

The curve depends on various parameters. It is advantageous to have a high normal force, but a slip phase that occurs at minimum BHA amplitude. In the case of an inertial mass, this can be achieved by using a high mass or by placing the contact mate at a point of high acceleration relative to the excited mode shape. In the case of contacting mates, a large relative displacement compared to the mode shape amplitude at the contact point, for example along the BHA axial axis, is advantageous. Thus, optimal placement of the damping device according to the high amplitude or relative amplitude is important. This can be achieved by applying the modeling results as described below. The normal force and friction coefficient can be applied to shift the curve to lower or higher amplitudes, but this does not have a strong effect on the damping maximum. If more than one friction damper is implemented, this will result in overlapping curves similar to those shown in Fig. 20. If the normal force and friction coefficients are adjusted to achieve a maximum at the same amplitude, this is useful for achieving overall damping. In addition, slightly offset damping curves would result in a resulting curve that could be broader in amplitude, which could be useful for accounting for impacts that could shift the amplitude to the right of the maximum. In this case, the amplitude would increase to a very high value in the case of self-excited systems, as indicated by negative damping. In this case, it is necessary to shift the amplitude again to the left of the maximum, for example by moving away from the face or by reducing the rotational speed of the system to lower levels. In this context, the amplitude is approximately linearly dependent on the average rotational speed, as shown and discussed with reference to Fig. 8B.

Referring again to Fig. 7, the column 704 and, therefore, the well system 702 rotate at a rotation speed dφ/dτ, which can be measured in revolutions per minute (rpm). The second element 712 is mounted on the first element 710. The normal force FN between the first element 710 and the second element 712 can be selected or adjusted by applying and using an adjusting element 716. The adjusting element 716 can be adjustable, for example, by means of a thread, an actuator, a piezoelectric actuator, a hydraulic actuator and/or a spring element for applying force, which has a component in a direction perpendicular to the contact surface 714 between the first element 710 and the second element 712. For example, as shown in Fig. 7, the control element 716 can apply a force in the axial direction from the well system 702, which is converted into a force component FN, which is perpendicular to the contact surface 714 of the first element 710 and the second element 712 due to

- 9 050247 non-zero angle between the axis of the well system 702 and the contact surface 714 of the first element 710 and the second element 712. In some configurations, the angle between the system 712 and the inert mass element is selected or determined to ensure sliding movement and prevent self-fixation.

The second element 712 has a moment of inertia J. When HFTO occurs during operation of the well system 702, both the well system 702 and the second element 712 accelerate in accordance with a vibration mode (e.g., determining the amplitude distribution along the dimensions of the drilling system, drill string and/or BHA) and an amplitude of the vibration mode (e.g., a scale of the amplitude of the vibration mode). Illustrative results of such operation are shown in Fig. 8A and Fig. 8B. Fig. 8A shows a graph of the tangential acceleration measured at the bit, and Fig. 8B shows the corresponding rotational speed.

Due to the tangential acceleration and inertia of the second element 712, relative inertial forces arise between the second element 712 and the first element 710. If these inertial forces exceed the threshold between sticking and sliding, that is, if these inertial forces exceed the static friction force between the first element 710 and the second element 710, a relative movement occurs between the elements 710, 712, which leads to energy dissipation. In such acceleration configurations, the coefficient of static and/or dynamic friction and the normal force determine the amount of energy to be dissipated. For example, the moment of inertia J of the second element 712 determines the relative force that must be transmitted between the first element 710 and the second element 712. High accelerations and moments of inertia increase the tendency to slide on the contact surface 714 and, thus, provide a higher energy dissipation and an equivalent damping coefficient provided by the damper.

Due to the energy dissipation caused by the frictional movement between the first element 710 and the second element 712, heat and wear will be generated on the first element 710 and/or the second element 712. In order to keep the wear below an acceptable level, materials that can withstand wear can be used for the first and/or second elements 710, 712. For example, drill diamonds or polycrystalline diamond bits can be used for at least a portion of the first and/or second elements 710, 712. Alternatively or additionally, coatings can help reduce wear due to friction between the first and second elements 710, 712. Heat can lead to high temperatures and can affect the reliability or durability of the first element 710, the second element 712 and/or other parts of the well system 702. The first element 710 and/or the second element 712 can be made of a material with high thermal conductivity or high heat capacity and/or can be in contact with a material with high thermal conductivity or heat capacity.

Such high thermal conductivity materials include, but are not limited to, metals or compounds, including a metal such as copper, silver, gold, aluminum, molybdenum, tungsten, or a thermal lubricant containing fat, grease, oil, epoxy resins, silicones, urethanes and acrylates, and optionally fillers such as diamond, a metal or chemical compounds including a metal (e.g., silver, aluminum in aluminum nitride, boron in boron nitride, zinc in zinc oxide), or silicon or chemical compounds including silicon (e.g., silicon carbide). Additionally or alternatively, one or both of the first element 710 and the second element 712 may be in contact with a fluid, such as a drilling mud, which is configured to remove heat from the first element 710 and/or the second element 712 to cool the corresponding element 710, 712. In addition, an amplitude limiting element (not shown), such as a manipulator, a recess or a spring element, may be used and configured to limit energy dissipation to an acceptable limit that reduces wear.

When arranging the damping system 700, a high normal force and/or static or dynamic friction coefficient prevents relative sliding movement between the first element 710 and the second element 712, and in such situations, energy will not be dissipated. In contrast, a low normal force and/or static or dynamic friction coefficient can lead to a low friction force, and sliding occurs, but the dissipated energy is low. In addition, a low normal force and/or a coefficient of static or dynamic friction can result in the friction on the outer surface of the second element 712, for example between the second element 712 and the formation 708, being higher than the friction between the first element 710 and the second element 712, which results in a situation where the relative velocity between the first element 710 and the second element 712 is not zero, but is in the range of the average velocity between the well system 702 and the formation 708. In this way, the normal force and the coefficient of static or dynamic friction and the placement of the damper element relative to the excited vibration shape and the vibration shape can be adjusted (for example, using the adjusting element 716) to achieve an optimized value for energy dissipation.

This can be accomplished by adjusting the normal force FN, the static friction coefficient μ ₀ , the dynamic friction coefficient μ, the placement of the damper element relative to the excited vibration mode, or combinations thereof. The normal force F _N can be adjusted by

- 10 050247 placing the regulating element 716 and/or the drive mechanisms that generate a force on one of the first and second elements with a component perpendicular to the contact surface of the first and second elements by regulating the pressure regime around the first and second elements or by increasing or decreasing the area on which the pressure acts. For example, by increasing the external pressure that acts on the second element, such as the pressure of the drilling fluid, the normal force FN will also be increased. The regulation of the pressure of the drilling fluid in the well can be achieved by regulating the pumps for the drilling fluid (for example, the pumps 34 for the drilling fluid shown in Fig. 1) on the surface or other equipment on the surface or in the well that affects the pressure of the drilling fluid, such as bypass valves, valves, hydraulic shock absorbers. The normal force can be adjusted in the same way so that it is harmonic with the same frequency as the free vibration frequency of the excited vibration mode and thus has low normal force values for low inertial mass acceleration and high normal force values for low inertial mass accelerations, and this ensures sliding motion with low acceleration values.

The normal force F _N can also be adjusted by a biasing element (not shown), such as a spring element, which applies a force to the second element 712, for example, a force in the axial direction from the first element 710 or to it. The adjustment of the normal force FN can also be performed in a controlled manner based on an input signal received from a sensor. For example, a suitable sensor (not shown) can provide one or more parameter values for a controller (not shown), the parameter value(s) are related to the relative movement of the first element 710 and the second element 712 or the temperature of one or both of the first element 710 and the second element 712. Based on the parameter value(s), the controller can provide a command to increase or decrease the normal force FN. For example, if the temperature of one or both of the first element 710 and the second element 712 exceeds a threshold temperature, the controller can provide a command to decrease the normal force FN to prevent damage to one or both of the first element 710 and the second element 712 due to exposure to high temperatures. Similarly, for example, if the distance, speed or acceleration of the second element 712 relative to the first element 710 exceeds a threshold, the controller can provide commands to increase or decrease the normal force FN to ensure optimal energy dissipation. By controlling the parameter value, the normal force F _N can be adjusted to achieve the desired results over a period of time. For example, the normal force F _N can be adjusted to ensure optimal energy dissipation while maintaining the temperature of one or both of the first element 710 and the second element 712 below the threshold for starting drilling or a portion thereof.

In addition, the coefficient of static or dynamic friction can be adjusted by using different materials, such as, but not limited to, a material with different rigidity, different roughness and/or different lubrication. For example, a surface with higher roughness often increases the coefficient of friction. Thus, the coefficient of friction can be adjusted by selecting a material with an appropriate coefficient of friction for at least one of the first and second elements or a part of at least one of the first and second elements. The material of the first and/or second element can also influence the wear of the first and second elements. In order to keep the wear of the first and second elements at a low level, it is advisable to select a material that can withstand the friction that is created between the first and second elements. The inertia, the coefficient of friction and the expected acceleration amplitudes (e.g. depending on the oscillation mode and the natural frequency) of the second element 712 are parameters that determine the dissipated energy and that must be optimized. The critical oscillation modes and acceleration amplitudes can be determined based on measurements or calculations or based on other known methods that will be understood by those skilled in the art. Examples are finite element analysis or transfer matrix method or finite difference method and based on this modal analysis or analytical models. The placement of the friction damper is optimal if high relative displacement or acceleration is expected.

Fig. 9A and Fig. 9B show an example of a well system 900 and corresponding modes. Fig. 9A is a schematic graph of the well system illustrating the shape of the well system depending on the distance from the bit, and Fig. 9B is an exemplary corresponding vibration modes of torsional vibrations that can be excited during operation of the well system shown in Fig. 9A. The images shown in Fig. 9A and Fig. 9B show a potential position and placement of one or more elements of the damping system on the well system 900.

As illustrated in Fig. 9A, the well system 900 has various components with different diameters (along with different masses, densities, configurations, etc.) and thus, during rotation of the well system 900, the different components may result in different shapes. The illustrative shapes show that there will be highest amplitudes that may require damping by using a damping system. For example, as

- 11 050247 is shown in Fig. 9B, the oscillation mode 902 of the first torsional oscillation, the oscillation mode 904 of the second torsional oscillation and the oscillation mode 906 of the third torsional oscillation of the well system 900 are shown. Based on the knowledge of the oscillation modes 902, 904, 906, the position of the first elements of the damping system can be optimized. At the maximum amplitude (peaks) of the oscillation modes 902, 904, 906, damping may be required and/or achieved. Accordingly, two potential positions for attaching or installing the damping system of the present invention are illustratively shown.

For example, the first damping position 908 is close to the bit of the well system 900 and mainly damps the first and third torsional vibrations (corresponds to the vibration modes 902, 906) and provides some damping relative to the second torsional vibration (corresponds to the vibration mode 904). Thus, the first damping position 908 should be approximately at the peak of the third torsional vibration (corresponds to the vibration mode 906), close to the peak of the first torsional vibration mode 902, and also from about half the value to the peak relative to the second torsional vibration mode 904.

The second damping position 910 is configured to primarily repeatedly provide damping of the third torsional oscillation mode 906 and to provide some damping relative to the first torsional oscillation mode 902. However, in the second damping position 910, no damping of the second torsional oscillation mode 904 will occur, since the second torsional oscillation mode 904 is substantially zero in the second damping position 910.

Although Fig. 9A and Fig. 9B show only two positions for placing the damping systems of the present invention, the embodiments should not be so limited. For example, any number and any placement of damping systems along the wellbore system is possible to provide damping of torsional vibration on the wellbore system. An example of a preferred installation position for a damper is where one or more of the expected vibration modes exhibit high amplitudes.

Because of the high amplitudes in the drill bit, for example, one suitable position of the damper is close to the drill bit or is located inside the drill bit. In addition, the first and second elements are not limited to a single housing, but can take any number of different configurations to achieve the desired damping. Thus, multiple housing (multi-housing) first or second elements (e.g., friction damping devices) can be used, with each housing having the same or different normal forces, friction coefficients, and moments of inertia. Such systems of multiple housing elements can be used, for example, when there is uncertainty about what vibration mode and corresponding acceleration are expected at a given position along the well system.

For example, two or more element housings can be used that can provide different relative sliding movements between them to dissipate energy. Multiple first element housings can be selected and assembled with different static or dynamic friction coefficients, angles between contact surfaces, and/or can have other mechanisms for influencing the amount of friction and/or the transition between sticking and sliding. Several levels of amplitude, excited vibration shapes, and/or free vibration frequencies can be damped by such configurations.

For example, Fig. 10 schematically shows a damping system 1000 in accordance with one embodiment of the present invention. The damping system 1000 may function similarly to that shown and described above with respect to Fig. 7.

The damping system 1000 comprises a first element 1010 and second elements 1012. However, in this embodiment, the second element 1012 mounted on the first element 1010 of the well system 1002 is formed from the first body 1018 and the second body 1020. The first body 1018 has a first contact surface 1022 between the first body 1018 and the first element 1010, and the second body 1020 has a second contact surface 1024 between the second body 1020 and the first element 1010. As shown, the first body 1018 is separated from the second body 1020 by a gap 1026. The gap 1026 is provided to prevent interaction between the first body 1018 and the second body 1020 such that they can function (for example, move) independently of each other or not interact directly with each other. In this embodiment, the first housing 1018 has a first coefficient of static or dynamic friction μ1; and a first force FN1 that is perpendicular to the first contact surface 1022, while the second housing 1020 has a second coefficient of static or dynamic friction _μ2 and a second force F _N2 that is perpendicular to the second contact surface 1024. In addition, the first housing 1018 can have a first moment of inertia J1 and the second housing 1020 can have a second moment of inertia _J2 . In some embodiments, at least one of the first coefficient of static or dynamic friction μ1, the first normal force FN1 and the first moment of inertia J1 is selected so that they differ from

- 12 050247 the second coefficient of static or dynamic friction μ ₂ , the second normal force F _N2 and the second moment of inertia J ₁ , respectively. Thus, the damping system 1000 can be designed with the possibility of taking into account a plurality of different vibration modes in substantially one position along the well system 1002.

Fig. 11 is a schematic illustration of a damping system 1100 in accordance with one embodiment of the present invention. The damping system 1100 may operate similarly to that shown and described above. However, in this embodiment, the second element 1112 mounted on the first element 1110 of the well system 1102 is formed from a first housing 1118, a second housing 1120 and a third housing 1128. The first housing 1118 has a first contact surface 1122 between the first housing 1118 and the first element 1110, and the second housing 1120 has a second contact surface 1124 between the second housing 1120 and the first element 1110, and the third housing 1128 has a third contact surface 1130 between the third housing 1128 and the first element 1110. As shown, the third housing 1128 is located between the first housing 1118 and the second housing 1020. In this embodiment, the three housings 1118, 1120, 1128 are in contact with each other and, thus, can have normal forces and static coefficients or dynamic friction between them.

The contact between the three housings 1118, 1120, 1128 can be established, can be supported or maintained by elastic connecting elements, such as spring elements between two or more elements 1118, 1120, 1128. Additionally or alternatively, the first housing 1118 can have a first coefficient of static or dynamic friction μ1 and a first force FN1 on the first contact surface 1122, the second housing 1120 can have a second coefficient of static or dynamic friction μ2 and a second force FN2 on the second contact surface 1124, and the third housing 1128 can have a third coefficient of static or dynamic friction μ ₃ and a third force F _N3 on the third contact surface 1130.

Additionally or alternatively, the first housing 1118 and the third housing 1128 may have a fourth force F _H13 and a fourth coefficient of static or dynamic friction μ ₁₃ between them at the contact surface between the first housing 1118 and the third housing 1128. Similarly, the third housing 1128 and the second housing 1120 may have a fifth force FN32 and a fifth coefficient of static or dynamic friction μ ₃₂ between them at the contact surface between the third housing 1128 and the second housing 1120.

In addition, the first housing 1118 may have a first moment of inertia J ₁ , and the second housing 1120 may have a second moment of inertia J2, and the third housing 1128 may have a third moment of inertia J3. In some embodiments, the static or dynamic friction coefficients μ ₁ , μ ₂ , μ ₃ , μ ₁₃ , μ ₃₂ , the forces F _N 1 , F _N2 , F _N3 , F ₁₃ , F ₃₂ , and the moment of inertia J ₁ , J ₂ , J ₃ can be selected to differ from each other such that the product μ_Η Ρ3_ί (where i=1, 2, 3, 13, 32) differs from at least a subrange of relative velocities of the first element 1110, the first housing 1118, the second housing 1120 and the third housing 1128. Moreover, the static or dynamic friction coefficients and the normal forces between adjacent housings can be selected to achieve different damping effects.

Although shown and described with respect to a limited number of embodiments and specific shapes, relative sizes and numbers of elements, it will be understood by those skilled in the art that the damping systems of the present invention can take any configuration. For example, shapes, sizes, geometric configurations, radial placements, contact surfaces, number of housings, etc. can be selected to achieve the desired damping effect. Although in the arrangement shown in Fig. 11, the first housing 1118 and the second housing 1120 are connected to each other by frictional contact with the third housing 1128, such arrangement and description should not be limiting. The connection between the first housing 1118 and the second housing 1120 can also be created by a hydraulic, electrical or mechanical connecting means or mechanism. For example, the mechanical connection between the first housing 1118 and the second housing 1120 can be created by a rigid or elastic connection of the first housing 1118 and the second housing 1120.

Fig. 12 shows a schematic illustration of a damping system 1200 according to one embodiment of the present invention. The damping system 1200 can function similarly to that shown and described above. However, in this embodiment, the second element 1212 of the damping system 1200 is partially fixedly attached to or connected to the first element 1210. For example, as shown in this embodiment, the second element 1212 has a fixed part 1232 (or end) and a movable part 1234 (or end). The fixed part 1232 is attached to the first element 1210 along the fixed connection 1236, and the movable part 1234 is in frictional contact with the first element 1210 via the contact surface 1214 (similar to the first element 1010 in frictional contact with the second element 1012 described in relation to Fig. 10).

- 13 050247

The movable part 1234 may have any desired length, which may be associated with the vibration modes, as shown in Fig. 9B. For example, in some embodiments, the movable part may be longer than a tenth of the distance between the maximum and the minimum of any of the vibration modes that could be calculated for a particular drilling assembly. In another example, in some embodiments, the movable part may be longer than a quarter of the distance between the maximum and the minimum of any of the vibration modes that could be calculated for a particular drilling assembly. In another example, in some embodiments, the movable part may be longer than half the distance between the maximum and the minimum of any of the vibration modes that could be calculated for a particular drilling assembly. In another example, in some embodiments, the movable part may be longer than the distance between the maximum and the minimum of any of the vibration modes that can be calculated for a particular drilling assembly.

Thus, even though it may not be known where the exact position of the maxima or minima of the shape is during deployment in the well, it is ensured that the second element 1212 is in frictional contact with the first element 1210 at the maximum amplitude position to achieve optimized damping. Although it will be understood by those skilled in the art that other arrangements of the partially fixed first elements are possible without departing from the scope of the present invention. For example, in one non-limiting embodiment, the fixed part may be located in a more central part of the first element such that the first element has two movable parts (e.g., at opposite ends of the first element). As shown in Fig. 12, the movable part 1234 of the second element 1212 is sufficiently elongated and can cover a part of the vibration modes (for example, vibration modes 902, 904, 906 in Fig. 9B) that correspond to the length of the movable part 1234 of the second element 1212. An elongated second element 1212 in frictional contact with the first element 1210 can have advantages over shorter second elements, since shorter second elements can be located in an undesirable part of the vibration modes, for example in the damping position 910, where the second vibration mode 904 is small or even zero, as described above with respect to Fig. 9B. The use of an elongated second element 1212 can ensure that at least a part of the second element is located at a distance from the positions in which one or more vibration modes are zero or at least close to zero.

In Fig. 13-19 and 21-22, more variations of the elongated second elements in frictional contact with the first elements are shown. In some embodiments, the elongated second elements may be elastic such that the movable part 1234 can move relative to the first element 1210, while the fixed part 1232 is fixed relative to the first element 1210. In some embodiments, the second element 1212 may have a plurality of contact points at a plurality of positions of the first element 1210.

In the embodiments described above and in the damping systems according to the present invention, the first elements are temporarily attached to the second element due to frictional friction. However, when the vibrations of the well systems increase and exceed a threshold, for example, when the inertial force exceeds the static friction force, the first elements (or parts thereof) move relative to the second elements, thus providing damping. That is, when the HFTOs increase predetermined thresholds (for example, amplitude, distance, speed and/or acceleration thresholds) in the well systems, the damping systems will automatically function, and thus the embodiments proposed in the present document include passive damping systems. For example, the embodiments include passive damping systems that automatically function without applying additional energy, and therefore do not use an additional energy source.

Fig. 13 is a schematic illustration of a damping system 1300 according to one embodiment of the present invention. In this embodiment, the damping system 1300 comprises one or more elongated first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f, each of which is located within the second element 1312 and is in contact with it. Each of the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f may have a length in the axial direction of the tool (for example, in the direction perpendicular to the cross-section shown in Fig. 13) and, optionally, a fixed point at which the respective first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f are attached to the second element 1312. For example, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f may be attached to respective upper ends, middle portions, lower ends, or a plurality of attachment points for different first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f or a plurality of points for a given one first element 1310a, 1310b, 1310c, 1310d, 1310e, 1310f. Furthermore, as shown in Fig. 13, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f may be optionally biased or engaged with the second element 1312 by a biasing element 1338 (for example, by a biasing spring element or a biasing actuator that applies a force with a component to the second element 1312). Each of the first elements 1310a, 1310b, 1310c, 1310d, 1310e,

- 14 050247

1310f can be positioned and selected to have the same or different normal forces, static or dynamic friction coefficients and mass moments of inertia, thus providing different damping configurations.

In some embodiments, the first elements may be substantially uniform in material, shape, and/or geometric configuration along their length. In other embodiments, the first elements may vary in shape and geometric configuration along their length. For example, with reference to Fig. 14, a schematic illustration of a damping system 1400 is shown according to one embodiment of the present invention. In this embodiment, the first element 1410 is located relative to the second element 1412, and the first element 1410 has a tapering and/or helical design relative to the second element 1412. Accordingly, in some embodiments, a portion of the first or second element may change geometric configuration or shape along its length relative to the second element, and such changes may also occur in the longitudinal direction around the second element and/or relative to the tool body or the well system.

Fig. 15 is a schematic illustration of another damping system 1500 according to one embodiment of the present invention. In the damping system 1500, the first member 1510 is a toothed (threaded) body that fits into a threaded second member 1512. The contact between the teeth (threads) of the first member 1510 and the threads of the second member 1512 can provide frictional contact between the two members 1510, 1512 to provide damping, as described herein. Due to the inclined surfaces of the first member 1510, the first member 1510 begins to move under the action of both axial and/or torsional vibrations. In addition, the movement of the first member 1510 in the axial direction or the circumferential direction also creates a movement in the circumferential direction or the axial direction, respectively, in this configuration. Thus, in the arrangement shown in Fig. 15, axial vibrations can be applied to soften or dampen torsional vibrations, as well as torsional vibrations that can be applied to soften or dampen axial vibrations. The positions in which axial and torsional vibrations occur can be different. For example, although axial vibrations can be uniformly distributed along the drilling assembly, torsional vibrations can follow a pattern of vibration modes as described above with reference to Figs. 9A-9B. Thus, regardless of where the vibrations occur, the configuration shown in Fig. 15 can be applied to dampen torsional vibrations when the first element 1510 moves relative to the second element 1512 caused by axial vibrations, and vice versa. As shown, an optional tightening member 1540 (e.g., a bolt) can be used to control the contact pressure or normal force between the two members 1510, 1512 and thereby control the friction force and/or other damping characteristics of the damping system 1500.

Next, in accordance with Fig. 16, a schematic illustration of a damping system 1600 is presented in accordance with another embodiment of the present invention. The damping system 1600, which comprises a first element 1610, which is a rigid rod, which is at one end fixed inside a second element 1612. In this embodiment, the end 1610a of the rod is configured to be in frictional contact with the limiter 1612a of the second element, in order to thus provide damping, as described in accordance with the embodiments of the present invention. The normal force between the end 1610a of the rod and the limiter 1612a of the second element can be adjustable, for example, by means of a threaded connection between the end 1610a of the rod and the first element 1610. In addition, the rigidity of the rod can be selected to optimize the damping or to influence the oscillation shape in a favorable manner to provide a greater relative displacement. For example, selecting a rod with a lower stiffness will result in higher torsional vibration amplitudes of the first element 1610 and higher energy dissipation.

Next, in accordance with Fig. 17, a schematic illustration of a damping system 1700 is shown according to another embodiment of the present invention. The damping system 1700, which comprises a first element 1710, which is frictionally attached or connected to a second element 1712, which is arranged in the form of a rigid rod and which is fixedly connected (for example, by welding, bolting, brazing, adhesion, etc.) to an outer tubular element 1714, such as a drill collar, at a fixed connection 1716. In one aspect, the rod can be a tubular element that contains electronic components, power sources, data carriers, batteries, microcontrollers, actuators, sensors, etc., which are subject to wear due to HFTO. Thus, in one aspect, the second element 1712 may be a probe, such as a probe for measuring directional information, including one or more of a gravimeter, a gyroscope and a magnetometer. In this embodiment, the first element 1710 is configured to frictionally contact, move or oscillate relative to and along the structure of the fixed rod of the second element 1712, so as to provide damping as described in accordance with embodiments

- 15 050247 implementation of the present invention. Although Fig. 17 shows that the first element 1710 is relatively small compared to the damping system 1700, this should not imply a limitation in this regard. Thus, the first element 1710 can be of any size and can have the same outer diameter as the damping system 1700. In addition, the position of the first element 1710 can be adjustable to move the first element 1710 closer to the maximum of the vibration mode in order to optimize damping softening.

Next, in accordance with Fig. 18, a schematic illustration of a damping system 1800 is presented according to another embodiment of the present invention. The damping system 1800 comprises a first element 1810, which is frictionally movable along a second element 1812. In this embodiment, the first element 1810 is arranged with an elastic spring element 1842, such as a coil spring or other element or means, for engaging the first element 1810 with the second element 1812, so as to provide a restoring force when the first element 1810 has moved and deflected relative to the second element. The restoring force is aimed at reducing the deflection of the first element 1810 relative to the second element 1812. In such embodiments, the elastic spring element 1842 can be located or tuned to resonance and/or to a critical frequency (for example, the lowest critical frequency) of the elastic spring element 1842 or an oscillatory system comprising the first element 1810 and the elastic spring element 1842.

Next, in accordance with Fig. 19, a schematic illustration of a damping system 1900 is shown according to another embodiment of the present invention. The damping system 1900 includes a first element 1910, which is frictionally movable about a second element 1912. In this embodiment, the first element 1910 is located with a first end 1910a having a first contact (for example, a normal force FNi of the first end, a coefficient of static or dynamic friction μ _i of the first end and a moment of inertia Ji of the first end) and a second contact at the second end 1910b (for example, a normal force FNi of the second end, a coefficient of static or dynamic friction μ _i of the second end and a moment of inertia Ji of the second end). In some such embodiments, the type of interaction between the corresponding first end 1910 or the second end 1910b and the second element 1912 can have different physical characteristics. For example, one or both of the first end 1910a and the second end 1910b may have a gripping contact/engagement, and one or both may have a sliding contact/engagement. The arrangements/configurations of the first and second ends 1910a, 1910b may be set to provide damping, as described in accordance with embodiments of the present invention.

Advantageously, embodiments proposed in the present document relate to systems for mitigating high-frequency torsional vibrations (HFTO) of wellbore systems by using damping systems mounted on a rotating string (e.g., a wellbore string or a drill string). First elements of the damping systems are at least partially frictionally connected for moving circumferentially relative to the axis of the string (e.g., frictionally connected for rotation about the axis of the string). In some embodiments, the second elements may be part of the drilling system or the bottom hole assembly and do not necessarily have to be a separately installed component or weight. The second element, or a portion thereof, is connected to the wellbore system such that the relative movement between the first element and the second element has a relative zero or near-zero velocity (i.e., no or slow relative movement) in the absence of HFTO. However, when HFTO occurs above a certain acceleration value, relative movement is possible between the first element and the second element and alternating positive and negative relative velocities are achieved. In some embodiments, the second element may be a mass or weight that is connected to the well system. In other embodiments, the second element may be a part of the well system (for example, a part of the drilling system or BHA) with friction between the first element and the second element, such as the rest of the well system, providing the functionality described herein.

As described above, the second elements of the damping systems are selected or designed such that when there is no vibration (i.e. HFTO) in the column, the second element will be frictionally connected to the first element by a static friction force. However, when there is vibration (HFTO), the second elements begin to move relative to the first element, and the frictional contact between the first and second elements is reduced, as described above with respect to Fig. 2, such that the second element can rotate (move) relative to the first element (or vice versa). When moving, the first and second elements provide energy dissipation, thereby mitigating HFTO. The damping systems, and in particular the first elements thereof, are located, weighted, positively mounted and sized to provide damping of one or more specific or specified vibration modes/frequencies. As described herein, the first elements are fixedly connected when there are no FHTO vibrations, but are then capable of moving in the presence of certain

- 16 050247 accelerations (e.g. in accordance with the FHTO vibration modes), thus providing HFTO damping across the relative velocity zero crossing (e.g. switching between positive and negative relative rotational velocities).

In the various configurations described above, the sensors can be used to evaluate and/or control the effectiveness and dissipated energy of the damper. Measuring the displacement, velocity and/or acceleration near the contact point or surface of two interacting objects, for example in combination with force or torque sensors, can be used to estimate the relative movement and calculate the dissipated energy. The force can also be known without measurement, for example when two interacting objects are engaged by a biasing element such as a spring element or an actuator. The dissipated energy can also be obtained from temperature measurements. Such measurement values can be transmitted to a controller or human operator, who can provide adjustment of parameters such as the normal force and/or the coefficient(s) of static or dynamic friction, to achieve a higher dissipated energy. For example, the measured and/or calculated values of displacement, speed, acceleration, force and/or temperature can be sent to a controller, such as a microcontroller, which has a set of commands stored on a data carrier, based on which it regulates and/or controls at least one of the force that interacts with two interacting objects, and/or the coefficients of static or dynamic friction. Preferably, the regulation and/or control is performed while the drilling process is ongoing, in order to achieve optimal HFTO damping results.

Although the embodiments described herein have been described with reference to specific figures, it should be understood that various changes may be made and equivalent elements may be substituted for individual elements without departing from the scope of the present invention. In addition, many modifications will be apparent to adapt a particular instrument, situation or material to the teachings of the present invention without departing from the scope thereof. It is therefore intended that the present description not be limited to the specific embodiments described, but that the present description includes all embodiments falling within the scope of the appended claims or the following description of possible embodiments.

Severe vibrations in drill strings and bottom hole assemblies can be caused by cutting forces on the bit or mass imbalances in downhole tools such as drilling motors. The negative effects include reduced drilling ROP, poor measurement quality and downhole failures, among other things.

There are different types of torsional vibration. In the literature, torsional vibration is mainly differentiated as stick/slip vibration of the entire drilling system and high-frequency torsional vibration (HFTO). Both of them are mainly excited by self-excitation mechanisms that arise from the interaction of the drill bit and the formation. The main differentiator between stick/slip vibration and HFTO is the frequency and typical vibration mode. In the case of HFTO, the frequency is more than 50 Hz compared to less than 1 Hz in the case of stick/slip vibration. In addition, the excited vibration mode of stick/slip vibration is the vibration mode of the entire drilling system, while the HFTO mode is usually localized in a small part of the drilling system and has a relatively high amplitude at the bit.

As a result of the high frequency, HFTO corresponds to high values of acceleration and torque along the BHA and can have a damaging effect on electronic components and mechanical parts. Based on the self-excitation theory, increased damping can mitigate HFTO if a certain limit of the damping value is reached (since self-excitation is unstable and can be interpreted as negative damping of the associated vibration mode).

One damping concept is based on friction. Friction between two parts in a BHA or drill string can dissipate energy and reduce the level of torsional vibration.

This concept describes a design principle that the inventors believe works best for damping with friction. Damping should be achieved by friction, with the operating point of the friction force in relation to the relative speed being around point 204 shown in Fig. 2. This operating point results in high energy dissipation since friction hysteresis is achieved, while point 202 shown in Fig. 2 results in energy being supplied to the system.

As discussed above, the friction forces between the drilling system and the wellbore will not create significant additional damping in the system. This is because the relative velocity between the contact surfaces (e.g., stabilizer and wellbore) does not have a zero mean. The two interacting friction damper objects must have an average velocity, or rotational velocity, relative to each other that is small enough that HFTO causes the relative velocity of the two interacting friction damper objects to change sign. In other words, the maximum relative velocities between the two interacting

- 17 050247 objects, the HFTO generated must be higher than the average relative velocity between the two interacting objects.

Energy dissipation occurs only in the slip phase through the interface between the damping device and the drilling system. Slippage occurs if the inertial force exceeds the limit between sticking and slipping, which is the static friction force: F_R>μ_0F_N (the static friction force is equal to the static friction coefficient multiplied by the normal force between both contacting surfaces). The normal force and/or the static or dynamic friction coefficient can be adjusted to achieve the optimum or desired energy dissipation. Adjusting at least one of the normal force and the static or dynamic friction coefficient can result in improved energy dissipation by the damping system.

As described in this document, the placement of the friction damper should be in the region of high HFTO accelerations, loads and/or relative displacement. Since this can affect various vibration modes, a design that is capable of damping all FHTO vibration modes is preferred (e.g., Fig. 9A and Fig. 9B).

As a friction damper tool according to the present invention, an equivalent can be used. A grooved weight pipe 2100 can be used, as shown in Fig. 21 and Fig. 22. Fig. 22 shows a cross-sectional view of the grooved weight pipe 2100. In one non-limiting embodiment, the grooved weight pipe 2100 has high flexibility and will lead to higher deformations if the friction devices 2102 are not included. A higher speed will lead to higher centrifugal forces, which will increase the pressing of the friction devices 2102 against the slots with optimized normal forces to provide high friction damping. In this configuration, other factors that can be optimized are the number and geometrical configuration of the slots, as well as the geometrical configuration of the damping devices. Additional normal force may be applied by spring elements 2104, as shown in Fig. 22, drive mechanisms and/or centrifugal forces, as described above.

The advantage of this principle is that the friction devices will be directly installed in the force flow. The torsion of the weighted pipe due to the excited vibration mode of the FHTO and the corresponding vibration mode will be partially supported by the friction devices, which will move up and down during one vibration period. The high relative movement together with the optimized friction coefficient and normal force leads to high energy dissipation.

In this case, the objective is to prevent the amplitude increase of the FHTO amplitudes (in this case represented by the tangential acceleration amplitudes). The (modal) damping that needs to be added to each variable torsional mode by the friction damper system needs to be higher than the energy input into the system. The energy input does not occur instantaneously, but over many periods until the worst case amplitude (zero RPM at the bit) is reached.

With this concept, a short collar can be used because the friction damper applies relative movement along the distance from the bit. There is no need for high tangential acceleration amplitude, but only some deflection (twisting) of the collar, which will be achieved at almost every location along the BHA. The collar and dampers should have a similar mass to stiffness ratio (impedance) compared to the BHA. This will allow the mode shape to propagate in the friction collar. High damping will be achieved, which will mitigate the HFTO if the parameters described above (normal force due to springs, etc.) are adjusted. The advantage over other friction damper principles is the application of the friction devices directly to the deflection force flow to the HFTO mode shape. The relatively high relative velocity between the friction devices and the collar will result in high energy dissipation.

The damper will be quite practical and will be suitable for various applications. HFTO leads to high costs due to significant repair and maintenance efforts, reliability issues with non-productive time and a small market share. The proposed friction damper will operate below the motor (this separates HFTO) as well as above the motor. It can be installed anywhere on the BHA, which also includes placement above the BHA if the vibration mode extends to this point. The vibration mode extends throughout the BHA if the mass and stiffness distribution is relatively uniform. The optimal placement can be determined, for example, by a torsional vibration operator that allows calculating the critical FHTO modes and the corresponding vibration modes.

Additionally, as noted above, due to the high amplitudes at the drill bit, one position of the damper as described herein may be inside the drill bit or may

- 18 050247 be in close proximity to it, for example, as part of or on a bit support unit. Thus, in accordance with some embodiments of the present invention, the dampers can be integrated into the bit support unit and constitute a part thereof. In such embodiments, the distance to the bit is substantially zero. Bit support units, as described herein, include, without limitation, bit couplings, drive shafts, couplings associated with the operations of fastening and driving into rotation/operation of the bit, guide mechanisms and/or elements associated with the direction of the drilling operation, bending mechanisms that are used in the bending motor for deflection, elements for entering into contact with the walls of the wellbore, fixed or slowly rotating couplings, etc. The bit support assemblies of the present invention may be part of a BHA that includes elements other than the disintegration device, and in some cases may include the disintegration device if such device is formed as a single unit with a portion of the bit support assembly.

A guiding mechanism (also called a guiding section or a guiding unit) is used and configured to drill directional wells. Such directional drilling may be referred to in the art as geosteering. The guiding mechanism in one non-limiting example includes a number of expandable elements (e.g. force application elements) located on a non-rotating sleeve (e.g. a sleeve of a downhole tool) configured to apply selected or predetermined forces to the borehole wall for directional drilling of wells. During the application of force to the borehole wall, the non-rotating sleeve occupies a geostationary position or only slowly rotates relative to the borehole wall, while a drive shaft that passes through the non-rotating sleeve rotates at the rotational speed of the disintegration device (e.g. at the rotational speed of the bit). The expandable elements may be driven by an actuator (e.g. a hydraulic, electric or electromechanical actuator).

In some such embodiments, the damper may be formed by a mass or inertia that is coupled to the bit support unit only by means of a damping force or a damping torque. The damping force may, for example and without limitation, be generated by means of viscous damping, frictional damping, hydraulic damping, magnetic damping (e.g., eddy current damping), piezoelectric (shunt) damping, etc. In some such embodiments, the damper may be combined with a spring, which may provide a tuned inertial damper or a tuned frictional damper. In these cases, the natural frequency of the damper will be tuned to the natural frequency of the vibration mode that is to be damped.

As described above, the analysis showed that the damping increases proportionally with the effective rotational inertia and increases quadratically with the mass-normalized mode shape at the bit. The additional constant factor depends on the damping type. Additional frictional damping with a mass damper is theoretically frequency independent, while hydraulic dampers are somewhat frequency dependent. This trade-off also applies to other damping types and can affect various force parameters (e.g., by harmonic adjustment of the normal force for friction damper configurations, selection of fluids that have properties that change the relative velocity of the components, etc.). As noted, the bit coupling or the bit is one location for a mass damper that may be preferable since the critical mode shapes tend to have the largest amplitude at the bit (e.g., as shown in Fig. 9B). One illustrative critical mode is 248 Hz, which has the highest amplitude at the bit, although various other modes/frequencies may be critical based on the specific configuration and well operations. Thus, the critical mode(s) may depend on various factors, and the 248 Hz mode is described only as an example for purposes of clarification. It is important to note that excitation also theoretically increases quadratically with the amplitude of the mode at the bit. In addition, the amount of damping required to mitigate vibrations may also increase quadratically with the amplitude of the mode at the bit.

In one non-limiting embodiment, the damper is located in the immediate vicinity of the bit, but not in/on the bit, and the friction damper can be a closed ring of any shape that is connected to the bit support unit and is configured to rotate torsionally. In another embodiment, the damper can be a linear mass that is tangentially connected to or included in the bit support unit and effectively causes a rotational force. Several separate dampers can be installed and implemented near or in the bit support unit (i.e., in the immediate vicinity of the end of the drill string). In another configuration, the damper can be formed from two positively connected portions of the bit support unit that are connected at different positions along the axis of the bit support unit (e.g., in the immediate vicinity of the bit connection and in the immediate vicinity of the connection with the drive shaft). The connection at different axial

- 19 050247 positions results in relative movement between two forcibly connected parts. An example of such a configuration may include, for example, a threaded connection with relative contact surfaces.

For example, referring to Fig. 23, a schematic representation of a bit support assembly 2300 is shown. The bit support assembly 2300 includes a bit sleeve 2302 configured to receive a bit in a bit opening 2304. The bit opening 2304 is configured (e.g., in shape, size, etc.) to receive a drill bit or other disintegration device. As will be understood by those skilled in the art, the bit sleeve 2302 is configured to retain and, in some configurations, to drive a bit installed in the bit opening 2304. The bit or other disintegration device may be configured to cut formation material (e.g., rock) during a drilling operation.

As shown, the bit coupling 2302 is mounted as part of the bit support assembly 2300 on the drive shaft 2306. The drive shaft 2306 can rotate to drive (e.g. rotate) the bit mounted in/on the hole 2304 for the bit. During operation, the drilling torque is transmitted from the drive shaft 2306 to the bit coupling 2304 by means of the torque sleeve 2308 and the sleeve 2310. The threaded connection 2312 creates an axial preload between the drive shaft 2306 and the bit coupling 2302. The torque is transmitted by means of friction between the various components of the bit support assembly 2300, which can depend on the axial surface pressure, the friction coefficients and the radius of the contact surfaces relative to the axis A _x of the tool. As will be understood by those skilled in the art, the first end surface 2314 of the torque sleeve 2308, which contacts the drive shaft 2306, can be coated with a friction-enhancing layer (for example, a diamond-containing material), which allows to increase the transmitted torque by means of a multiplication factor. The second end surface 2316, providing contact between the drive shaft 2306 and the bit coupling 2302, can be configured to increase the make-up and break-out torque (MUT - English: make-up torque). Due to the coating on the first end surface 2314, it is not expected that there will be a movement of the torque sleeve 2308 relative to, for example, the drive shaft 2306. The sleeve 2310 has a larger radius than the torque sleeve 2308, i.e. relative to the axis A _x of the tool, and the transmitted torque on the first end surface 2314 is greater than on the second end surface 2316.

A typical design of the bit coupling or so-called lower drive shaft is a thread with contact on both ends, as shown in Fig. 23. However, in some alternative configurations, the coupling, torque sleeve and/or the bit may be connected together as a single part/component. In such configurations, when the connection is made, the relative movement occurs on both ends (for example, the first and second end surfaces 2314, 2316 shown in Fig. 23). Accordingly, it is not possible to use a friction-enhancing coating on the first end surface, as described above. Thus, this leads to a significant reduction in the permissible torque due to a reduced friction coefficient and a smaller effective radius.

As shown, the drive shaft 2306 and the torque sleeve 2308 can be located in the tool sleeve 2318. As will be understood by those skilled in the art, the tool sleeve 2318 can be a non-rotating or slowly rotating coupling. The tool sleeve 2318 can be configured to interact with or connect to the BHA or to another downhole assembly and/or tool string.

As described above, various types of dampers can be included in various aspects of the drilling system. In this illustrative embodiment, a bit support assembly 2300 is shown, wherein said bit support assembly 2300 comprises a damper element 2320, illustratively shown as rotational inertia. The damper element 2320 in this embodiment is decoupled from the point of view of rotation by various bearings 2322 (for example, radial, such as needle bearings or polycrystalline diamond (PDC) bearings and/or thrust bearings). The damper element 2320 is configured to remain free and can rotate on the bit support assembly 2300 (for example, relative to the bit coupling 2302 and/or the torque sleeve 2308). The effect of the damping element 2320 can be maximized by a high density material and a geometric shape with certain characteristics. For example, as shown in Fig. 23, the volume of the damping element 2320 can be selected and/or optimized in the sense that the mass of the damping element 2320 has a specific or certain radial distance from the axis A _x of the tool. For example, as shown, the bearings 2322 (and the friction contact) can be located closer to the axis A _x of the tool in the radial direction than the damping element 2320 in order to leave space and optimize the sleeve 2310 of the cover and the damping element 2320. Such space allows to ensure that aspects of the damping system are able to withstand the expected loads during operation, and also allows to select the geometric properties and material of the damping element 2320 in such a way as to maximize the rotational inertia and achieve the required damping.

- 20 050247

In some embodiments, as shown, the axial spring 2324 may be configured to apply an axial force to the damper element 2320. In this illustrative configuration, the axial spring 2324 is configured to transmit the axial force through the bearing 2322 (for example, a thrust bearing) and the damper element 2320 to the friction surface 2326 between the damper element 2320 and the bit sleeve 2302. In some embodiments, the friction surface 2326 may be replaced by any other type of damping mechanism. The axial contact pressure and the existing coefficient of friction for the friction surface 2326 create a frictional coupling between the damper element 2320 and the bit sleeve 2302. The stiffness of the axial spring 2324 and the coefficient of friction on the friction surface 2326 can be selected so as to ensure that maximum damping is achieved in terms of amplitude, which at the same time does not reduce the service life of the bit support unit 2300 and/or the bit installed therein.

As shown in Fig. 23, the damper element 2320 is enclosed in the sleeve 2310. The sleeve 2310 is selected so as to withstand the external hydrostatic pressure based on the wall thickness, while the external diameter of the damper element 2320 can be taken into account. In some embodiments, the damper element 2320 (illustratively shown as a physical component) can be made in the form of a viscous damper. In some such embodiments, the installation location of the damper element 2320 can be filled with a fluid, and pressure compensation can make it possible to increase the external diameter of the damper element due to achieving a design space in the size of the sleeve and other parts. As a non-limiting example, the fluid can be an incompressible fluid. In another embodiment, the sleeve 2310 can be omitted. In some such embodiments, a maximum outer diameter of the damper element may be obtained, and in some such embodiments, due to the influence of the external environment of the wellbore, damper elements resistant to drilling fluid may be required. In this context, the inertial mass or damper element may be adjusted to cover parts of the bending load that must be transmitted. The system exposed to drilling fluid may also include a sleeve that is partially slotted to cover the bend on one side, but also leaves a larger structural space for the inertial mass/damper element, which can partially fill the slots between the sleeves.

In some embodiments of the present invention, a purely rotational damper may be installed in the bit support unit, and such a configuration may be useful for high-amplitude vibration modes on the bit itself or in close proximity to it. Some such arrangements may provide for the arrangement of the damper elements with a smaller radial distance, i.e. closer to the axis A _x of the tool. Thus, a smaller radius of the damper element may limit the damping effect, but such a limitation may be compensated for by the fact that an increased mass may be placed on the bit support unit. Thus, the choice of mass and radial position relative to the axis A _x of the tool may be determined based on the desired vibration or vibration mode to be damped, as well as based on the input energy of the expected excitation, which may be described by negative damping (for example, as shown in Fig. 20).

Sufficient damping to minimize or eliminate vibrations in the downhole section of the well can be achieved by determining the location of damping elements in or on the bit support assembly (e.g. in or on the bit collar or on another part of the guide assembly). The reason is that in almost all cases the mass-normalized amplitude of the critical vibration mode is greatest at the bit or disintegration device. This can be physically explained by the fact that the excitation and the probability that any vibration mode is excited also increase quadratically with the amplitude of the vibration mode at the bit (or at the excitation point), if the speed-torque reduction characteristic at the bit is taken relative to the average rotational speed. The inclusion of a damper/damper element in the bit support assembly may impose restrictions on the axial length of the damper/damper element. However, since the damping is high due to the high amplitude of the mode shape at or near the bit, the damper/damper element can be relatively short and still provide sufficient damping effect. The damper at the bit support unit can be less than 30 cm, or 40 cm, or 50 cm, or 100 cm, or 150 cm.

One type of damper element that may be installed in or near the bit support assembly in accordance with the present invention is a linear viscous damper. Such a damper element could include a mass and a force element that transfers force from the bit support assembly to the mass/inertia. Such a damper element would have a force element that points, is located, or is oriented in a tangential direction to damp the HFTO. The force element may be a linear viscous or frictional damper.

- 21 050247 element, as will be understood by those skilled in the art given the teachings presented herein.

The indicated damping element 2320 can be a single element/structure or a plurality of elements/structures. For example, the damping element 2320 can be an inertia ring or another ring-type structure, which can be a closed or discontinuous ring, such as half-shells. In some embodiments, two half-shells (or other partial shells) can be used when it is not possible to install a full ring due to the design or configuration of the bit or the support unit of the bit. The half-shells can be assembled around a radial friction contact or a radial bearing (for example, some of the bearings 2322), which can be located relative to the inner diameter of the damping element 2320 and can be similar in position and shape. The bearing(s) may be divided to accommodate bearings 2322 and/or a damper element 2320. In some embodiments, the normal force may be applied through the half-shells, and it may be controlled by the elasticity of the half-shells and the applied normal force/connection force. In some embodiments, for applying radial friction forces between, for example, the half-shells of the damper element and creating radial friction, casings with a radial wave spring may also be used.

For the damping element(s) (e.g. the inertia ring), various geometric configurations can be applied, which can be useful for increasing the inertia. In this sense, the density of the material selected for the damping element can be selected as high as possible, with the mass distribution radius being in a large radius relative to the longitudinal axis of the drilling system or the bit support unit. The inertia (or inertia half-shells) can include additional masses (inertia), which are preferably installed or located around the bit support unit.

In some embodiments, a limiting stop may optionally be provided to prevent free or continuous movement of the annular-shaped damping element (e.g., rotation by more than 10°). Normal forces between the damping element and the bit sleeve or other part of the bit support unit may be applied in the radial or axial direction using springs or other mechanisms. Radial friction forces may be achieved by means of springs or an elastic design of the annular-type damping element. In some such embodiments, the double damping element of the half-casing may be preloaded to achieve the required friction force. The axial normal force may be provided by springs, wherein the mass weight/inertia in the vertical wellbore and the springs may be made in the form of casings, etc. The material of the bit support unit may be a steel housing or base (e.g., made of composite materials). A thrust bearing may be used to decouple the potential normal force of the spring package and the rotational movement of the inertial mass.

In some embodiments, tangential damping elements may be used in the bit coupling or other part of the bit support unit. The dampers for tangential damping may be installed in a position with a significant radius relative to the longitudinal axis of the drilling system (for example, in the radial direction relative to the axis A _x of the tool).

In the case of dampers that are installed with free movement in the tangential direction (the direction of the tangential acceleration), (steel) pipes can be used, which are screwed into the bit support unit. The tangential dampers can be assembled in pipes containing a mechanism for applying normal forces between the inertial mass (for example, the damper element) and the support unit (for example, the bit coupling), preferably perpendicular to the tangential direction. In some embodiments, the tangential damper elements can be installed as part of a corresponding housing or be a part thereof, which can be attached to the bit coupling or another part of the bit support unit, for example, by means of threaded connections. The said housings can have any geometric configuration and can be installed in different positions on the bit support unit.

As described above, in accordance with embodiments of the present invention, a damper element or assembly is described that consists, in some configurations, of a rotational inertial damper element that can be coupled to the drilling system only by means of a damping force or moment at the top of the drive shaft. As will be understood by those skilled in the art and taking into account the teachings presented herein, the damping force can be created, for example, by viscous damping, frictional damping, piezoelectric or magnetic damping, such as by means of eddy currents, etc. In some embodiments, the damper element can be combined with a spring that can provide a damper with an adjustable mass or a damper with an adjustable friction. In some such embodiments, the natural frequency of the damper and the adjustable force elements that provide stiffness (e.g., a spring) and damping ability can be

- 22 050247 are tuned to the natural frequency of the vibration mode that needs to be damped.

The bit is connected to a support unit (e.g., a bit coupling) having a damping element as described above. In some configurations, another threaded connection may be used between the lower drive shaft and the bit support unit, which allows for the optional inclusion of a friction damper with an inertia ring. The damping element may be protected by a sleeve, which is frictionally connected at the upper and lower ends. The sleeve does not necessarily provide damping, since normal forces theoretically prevent slippage between the contact surfaces between the sleeve and other components of the bit support unit (e.g., the bit coupling and the tool sleeve). Frictional forces are determined by the coefficient of friction and the normal force, which is created by the threaded connection between the lower drive shaft and the bit support unit.

According to some embodiments of the present invention, the damping element (for example, an inertial damper) is a ring located under the sleeve. The damping element is free to rotate relative to the drilling system, the bit support unit or other structures. In some embodiments, the array of the damping element can be made of a non-magnetic material to prevent interaction and / or interference with measurements performed by a magnetometer, which can be located in close proximity to the bit and / or the bit support unit. Similarly, the material of the damping element can be selected so as to minimize or prevent a negative impact on formation evaluation measurements or other measurements or operations in the bottomhole. As noted above, in some embodiments, the damping element can be supported by a radial bearing that is frictionless or substantially frictionless. The damping element (for example, the inertia ring) is configured to interact with the drilling system through friction surfaces, for example, on a contact or other surface between the damping element and the bit support unit (for example, the friction surface 2326 shown in Fig. 23). In some embodiments, the various friction surfaces are aligned in the axial direction. The normal force to the friction surface is applied by an axial spring (for example, the axial spring 2324 shown in Fig. 23). The friction coefficient depends on the material properties of the interacting surfaces. In some embodiments, the axial spring can be decoupled from the point of view of rotational motion with inertia by means of a thrust bearing.

Fig. 24-25 show schematic illustrations of damper elements 2400, 2500. Damper elements 2400, 2500 are configured to be installed inside the support unit of the bit, as described above. Each damper element 2400, 2500 comprises a corresponding body 2402, 2502 for accommodating and containing components of the corresponding damper elements 2400, 2500. The first damper element 2400 has a substantially rectangular geometric configuration (with curved corners), and the second damper element 2500 has a substantially circular geometric configuration. The bodies 2402, 2502 are configured to be installed in the support unit of the bit (for example, as shown in Fig. 23).

Each of the damper elements 2400, 2500 comprises a mass element 2404, 2504, mounted with the possibility of movement inside the housings 2402, 2502. The mass element 2404, 2504 is located between the mounting element 2406, 2506 and the contact element 2408, 2508. The mounting elements 2406, 2506 are designed with the possibility of applying a force to the corresponding mass element 2404, 2504 in the direction of the contact elements 2408, 2508. Thus, frictional contact can be achieved between the corresponding mass element 2404, 2504 and the contact elements 2408, 2508. The mass elements 2404, 2504 may be arranged with one or more limit stops 2410, 2510 inside the corresponding housings 2402, 2502. The limit stops 2410, 2510 may include optional rigidity or hydraulic elements for damping the movement of the mass elements 2404, 2504.

In addition, the limit stops 2410, 2510 can prevent the mass elements 2404, 2504 from getting stuck at one edge of the housing 2402, 2502. The limit stops 2410, 2510 can be made with springs or other elements to avoid damaging the mass elements 2404, 2504 and to press the mass elements 2404, 2504 to the middle position or the rest position relative to the housing. In some embodiments, it may be preferable to optimize the spring stiffness and/or the clearance in the housing 2402, 2502 to allow the mass elements 2404, 2504 to move inside the housing 2402, 2502. The damper elements 2400, 2500 can be arranged in the form of inserts (for example, the housing 2402, 2502 is configured to be installed). The insertable damping elements 2400, 2500 can be installed in such a way that the mass elements 2404, 2504 are located in a position of a significant radius relative to the axis (for example, the longitudinal axis) of the drilling system to increase the rotational inertia relative to this axis in order to increase the damping efficiency.

The mounting element 2406, 2506 is configured to apply a normal force to the mass elements 2404, 2504. For example, the mounting element 2406, 2506 can be arranged in the form

- 23 050247 spring housings for pressing the mass elements 2404, 2504 with entering into contact with the contact element 2408, 2508. In addition, the mounting elements 2406, 2506 and/or the contact elements 2408, 2508 can be configured to control the tangential movement of the mass elements 2404, 2504 to provide HFTO damping. In some embodiments, the mounting elements 2406, 2506 press the mass elements 2404, 2504 with entering into contact with the contact element 2408, 2508 to create a frictional force. The frictional force is applied, for example, through a material that is useful relative to the coefficient of friction and the expected wear, which should be as low as possible.

According to embodiments of the present invention, damping can be integrated into the bit support unit. Damping can be applied by any axial, tangential and/or radial force or corresponding torque capable of dissipating energy. In the case of coupled vibration modes, damping forces in the axial direction are also capable of dissipating energy from the twisting direction. As described for frictional damping, the contact surfaces applied with a friction coefficient and a normal force can be optimized and/or selected to damp one or more critical vibration modes. In some embodiments, useful materials or structures can be used to prevent wear (for example, of copper or polycrystalline diamond bits). A plurality of contacts with different properties can be used to configure the system with an advantageous friction coefficient or characteristic. In some embodiments, the damper element is configured to move relative to the bit support unit at a speed that is the sum of periodic speed changes having an amplitude and an average speed, wherein the average speed is lower than the amplitude of the periodic speed changes.

Depending on the type of force applied, various configurations are possible. As described above, Fig. 2 shows a typical force characteristic for friction contacts. The force characteristic has a velocity-decreasing effect for relative velocities that are not close to zero. As described above, a harmonic or periodic relative movement between two elements will result in energy being supplied to the system. In addition, as described above, damping in this case is only effective for a relative movement of the interacting surfaces close to zero (e.g., point 204 in Fig. 2). An alternative (or in combination with a friction damper) may be a viscous damper.

Next, in accordance with Fig. 26, an illustrative graph 2600 is shown of the dependence of various torque (T)/force (F) characteristics of viscous fluids on the relative displacement ((e,) x) (e.g., relative displacement/velocity) between two parts that are connected by a connecting force of some kind. In this graph, curve 2602 represents the properties of a Newtonian fluid, curve 2604 represents the properties of a non-Newtonian shear thinning fluid, and curve 2606 represents the properties of a non-Newtonian shear thickening fluid. Although graph 2600 illustrates fluids, such principles can be applied to other types of dampers, such as non-contact damping (e.g., eddy current damping). In graph 2600, curve 2602 includes points 1, 2, 3, curve 2604 includes points 4, 5, 6, and curve 2606 includes points 7, 8, 9. Points 1-9 represent differences in the dependence of torque T or force F on relative displacement ((e,) x).

In the graph 2600, the slope of the curves 2602, 2604, 2606, for example, at points 1-9, is positive, and the relative movement (including the average velocity (e,) x at this point and the change in the relative displacement, velocity or acceleration with respect to the forcibly connected parts, which is caused by a periodic superimposed oscillation, for example, caused by high-frequency torsional oscillations) relative to these points provides damping of the system. The relative movement can, for example, occur between one part, which is connected to the wall of the wellbore, for example, by sticking friction in the tangential direction, as occurs with a non-rotating coupling of the guide mechanism. Two interacting objects, which are forcibly connected according to a characteristic of this type, could also provide damping of high-frequency torsional oscillations if a positive average rotational speed is applied. The disadvantage is that this type of characteristic will also result in an average static force (T, F in Fig. 26 and corresponding to points 1-9) from the contacting surfaces, which reduces the power from rotation that can be applied to break the rock. That is, the damper acts as a brake on the rotation of the borehole system. Thus, in these cases, higher power may be required on the surface rotation system that drives the cutting function of the bit.

The required damping effect depends linearly on the slope of the various torque versus relative displacement curves, which may be referred to as the viscous damping coefficient d(d1- _d9 ) in Fig. 26 and increases quadratically with the mass-normalized amplitude of the mode shape, such as shown in Fig. 9B. The static dissipated energy from a constant relative displacement also increases linearly with the viscous damping coefficient

- 24 050247 damping d. Since the amplitude of the vibration mode is very localized and very high at the bit, and therefore the relative movement between the two forcedly connected surfaces as described above is high, the static energy dissipation is also high and the damping is effective. As a result of the localized and high amplitude of the vibration mode, the length of the damper can be relatively small (e.g. in the axial direction). The braking force of a relatively short damper is less than the braking force of a relatively longer damper. Thus, the compromise relationship between the damping, which is provided dynamically, for example to soften high-frequency torsional vibrations, and the (undesirable) static energy dissipation, is particularly suitable in the vicinity of the bit or the bit support unit.

Referring now to Fig. 27, there is shown a bit support assembly 2700 having a damping element 2701 in the form of a viscous damper or an eddy current damper. The bit support assembly 2700 may be similar to that shown and described above, having a bit coupling 2702 attached to a drive shaft 2706, wherein the bit coupling 2702 is formed with a bit opening 2704 intended to receive a bit or other disintegration device. The drive shaft 2706 and the torque sleeve 2708 may be located inside the tool sleeve 2718. As will be understood by those skilled in the art, the tool sleeve 2718 may be a non-rotating or slowly rotating coupling. The tool sleeve 2718 may be configured to interact with or be connected to the BHA or to another downhole assembly and/or tool string, such as a guide mechanism. As will be understood by those skilled in the art, in this embodiment, as shown, the tool sleeve 2718 may engage the wall 2750 of the wellbore using a force application element 2752, such as a rib or a plurality of ribs, extension devices, etc. The tool sleeve may include, for example, three force application elements. The specified assembly may also include any type of non-rotating stabilizer known in the art.

The torque sleeve 2708 and the drive shaft 2706 will rotate to drive the bit coupling 2702 and, thus, the bit or the disintegration device installed therein. However, the tool sleeve 2718 can be positively connected to the borehole wall 2750 by means of the force application element 2752. In some non-limiting embodiments, the force application element 2752 can be a guide device that applies forces to change the drilling direction. As a result, the tool sleeve 2718 has an average rotation speed close to zero. In addition, the force application element 2752 is decoupled from the dynamic component of high-frequency torsional vibrations that is excited by the disintegration device, since bearings or any other device(s) for decoupling are used between the torque sleeve 2708 and the tool sleeve 2718.

The torque sleeve 2708 is subjected to a load from high-frequency torsional vibrations, which is a harmonic or periodic displacement, speed or acceleration and a dynamic torque. Thus, the dynamic relative movement due to the high-frequency torsional vibrations is superimposed on the average relative movement between the torque sleeve 2708 and the tool sleeve 2718. This dynamic relative movement can be used to dampen the high-frequency torsional vibrations inside the bit support unit 2700. The damping force is provided by the damping element 2701 and can be adjusted over the entire circumference or only on specific parts of the diameter and can be positively connected to the torque sleeve 2708 and the tool sleeve 2718 by means of a damping force device with a characteristic similar to that described with reference to Fig. 26. More specifically, at operating points 1-9 in Fig. 26 requires a positive slope with respect to the relative speed (x-axis) and the transmitted force or torque. Such behavior is not limited to hydraulic damping, but can be achieved by any other damping forces or a combination of damping forces, as described herein. Thus, the damping element 2701 can be, but is not limited to, a viscous or hydraulic damper. For example, an eddy current damper can be used, which has a purely linear relationship between torque and relative speed, similar to Newtonian fluids (curve 2602 shown in Fig. 26). In this context, two parts that are forced together can be used to damp the system, with an average relative speed close to zero or not equal to zero, or without it, if the relative movement has a dynamic component from oscillations associated with high-frequency torsional oscillations. In this example, one of the two forcedly connected parts has a zero dynamic component, since it is an approximation, separated from the dynamic movement of the bit support unit, the drive shaft or similar parts that transmit torque. Some of the energy from the torsional vibrations can be transmitted to the tool sleeve 2718 by means of the damping force on the damping element 2701. Thus, it may be advantageous to design the tool sleeve 2718 or other component/part (e.g., the tool

- 25 050247 columns, well strings, drilling systems, BHAs, etc.) that will not vibrate excessively as part of these mechanisms, for example, due to a different free oscillation frequency or a first free oscillation frequency that is higher than that of the high-frequency torsional oscillations, the free oscillation frequency of the downhole assembly or drilling system.

Thus, one form of damping that can be used in embodiments of the present invention is hydraulic damping. Such hydraulic damping can be implemented using a system that is either included in the bit coupling or located in close proximity to the bit support unit or in other positions in the bit. In some such embodiments, a viscous fluid (for example, a viscous fluid in chambers) can be located and mounted in similar positions as described above. In some such applications, the stresses (shears) in the fluid between the inertial ring/mass and the bit support unit can be selected to achieve a (damping) force tangential to the tangential acceleration and the associated harmonic motion for damping high-frequency torsional vibrations. In the case of ring shear, the fluid provides a damping force between the inertia ring and the bit support unit (e.g., the bit collar). In this case, the ring may require a closed housing and, possibly, a well-defined geometric configuration of the gaps between the ring and the housing, which can be achieved by using the specified sleeve. With hydraulic damping, the viscous damping forces are sensitive to changes in the parameters of the gaps and the viscous fluid. Thus, a temperature-insensitive fluid may be preferable. To achieve a useful regime, fluids with different shear stresses depending on the shear rate can be used. Some such illustrative fluids include, without limitation, Newtonian fluids, non-Newtonian fluids (e.g., diluents, shear-thickening or shear-thinning fluids), pseudoplastic, Bingham plastic, Bingham pseudoplastic fluids, etc.

In addition, in some embodiments, magnetic damping can be used. Magnetic damping can be achieved by using a permanent magnet (e.g. mounted on an inertial ring or mass element) that is allowed to move relative to the coil and can be used to damp the HFTO. Depending on the magnetic principle, the damping force characteristic is similar to a hydraulic force (e.g. by eddy currents) or a friction force (hysteresis). In some such configurations, the force will act in the direction of the tangential acceleration or in any other direction that can lead to damping in the direction of the twist or in the direction to be damped.

In addition, in some embodiments, piezoelectric damping principles can be used to prevent HFTO on a bit. A piezoelectric material can be used, connected to an inertial ring or a tangential mass on one side, and a bit support unit on the other side. The electrodes of the piezoelectric material can be connected to a circuit including coils, resistors and capacitors or semi-active or active electronic components. A combination of electrical components can be used to achieve useful damping characteristics between the inertial ring and the bit support unit. The circuit can be adjusted to the free vibration frequency of the system to operate as a tuned inertial damper (i.e., for one or more desired vibration modes). The resistor can be configured to directly dissipate energy if the piezoelectric block is deformed by a relative force between the mass element and the bit support unit. In addition, the stiffness of the piezoelectric material and the mass of the inertia ring can also be tuned to a specific frequency. The electrodes of the piezoelectric material can be designed to damp torsional vibrations. The direction of the damping forces can differ from the direction of the electrodes using the effect of a favorable conversion from a mechanical force to an electrical signal, which is offered by the design of the piezoelectric element. Well-known effects of piezoelectric coefficients are D ₃₃ (electrodes in the direction of the force), D ₃₁ (perpendicular to the direction of the force) and D ₁₅ (shear stress). The piezoelectric material can be placed to optimize or control the coupling between the mechanical and electrical system for a specific vibration mode or a plurality of vibration modes that are critical for high-frequency torsional vibrations. In addition, various materials in which a mechanical force or stress or associated loads are converted into electrical signals can be used without departing from the scope of the present invention.

Additionally, the internal damping and the resulting material forces can be used to reduce HFTO. In this way, material damping can be achieved passively by using the damping properties of highly damping materials. Some such materials may include, but are not limited to, polymers, elastomers, rubbers, etc., as well as the damping effect of multifunctional materials such as shape memory alloys. The material properties of some materials such as shape memory alloys can be actively influenced or

- 26 050247 can be controlled to achieve greater damping effect.

Other damping configurations are possible without departing from the scope of the present invention. For example, negative capacitances and semi-active components using switching techniques can be used. Additional damping methods and components can be used, and the embodiments and variations described above are provided for illustrative and explanatory purposes and are not intended to be limiting. All damping principles described herein can be adjusted to operate as a tuned inertial damper by adding mechanical springs adjusted to a specific frequency and by adding damping of any type. In addition, one or more damping principles described herein (or other methods/mechanisms) can be combined in a multi-base configuration. For example, ring-type inertial dampers can be combined with tangential mass inertial dampers mounted inside or attached to the blades of the disintegration device. In addition, magnetic, hydraulic, frictional, piezoelectric forces and principles, as well as material damping forces and principles, can be combined to achieve a reliable damping effect, for example with respect to temperature.

As described above, one or more damping elements can be integrated into the bit sleeve or other part of the bit support assembly. For example, an annular damper can be located in or near the bit support assembly, as shown and described. In some configurations, the inertial ring of the damper can be lubricated with drilling fluid or covered by the sleeve structure. In some configurations, a closed or solid ring can be used. In other configurations, partial arcs can be assembled near the bit support assembly (for example, they can be installed if the ring cannot be assembled in another way). In some such embodiments, two semi-annular arcs can be used. In other embodiments, more than two annular arcs can be used to form a complete (longitudinal) annular casing structure or less than a complete (longitudinal) annular casing, depending on the particular configuration used.

In some embodiments, a split ring structure may be used in which discrete masses are located near a portion of the bit support unit. In another example, the entire ring structure may be located near the bit support unit, but specific additional mass elements or ring elements may be located relative to specific portions of the bit that is mounted on the bit support unit (for example, the blades of the bit mounted in the bit coupling). One such example may have a relatively thick ring in position relative to the blades of the bit mounted in the bit coupling, and a smaller thickness to allow the flow of cuttings to pass along the bit support unit.

In some embodiments, a limiting stop may be provided for the annular damping element, which may prevent the ring from moving freely around the circumference of the bit support unit. Such a limiting stop may be provided in embodiments in which the mass or a higher mass is located behind or near specific blades or other cutting elements of the bit installed in the bit coupling. In such cases, the limiting stop may ensure that the mass or increased mass remains in position relative to the cutting elements.

It should be understood that the friction damping elements of the friction type according to the present invention can apply radial and/or axial friction forces. The radial friction forces can be achieved by means of springs or an elastic structure of the inertia ring, which has two half-shells and is preloaded. The axial normal force can be achieved by means of springs, wherein the mass/inertia weight in the vertical wellbore and/or the springs can be made in the form of shells, etc. The material of the bit support unit can be steel, or a matrix composite, or another suitable material. In some embodiments, a bearing can be used to ensure the movement of the inertial ring in the radial direction. Thus, a bearing can be provided to ensure the circumferential and/or tangential movement of the damping element. An axial bearing can be used to separate the spring set of the potential normal force from the rotational movement.

In some embodiments, as an alternative to or in combination with the annular type damping element, tangential damping elements may be implemented as part of or mounted on other parts of the bit support assembly. In some such embodiments, the tangential damping elements may be mounted inside housings that are screwed into the bit support assembly (e.g., into the bit sleeve). In some such configurations, one or more limit stops may be provided to prevent the tangential dampers from sticking at an edge or corner of the housing. Contact between the limit stop and the tangential damper mass may be achieved using springs or other biasing elements or structures. In some embodiments, the spring constant or the gap in the housing may be selected so as to allow the tangential damper mass to move

- 27 050247 ferra inside the housing and thus providing vibration damping as described above.

Also, control elements can be applied that change the properties of the contact between the contacting elements in the support unit of the bit. For example, the normal force can be adjusted in a frictional contact. The gap between two interacting surfaces that provide damping by means of relative movement can be increased or decreased to change the damping properties. For example, in the case of magnetic damping, the damping value depends on the size of the gap, for example, on the damping element 2701 shown in Fig. 27. Adjustment is possible for all parameters that affect damping and is not limited to temperature, geometry and/or electric field. In addition, the effectiveness of the damping device can be measured by means of load and acceleration or by means of other vibration measuring devices, and the obtained data, as necessary, can be transmitted to the feedback loop to provide additional adjustment of the damping parameters.

Accordingly, embodiments of the present invention relate to determining the position of a damping system, such as a ring-type damper or a tangential damper, near or as part of a bit support unit of a well system. By determining the position of the damping system near or as part of the bit support unit, improved damping of high-frequency torsional vibrations or other forms of vibration can be achieved.

Embodiment 1. A system for damping torsional vibrations of borehole systems, wherein such a system comprises: a borehole string; a bit support unit configured to secure and receive a disintegration device, wherein said disintegration device is located at the end of the borehole string and mounted on the bit support unit; and a damping system configured to at least one of: be installed on the bit support unit or as part of it, wherein said damping system comprises at least one damper element configured to contact a section of the bit support unit.

Embodiment 2. The system according to any of the preceding embodiments, in which the damper element is configured to move, at least partially, relative to the support unit of the bit at a speed that is the sum of periodic changes in speed having an amplitude and an average speed.

Embodiment 3. The system according to any of the preceding embodiments, in which the disintegration device is a bit that engages with a bit sleeve of a bit support assembly.

Embodiment 4. The system according to any of the previous embodiments, in which the bit support unit comprises: a drive shaft; a torque sleeve in which the bit coupling comes into rotational contact with the drive shaft, wherein the torque sleeve is configured to be in working contact with the drive shaft.

Embodiment 5. The system according to any of the preceding embodiments, in which the bit coupling is connected to the drive shaft by means of a threaded connection.

Embodiment 6. The system according to any of the preceding embodiments, further comprising a tool sleeve located externally relative to the torque sleeve, wherein at least one damping element is located between the torque sleeve and the tool sleeve.

Embodiment 7. The system according to any of the preceding embodiments, in which at least one damper element is located on the support unit of the bit.

Embodiment 8. The system according to any of the preceding embodiments, wherein at least one damper element is a ring-type structure located circumferentially near the support unit of the bit.

Embodiment 9. The system according to any of the preceding embodiments, in which the ring-type structure comprises two half-shells located near the support unit of the bit.

Embodiment 10. The system according to any of the preceding embodiments, further comprising a sleeve located externally relative to the at least one damping element such that the at least one damping element is located between the sleeve and the support unit of the bit.

Embodiment 11. The system according to any of the preceding embodiments, further comprising at least one bearing configured to be disengaged from the point of view of rotational movement of at least a portion of at least one damper element relative to movement of the support unit of the bit.

Embodiment 12. The system of any of the preceding embodiments, wherein the at least one bearing comprises at least one of a radial bearing and a thrust bearing.

Embodiment 13. The system according to any of the preceding embodiments, further comprising an axial spring configured to force at least

- 28 050247 at least part of at least one damper element for friction coupling with the support unit of the bit.

Embodiment 14. The system of any of the preceding embodiments, wherein at least one damper element is a tangential damper element.

Embodiment 15. The system of any of the preceding embodiments, wherein the bit support assembly comprises a guide mechanism.

Embodiment 16. The system according to any of the preceding embodiments, in which at least one damper element further comprises a limiting stop configured to prevent rotation of at least one portion of at least one damper element around the support assembly of the bit.

Embodiment 17. A system according to any of the preceding embodiments, wherein said damping system is configured to provide at least one of the following damping options on the bit support unit: viscous damping, frictional damping, hydraulic damping, piezoelectric damping, eddy current damping, and magnetic damping.

Embodiment 18. The system of any of the preceding embodiments, wherein the well string is a drill string, wherein said support assembly is mounted at the end of the drill string.

Embodiment 19. A method for damping torsional vibrations of a well system in a wellbore, wherein said method comprises: installing a damping system in at least one of the variants: on a support unit of a bit or as part of it, which is located on a well string of a well system, wherein the support unit of the bit has a disintegration device attached to it, wherein said damping system comprises: at least one damping element located in contact with a section of the support unit of the bit, wherein at least a portion of the damping element moves relative to the support unit of the bit at a speed that is the sum of periodic speed oscillations having an amplitude and an average speed.

Embodiment 20. The method according to any of the preceding embodiments, wherein at least one damper element comprises a ring-type structure installed near the support unit of the bit.

Various analysis components, including a digital and/or analog system, can be used to support the teachings presented herein. For example, controllers, computer processing systems, and/or geosteering systems presented herein and/or used with the embodiments described herein can include digital and/or analog systems. The systems can have components such as processors, storage media, memory, inputs, outputs, communication lines (e.g., wired, wireless, optical, or other), user interfaces, software products, signal processors (e.g., digital or analog), and other similar components (e.g., resistors, capacitors, inductors, and others) to support the operation and analysis of the apparatus and methods described herein in any of several ways well understood in the art. It is believed that these concepts may be, but are not necessarily, implemented in combination with a set of computer-executable instructions stored on a non-volatile computer-readable medium, including a memory device (e.g., ROM, RAM), an optical device (e.g., CD-ROM) or a magnetic device (e.g., disks, hard disks) or any other type of device that, when executed, causes a computer to implement the methods and/or processes described herein. These instructions may provide equipment operation, control, data collection, analysis and other functions that are considered significant by the system developer, its owner, user or other similar personnel, in addition to the functions described herein. Processed data, such as the result of the implemented method, can be transmitted as a signal through an output interface of the processor to a signal receiving device. The signal receiving device may be a screen monitor or a printer for presenting the result to the user. Alternatively or additionally, the signal receiving device may be a storage device or a data carrier. It should be understood that storing the result in a memory device or storage medium may transform the memory device or storage medium into a new state (i.e., containing the result) from a previous state (i.e., not containing the result). In addition, in some embodiments, a warning signal may be transmitted from the processor to the user interface if the result exceeds a threshold.

In addition, various other components may be included and described to provide aspects of the concepts presented herein. For example, a sensor, a transmitter, a receiver, a transceiver, an antenna, a controller, an optical unit, an electrical unit, and/or an electromechanical unit may be included to support the various aspects described herein, or in

-

Claims (14)

support for other functions that deviate from the scope of this description. The use of singular and plural forms and similar references in the context of the description of the invention (especially in the context of the claims below) should be understood as covering both the singular and the plural, unless otherwise indicated herein or unless clearly contradicted by the context. It should be further noted that the terms first, second, etc. in this document do not denote any order, quantity or importance, but are used to distinguish one element from another. The modifier about, when used in connection with a quantity, includes the stated quantity and has a meaning determined by the context (e.g. includes the degree of error associated with the measurement of a specified quantity). It should be understood that various components or technologies may provide certain necessary or useful functionalities or features. Accordingly, these functions and features, which may be required to support the appended claims and their variants, are recognized as inherently part of the ideas presented herein and part of the present invention. The concepts presented in this specification can be used in a variety of different well operations. These operations can include the use of one or more treatment agents in treating a formation, fluids in the formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents can be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Examples of treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, corrosion inhibitors, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, drag reducing agents, and the like. Examples of well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, and the like. Although the embodiments described herein have been described with reference to various embodiments, it should be understood that various changes may be made and equivalent elements may be substituted for individual elements without departing from the scope of the present invention. In addition, many modifications will be apparent to adapt a particular instrument, situation or material to the teachings of the present invention without departing from the scope thereof. Thus, it is not intended that the present invention be limited to the specific embodiments described as the best mode contemplated for carrying out the described features, but that the present invention includes all embodiments falling within the scope of the claims. Accordingly, the embodiments of the present invention should not be construed as limiting the above description, but instead are limited only by the scope of the appended claims. CLAUSE OF INVENTION 1. A well system (1002) comprising: well column (704); a support unit (2300) of the bit, designed with the possibility of fastening and receiving a disintegration device (50), in which the said disintegration device (50) is located at the end of the well string (704) and is mounted on the support unit (2300) of the bit; and a damping system (1000) for damping torsional vibrations of the well system, configured with the possibility of at least one of: installation on the support unit (2300) of the bit or as part of it, wherein said damping system (1000) comprises at least one damper element (2320) configured in contact and in interaction with a section of the support unit (2300) of the bit, which ensures, in the presence of high-frequency torsional vibrations (HFTO), the possibility of moving the damper element (2320) relative to the support unit (2300) of the bit at a speed of the damper element (2320) representing the sum of the average speed of the well system and periodic changes in the speed of the well system, having an amplitude and leading to a change in the sign of the relative speed between the damper element (2320) and the support unit (2300) of the bit under the influence of HFTO. 2. The system according to claim 1, in which the disintegration device (50) is a bit that comes into contact with the bit coupling (2302) of the bit support unit (2300). 3. The system according to claim 2, in which the support unit (2300) of the bit comprises: a drive shaft (2306); and a torque sleeve (2308), in which the bit coupling (2302) is in rotatably contact with the drive shaft (2306), wherein the torque sleeve (2308) is in working contact with the drive shaft (2306); - 30 050247 wherein preferably at least one of: the coupling (2302) of the bit is connected by means of a thread to the drive shaft (2306); and a tool sleeve (2318) located outside relative to the torque sleeve (2308), wherein at least one damper element (2320) is located between the torque sleeve (2308) and the tool sleeve (2318). 4. A system according to any of the preceding claims, wherein at least one damping element (2320) is mounted on the support unit (2300) of the bit. 5. A system according to any of the preceding claims, wherein at least one damper element (2320) is a ring-type structure located circumferentially near the support unit (2300) of the bit, wherein it is preferable that said ring-type structure comprises two half-shells located near the support unit (2300) of the bit. 6. The system according to any one of the preceding claims, further comprising a sleeve located externally relative to at least one damping element (2320) such that at least one damping element (2320) is located between the sleeve and the support unit (2300) of the bit. 7. The system according to any one of the preceding claims, further comprising at least one bearing (2322) configured to be disengaged from the point of view of rotational movement of at least a portion of the at least one damper element (2320) relative to the movement of the support unit (2300) of the bit, wherein it is preferable that the at least one bearing (2322) comprises at least one of a radial bearing (2322) and a thrust bearing (2322). 8. The system according to any one of the preceding claims, further comprising an axial spring (2324) configured to force at least a portion of at least one damper element (2320) into frictional engagement with the support unit (2300) of the bit. 9. The system according to any one of the preceding claims, wherein at least one damper element (2320) is a tangential damper element (2320). 10. A system according to any one of the preceding claims, wherein the support unit (2300) comprises a guide mechanism (62). 11. A system according to any one of the preceding claims, wherein at least one damper element (2320) further comprises a limiting stop configured to prevent rotation of at least a portion of the at least one damper element (2320) around the support unit (2300) of the bit. 12. The system according to any of the preceding claims, wherein the damping system (1000) is configured to provide at least one of: viscous damping, frictional damping, hydraulic damping, piezoelectric damping, eddy current damping and magnetic damping on the support unit (2300). 13. A system according to any one of the preceding claims, wherein the well string (704) is a drill string (20), in which the support assembly (2300) is mounted at the end of the drill string (20). 14. A method for damping torsional vibrations in a well system (1002) according to any of the preceding paragraphs, including installing a damping system (1000) in at least one of the following variants: on a support unit (2300) of a bit or as part of it, which is located on a well string (704). -