Dampers for reducing vibration in downhole tools

Abstract

The present invention describes a system and method for damping torsional oscillations of a downhole system. The system includes a downhole tubular string including a fragmentation device, and a damping system located at least one of: in and / or on the downhole tubular string, the damping system configured to damp torsional oscillations of the downhole tubular string. The method includes installing the damping system at least one of: on and / or in the downhole system, wherein the downhole system includes a downhole tubular string including a fragmentation device, and the damping system configured to damp torsional oscillations of the downhole tubular string.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. patent application 16 / 568,809, filed September 12, 2019, which is incorporated herein by reference in its entirety. Background Art 1. Technical Field

[0004] The present invention generally relates to downhole operations and systems for damping vibrations of a downhole system during operation.

[0005] 2. Description of Related Technology

[0006] Boreholes are drilled deep underground for many applications, such as carbon dioxide storage, geothermal production, and oil and gas exploration and production. In all of these applications, the boreholes are drilled to penetrate or allow access to materials (e.g., gases or fluids) contained in formations (e.g., storage tanks) below the Earth's surface. Different types of tools and instruments may be placed in the boreholes to perform various tasks and measurements.

[0007] During operation, downhole components may experience vibrations that can affect operational efficiency. For example, severe vibrations in the drill string and bottom hole assembly can be caused by cutting forces at the drill bit or mass imbalances in downhole tools, such as mud motors. The effects of such vibrations can include, but are not limited to, reduced penetration rates, reduced measurement quality, and excessive fatigue and wear of downhole components, tools, and / or equipment. Summary of the Invention

[0008] Disclosed herein are systems and methods for damping oscillations, such as torsional oscillations, in a downhole system. The system includes a downhole system arranged to rotate within a borehole and a damping system configured on the downhole system. The damping system includes one or more dampers mounted at or in a drill bit or other fragmentation equipment of the downhole system. The dampers are arranged to reduce or eliminate one or more specific vibration modes, thereby enabling improved downhole operation and / or efficiency.

[0009] According to some embodiments, a system for damping torsional oscillations of a downhole system is provided. The system includes a downhole tubular string including a fragmentation device, and a damping system located at least one of: in and / or on the downhole tubular string, the damping system configured to damp the torsional oscillations of the downhole tubular string. The damping system is located at least one of: on and / or in the fragmentation device, the damping system including at least one damper element arranged to contact a portion of the fragmentation device.

[0010] In some such embodiments, the damper element may be disposed on or in a fracturing device or drill bit attached to a downhole tubular string.

[0011] In some embodiments, a method of damping torsional oscillations of a downhole system in a borehole is provided. The method includes installing a damping system on at least one of: on and / or in the downhole system, the downhole system including a downhole tubular string having a fracturing device, and the damping system being configured to damp the torsional oscillations of the downhole tubular string. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of this specification. The foregoing and other features and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings in which like elements are numbered in a similar manner and in which:

[0013] Figure 1 are examples of systems for performing downhole operations in which embodiments of the present disclosure may be employed;

[0014] Figure 2 is an illustrative graph of a typical curve of friction or torque versus relative velocity or relative rotational speed between two interacting bodies;

[0015] Figure 3 is a hysteresis plot of friction force versus displacement for a positive relative mean velocity with additional small velocity fluctuations;

[0016] Figure 4 is a graph of friction, relative velocity, and the product of the two versus time for a positive relative mean velocity with additional small velocity fluctuations;

[0017] Figure 5 is a hysteresis plot of friction force versus displacement for zero relative mean velocity with additional small velocity fluctuations;

[0018] Figure 6 is a graph of friction, relative velocity, and the product of the two for zero relative mean velocity with additional small velocity fluctuations;

[0019] Figure 7 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0020] Figure 8A is a graph of the tangential acceleration measured at the drill bit;

[0021] Figure 8B corresponds to Figure 8A A graph showing rotational speed;

[0022] Figure 9Ais a schematic graph of a downhole system, which shows the change of the vibration mode of the downhole system with the distance from the drill bit:

[0023] Figure 9B Shows that the Figure 9A Exemplary corresponding mode shapes of torsional vibrations excited during operation of the downhole system:

[0024] Figure 10 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0025] Figure 11 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0026] Figure 12 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0027] Figure 13 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0028] Figure 14 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0029] Figure 15 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0030] Figure 16 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0031] Figure 17 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0032] Figure 18 is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0033] Figure 19 is a schematic diagram of a damping system according to one embodiment of the present disclosure; and

[0034] Figure 20 is a diagram of the modal damping ratio versus the local vibration amplitude;

[0035] Figure 21 is a schematic diagram of a downhole tool having a damping system;

[0036] Figure 22 yes Figure 21 a cross-sectional view of a downhole tool;

[0037] Figure 23is a schematic diagram arrangement of a drill bit having a plurality of damper elements disposed within blades of a drill bit of a downhole tool according to one embodiment of the present disclosure;

[0038] Figure 24 is a schematic diagram of a drill bit according to one embodiment of the present disclosure having a damper element disposed about a drill shank;

[0039] Figure 25 is a schematic diagram of a drill bit according to one embodiment of the present disclosure, the drill bit having an annular damper element disposed about a drill shank;

[0040] Figure 26 is a schematic diagram of a drill bit according to one embodiment of the present disclosure, the drill bit having an annular damper element disposed about a drill shank and a tangential damper element mounted in a blade;

[0041] Figure 27 is a schematic diagram of a tangential damper element according to one embodiment of the present disclosure;

[0042] Figure 28 is a schematic diagram of a tangential damper element according to one embodiment of the present disclosure; and

[0043] Figure 29 is an illustrative graph of a typical curve of force or torque versus relative velocity or relative rotational speed between two interacting bodies associated with a hydraulic damper element. DETAILED DESCRIPTION

[0044] Figure 1 A schematic diagram of a system for performing downhole operations is shown. As shown, the system is a drilling system 10 that includes a drill string 20 having a drilling assembly 90 (also known as a bottom hole assembly (BHA)) that is conveyed in a borehole 26 penetrating a formation 60. The drilling system 10 includes a conventional derrick 11 that stands on a base plate 12 that supports a rotary table 14 that is rotated at a desired rotational speed by a prime mover, such as an electric motor (not shown). The drill string 20 includes drilling tubulars 22, such as drill pipe, that extend from the rotary table 14 downwardly into the borehole 26. A fragmentation device 50, such as a drill bit attached to the end of the BHA 90, fragments the geological formation as it rotates to drill the borehole 26. The drill string 20 is coupled to surface equipment, such as a system for lifting, rotating, and / or propelling (including but not limited to) a drawworks 30 via a pulley 23 via a kelly joint 21, a swivel 28, and a pipeline 29. In some embodiments, the surface equipment may include a top drive (not shown). During drilling operations, the drawworks 30 is operated to control the weight on bit, which affects the rate of penetration. The operation of the drawworks 30 is well known in the art and will not be described in detail herein.

[0045] During drilling operations, a suitable drilling fluid 32 (also referred to as "mud") from a source or mud pit 31 is circulated under pressure through the drill string 20 by a mud pump 34. The drilling fluid 31 enters the drill string 20 via a surge suppressor 36, a fluid line 38, and a kelly joint 21. The drilling fluid 31 is discharged at the bottom of the borehole 51 through an opening in the fracturing device 50. The drilling fluid 31 circulates upward through the wellbore through the annular space 27 between the drill string 20 and the borehole 26 and returns to the mud pit 32 via a return line 35. A sensor S1 in the fluid line 38 provides information about the fluid flow rate. Surface torque sensors S2 and S3 associated with the drill string 20 provide information about the torque and rotational speed of the drill string, respectively. In addition, one or more sensors (not shown) associated with the line 29 provide information about the hook load of the drill string 20 and other desired parameters related to the drilling of the borehole 26. The system may also include one or more downhole sensors 70 positioned on the drill string 20 and / or the BHA 90 .

[0046] In some applications, the fragmentation device 50 is rotated solely by rotating the drill pipe 22. However, in other applications, a drilling motor 55 (e.g., a mud motor) disposed in the drilling assembly 90 is used to rotate the fragmentation device 50 and / or to superimpose or supplement the rotation of the drill string 20. In either case, for a given formation and a given drilling assembly, the rate of penetration (ROP) of the fragmentation device 50 into the formation 60 depends largely on the weight on bit and the speed of the drill bit rotation. Figure 1 In one aspect of the embodiment of the present invention, a drilling motor 55 is coupled to the fragmentation device 50 via a drive shaft (not shown) disposed in a bearing assembly 57. When drilling fluid 31 is passed under pressure through the drilling motor 55, the drilling motor 55 rotates the fragmentation device 50. The bearing assembly 57 supports the radial and axial forces of the fragmentation device 50, the downward thrust of the drilling motor, and the reactive upward load from the applied weight on bit. A stabilizer 58 coupled to the bearing assembly 57 and / or other suitable location acts as a centralizer for the drilling assembly 90 or a portion thereof.

[0047] The surface control unit 40 receives signals from downhole sensors 70 and equipment via transducers 43 placed in the fluid line 38, such as pressure transducers, as well as signals from sensors S1, S2, S3, hook load sensors, RPM sensors, torque sensors, and any other sensors used in the system, and processes such signals according to programmed instructions provided to the surface control unit 40. The surface control unit 40 displays the desired drilling parameters and other information on a display / monitor 42 that is used by operators at the rig site to control drilling operations. The surface control unit 40 includes a computer; memory for storing data, computer programs, models, and algorithms accessible to the processor in the computer; a recorder, such as a magnetic tape unit, a memory unit, etc., for recording data; and other peripheral devices. The surface control unit 40 may also include a simulation model used by the computer to process data according to programmed instructions. The control unit responds to user commands entered through a suitable device, such as a keyboard. The surface control unit 40 is adapted to activate an alarm 44 when certain unsafe or undesirable operating conditions occur.

[0048] The drilling assembly 90 also includes other sensors and equipment or tools for providing various measurements related to the formation surrounding the borehole and for drilling the borehole 26 along the desired path. Such equipment may include equipment for measuring the resistivity of the formation near and / or ahead of the drill bit, a gamma ray device for measuring the gamma ray intensity of the formation, and equipment for determining the inclination, azimuth, and position of the drill string. A formation resistivity tool 64 made according to the embodiments described herein may be coupled at any suitable location (including above the lower initiator assembly 62) to estimate or determine the resistivity of the formation near or ahead of the fracturing device 50 or at other suitable locations. An inclinometer 74 and a gamma ray device 76 may be appropriately positioned to determine the inclination of the BHA and the gamma ray intensity of the formation, respectively. Any suitable inclinometer and gamma ray device may be used. In addition, an azimuth device (not shown), such as a magnetometer or gyroscope, may be used to determine the drill string azimuth. Such equipment is known in the art and will not be described in detail herein. In the exemplary configuration described above, the drilling motor 55 transmits power to the fragmentation device 50 via a shaft that also enables drilling fluid to be transferred from the drilling motor 55 to the fragmentation device 50. In alternative embodiments of the drill string 20, the drilling motor 55 may be coupled below the resistivity measurement device 64 or at any other suitable location.

[0049] Still refer to Figure 1Other 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 placed at appropriate locations in the drilling assembly 90 to provide information useful for evaluating subsurface formations along the borehole 26. Such equipment may include, but is not limited to, temperature measurement tools, pressure measurement tools, borehole diameter measurement tools (e.g., calipers), acoustic tools, nuclear tools, nuclear magnetic resonance tools, and formation testing and sampling tools.

[0050] The above-described equipment transmits data to a downhole telemetry system 72, which in turn transmits the received data up the wellbore to the surface control unit 40. The downhole telemetry system 72 also receives signals and data from the surface control unit 40 and transmits such received signals and data to appropriate downhole equipment. In one aspect, a mud pulse telemetry system can be used to transmit data between the downhole sensors 70 and equipment and surface equipment during drilling operations. A transducer 43 placed in a fluid line 38 (e.g., a mud supply line) detects mud pulses in response to the data transmitted by the downhole telemetry system 72. The transducer 43 generates an electrical signal in response to changes in mud pressure and transmits such signal to the surface control unit 40 via a conductor 45. In other aspects, any other suitable telemetry system may be used for bidirectional data communication (e.g., downlink and uplink) between the surface and the BHA 90, including, but not limited to, acoustic telemetry systems, electromagnetic telemetry systems, optical telemetry systems, and wired pipe telemetry systems, which may utilize wireless couplers or repeaters within the drill string or borehole. A wired pipe telemetry system may be constructed by connecting drill pipe segments, each segment including a data communication link (such as an electrical wire) extending along the segment. The data connection between the segments may be established by any suitable method, including, but not limited to, hardwired or optical connections, induction, capacitance, resonant coupling (such as electromagnetic resonant coupling), or directional coupling methods. In the case of using coiled tubing as the drill pipe 22, the data communication link may extend along the side of the coiled tubing.

[0051] The drilling systems described thus far relate to those that utilize drill pipe to deliver the drilling assembly 90 into the borehole 26, wherein the weight on bit is typically controlled from the surface by controlling the operation of a drawworks. However, many current drilling systems, particularly those used for drilling highly deviated and horizontal boreholes, utilize coiled tubing to deliver the drilling assembly downhole. In such applications, thrusters are sometimes deployed in the drill string to provide the desired force on the drill bit. Additionally, when coiled tubing is utilized, the tubing is not rotated by a rotary table, but rather injected into the borehole by a suitable injector while a downhole motor (such as drilling motor 55) rotates the fragmentation device 50. For offshore drilling, an offshore drilling rig or vessel is used to support the drilling equipment, including the drill string.

[0052] Still refer to Figure 1 A resistivity tool 64 may be provided, comprising, for example, a plurality of antennas, including, for example, transmitters 66a or 66b and / or receivers 68a or 68b. Resistivity may be a formation property of interest when making drilling decisions. Those skilled in the art will appreciate that other formation property tools may be used in conjunction with or in place of the resistivity tool 64.

[0053] Liner drilling can be a configuration or operation for providing a fracturing device and is becoming increasingly attractive in the oil and gas industry because it has several advantages over conventional drilling. An example of such a configuration is shown and described in co-owned U.S. Patent No. 9,004,195, entitled "Apparatus and Method for Drilling a Borehole, Setting a Liner and Cementing the Borehole During a Single Trip," which is incorporated herein by reference in its entirety. Importantly, despite the relatively low penetration rate, the liner is lowered while the borehole is being drilled, thereby reducing the time it takes to align the liner with the target. This can be beneficial in expansive formations where shrinkage of the wellbore would hinder installation of the liner. In addition, drilling with a liner in depleted and unstable reservoirs minimizes the risk of the pipe or drill string becoming stuck due to borehole collapse.

[0054] although Figure 1 While shown and described with respect to drilling operations, those skilled in the art will appreciate that similar configurations, albeit with different components, can be used to perform various downhole operations. For example, wireline, wireline pipe, liner drilling, hole reaming, coiled tubing, and / or other configurations may be used, as is known in the art. Furthermore, production configurations may be employed for extracting material from and / or injecting material into a formation. Thus, the present disclosure is not limited to drilling operations, but rather may be used for any suitable or desired downhole operation or operations.

[0055] Severe vibrations in the drill string and bottom hole assembly during drilling operations can be caused by cutting forces at the drill bit or mass imbalances in downhole tools (such as drilling motors). Such vibrations can lead to a reduction in penetration rate, a decrease in the quality of measurements made by tools in the bottom hole assembly, and can cause wear, fatigue, and / or failure of downhole components. As those skilled in the art understand, there are different types of vibrations, such as lateral vibration, axial vibration, and torsional vibration. For example, stick / slip and high-frequency torsional oscillations (“HFTO”) of the entire drilling system are types of torsional vibration. The terms “vibration,” “oscillation,” and “fluctuation” are used in the same broad sense to refer to repetitive and / or periodic movements or periodic deviations from an average value (such as average position, average velocity, average acceleration, average force, and / or average torque). Specifically, these terms are not intended to be limited to harmonic deviations, but rather can include all types of deviations, such as, but not limited to, periodic, harmonic, and statistical deviations. Torsional vibrations can be excited by self-excited mechanisms that occur due to the interaction of the drill bit or any other cutting structure (such as a reamer bit) with the formation. The main difference between stick / slip and HFTO is the frequency and typical mode shapes: for example, HFTO has a frequency typically above 50 Hz, compared to stick / slip torsional vibrations, which typically have frequencies below 1 Hz. In addition, the excited mode shape of stick / slip is usually the first mode shape of the entire drilling system, while the mode shape of HFTO can be high-order and is typically confined to a smaller part of the drilling system and has relatively high amplitude at the excitation point, which can be the drill bit or any other cutting structure (such as a reamer bit) or any contact between the drilling system and the formation (for example, achieved by stabilizers).

[0056] Due to the high frequency of vibration, HFTO corresponds to high acceleration and torque values ​​along the BHA. Those skilled in the art will understand that for torsional motion, one of acceleration, force, and torque is always accompanied by the other two of acceleration, force, and torque. In this sense, acceleration, force, and torque are equivalent in the sense that any one of these would not occur without the other two. The load of high frequency vibrations can have a negative impact on the efficiency, reliability, and / or durability of the electronic and mechanical components of the BHA. The embodiments provided herein relate to providing torsional vibration damping on a downhole system to mitigate HFTO. In some embodiments of the present disclosure, torsional vibration damping can be activated if a threshold of a measured characteristic (such as torsional vibration amplitude or frequency) is achieved within the system.

[0057] According to non-limiting embodiments provided herein, a torsional vibration damping system can be based on a friction damper. For example, according to some embodiments, friction between two components (such as two interacting bodies) in a BHA or drill string can dissipate energy and reduce the level of torsional oscillations, thereby mitigating potential damage caused by high-frequency vibrations. Preferably, the energy dissipated by the friction damper is at least equal to the HFTO energy input caused by the drill bit-rock interaction.

[0058] Friction dampers, as provided herein, can cause significant energy dissipation and, therefore, reduce torsional vibrations. When two components or interacting bodies are in contact and move relative to each other, friction forces act in a direction opposite to the velocity of the relative motion between the contacting surfaces of the components or interacting bodies. Friction forces cause energy dissipation.

[0059] Although specifically described with respect to friction dampers, the dampers, damper elements, and damper systems of the present disclosure are not limited to friction. That is, as described below, dampers having different configurations may be used to implement other principles of damping. For example, damping may be generated by viscous damping, friction damping, hydraulic damping, magnetic damping (e.g., eddy current damping), piezoelectric (shunt) damping, and the like. As used herein, a damper element may be part of a damping system configured to dissipate energy caused by relative movement between at least a portion of the damper element and a downhole tubular. That is, relative movement of the damper element or a portion thereof enables energy (e.g., HFTO) to be dissipated and, therefore, vibrations within or along the downhole tubular may be reduced.

[0060] Figure 2 FIG2 is an exemplary graph 200 of a typical curve of friction force or torque versus relative velocity v (eg, or relative rotational speed) between two interacting bodies. The two interacting bodies have contact surfaces and a force component F perpendicular to the contact surfaces engaging the two interacting bodies. N Graph 200 shows the correlation between the friction force or torque of two interacting bodies and the frictional contact or characteristic of speed-weakening behavior, such as cutting behavior. At higher relative speeds (v>0) between the two interacting bodies, the friction force or torque has different values, shown by point 202. Reducing the relative speed will cause increased friction force or torque (also known as speed-weakening behavior). When the relative speed is zero, the friction force or torque reaches its maximum value. Maximum friction force is also called static friction, adhesive friction, or stiction.

[0061] Usually, the friction force F R Depends on the normal force, as in equation F R =μ·F Nwhere the friction coefficient is μ. In general, the friction coefficient μ is a function of velocity. In this context, the normal force may also fluctuate in response to the excited vibration in the normal direction. When the relative velocity between the two interacting bodies is zero (v=0), the static friction force F S With the normal force component F N Related, the equation is F S =μ0·F N , where the static friction coefficient is μ0. When the relative velocity between the two interacting bodies is non-zero (v≠0), the friction coefficient is referred to as the kinetic friction coefficient μ. If the relative velocity is further reduced to a negative value (i.e., if the direction of relative motion of the two interacting bodies switches to the opposite direction), the friction force or torque switches to the opposite direction and has a high absolute value at point 204 in graph 200, corresponding to a step from a positive maximum to a negative minimum. That is, the relationship between the friction force and the velocity shows a sign change at the point where the velocity changes sign and is discontinuous at point 204 in graph 200. The velocity-weakening characteristic is a well-known effect between interacting bodies that are frictionally connected. The velocity-weakening characteristic of contact force or torque is considered a potential root cause of stick / slip. The velocity-weakening characteristic can also be achieved by utilizing a dispersive fluid that has a higher viscosity at lower relative speeds and a lower viscosity at higher relative speeds. The same effect can be achieved if the dispersive fluid is forced through a relatively small channel, because the flow resistance is relatively high or low at low or high relative speeds, respectively.

[0062] refer to Figures 8A to 8B , Figure 8A The measured torsional acceleration versus time of the downhole system is shown. Figure 8A In the 5-second measurement time shown, Figure 8A An oscillating torsional acceleration with an average acceleration of approximately 0 g is shown, which is superimposed by an oscillating torsional acceleration with a relatively low amplitude between approximately 0 s and 3 s and a relatively high amplitude of up to 100 g between approximately 3 s and 5 s. Figure 8B Shown with Figure 8A The corresponding rotation speed in the same time period. Figure 8A , Figure 8B shows the average speed v0 (in Figure 8B The average speed is relatively constant at about 190 rpm. Figure 8AThe relatively low and high acceleration amplitudes in the embodiment of the present invention are superimposed on an oscillating rotational speed variation having a relatively low amplitude between approximately 0 s and 3 s and a relatively high amplitude between approximately 3 s and 5 s. It is noteworthy that even during the time period between approximately 3 s and 5 s when the amplitude of the rotational speed oscillation is relatively high, the oscillating rotational speed does not cause negative values ​​of the rotational speed.

[0063] Reference again Figure 2 , point 202 shows the average velocity of the two interacting bodies, which corresponds to Figure 8B The average speed v0 in . Figure 2 In the schematic diagram, Figure 8B The data of corresponds to points with a velocity that oscillates at a relatively high frequency around an average velocity v0 due to HTFO, which changes relatively slowly with time compared to HFTO. Figure 8B The data point is Figure 2 , without ever or only rarely reaching negative velocity values. Therefore, the corresponding friction force or torque oscillates around a positive average friction force or average friction torque and is generally positive or only rarely reaches negative values. As discussed further below, point 202 shows the position where the positive average value of the relative velocity corresponds to the static torque, and point 204 shows the favorable point for friction damping. It should be noted that the friction force or torque between the drilling system and the borehole wall does not produce additional damping of the high frequency oscillations in the system. This is because the average velocity of the relative velocity between the contact surfaces of the interacting bodies (e.g., the stabilizer and the borehole wall) is not so close to zero that the HFTO causes a sign change of the relative velocity of the two interacting bodies. Instead, the relative velocity between the two interacting bodies has a high average value at a certain distance from zero that is large enough that the HFTO does not cause a sign change of the relative velocity of the two interacting bodies (e.g., caused by Figure 2 202 in FIG. 1 ).

[0064] As will be understood by those skilled in the art, Figure 2 The weakening behavior of the contact force or torque relative to the relative velocity shown results in energy being applied to the system for causing the relative motion of the interacting bodies to oscillate at an average velocity v0, which is high compared to the velocity of the oscillatory motion. In this context, other examples of self-excitation mechanisms, such as coupling between axial and torsional degrees of freedom, can induce similar behavior.

[0065] The corresponding lag is Figure 3 Depicted and Figure 4 A time graph of friction force and speed is shown in FIG. Figure 3 The friction force F is shown r(sometimes also referred to in this context as cutting force) to the hysteresis relationship of the displacement relative to the position, which moves at a positive mean relative velocity with additional small velocity fluctuations (causing additional small displacement dx). Therefore, Figure 4 The friction force (F) is shown for a positive mean relative velocity with additional small velocity fluctuations (causing additional small displacements dx). r ), relative speed and the product of the two (given by Figure 4 Those skilled in the art will appreciate that the area between the friction force and velocity over time is equal to the energy dissipated (i.e., the area between line 400 and the zero axis), which is given by Figure 3 and Figure 4 In the case shown in , it is negative. Figure 3 and Figure 4 In the case shown in FIG, energy is transferred from friction to oscillation via frictional contact.

[0066] Reference again Figure 2 , point 204 represents the favorable average velocity for frictional damping of small velocity fluctuations or oscillations in addition to the average velocity. For small fluctuations in relative motion between two interacting bodies, Figure 2 The discontinuity at point 204 in the equation and the sign change of the relative velocities of the interacting bodies also cause a sudden sign change in the friction or torque. This sign change causes hysteresis, which results in a large amount of dissipated energy. For example, compare Figure 5 and Figure 6 , Figure 5 and Figure 6 Respectively Figure 3 and Figure 4 A similar graph is shown, but showing the case of zero mean relative velocity with additional small velocity fluctuations or oscillations. Figure 6 The line below 600 corresponds to the product The area of ​​​​is equal to the energy dissipated during one period and is positive in this case.

[0067] That is, in Figure 5 and Figure 6 In the case shown, energy is transferred from high frequency oscillations to friction via frictional contact. Figure 3 and Figure 4 Compared to the case shown, the effect is considerably higher and has the expected sign. Figure 2 、 Figure 5 and Figure 6 It is also clear from the comparison that the dissipated energy depends significantly on v = 0 (i.e., Figure 2The greater the difference between the maximum friction and the minimum friction at position 204 in the figure, the higher the dissipated energy. Figures 3 and 4 By using speed-weakening features such as Figure 2 The present invention relates to a characteristic (shown in FIG. 1 ), but the embodiments of the present disclosure are not limited to this type of characteristic. The apparatus and methods disclosed herein will work for any type of characteristic provided that the friction force or torque undergoes a step with a change in sign when the relative velocity between the two interacting bodies changes its sign.

[0068] The friction damper according to some embodiments of the present disclosure will now be described. The friction damper is installed in a drilling system (such as Figure 1 The friction damper is part of a friction damping system having two interacting bodies, such as a first element and a second element having a friction contact surface with the first element. The friction damping system of the present disclosure is arranged so that the average speed of the first element is related to the rotational speed of the drilling system in which the first element is installed. For example, the first element may have a similar or identical average speed or rotational speed as the drilling system so that small fluctuations in the oscillations caused by the first element are proportional to the rotational speed of the drilling system. Figure 2 At point 204 in FIG, the relative velocity between the first element and the second element changes sign or crosses zero.

[0069] It should be noted that friction or torque between the drilling system and the borehole wall does not produce additional damping of high frequency oscillations in the system. This is because the relative velocity between the contacting surfaces (e.g. stabilizer and borehole) does not have a zero mean value (e.g. Figure 2 Point 202 in FIG. 1 ). According to the embodiments described herein, the static friction between the first element and the second element is set high enough so that the first element is able to accelerate the second element (during rotation) to an average velocity v0 of the same value as the drilling system. The additional high frequency oscillation is thus equal to or close to Figure 2 Point 204 Figure 2 Oscillations around the position in induce slip between the first element (eg, damping device) and the second element (eg, drilling system) at positive or negative speeds. I Slippage occurs when the static friction force is exceeded, which is expressed as the coefficient of static friction between two interacting bodies multiplied by the normal force: F I >μ0·F N According to an embodiment of the present disclosure, the normal force F NThe coefficient of static friction μ0 (e.g., caused by the contact and surface pressure of the contact surfaces between two interacting bodies) is adjusted to achieve optimal energy dissipation and optimal amplitude. In addition, the moment of inertia (torsion), the contact and surface pressure of the contact surfaces, and the arrangement of the damper or contact surface relative to the distance from the drill bit can be optimized.

[0070] For example, turning Figure 7 , shows a schematic diagram of a damping system 700 according to one embodiment of the present disclosure. The damping system 700 is part of a downhole system 702 (such as a bottom hole assembly and / or drilling assembly). The downhole system 702 includes a drill string 704 that rotates to enable drilling operations of the downhole system 702 to form a borehole 706 within a formation 708. As discussed above, the borehole 706 is typically filled with a drilling fluid, such as drilling mud. The damping system 700 includes a first element 710 that is operatively coupled (e.g., fixedly connected) or an integral part of the downhole system 702 to ensure that the first element 710 rotates at an average speed that is related to (e.g., similar to or the same as) the average speed of the downhole system 702. The first element 710 is in frictional contact with a second element 712. The second element 712 is at least partially movably mounted on the downhole system 702, with a contact surface 714 located between the first element 710 and the second element 712.

[0071] In terms of friction, the difference between the minimum and maximum friction is directly related to the normal force and the coefficient of static friction. The dissipated energy increases with the friction and harmonic displacement, but 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 in the sticking phase increases linearly with the normal force and the coefficient of friction in the contact interface. This is because one of the contacting bodies is The reaction force in the contact interface caused by the inertia J of the contact body under acceleration The torque M must be above the limit between sticking and slipping H =F N μ H r. As used herein, F N is the normal force, and μ H is the effective friction coefficient, and r is the effective or average radius of the frictional contact area. For complex frictional contact of interacting bodies, both sticking and sliding can occur simultaneously. In this paper, the contact pressure is optimized to achieve optimal damping and amplitude.

[0072] A similar mechanism applies if the contact force is caused by displacement and spring elements. Acceleration of the contact area can be attributed to the excitation of the mode and depends on the corresponding mode shape, as shown below with respect to Figure 9BFurther discussion. As far as the additional inertial mass J is concerned, as long as the contact interface is viscous, the acceleration is equal to the acceleration of the excited mode and the corresponding mode shape at the additional position.

[0073] The normal force and the friction force must be adjusted to ensure that the sliding phase is within a suitable or permissible amplitude range. The permissible amplitude range can be defined by an amplitude between zero and a load limit, which is given, for example, by the design specifications of the tool and the component. The limit can also be given by a percentage of the expected amplitude without the damper. The dissipated energy, which can be compared with the energy input (e.g., by forced excitation or self-excitation), is a measure of the efficiency of the damper. Another measure is the equivalent damping provided by the system, which is proportional to the ratio of the energy dissipated in one cycle of the harmonic vibration in the system to the potential energy during one cycle of the vibration. This measure is particularly effective for self-excited systems. In the case of self-excited systems, the excitation can be estimated by a negative damping coefficient and both the equivalent damping and the negative damping can be directly compared. The damping force provided by the damper is nonlinear and strongly depends on the amplitude.

[0074] like Figure 20 As shown, the damping is in the viscous stage ( Figure 20 = (left end of the graph of ), where the relative motion between the interacting bodies is zero. If, as described above, the limit between the sticking and sliding phases is exceeded by the forces transmitted through the contact interface, a relative sliding motion occurs, which causes energy dissipation. The damping ratio provided by the frictional damping then increases to a maximum value and then decreases to a minimum value. The amplitude that will occur depends on the excitation that can be described by the negative damping term. In this paper, as Figure 20 As depicted, the maximum value of the damping provided must be higher than the negative damping from the self-excitation mechanism. The amplitude occurring in the so-called limit cycle can be determined by the intersection of the negative damping ratio provided by the friction damper and the equivalent damping ratio.

[0075] This curve depends on different parameters. It is advantageous to have a high normal force but for the sliding phase to occur at minimum amplitudes of the system of the bottom hole assembly. In terms of inertial masses this can be achieved by having a high mass or by placing the contact interface at a point of high acceleration relative to the excited mode shape. In terms of the contact interface, high relative displacements compared to the amplitude of the mode shape at the contact point, for example along the axial axis of the BHA, are advantageous. Therefore, an optimal arrangement of the damping devices according to the high amplitudes or relative amplitudes is important. This can be achieved by using simulation results, as discussed below. The normal force and the friction coefficient can be used to shift this curve to lower or higher amplitudes, but do not have a large influence on the damping maximum. If more than one friction damper is implemented, this will cause Figure 20If the normal force and the friction coefficient are adjusted to achieve the same maximum value for the amplitude, this can benefit the overall damping achieved. Furthermore, a slightly shifted damping curve will cause the resulting curve to be wider relative to the amplitude, which can be beneficial to take into account influences that can shift the amplitude to the right of the maximum. In this case, for a self-excited system, the amplitude will increase to very high values, as indicated by negative damping. In this case, the amplitude needs to be moved to the left of the maximum again, for example by moving away from the bottom or by reducing the rotation speed of the system to a lower level. The amplitude in this context is expressed as Figure 8B The indicated and discussed average rotational speeds scale approximately linearly.

[0076] Reference again Figure 7 , the tubing string 704 and thus the downhole system 702 rotates at a speed The second element 712 is mounted to the first element 710. The normal force F between the first element 710 and the second element 712 can be selected or adjusted by the application and use of the adjustment element 716. N The adjustment element 716 may be adjustable, for example, via a thread, an actuator, a piezoelectric actuator, a hydraulic actuator, and / or a spring element, to apply a force having a component in a direction perpendicular to the contact surface 714 between the first element 710 and the second element 712. Figure 7 As shown, the adjustment element 716 can apply a force in the axial direction of the downhole system 702. Since the axis of the downhole system 702 forms a non-zero angle with the contact surface 714 of the first element 710 and the second element 712, the force is converted into a force component F perpendicular to the contact surface 714 of the first element 710 and the second element 712. N In some configurations, the angle between the system 712 and the inertial mass element is selected or defined to allow sliding motion and avoid self-locking.

[0077] The second element 712 has a moment of inertia J. When HFTO occurs during operation of the downhole system 702, both the downhole system 702 and the second element 712 are accelerated according to the mode shape (e.g., amplitude distribution defined along dimensions of the drilling system, drill string, and / or BHA) and the amplitude of the mode (e.g., amplitude of the scaled mode shape). Figure 8A and Figure 8B An exemplary result of this operation is shown in . Figure 8A is a graph of the tangential acceleration measured at the drill bit, and Figure 8B is the corresponding rotation speed.

[0078] 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 slipping—that is, if they exceed the static friction between the first and second elements 710, 710—relative motion occurs between the elements 710, 712, resulting in energy dissipation. In this type of arrangement, the acceleration, the coefficient of static and / or kinetic friction, and the normal force determine the amount of energy dissipated. For example, the moment of inertia J of the second element 712 determines the relative force that must be transmitted between the first and second elements 710, 712. High acceleration and moment of inertia increase the tendency for slippage at the contact surface 714, thereby resulting in higher energy dissipation and equivalent damping ratio provided by the damper.

[0079] 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. To keep the wear below an acceptable level, a wear-resistant material can be used for the first element 710 and / or the second element 712. For example, diamond or polycrystalline diamond compacts can be used for at least a portion of the first element 710 and / or the second element 712. Alternatively or in addition, a coating can help reduce the wear caused by the friction between the first element 710 and the second element 712. The heat can cause high temperatures and can affect the reliability or durability of the first element 710, the second element 712, and / or other components of the downhole system 702. The first element 710 and / or the second element 712 can be made of a material having high thermal conductivity or high heat capacity, and / or can be in contact with a material having high thermal conductivity or heat capacity.

[0080] Such materials with high thermal conductivity include, but are not limited to, metals or metal-containing compounds such as copper, silver, gold, aluminum, molybdenum, tungsten, or thermal greases including fats, greases, oils, epoxies, silicones, polyurethanes, and acrylates, and optionally fillers such as diamond, metals or metal-containing chemical compounds (e.g., silver, aluminum in aluminum nitride, boron in boron nitride, zinc in zinc oxide), or silicon or silicon-containing chemical compounds (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 (e.g., drilling fluid) configured to remove heat from the first element 710 and / or the second element 712 in order to cool the respective elements 710, 712. Furthermore, amplitude limiting elements (not shown) such as keys, grooves, or spring elements may be used and configured to limit energy dissipation to acceptable limits, thereby reducing wear.

[0081] When the damping system 700 is arranged, a high normal force and / or static or kinetic friction coefficient will prevent relative sliding motion between the first element 710 and the second element 712, and in such circumstances, no energy is dissipated. In contrast, a low normal force and / or static or kinetic friction coefficient can result in low friction, and sliding will occur, but with less energy dissipated. Additionally, a low normal force and / or static or kinetic friction coefficient can result in a situation where the friction at the outer surface of the second element 712 (e.g., between the second element 712 and the formation 708) is higher than the friction between the first element 710 and the second element 712, thereby causing the relative velocity between the first element 710 and the second element 712 to be not equal to or close to zero, but rather within the range of the average velocity between the downhole system 702 and the formation 708. Therefore, the normal force and static or kinetic friction coefficient, as well as the arrangement of the damper elements relative to the excited modes and mode shapes, can be adjusted (e.g., by using the adjustment element 716) to achieve an optimized value for energy dissipation.

[0082] This can be achieved by adjusting the normal force F N , static friction coefficient μ0, dynamic friction coefficient μ, arrangement of damper elements relative to the excited mode shape, or a combination thereof. The normal force F can be adjusted by N Positioning the adjustment element 716 and / or causing the actuator to generate a force on one of the first and second elements having a component perpendicular to the contact surface of the first and second elements, adjusts the pressure state around the first and second elements, or increases or decreases the area where the pressure acts. For example, by increasing the external pressure (such as mud pressure) acting on the second element, the normal force F will also increase. N The pressure of the downhole mud can be adjusted by adjusting the mud pump on the surface (e.g. Figure 1 The mud pump 34 shown in the figure or other equipment on the surface or downhole that affects the mud pressure (such as bypass, valve, surge eliminator) can be used to achieve this. The normal force can be adjusted to a harmonic of the natural frequency of the excited mode shape, and thus have a low normal force value for low acceleration of the inertial mass and a high normal force value for low acceleration of the inertial mass, thereby allowing sliding motion at low acceleration values.

[0083] The normal force F may also be adjusted by a biasing element (not shown) such as a spring element N , the biasing element applies a force to the second element 712, such as a force in an axial direction away from or toward the first element 710. The normal force F may also be applied in a controlled manner based on input received from a sensor. NFor example, a suitable sensor (not shown) may provide one or more parameter values ​​to a controller (not shown) that are related to the relative motion 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 these parameter values, the controller may provide an increase or decrease in the normal force F. N 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 may provide an instruction to reduce the normal force F N Similarly, for example, if the distance, velocity, or acceleration of the second element 712 relative to the first element 710 exceeds a threshold, the controller may provide an instruction to increase or decrease the normal force F N By monitoring the parameter value, the normal force F can be controlled N To achieve the desired result within a time period. For example, the normal force F can be controlled N To provide optimal energy dissipation while maintaining the temperature of one or both of the first element 710 and the second element 712 below a threshold value during a drilling stroke or a portion thereof.

[0084] Additionally, the static or kinetic coefficient of friction can be adjusted by utilizing different materials, such as, but not limited to, materials with different stiffness, roughness, and / or lubricity. For example, surfaces with higher roughness generally increase the coefficient of friction. Therefore, 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 portion of at least one of the first and second elements. The material of the first and / or second elements can also affect the wear of the first and second elements. To keep the wear of the first and second elements low, it is advantageous to select a material that can withstand the friction generated between the first and second elements. The inertia, friction coefficient, and expected acceleration amplitude of the second element 712 (e.g., as a function of modal vibration shapes and eigenfrequencies) are parameters that determine the energy dissipated and require optimization. Critical mode shapes and acceleration amplitudes can be determined by measurement or calculation, or based on other known methods as understood by those skilled in the art. Examples include finite element analysis, transfer matrix method, or finite difference method based on this modal analysis or analytical mode. It is optimal to place friction dampers where high relative displacement or acceleration is expected.

[0085] Now turn Figure 9A and Figure 9B , shows an example of a downhole system 900 and corresponding modalities. Figure 9A is a schematic graph of a downhole system showing how the vibration mode of the downhole system varies with distance from the drill bit, and Figure 9B Shows that the Figure 9A Example corresponding torsional oscillation mode shapes excited during operation of the downhole system. Figure 9A and Figure 9B The schematic diagram of FIG. 900 illustrates potential locations and arrangements of one or more components of the damping system on the downhole system 900 .

[0086] like Figure 9A As shown schematically, the downhole system 900 includes various components having different diameters (and different masses, densities, configurations, etc.), and thus the different components may give rise to various modes during rotation of the downhole system 900. Exemplary modes indicate where the highest amplitudes will be present, which may require damping by applying a damping system. For example, Figure 9B , a first torsional oscillation mode shape 902, a second torsional oscillation mode shape 904, and a third torsional oscillation mode shape 906 of a downhole system 900 are shown. Based on knowledge of mode shapes 902, 904, 906, the position of the first element of the damping system can be optimized. Damping may be required and / or achieved when the amplitudes of mode shapes 902, 904, 906 are at their maximum (peak) values. Thus, two potential locations for attaching or installing the damping system of the present disclosure are shown as examples.

[0087] For example, the first damping location 908 is near the drill bit of the downhole system 900 and primarily damps the first and third torsional oscillations (corresponding to mode shapes 902, 906) and provides some damping for the second torsional oscillation (corresponding to mode shape 904). That is, the first damping location 908 is approximately at the peak of the third torsional oscillation (corresponding to mode shape 906), near the peak of the first torsional oscillation mode shape 902, and approximately halfway relative to the peak of the second torsional oscillation mode shape 904.

[0088] The second damping position 910 is arranged to again primarily provide damping of the third torsional oscillation mode shape 906 and to provide some damping for the first torsional oscillation mode shape 902. However, in the second damping position 910, no damping of the second torsional oscillation mode shape 904 occurs because the second torsional oscillation mode shape 904 is close to zero at the second damping position 910.

[0089] Despite Figure 9A and Figure 9B While only two locations for deploying the damping systems of the present disclosure are shown, embodiments are not so limited. For example, any number and arrangement of damping systems may be installed along a downhole system to provide torsional vibration damping for the downhole system. Examples of preferred locations for the dampers are locations where one or more of the mode shapes are expected to exhibit high amplitudes.

[0090] Due to the high amplitude at the drill bit, for example, a good location for the damper is near or even within the drill bit. Furthermore, the first and second elements are not limited to a single body, but can take any number of various configurations to achieve the desired damping. That is, a multi-body first or second element (e.g., a friction damping device) can be employed, with each body having the same or different normal forces, coefficients of friction, and moments of inertia. For example, if it is uncertain which mode shape and corresponding acceleration to expect at a given location along the downhole system, such a multi-body element arrangement can be used.

[0091] For example, two or more element bodies can be used that can achieve different relative sliding motions with respect to each other to dissipate energy. The multiple bodies of the first element can be selected and assembled using different static or dynamic friction coefficients, angles between contacting surfaces, and / or other mechanisms that affect the amount of friction and / or the transition between sticking and slipping. Such a configuration can be used to damp a number of amplitude levels, excited mode shapes, and / or natural frequencies.

[0092] For example, turning Figure 10 , shows a schematic diagram of a damping system 1000 according to an embodiment of the present disclosure. The damping system 1000 can be the same as the damping system 1000 described above. Figure 7 The damping system 1000 operates in a similar manner as shown and described. The damping system 1000 includes a first element 1010 and a second element 1012. However, in this embodiment, the second element 1012 of the first element 1010 mounted to the downhole system 1002 is formed by a first body 1018 and a 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 and the second body 1020 are separated by a gap 1026. The gap 1026 is provided to prevent interaction between the first body 1018 and the second body 1020 so that they can operate (e.g., move) independently of each other or do not directly interact with each other. In this embodiment, the first body 1018 has a first static friction coefficient or a dynamic friction coefficient μ1 and a first force F perpendicular to the first contact surface 1022. N1 , and the second body 1020 has a second static friction coefficient or a dynamic friction coefficient μ2 and a second force F perpendicular to the second contact surface 1024 N2 In addition, the first body 1018 may have a first moment of inertia J1, and the second body 1020 may have a second moment of inertia J2. In some embodiments, the first static friction coefficient or dynamic friction coefficient μ1, the first normal force F N1At least one of the first moment of inertia J1 and the second static friction coefficient or the dynamic friction coefficient μ2, the second normal force F N2 and the second moment of inertia J1 . Thus, the damping system 1000 can be configured to account for multiple different mode shapes at a substantially single location along the downhole system 1002 .

[0093] Now turn Figure 11 , shows a schematic diagram of a damping system 1100 according to one embodiment of the present disclosure. Damping system 1100 can operate in a manner similar to that shown and described above. However, in this embodiment, second element 1112 of first element 1110, which is mounted to downhole system 1102, is formed from a first body 1118, a second body 1120, and a third body 1128. First body 1118 has a first contact surface 1122 between first body 1118 and first element 1110, second body 1120 has a second contact surface 1124 between second body 1120 and first element 1110, and third body 1128 has a third contact surface 1130 between third body 1128 and first element 1110. As shown, third body 1128 is positioned between first body 1118 and second body 1120. In this embodiment, the three bodies 1118, 1120, and 1128 are in contact with one another, and thus can have a normal force and a static or kinetic coefficient of friction between them.

[0094] The contact between the three bodies 1118, 1120, 1128 can be established, maintained, or supported by an elastic connection element (such as a spring element) between two or more of the bodies 1118, 1120, 1128. In addition or alternatively, the first body 1118 can have a first static friction coefficient or a dynamic friction coefficient μ1 and a first force F at the first contact surface 1122. N1 , the second body 1120 may have a second static friction coefficient or a dynamic friction coefficient μ2 and a second force F at the second contact surface 1124 N2 , and the third body 1128 may have a third static friction coefficient or dynamic friction coefficient μ3 and a third force F at the third contact surface 1130 N3 .

[0095] Additionally or alternatively, the first body 1118 and the third body 1128 may have a fourth force F between each other at a contact surface between the first body 1118 and the third body 1128. N13 and the fourth coefficient of static friction or dynamic friction μ 13 Similarly, the third body 1128 and the second body 1120 may have a fifth force F between each other at a contact surface between the third body 1128 and the second body 1120. N32 and the fifth coefficient of static friction or dynamic friction μ32 .

[0096] In addition, the first body 1118 may have a first moment of inertia J1, the second body 1120 may have a second moment of inertia J2, and the third body 1128 may have a third moment of inertia J3. In some embodiments, the static or kinetic friction coefficients μ1, μ2, μ3, μ 13 、μ 32 , force F N1 、F N2 、F N3 、F 13 、F 32 The moments of inertia J1, J2, J3 may be chosen to be different from one another so that for at least a sub-range of relative velocities of the first element 1110, the first body 1118, the second body 1120, and the third body 1128, the product μ i ·F i (where i=1, 2, 3, 13, 32) are different. In addition, the static friction coefficient or the dynamic friction coefficient and the normal force between adjacent bodies can be selected to achieve different damping effects.

[0097] Although shown and described with respect to a limited number of embodiments and specific shapes, relative sizes, and numbers of elements, those skilled in the art will appreciate that the damping system of the present disclosure may take any configuration. For example, the shape, size, geometry, radial arrangement, contact surface, number of bodies, etc. may be selected to achieve the desired damping effect. Figure 11 In the illustrated arrangement, the first and second bodies 1118, 1120 are coupled to each other via frictional contact with the third body 1128, but this arrangement and description are not intended to be limiting. The coupling between the first and second bodies 1118, 1120 may also be achieved via hydraulic, electrical, or mechanical coupling devices or mechanisms. For example, a mechanical coupling device between the first and second bodies 1118, 1120 may be achieved via a rigid or elastic connection between the first and second bodies 1118, 1120.

[0098] Now turn Figure 12 , shows a schematic diagram of a damping system 1200 according to one embodiment of the present disclosure. The damping system 1200 can operate in a similar manner as shown and described above. However, in this embodiment, the second element 1212 of the damping system 1200 is partially fixedly attached or connected to the first element 1210. For example, as shown in this embodiment, the second element 1212 has a fixed portion 1232 (or fixed end) and a movable portion 1234 (or movable end). The fixed portion 1232 is fixed to the first element 1210 along a fixed connection 1236, and the movable portion 1234 is in frictional contact with the first element 1210 across a contact surface 1214 (similar to the embodiment with respect to FIG. Figure 10The first element 1010 is depicted as being in frictional contact with the second element 1012).

[0099] The movable portion 1234 may have a Figure 9B The movable portion may be any desired length associated with the modal shapes shown. For example, in some embodiments, the movable portion may be longer than one-tenth of the distance between the maximum and minimum of any modal shape that may have been calculated for a particular drilling assembly. In another example, in some embodiments, the movable portion may be longer than one-quarter of the distance between the maximum and minimum of any modal shape that may have been calculated for a particular drilling assembly. In another example, in some embodiments, the movable portion may be longer than half the distance between the maximum and minimum of any modal shape that may have been calculated for a particular drilling assembly. In another example, in some embodiments, the movable portion may be longer than the distance between the maximum and minimum of any modal shape that may have been calculated for a particular drilling assembly.

[0100] Thus, even though the exact location of the modal maximum or minimum may not be known during downhole deployment, it is ensured that the second element 1212 is in frictional contact with the first element 1210 at the location of maximum amplitude to achieve optimized damping. Although illustrated using a specific arrangement, those skilled in the art will understand that other arrangements of partially fixed first elements are possible without departing from the scope of this disclosure. For example, in one non-limiting embodiment, the fixed portion may be in a more central portion of the first element, such that the first element has two movable portions (e.g., at opposite ends of the first element). As shown in Figure 12 As can be seen in FIG, the movable portion 1234 of the second element 1212 is quite slender and can cover a modal vibration shape corresponding to the length of the movable portion 1234 of the second element 1212 (such as Figure 9B 906). An elongated second element 1212 in frictional contact with the first element 1210 may be preferred over a shorter second element because the shorter second element may be located in an undesirable portion of the mode shape, such as in a damping location 910 where the second mode shape 904 is small or even zero, as discussed above with respect to Figure 9B Utilizing an elongated second element 1212 ensures that at least a portion of the second element is at a distance from a location where one or more of the mode shapes are zero or at least close to zero. Figures 13 to 19 and Figures 21 to 22More variations of the elongated second element in frictional contact with the first element are shown. In some embodiments, the elongated second element can be resilient so that the movable portion 1234 can move relative to the first element 1210 while the fixed portion 1232 remains stationary relative to the first element 1210. In some embodiments, the second element 1212 can have multiple points of contact at multiple locations on the first element 1210.

[0101] In the above-described embodiments, and in damping systems according to the present disclosure, the first element is temporarily fixed to the second element due to frictional contact. However, when the vibration of the downhole system increases and exceeds a threshold, for example, when the inertial force exceeds the static friction force, the first element (or a portion thereof) moves relative to the second element, thereby providing damping. That is, when the HFT0 increases above a predetermined threshold (e.g., a threshold of amplitude, distance, velocity, and / or acceleration) within the downhole system, the damping system will automatically operate, and thus the embodiments provided herein include passive damping systems. For example, embodiments include passive damping systems that operate automatically without utilizing additional energy, and therefore do not utilize additional energy sources.

[0102] Now turn Figure 13 , shows a schematic diagram of a damping system 1300 according to one embodiment of the present disclosure. In this embodiment, the damping system 1300 includes one or more elongated first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f, each of which is disposed within and in contact with a second element 1312. Each of the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f can be axially displaced in the tool direction (e.g., in the direction of contact with the tool). Figure 13 1310f) has a length and, optionally, a fixing point at which the respective first element 1310a, 1310b, 1310c, 1310d, 1310e, 1310f is fixed to the second element 1312. For example, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f can be fixed at the respective upper end, middle portion, lower end, or multiple fixing points of different first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f, or multiple points of a given single first element 1310a, 1310b, 1310c, 1310d, 1310e, 1310f. In addition, as Figure 13As shown, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f can optionally be biased or coupled to the second element 1312 by a biasing element 1338 (e.g., by applying a force having a component toward the second element 1312 via a biasing spring element or a biasing actuator). Each of the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f can be arranged and selected to have the same or different normal forces, static or dynamic friction coefficients, and mass moments of inertia to achieve various damping configurations.

[0103] In some embodiments, the first element may be substantially uniform in material, shape, and / or geometry along its length. In other embodiments, the first element may vary in shape and geometry along its length. For example, referring to Figure 14 , shows a schematic diagram of a damping system 1400 according to an embodiment of the present disclosure. In this embodiment, a first element 1410 is arranged relative to a second element 1412, and the first element 1410 has a tapered and / or spiral arrangement relative to the second element 1412. Thus, in some embodiments, a portion of the first element or the second element may change geometry or shape along its length relative to the second element, and such changes may also occur across a circumferential span around or relative to the second element and / or relative to the tool body or downhole system.

[0104] Now turn Figure 15 , shows a schematic diagram of another damping system 1500 according to an embodiment of the present disclosure. In the damping system 1500, the first element 1510 is a toothed (threaded) body that fits within a threaded second element 1512. The contact between the teeth (threads) of the first element 1510 and the threads of the second element 1512 can provide frictional contact between the two elements 1510, 1512 to achieve damping as described herein. Due to the inclined surface of the first element 1510, the first element 1510 will begin to move under axial vibration and / or torsional vibration. In addition, the movement of the first element 1510 in the axial or circumferential direction will also produce movement in the circumferential or axial direction, respectively, in this construction. Therefore, utilizing Figure 15 In the arrangement shown, axial vibration can be used to mitigate or damp torsional vibration, and torsional vibration can be used to mitigate or damp axial vibration. The locations where axial and torsional vibration occur can be different. For example, while axial vibration can be evenly distributed along the drilling assembly, torsional vibration can follow the same distribution as described above with respect to Figures 9A to 9B Therefore, no matter where the vibration occurs, Figure 15The configuration shown can be used to damp torsional vibrations using axial vibration-induced movement of the first element 1510 relative to the second element 1512 (or vice versa). As shown, optional fastening elements 1540 (e.g., bolts) can be used to adjust the contact pressure or normal force between the two elements 1510, 1512, thereby adjusting the friction and / or other damping characteristics of the damping system 1500.

[0105] Now turn Figure 16 , shows a schematic diagram of a damping system 1600 according to one embodiment of the present disclosure. Damping system 1600 includes a first element 1610, which is a rigid rod that is fixed at one end within a second element 1612. In this embodiment, rod end 1610a is arranged to frictionally contact second element stop 1612a, thereby providing damping as described according to embodiments of the present disclosure. The normal force between rod end 1610a and second element stop 1612a can be adjusted, for example, by a threaded connection between rod end 1610a and first element 1610. In addition, the stiffness of the rod can be selected to optimize damping or to influence the modal vibration shape in a favorable manner to provide greater relative displacement. For example, selecting a rod with a lower stiffness will result in a higher amplitude and higher energy dissipation of the torsional oscillations of first element 1610.

[0106] Now turn Figure 17 , shows a schematic diagram of a damping system 1700 according to an embodiment of the present disclosure. The damping system 1700 includes a first element 1710 frictionally attached or connected to a second element 1712, which is arranged as a rigid rod and is fixedly connected (e.g., by welding, screwing, brazing, adhering, etc.) to an outer tubular member 1714, such as a drill collar, at a fixed connection 1716. In one aspect, the rod may be a tubular member that includes electronic components, power supplies, storage media, batteries, microcontrollers, actuators, sensors, etc. that are susceptible to wear due to HFTO. That is, in one aspect, the second element 1712 may be a probe, such as a probe that measures directional information, including one or more of a gravimeter, a gyroscope, and a magnetometer. In this embodiment, the first element 1710 is arranged to frictionally contact the fixed rod structure of the second element 1712, move or oscillate relative to and along the fixed rod structure, thereby providing damping as described according to an embodiment of the present disclosure. Although the first element 1710 is Figure 17 1700, but is not intended to be limiting in this regard. Thus, first element 1710 can be of any size and can have the same outer diameter as damping system 1700. Furthermore, the position of first element 1710 can be adjustable to move first element 1710 closer to the modal maximum, thereby optimizing damping reduction.

[0107] Now turn Figure 18 , shows a schematic diagram of a damping system 1800 according to one embodiment of the present disclosure. Damping system 1800 includes a first element 1810 that is frictionally movable along a second element 1812. In this embodiment, first element 1810 is configured with a resilient spring element 1842 (such as a coil spring or other element or device) to engage first element 1810 with second element 1812, thereby providing a restoring force when first element 1810 has moved and deflected relative to the second element. This restoring force is directed to reduce the deflection of first element 1810 relative to second element 1812. In such embodiments, resilient spring element 1842 can be arranged or tuned to a resonance and / or critical frequency (e.g., a lowest critical frequency) of either resilient spring element 1842 or an oscillating system including first element 1810 and resilient spring element 1842.

[0108] Now turn Figure 19 , shows a schematic diagram of a damping system 1900 according to one embodiment of the present disclosure. The damping system 1900 includes a first element 1910 that is frictionally movable around a second element 1912. In this embodiment, the first element 1910 is arranged with a first end 1910a having a first contact (e.g., a first end normal force F Ni , static friction coefficient or dynamic friction coefficient μ at the first end i and the moment of inertia J at the first end i ), and having a second contact at the second end 1910b (eg, a second end normal force F Ni , the second end static friction coefficient or dynamic friction coefficient μ i and the moment of inertia of the second end J i ). In some such embodiments, the type of interaction between the respective first end 1910a or 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 can have a viscous contact / engagement, and one or both can have a sliding contact / engagement. The arrangement / configuration of the first end 1910a and the second end 1910b can be configured to provide damping as described in accordance with embodiments of the present disclosure.

[0109] Advantageously, the embodiments provided herein relate to a system for mitigating high-frequency torsional oscillations (HFTO) in a downhole system by applying a damping system mounted on a rotating tubular string (e.g., a downhole tubular string or drill string). The first element of the damping system is at least partially frictionally connected to move circumferentially relative to the axis of the drill string (e.g., frictionally connected to rotate around the axis of the drill string). In some embodiments, the second element may be part of the drilling system or bottom hole assembly and need not be a separately mounted component or weight. The second element or a portion thereof is connected to the downhole system in a manner such that, in the absence of HFTO, the relative motion between the first and second elements has zero or near-zero relative velocity (i.e., no relative motion or slow relative motion). However, when HFTO occurs above different acceleration values, relative motion between the first and second elements is possible and alternating positive and negative relative velocities are achieved. In some embodiments, the second element may be a mass or weight connected to the downhole system. In other embodiments, the second element may be part of the downhole system (e.g., part of the drilling system or BHA, such as the rest of the downhole system that provides the functionality described herein) and has friction between the first and second elements.

[0110] As described above, the second element of the damping system is selected or configured so that when there is no vibration in the drill string (i.e., HFTO), the second element will be frictionally connected to the first element by static friction. However, when there is vibration (HFTO), the second element moves relative to the first element and as described above relative to Figure 2 As described herein, the frictional contact between the first element and the second element is reduced so that the second element can rotate (move) relative to the first element (and vice versa). When in motion, the first element and the second element dissipate energy, thereby reducing HFTO. The damping system, in particular the first element thereof, has a certain position, weight, external force and size to achieve damping under one or more specific or predefined vibration modes / frequencies. As described herein, the first element is fixedly connected in the absence of HFTO vibrations, but is then able to move in the presence of certain accelerations (e.g., according to the HFTO mode), thereby achieving damping of the HFTO by zero crossing of the relative velocity (e.g., switching between positive and negative relative rotational velocities).

[0111] In the various configurations discussed above, sensors can be used to estimate and / or monitor the efficiency and dissipated energy of the damper. For example, measurements of displacement, velocity, and / or acceleration near the contact point or surface of two interacting bodies, in combination with force or torque sensors, can be used to estimate relative motion and calculate dissipated energy. For example, when the two interacting bodies are engaged by a biasing element (such as a spring element or actuator), the force can be known without measurement. The dissipated energy can also be derived from temperature measurements. Such measurements can be transmitted to a controller or operator so that parameters such as the normal force and / or the static or kinetic friction coefficient can be adjusted to achieve higher dissipated energy. For example, measurements and / or calculated values ​​of displacement, velocity, acceleration, force, and / or temperature can be sent to a controller (such as a microcontroller) having an instruction set stored on a storage medium, which, based on the instruction set, adjusts and / or controls at least one of the force and / or the static or kinetic friction coefficient engaging the two interacting bodies. Preferably, the adjustment and / or control is done while the drilling process is ongoing to achieve optimal HFTO damping results.

[0112] Although the embodiments described herein have been described with reference to specific drawings, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications will be made to adapt specific instruments, situations, or materials to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, it is intended that the present disclosure is not limited to the specific embodiments disclosed, but that the present disclosure will include all embodiments that fall within the scope of the appended claims or the following description of possible embodiments.

[0113] Severe vibrations in the drill string and bottom hole assembly can be caused by cutting forces at the drill bit or mass imbalances in downhole tools such as drilling motors. Negative effects are reduced penetration rate, reduced measurement quality, and downhole failures, among others.

[0114] There are different kinds of torsional vibrations. In the literature, torsional vibrations are mainly distinguished between stick / slip of the entire drilling system and high-frequency torsional oscillations (HFTO). Both are mainly excited by self-excitation mechanisms that occur due to the interaction of the drill bit with the formation. The main difference between stick / slip and HFTO is the frequency and the typical mode shapes: compared to below 1 Hz for stick / slip, the frequencies are above 50 Hz for HFTO. Moreover, the excited mode shapes of stick / slip are the first mode shapes of the entire drilling system, while the mode shapes of HFTO are usually limited to a small part of the drilling system and have relatively high amplitudes at the drill bit.

[0115] Due to the high frequency, HFTO corresponds to high acceleration and torque values ​​along the BHA and can have damaging effects on electronic devices and mechanical components. Based on the theory of self-excitation, increased damping can alleviate HFTO up to a certain limit of damping value (this is due to self-excitation instabilities and can be interpreted as negative damping of the associated mode).

[0116] One damping concept is based on friction. Friction between two components in a BHA or drill string can dissipate energy and reduce the level of torsional oscillations.

[0117] Based on this concept, the inventors discussed the design principle that is most suitable for damping caused by friction. Damping should be achieved by friction, where the operating point of friction relative to relative speed must be Figure 2 Around the point 204 shown. This operating point will cause high energy dissipation due to the friction hysteresis. Figure 2 Point 202 will cause energy to be input into the system.

[0118] As discussed above, the friction between the drilling system and the borehole does not produce significant additional damping in the system. This is because the relative velocity between the contacting surfaces (e.g., stabilizer and borehole) does not have a zero average value. The two interacting bodies of the friction damper must have an average velocity or rotational speed relative to each other that is sufficiently small so that the HFTO causes a sign reversal of the relative velocity of the two interacting bodies of the friction damper. In other words, the maximum value of the relative velocity between the two interacting bodies produced by the HFTO needs to be higher than the average relative velocity between the two interacting bodies.

[0119] Energy dissipation occurs only during the sliding phase via the interface between the damping device and the drilling system. Sliding occurs when the inertial force exceeds the limit between sticking and sliding (ie, static friction): F R >μ0·F N (wherein the static friction force is equal to the coefficient of static friction multiplied by the normal force between the two contacting surfaces.) The normal force and / or the coefficient of static friction or the coefficient of kinetic friction may be adjustable to achieve optimal or desired energy dissipation. Adjusting at least one of the normal force and the coefficient of static friction or the coefficient of kinetic friction may improve the energy dissipation caused by the damping system.

[0120] As discussed herein, the placement of friction dampers should be in areas of high HFTO acceleration, load, and / or relative motion. Because different modes may be affected, a design that mitigates all HFTO modes is preferred (e.g., Figure 9A and Figure 9B ).

[0121] Equivalents can be used as friction damper tools of the present disclosure. A slotted drill collar 2100 can be used, such as Figure 21 and Figure 22 shown. Figure 22 A cross-sectional view of a slotted drill collar 2100 is shown in FIG. In one non-limiting embodiment, the slotted drill collar 2100 is highly flexible and will result in higher deformations without the addition of the friction device 2102. Higher speeds will result in higher centrifugal forces, which will push the friction device 2102 into the slots under optimized normal forces to allow for high friction damping. Other factors that may be optimized in this configuration are the number and geometry of the slots and the geometry of the damping device. The additional normal force may be provided by the spring element 2104 (e.g., as discussed above) as discussed above. Figure 22 shown), actuators and / or applied by centrifugal force.

[0122] The advantage of this principle is that the friction device is directly integrated into the force flow. The torsion of the drill collar caused by the excited HFTO mode and the corresponding mode shape is partially supported by the friction device, which moves up and down during one cycle of vibration. The high relative motion, combined with the optimized friction coefficient and normal force, results in high energy dissipation.

[0123] The goal is to prevent the HFTO amplitude (in this case represented by the tangential acceleration amplitude) from increasing in amplitude. The (modal) damping that must be added by the friction damper system to each unstable torsional mode needs to be higher than the energy input into the system. The energy input does not occur instantaneously, but rather occurs over multiple cycles until the worst-case amplitude (zero RPM at the drill bit) is reached.

[0124] According to this concept, relatively short drill collars can be used because the friction damper uses relative motion along the distance from the drill bit. It is not necessary to have high tangential acceleration amplitudes, but only some deflection of the drill collar ("twist"), which will be achieved in almost everywhere along the BHA. The drill collar and the damper should have a similar mass to stiffness ratio ("impedance") compared to the BHA. This will allow the mode shape to propagate in the friction drill collar. High damping will be achieved, which will mitigate HFTO under adjustment of the parameters discussed above (normal force due to springs, etc.). The advantage compared to other friction damper principles is that the friction device is directly applied to the force flow of the HFTO modal deflections. The relatively high relative speed between the friction device and the drill collar will cause high energy dissipation.

[0125] The damper will be highly cost-effective and effective for different applications. HFTO causes high costs due to extensive repair and maintenance work, reliability issues with non-productive time, and a small market share. The proposed friction damper will work below the motor (decoupling the HFTO) and also above the motor. It can be installed in every place of the BHA, which will also include arrangements above the BHA if the modal shapes propagate to that point. If the mass and stiffness distributions are relatively similar, the modal shapes will propagate through the entire BHA. The optimal arrangement can be determined, for example, by a torsional oscillation advisor, which allows calculation of critical HFTO modes and corresponding modal shapes.

[0126] Furthermore, as described above, due to the high amplitudes at the drill bit, one location for a damper as described herein may be within the drill bit. That is, according to some embodiments of the present disclosure, the damper may be integrated into and become part of the drill bit or other fragmentation device. In such embodiments, the distance to the drill bit is zero or substantially zero. Incorporating a damper / damper element into the drill bit may impose a limit on the axial length of the damper / damper element. However, because damping is high due to the high amplitudes of the modal vibration shapes at or near the drill bit, the damper / damper element may be relatively short and still achieve a sufficient damping effect. The damper at or in the drill bit may be less than 30 cm, or 40 cm, or 50 cm, or 100 cm, or 150 cm.

[0127] In some such embodiments, the damper may be formed by a mass or inertia coupled to the drill bit solely through a damping force or torque. The damping force may be generated, for example, but not limited to, by viscous damping, friction damping, hydraulic damping, magnetic damping (e.g., eddy current damping), piezoelectric (shunt) damping, and the like. In some such embodiments, the damper may be combined with a spring to enable a tuned mass damper or a tuned friction damper. In these cases, the damper's eigenfrequency will be tuned to the eigenfrequency of the mode to be damped.

[0128] As discussed above, analysis has shown that damping increases proportionally with the effective rotational inertia and quadratically with the mass normalized mode shapes at the drill bit. The additional constant factor depends on the type of damping. The additional friction damping with an inertial damper is theoretically independent of frequency, and hydraulic dampers have some frequency dependence. This trade-off also applies to other types of damping and can be influenced using different parameters of the force (e.g., by harmonically adjusting the normal force of the friction damper configuration, choosing a fluid that has properties that change with the relative velocity of the components, etc.). As mentioned, the drill bit or other fragmentation equipment is one location where an inertial damper is used, which can be advantageous because the critical modes typically have maximum amplitudes at the drill bit (e.g., as shown in FIG. 2 ). Figure 9B (as shown). One exemplary critical mode is at 248 Hz, with maximum amplitude at the drill bit, but various other modes / frequencies may be critical depending on the specific configuration and downhole operations. That is, the critical mode may depend on various considerations, and for explanatory purposes, only the 248 Hz mode is described as an example. It is important to note that excitability also theoretically increases quadratically with the amplitude of the mode shape at the drill bit. Furthermore, the amount of damping required to mitigate vibrations may also increase quadratically with the mode shape at the drill bit.

[0129] In one non-limiting embodiment of a damper positioned at the drill bit, the friction damper can be a closed loop having any vibration mode that is connected to the drill bit and configured to rotate torsionally. In another embodiment, the damper positioned at the drill bit can be a linear mass that is connected to the drill bit in a tangential direction and effectively causes a rotational force. Several separate dampers can be installed and configured around the drill bit or other fragmentation equipment (i.e., at the end of the drill string). In another configuration, the damper can be formed by two forcibly connected parts of the drill bit that are connected to the drill bit at different axial positions. The connection at the different axial positions causes relative movement between the two forcibly connected parts. Examples of such configurations may include, for example, a threaded connection with opposing contact surfaces. The drill bit can be a fixed cutter drill bit such as a polycrystalline diamond cutter ("PDC"), a diamond or impregnated drill bit, a roller drill bit such as a roller cone drill bit, or a hybrid drill bit.

[0130] For example, turning Figure 23 , shows a schematic diagram of a fragmentation device 2300. The fragmentation device 2300 includes a plurality of blades 2302. Each of the blades 2302 is configured to cut material (e.g., rock) of the formation during drilling operations. As shown, each blade 2302 includes a corresponding damper element 2304. Figure 23 The diagram of FIG. 23 is a schematic end view with the axial length of the fragmentation device 2300 extending into and out of the page. In one non-limiting example, the damper elements 2304 may each have a length L=0.08 m in the axial direction and a load of 15,000 kg / m 2 The density of the damper element 2304 is 0.6, 0.8, 0.8, 0.9, 1, and 1.1 mass-normalized mode shape amplitudes. The damping achieved varies from approximately 0.1% to 0.32%. Analysis indicates that for a critical mode shape at 248 Hz with an amplitude of 1.1 at the fragmentation device 2300, the necessary damping is approximately 0.2%. It is noted that the damper element 2304 has a relatively small inertial mass sufficient to limit the amplitude associated with HFTO and, therefore, reduce vibrations in a downhole tool having the fragmentation device 2300.

[0131] In some embodiments, a purely rotational damper can be mounted within the drill bit shank, and this configuration will also benefit from the high modal vibration amplitudes at the drill bit. However, this mounting can result in a smaller radial position of the damper element. Consequently, the smaller radius of the inertial member will limit the damping effect, but this can be compensated by the fact that a higher mass can be placed at the drill bit shank. That is, the choice of mass and radial position relative to the central axis of the fragmentation device can be determined based on the desired vibration or mode to be damped.

[0132] By locating the damper element in or at the drill bit or other fracturing equipment, a sufficient amount of damping can be achieved to minimize or eliminate downhole vibrations. This is because, in almost all cases, the mass-normalized modal shape amplitude is greatest at the drill bit or fracturing equipment. This can be physically explained by the fact that if the speed at the drill bit is assumed to weaken the torque characteristics relative to the average rotational speed, the excitability and probability of exciting the mode also increases quadratically with the amplitude of the modal shape at the drill bit.

[0133] According to the present disclosure, one type of damper element that can be installed within a fragmentation device is a linear viscous damper. This damper element will include a mass and force element that transmits force from the drill bit to the mass / inertia member. This damper element will have a force element that is directed, arranged, or oriented in a tangential direction to damp the HFTO. The force element can be a linear viscous or friction damping element, as will be understood by those skilled in the art, in accordance with the teachings herein.

[0134] Now turn Figure 24 , shows a schematic diagram of a drill bit-based damping system 2400 according to one embodiment of the present disclosure. The drill bit-based damping system 2400 includes a drill bit 2402 and one or more damper elements 2404. The drill bit 2402 has a drill bit body 2406 and an attachment portion 2408 for attaching and engaging with a tubular string (e.g., a drill string). A drill bit shank 2410 extends between the attachment portion 2408 and the drill bit body 2406. The drill bit body 2406 is configured to enable cutting, breaking, or fragmenting material in a downhole formation to form a borehole or wellbore. Mounted to the drill bit 2402 are one or more damper elements 2404. The damper elements 2404 of this embodiment are mounted to the drill bit shank 2410.

[0135] In this embodiment, damper element 2404 is formed from three separate elements to achieve the damping effect. First element 2412 is in direct contact with drill shank 2410 and, in some embodiments, may be an axial wave spring housing. External to first element 2412 is second element 2414, which may be a radial friction surface housing. Forming the outer, or outermost, portion of damper element 2404 is third element 2416, which may be an inertia stem housing. During operation, third element 2416 (inertia stem housing) can move relative to second element 2414 (radial friction surface housing) and / or first element 2412 (axial wave spring housing). This relative movement can be achieved during specific modes and, therefore, can achieve vibration damping, as described above. Thus, first element 2412, second element 2414, and third element 2416 form a damper inertia ring arranged around drill shank 2410.

[0136] In some embodiments, as Figure 24 As shown, the damper inertia ring mounted in / on or near the drill bit shank may be lubricated by mud or covered by an optional cover sleeve 2418. The cover sleeve 2418 may be arranged around the third element 2416 to protect the contact area from the effects of mud and thereby allow a more controlled application of the normal force and coefficient of friction. In some embodiments, the cover sleeve 2418 may be omitted and the inertial mass may be increased, which will significantly increase the achievable damping. In some embodiments of the present disclosure, the contact surface providing friction damping may need to be robust, for example, utilizing polycrystalline diamond cutters, copper, sintered materials, or materials designed for fracture, as will be understood by those skilled in the art. In some embodiments, optional bearings may be used in the radial direction to ensure that the damper inertia ring (e.g., Figure 24 Rotational movement of the damper element 2404) shown.

[0137] As described, the damper element 2404 can be a single or multiple elements / structures. For example, the inertia ring itself can be a closed or interrupted ring, such as a half shell. In some embodiments, when a full ring is not possible due to the drill bit design or configuration, a half shell can be used. The half shell can be assembled around a radial friction contact or radial bearing that can be relative to the radial friction contact or radial bearing. Figure 24 The first element 2412 and the second element 2414 of the damper element 2404 are shown arranged and similar in position and mode shape. The bearings can also be separated to allow for installation. Normal forces can also be applied through the half-shells, controlled by their elasticity and the applied normal / connection forces. Radial wave spring housings can also be used to apply radial friction forces between the inertia half-shells and the radial friction surface housings.

[0138] Different geometries can be employed for the damper element (e.g., the inertia ring), which can be advantageous in increasing inertia. In this regard, the density of the material selected for the damper element can be chosen to be as high as possible, so that the mass is distributed over a large radius relative to the axial axis of the drilling system or drill bit. The inertia element (or inertia half-shell) can be combined with an additional mass (inertia element) preferably mounted behind the blades to prevent flow disruption. The diameter of the ring behind the blades can be higher than would be required for the cutting flow, as a low diameter is desirable.

[0139] Go to Figure 25 , shows a schematic diagram of a fragmentation device 2500. The fragmentation device 2500 includes a plurality of blades 2502. Each of the blades 2502 is configured to cut material (e.g., rock) of the formation during a drilling operation. In this embodiment, rather than Figure 23 Rather than incorporating the damper element directly into the blade as shown and described, a single ring damper element 2504 is disposed about the drill shank or other part of the fragmenting device 2500 . Figure 25 The diagram of FIG is a schematic end view with the axial length of the fragmentation device 2500 extending into and out of the page. In this embodiment, the damper element 2504 is an inertia ring, similar to an inertia ring relative to FIG. Figure 24 The inertia ring shown and described above is positioned adjacent to and oriented relative to the blades 2502. As shown, the damper element 2504 may include one or more mass structures 2506 that may be positioned behind or relative to one or more of the blades 2502. The mass structures 2506 may be selected and configured to damp vibrations of the fragmentation device 2500.

[0140] In some embodiments, a limit stop may optionally be provided to prevent the ring-configured damper element from moving freely or continuously (e.g., more than 10° of rotation). The normal force between the damper element and the drill shank or other part of the drill bit may be applied radially or axially by a spring or other mechanism. The radial friction force may be achieved by a spring or by an elastic design of the ring damper element. In some such embodiments, the double half-shell damper element may be prestressed to achieve the desired friction force. The axial normal force may be achieved by a spring, where the weight of the mass / inertia in the vertical borehole and the spring may be constructed from a housing or the like. The material of the drill bit may be a steel body drill bit or a matrix drill bit. Axial bearings may be used to decouple the potential normal force spring stack from the rotational movement of the inertial mass.

[0141] In some embodiments, tangential damper elements may be employed within the blades of a drill bit or other fragmenting device.Dampers for tangential damping may be mounted in locations having a high radius relative to the axial axis of the drilling system.

[0142] For dampers mounted to move freely in the tangential direction (the direction of tangential acceleration), a (steel) tube threaded into the blade can be used. The tangential damper can be assembled into the tube, thereby incorporating a mechanism for applying a normal force between the inertial mass and the tube or drill body, preferably orthogonal to the tangential direction. In some embodiments, the tangential damper element can be mounted, for example by a threaded connection, into a corresponding housing or portion of the blade that can be fixed to the fragmentation device. The housing can have any geometry that can be mounted to the blade.

[0143] Steering Figure 26 , shows a schematic diagram of a drill bit based damping system 2600. The drill bit 2602 is arranged with an annular damper element 2604, similar to the above with respect to Figure 24 26. Drill bit 2602 is shown and described. Drill bit 2602 has a drill bit body 2606 and an attachment portion 2608 for attaching and engaging with a tubular string (e.g., a drill string). A drill bit shank 2610 extends between the attachment portion 2608 and the drill bit body 2606. The drill bit body 2606 is configured to enable cutting, breaking, or fragmenting material in a downhole formation to form a borehole or wellbore. Accordingly, the drill bit body 2606 may include one or more blades to perform the cutting action. An annular damper element 2604 is mounted to the drill bit shank 2610 and may be a complete hoop structure formed from a single piece or two or more pieces.

[0144] The drill bit-based damping system 2600 further includes one or more blade-type damper elements 2620. The blade-type damper elements 2620 are configured to be mounted within or to the blades of the drill bit 2602. The blade-type damper elements 2620 can be tangential dampers. Blade-type damper elements 2620 for tangential damping can be mounted in a location with a high radius relative to the axial axis of the drilling system (e.g., within the blades or the radial ends of the blades). In some embodiments, the blade-type damper elements 2620 can be mounted and freely move in the tangential direction (i.e., the direction of tangential acceleration). To achieve this, a pipe (e.g., formed of steel) can be threaded into the blades. The blade-type damper elements 2620 can then be assembled into a pipe or other housing structure, thereby incorporating a mechanism for applying a normal force between the inertial mass and the pipe or drill bit body 2606. In some embodiments, this mounting can be orthogonal to the tangential direction. The housing structure may have a blade that can be mounted to the fragmentation device 2602 or any geometric structure in the blade.

[0145] Now turn Figures 27 and 28, shows a schematic diagram of the damper elements 2700, 2800. As described above, the damper elements 2700, 2800 are configured to be mounted within a blade of a fragmentation device. Each damper element 2700, 2800 includes a respective housing 2702, 2802 for accommodating and containing the components of the respective damper element 2700, 2800. The first damper element 2700 has a substantially rectangular geometry (with curved corners), and the second damper element 2800 has a substantially circular geometry. The housings 2702, 2802 are configured to be mounted into a blade of a fragmentation device (e.g., Figure 26 shown).

[0146] The damper elements 2700, 2800 each include a mass element 2704, 2804 movably mounted within a housing 2702, 2802. The mass elements 2704, 2804 are arranged between mounting elements 2706, 2806 and contact elements 2708, 2808. The mounting elements 2706, 2806 are configured to exert a force on the respective mass element 2704, 2804 toward the contact elements 2708, 2808. Thus, frictional contact may be achieved between the respective mass element 2704, 2804 and the contact elements 2708, 2808. The mass elements 2704, 2804 may be arranged within the respective housing 2702, 2802 together with one or more limit stops 2710, 2810. The limit stops 2710, 2810 may include optional stiffness or hydraulic elements for damping the movement of the mass elements 2704, 2804,

[0147] In addition, the limit stop 2710, 2810 can prevent the mass element 2704, 2804 from getting stuck in one edge of the housing 2702, 2802. The limit stop 2710, 2810 can be configured with a spring or other element to avoid damaging the mass element 2704, 2804 and to urge the mass element 2704, 2804 toward a neutral or resting position relative to the housing. In some embodiments, it can be advantageous to optimize the spring rate and / or gap 2711, 2811 in the housing 2702, 2802 to allow the mass element 2704, 2804 to move within the housing 2702, 2802. The damper element 2700, 2800 can be arranged as an insert (e.g., the housing 2702, 2802 is configured for installation). The insertable damper elements 2700, 2800 may be mounted so as to place the mass element 2704, 2804 at a high radius relative to the axis of the drilling system to increase rotational inertia.

[0148] The mounting elements 2706, 2806 are configured to exert a normal force on the mass elements 2704, 2804. For example, the mounting elements 2706, 2806 can be arranged as spring housings to push the mass elements 2704, 2804 into contact with the contact elements 2708, 2808. In addition, the mounting elements 2706, 2806 and / or the contact elements 2708, 2808 can be configured to control the tangential movement of the mass elements 2704, 2804 to enable damping of the HFTO. In some embodiments, the mounting elements 2706, 2806 push the mass elements 2704, 2804 into contact with the contact elements 2708, 2808 to generate friction. For example, the friction is applied by a material that is favorable with respect to the coefficient of friction and the expected wear, which should be as low as possible.

[0149] According to embodiments of the present disclosure, it is possible to integrate damping into the drill bit. Damping can be applied by any axial, tangential, and / or radial force or corresponding torque capable of dissipating energy. In the case of a coupling mode, the damping force in the axial direction can also dissipate energy in the torsional direction. Coupling can also be achieved dynamically, such as through drill bit rock interaction. As described for friction damping, the contact surfaces with applied friction coefficients and normal forces can be optimized and / or selected to damp one or more critical modes. In some embodiments, favorable materials or designs can be used to prevent wear (e.g., copper or polycrystalline diamond cutters). Multiple contacts with different properties can be used to tune the system to a favorable friction coefficient or characteristic.

[0150] Another form of damping that can be employed is hydraulic damping. This hydraulic damping can be achieved by a system located in the drill bit blades or arranged in other locations around the drill bit or fragmentation device, or located in such other locations. In some such embodiments, a viscous fluid (e.g., a viscous fluid in a chamber) can be arranged and installed in a location similar to that described above. In some such applications, the (shear) stress in the fluid between the inertia ring / mass and the drill bit / drilling system can be selected to achieve a (damping) force tangential to the tangential acceleration and the associated harmonic motion to damp the HFTO. In the case of ring shear, the fluid provides the damping force between the inertia ring and the drill bit. In this case, the ring may require a well-defined geometry that closes the housing and potentially the gap between the ring and the housing. In hydraulic damping, the viscous damping force is sensitive to changes in the parameters of the gap and the viscous fluid. Therefore, a fluid that is not temperature sensitive may be preferred. Fluids with different shear stresses that vary with shear rate can be used to achieve favorable behavior. Some such exemplary fluids include, but are not limited to, Newtonian fluids, dilatants (eg, shear-thickening fluids), pseudoplastics, Bingham plastomers, Bingham pseudoplastic fluids, and the like.

[0151] Depending on the type of force applied, different configurations are possible. As discussed above, Figure 2 The typical force characteristics for frictional contacts are described. The force characteristics have a velocity weakening effect for relative velocities that are not close to zero. As discussed above, harmonic or periodic relative motion between two elements will cause energy to be input into the system. Furthermore, as mentioned above, damping in this case is only effective when the relative motion of the interacting surfaces is close to zero (e.g., Figure 2 An alternative (or combination with a friction damper) could be a viscous damper.

[0152] Now turn Figure 29 , illustratively showing different torque (T) / force (F) characteristics of a viscous fluid with respect to the relative displacement between two parts connected by a connecting force Graph 2900 of a relative displacement (e.g., relative movement / velocity) is provided. In the graph, curve 2902 represents properties of a Newtonian fluid, curve 2904 represents properties of a shear-thinning non-Newtonian fluid, and curve 2906 represents properties of a shear-thickening non-Newtonian fluid. Although graph 2900 is illustrative of fluids, such principles may be applied to other types of dampers, such as non-contact damping (e.g., eddy current damping). On graph 2900, curve 2902 includes points 1, 2, and 3, curve 2904 includes points 4, 5, and 6, and curve 2906 includes points 7, 8, and 9. Points 1-9 represent torque T or force F relative to relative displacement. difference relationship.

[0153] In graph 2900, the slopes of curves 2902, 2904, 2906 (e.g., at points 1-9) are positive, and the relative movement of these points (including the average velocity at the points) is positive. The system will be damped by the relative displacement, velocity or acceleration fluctuations of the forcibly connected parts caused by periodic superimposed oscillations (e.g. caused by HFTO). Relative movement can occur, for example, between a part connected to the borehole wall, for example by viscous friction in the tangential direction, as would be the case with a non-rotating sleeve or steering unit. If a positive average rotational speed is applied, two interacting bodies forcibly connected by this characteristic will also provide damping for HFTO. On the downside, this characteristic will also result in a mean static force ( Figure 26 (T, F in

[0015] and corresponding to points 1-9), this average static force reduces the power from the rotation available for rock breaking. That is, the damper acts as a brake for the downhole system's rotation. Therefore, in such cases, higher power may be required at the surface rotary system, which drives the cutting action at the drill bit.

[0154] The required damping depends linearly on the slope of the torque versus relative displacement curve, which can be found in Figure 29The viscous damping coefficients d(d1-d9) are named in , and the modal shape amplitudes are normalized with mass (e.g., Figure 9B (as shown). The static energy dissipation from constant relative motion also increases linearly with the viscous damping coefficient d. Because the modal shape amplitudes are very localized and very high at the drill bit and therefore the relative motion between the two forcibly connected surfaces is high as described above, the static energy dissipation is also high and the damping is effective. Due to the localization and high modal shape amplitudes, the length of the damper can be relatively short (e.g., axially). The braking force of a relatively short damper is less than that of a relatively long damper. Therefore, the trade-off between dynamically provided damping (e.g., to mitigate HFTO) and (unwanted) static energy dissipation is particularly good near, at, or in the drill bit.

[0155] In addition, in some embodiments, magnetic damping can be used. Magnetic damping can be achieved by permanent magnets (e.g., mounted on an inertia ring or mass element) that are allowed to move relative to the coil and can be used to damp the HFTO. Based on magnetic principles, the damping force characteristics are similar to hydraulic (e.g., eddy current) or friction (hysteresis) forces. In some such configurations, the force will act in the direction of tangential acceleration or any other direction that can cause damping in the torsional direction or direction to be damped.

[0156] Furthermore, in some embodiments, the piezoelectric damping principle may be employed to prevent HFTO at the drill bit. A piezoelectric material may be used that is connected to an inertia ring or tangential mass on one side and to the drill bit on the other side. The electrodes of the piezoelectric material may be connected to an electrical circuit that incorporates coils, resistors, and capacitors or semi-active or active components. A combination of electrical components may be used to achieve advantageous damping characteristics between the inertia ring and the drill bit component. The circuit may be tuned to the natural frequency of the system to act as a tuned mass damper (i.e., for one or more desired modes). If the piezoelectric stack is deformed by the relative forces between the mass element and the drill bit component, the resistors may be arranged to dissipate the energy directly. Additionally, the stiffness of the piezoelectric material and the inertia ring mass may also be tuned to a specific frequency. The electrodes of the piezoelectric material may be arranged to damp torsional vibrations. The direction of the damping force may be different from the direction of the electrodes using the advantageous conversion effect from mechanical force to electrical signal proposed by the design of the piezoelectric actuator. The well-known piezoelectric coefficient effect is D 33 (in the direction of force), D 31 (perpendicular to the direction of the force) and D 15 (shear stress). The arrangement of the piezoelectric material can be placed to optimize or control the coupling between the mechanical and electrical systems for a specific mode or multiple mode shapes that are important for HFTO. In addition, a variety of different materials that transfer mechanical forces or stresses or related loads into electrical signals can be used without departing from the scope of the present disclosure.

[0157] Furthermore, internal damping and the resulting material forces can be used to reduce HFTO. That is, material damping can be passively achieved through the damping properties of high-damping materials. Some such materials may include, but are not limited to, polymers, elastomers, rubbers, and the like, as well as the damping effects of multifunctional materials such as shape memory alloys. The material properties of some materials (such as shape memory alloys) can be actively influenced or controlled to achieve greater damping effects.

[0158] Without departing from the scope of the present disclosure, other damping configurations are possible. For example, negative capacitance and semi-active components using switching techniques may be employed. Additional damping techniques and components may be used, and the above embodiments and variations are provided for purposes of illustration and explanation and are not intended to be limiting. All of the damping principles described herein may be tuned to act as tuned mass dampers by adding mechanical springs tuned to specific frequencies and by adding any type of damping. Furthermore, one or more of the damping principles described herein (or other methods / mechanisms) may be combined in a multi-principle configuration. For example, an annular inertial damper may be combined with a tangential mass inertial damper mounted within or attached to the blades of the fragmentation apparatus. Furthermore, magnetic damping forces, hydraulic damping forces, friction damping forces, piezoelectric damping forces, and material damping forces and principles may be combined to achieve a robust damping effect, such as, for example, with respect to temperature.

[0159] As described above, one or more damper elements can be integrated into a drill bit or other fragmentation device. For example, a ring-type drill bit damper can be positioned within or around the drill bit shank. In some configurations, the damper inertia ring can be mud-lubricated or covered by a sleeve design. In some configurations, a closed or uninterrupted ring can be used. In other configurations, a partial arc can be assembled around the drill bit shank (e.g., to allow installation in situations where the ring cannot be assembled otherwise). In some such embodiments, two half-ring arcs can be used. In other embodiments, more than two ring arcs can be used to form a complete hoop (circumference) structure or less than a complete hoop (circumference) structure, depending on the specific configuration implemented.

[0160] In some embodiments, a broken ring structure may be employed, wherein discrete masses are positioned behind or adjacent to the blades of the drill bit. In another example, a full ring structure may be positioned adjacent to the blades, but specific additional mass elements or features of the ring may be positioned relative to specific blades of the drill bit. One such example may have a relatively thick ring and a lower thickness at the location of the blades to allow for chip flow along the drill bit.

[0161] In some embodiments, a limit stop may be provided for the ring-type damper element and may prevent the ring from freely moving around the circumference of the drill bit. Such a limit stop may be provided in embodiments where a mass or higher mass is located behind or adjacent to a specific blade. In such cases, the limit stop may ensure that the mass or higher mass remains in a certain position relative to the blade.

[0162] It should be understood that the friction-type damper elements of the present disclosure may employ radial and / or axial friction forces. The radial friction force may be achieved by a spring or by an elastic design of an inertia ring having two half shells and may be prestressed. The axial normal force may be achieved by a spring, the weight of the mass / inertia member in the vertical hole and / or the spring may be constructed from the shell, etc. The material of the drill bit or other fragmentation equipment may be steel or a matrix composite material, etc. In some embodiments, bearings may be used in the radial direction to ensure movement of the inertia ring. That is, bearings may be provided to ensure circumferential and / or tangential movement of the damper element. Axial bearings may be used to decouple the potential normal force spring stack from rotational movement.

[0163] In some embodiments, alternatively from or in combination with an annular damper element, a tangential damper element can be implemented in or on the blade of the fragmentation device. In some such embodiments, the tangential damper element can be mounted in a housing that is threaded into the blade. In some such configurations, one or more limit stops can be provided to prevent the tangential damper from sticking or wedging into an edge or corner of the housing. A spring or other biasing element or structure can be used to achieve contact between the limit stop and the mass of the tangential damper. In some embodiments, the spring rate or gap in the housing can be selected to allow the mass of the tangential damper to move within the housing and thereby enable vibration damping to occur, as described above.

[0164] Adjustment elements that change the nature of the contact between contact elements in the drill bit can also be used. For example, the normal force in the friction contact can be adjusted. In addition, the efficiency of the damping device can be measured by load and acceleration or other vibration measurement sensing devices.

[0165] Thus, embodiments of the present disclosure relate to positioning a damping system, such as an annular damper or a tangential damper, at or in a drill bit or other fracturing equipment of a downhole system. By positioning the damping system at or in the drill bit, improved damping of HFTO or other vibration modes may be achieved.

[0166] Embodiment 1: A system for damping torsional oscillations of a downhole system, the system comprising: a downhole tubular string including a fragmentation device; and a damping system located at least one of: in and / or on the downhole tubular string, the damping system being configured to damp torsional oscillations of the downhole tubular string.

[0167] Embodiment 2: The system according to any preceding embodiment, wherein the damping system is arranged to provide viscous damping.

[0168] Embodiment 3: The system according to any preceding embodiment, wherein the damping system is arranged to provide piezoelectric damping.

[0169] Embodiment 4: The system according to any preceding embodiment, wherein the damping system is arranged to provide eddy current damping.

[0170] Embodiment 5: The system according to any preceding embodiment, wherein the damping system comprises at least one damper element arranged in contact with a portion of the fragmentation device.

[0171] Embodiment 6: The system of any preceding embodiment, wherein the damper element is configured to move relative to the fragmentation device at a velocity that is a sum of periodic velocity fluctuations having an amplitude and an average velocity.

[0172] Embodiment 7: The system according to any preceding embodiment, wherein the fragmentation device is a drill bit comprising a drill bit body and a drill bit shank.

[0173] Embodiment 8: The system of any preceding embodiment, wherein at least one damper element is disposed about the drill shank.

[0174] Embodiment 9: A system according to any of the preceding embodiments, wherein: the at least one damper element is an annular structure arranged circumferentially around the drill bit shank, the drill bit body includes a plurality of blades, and the annular structure includes one or more mass structures, wherein at least one mass structure is arranged relative to one of the plurality of blades.

[0175] Embodiment 10: A system according to any of the preceding embodiments, wherein the at least one damper element includes: a first element, which is arranged to contact the drill shank; a second element, which is arranged outside the first element; and a third element, which is arranged outside the second element.

[0176] Embodiment 11: The system of any preceding embodiment, wherein the first element is an axial wave spring, the second element is a radial friction surface housing, and the third element is an inertia stem housing.

[0177] Embodiment 12: The system of any preceding embodiment, further comprising: a cover sleeve disposed around the at least one damper element disposed around the drill shank, the cover sleeve being configured to protect the at least one damper element disposed around the drill shank.

[0178] Embodiment 13: The system of any preceding embodiment, wherein the fragmentation device comprises at least one blade, wherein at least one damper element is disposed in the at least one blade.

[0179] Embodiment 14: The system of any preceding embodiment, wherein the at least one damper element is a tangential damper element.

[0180] Embodiment 15: The system of any preceding embodiment, wherein the at least one damper element comprises: a housing configured to be mounted within the at least one blade; and a mass element disposed within the housing and movable within the housing.

[0181] Embodiment 16: A system according to any of the preceding embodiments, wherein the at least one damper element further comprises: a mounting element located within the housing; and a contact element located within the housing, wherein the mass element is arranged between the mounting element and the contact element, and wherein the mounting element is configured to push the mass element toward the contact element within the housing.

[0182] Embodiment 17: The system of any preceding embodiment, wherein the at least one damper element further comprises: a limit stop disposed within the housing and configured to prevent the mass element from sticking within the housing.

[0183] Embodiment 18: A method for damping torsional oscillations of a downhole system in a borehole, the method comprising: installing a damping system at at least one of: on and / or in the downhole system, the downhole system comprising a downhole tubing having a fragmentation device, and the damping system being configured to damp the torsional oscillations of the downhole tubing.

[0184] Embodiment 19: The method according to any preceding embodiment, wherein the damping system comprises at least one damper element arranged in contact with a portion of the fragmentation device.

[0185] Embodiment 20: A method according to any preceding embodiment, wherein the damper element moves relative to the fragmentation device at a speed that is the sum of periodic velocity fluctuations having an amplitude and an average velocity, wherein the average velocity is lower than the amplitude of the periodic velocity fluctuations.

[0186] Embodiment 21: The method of any preceding embodiment, wherein the damping system is arranged to provide at least one of viscous damping, frictional damping, hydraulic damping, piezoresistive damping, eddy current damping, and magnetic damping to torsional oscillations of the downhole tubular string.

[0187] To support the teachings herein, various analysis components may be used, including digital and / or analog systems. For example, a controller, computer processing system, and / or geosteering system as provided herein and / or used with the embodiments described herein may include a digital and / or analog system. These systems may have components such as processors, storage media, memory, inputs, outputs, communication links (e.g., wired, wireless, optical, or other), user interfaces, software programs, signal processors (e.g., digital or analog), and other such components (e.g., resistors, capacitors, inductors, etc.) for providing operation and analysis of the apparatus and methods disclosed herein in any of several ways well known in the art. It is contemplated that these teachings may, but need not, be implemented in conjunction with a set of computer-executable instructions stored on a non-transitory computer-readable medium, including memory (e.g., ROM, RAM), optical media (e.g., CD-ROM), or magnetic media (e.g., disk, hard drive), or any other type of media, which, when executed, cause a computer to implement the methods and / or processes described herein. In addition to the functions described in this disclosure, these instructions may also provide equipment operation, control, data collection, analysis and other functions that the system designer, owner, user or other such personnel consider relevant. Processed data (such as the result of the implemented method) may be transmitted to a signal receiving device via a processor output interface as a signal. The signal receiving device may be a display monitor or printer for presenting the result to the user. Alternatively or in addition thereto, the signal receiving device may be a memory or a storage medium. It should be understood that storing the result in a memory or a storage medium may convert the memory or the storage medium from a previous state (i.e., not including the result) to a new state (i.e., including the result). In addition, in some embodiments, if the result exceeds a threshold value, an alarm signal may be transmitted from the processor to the user interface.

[0188] In addition, various other components may be included and required to provide various aspects of the teachings herein. For example, sensors, transmitters, receivers, transceivers, antennas, controllers, optical units, electrical units, and / or electromechanical units may be included to support various aspects discussed herein or to support other functionality beyond the present disclosure.

[0189] In the context of describing the present invention (especially in the context of the appended claims), the use of the terms "a," "an," and "the," and similar referents are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Furthermore, it should be noted that the terms "first," "second," and the like, as used herein, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier "about" used in connection with a quantity is inclusive of the stated value and has a meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

[0190] It should be recognized that various components or techniques may provide certain necessary or advantageous functions or features. Therefore, these functions and features that may be required to support the appended claims and their variants are considered to be inherently included as part of the teachings herein and part of the present disclosure.

[0191] The teaching content of the present disclosure can be used for multiple well operations.These operations can relate to using one or more treatment agents to treat the fluid, drilling and / or equipment in the drilling hole, such as production tubing, resident in the stratum.The treatment agent can be in the form of liquid, gas, solid, semi-solid, and their mixture.Illustrative treatment agents include but are not limited to fracturing fluid, acid, steam, water, brine, preservative, cement, permeability regulator, drilling mud, emulsifier, demulsifier, tracer, flow improver etc.Illustrative well operations include but are not limited to hydraulic fracturing, production increase, tracer injection, cleaning, acidizing, steam injection, water injection, cementing etc.

[0192] Although the embodiments described herein have been described with reference to various embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications will be made to adapt specific instruments, situations, or materials to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, it is intended that the present disclosure is not limited to the specific embodiments disclosed as the best mode contemplated for implementing the described features, but that the present disclosure will include all embodiments falling within the scope of the appended claims.

[0193] Accordingly, the disclosed embodiments are not to be seen as limited by the foregoing description, but are only limited by the scope of the appended claims.

Claims

1. A system for damping torsional oscillations of a downhole system, the system comprising: A downhole tubular string, the downhole tubular string including a fragmentation device; as well as a damping system located in and / or on the fragmentation device, the damping system being configured to damp torsional oscillations of the downhole tubular string; wherein the damping system comprises at least one damper element arranged in contact with a portion of the fragmentation apparatus; and wherein the at least one damper element is configured to move relative to the fragmentation device at a velocity that is a sum of periodic velocity fluctuations having an amplitude and an average velocity.

2. A system for damping torsional oscillations of a downhole system according to claim 1, wherein the damping system is arranged to also provide at least one of viscous damping, piezoelectric damping, eddy current damping.

3. The system for damping torsional oscillations of a downhole system according to claim 1 or 2, wherein the fragmentation device is a drill bit comprising a drill bit body and a drill bit shank.

4. The system for damping torsional oscillations of a downhole system according to claim 3, wherein the at least one damper element is disposed about the drill bit shank.

5. The system for damping torsional oscillations of a downhole system according to claim 4, wherein the system for damping torsional oscillations of a downhole system further comprises: A cover sleeve is arranged around the at least one damper element arranged around the drill shank, the cover sleeve being configured to protect the at least one damper element arranged around the drill shank.

6. The system for damping torsional oscillations of a downhole system according to claim 3, wherein: The at least one damper element is an annular structure arranged circumferentially around the drill shank, The drill bit body includes a plurality of blades, and The ring structure includes one or more mass structures, wherein at least one mass structure is disposed relative to a blade of the plurality of blades.

7. The system for damping torsional oscillations of a downhole system according to claim 3, wherein the at least one damper element comprises: a first member disposed in contact with the drill shank; a second element disposed outside the first element; as well as A third element is arranged outside the second element.

8. The system for damping torsional oscillations of a downhole system of claim 7, wherein the first element is an axial wave spring, the second element is a radial friction surface housing, and the third element is an inertia stem housing.

9. The system for damping torsional oscillations of a downhole system according to claim 1 or 2, wherein the fragmentation device comprises at least one blade, wherein the at least one damper element is arranged in the at least one blade.

10. A system for damping torsional oscillations of a downhole system according to claim 9, wherein the at least one damper element is one of the following: a tangential damper element, or includes a housing configured to be mounted within the at least one blade and a mass element arranged within the housing and capable of moving within the housing.

11. The system for damping torsional oscillations of a downhole system according to claim 10, wherein the at least one damper element further comprises: a mounting element positioned within the housing; as well as a contact element, said contact element being located within said housing, wherein the mass element is arranged between the mounting element and the contact element, and wherein the mounting element is configured to urge the mass element towards the contact element within the housing.

12. The system for damping torsional oscillations of a downhole system according to claim 11, wherein the at least one damper element further comprises a limit stop disposed within the housing and configured to prevent the mass element from sticking within the housing.

13. A method of damping torsional oscillations of a downhole system in a borehole, the downhole system comprising a downhole tubular string having a fracturing device, the method comprising: installing a damping system in and / or on the fragmentation device, and utilizing the damping system to damp the torsional oscillation of the downhole tubular string; wherein the damping system comprises at least one damper element arranged in contact with a portion of the fragmentation apparatus; and wherein the at least one damper element is configured to move relative to the fragmentation device at a velocity that is a sum of periodic velocity fluctuations having an amplitude and an average velocity. The method of claim 13 , wherein the average speed is lower than the amplitude of the periodic speed fluctuations.

15. The method of any one of claims 13 to 14, wherein the damping system is arranged to also provide at least one of viscous damping, hydraulic damping, piezoelectric damping, and magnetic damping to torsional oscillations of the downhole tubular string.

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