Optimizing placement of vibration dampers by modal shape tuning

Abstract

Systems and methods for damping torsional oscillations of a downhole system are described. The system includes a downhole drilling system disposed in operative connection with a drill bit at an end of the downhole system. A damping system is mounted on the downhole drilling system, the damping system having at least one damper element configured to damp at least one HFTO mode. At least one mode-shape tuning element is disposed on the drilling system. The at least one mode-shape tuning element is configured and positioned on the drilling system to modify at least one of: a shape of the HFTO mode, a frequency of the HFTO mode, an excitable nature of the HFTO mode, and a damping efficiency of the at least one damper element.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefits of U.S. Provisional Application Serial Nos. 62 / 899,354, 62 / 899,291, 62 / 899,331, and 62 / 899,332, all filed on September 12, 2019, the entire disclosures of which are incorporated herein by reference. Background Technology 1. Technical Field

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

[0005] 2. Description of related technologies

[0006] Drilling boreholes deep underground is used for many applications, such as carbon dioxide sequestration, geothermal production, and oil and gas exploration and production. In all these applications, boreholes are drilled so that they penetrate or allow access to materials (e.g., gases or fluids) contained in strata located below the surface (e.g., sequestration chambers). Different types of tools and instruments can be set in the boreholes to perform a variety of tasks and measurements.

[0007] During operation, downhole components can be subjected to vibration, which can affect operational efficiency. For example, severe vibration 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 vibration can include, but are not limited to, reduced drilling rates, reduced measurement quality, and excessive fatigue and wear of downhole components, tools, and / or equipment. Summary of the Invention

[0008] This document discloses systems and methods for damping oscillations (such as torsional oscillations) in downhole systems. 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 within the drill bit or other fracturing equipment of the downhole system. These dampers are arranged to reduce or eliminate one or more specific vibration modes, and thus enable improved downhole operation and / or efficiency.

[0009] According to some embodiments, a system for damping torsional oscillations in a downhole system is provided. The system includes: a drilling system comprising a bottom hole assembly disposed at an end of a drill string; at least one modal-mode tuning element disposed on the drilling system, the at least one modal-mode tuning element being configured to offset the position of a maximum value of a high-frequency torsional oscillation (HFTO) mode; and a damping system disposed on the drilling system, the damping system comprising at least one damper element disposed at the offset position of the maximum value.

[0010] According to some embodiments, a method is provided for damping torsional oscillations in a downhole system in a borehole. The method includes: mounting at least one modal-mode tuning element on a drilling system comprising a drill string and a bottom hole assembly, the at least one modal-mode tuning element being configured to offset the position of a maximum value of a high-frequency torsional oscillation (HFTO) mode of the drilling system; and mounting a damping system on the drilling system, the damping system comprising at least one damper element disposed at the offset position of the maximum value. Attached Figure Description

[0011] The subject matter considered to be in this invention is specifically pointed out and explicitly claimed in the claims at the end of this specification. The foregoing and other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein similar elements have similar reference numerals, in which:

[0012] Figure 1 Examples of systems for performing downhole operations that can adopt embodiments of this disclosure;

[0013] Figure 2 It is an illustrative graph of the typical curve of friction or torque between two interacting subjects versus relative velocity or relative rotational speed;

[0014] Figure 3 It is a graph showing the hysteresis curve of friction force versus displacement for a positive relative average velocity with additional small velocity fluctuations.

[0015] Figure 4 It is a graph of friction, relative velocity, and their product against time for a positive relative average velocity with additional small velocity fluctuations.

[0016] Figure 5 It is a graph showing the hysteresis curve of friction force versus displacement for a zero relative average velocity with additional small velocity fluctuations.

[0017] Figure 6It is a graph of friction, relative velocity, and the product of the two for zero relative average velocity with additional small velocity fluctuations;

[0018] Figure 7 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0019] Figure 8A It is a graph of tangential acceleration measured at the drill bit;

[0020] Figure 8B It corresponds to Figure 8A The graph shows the rotational speed;

[0021] Figure 9A This is a schematic diagram of the downhole system, showing how the mode shape of the downhole system changes with distance from the drill bit;

[0022] Figure 9B It shows that it can be used Figure 9A Exemplary corresponding mode shapes of torsional vibrations excited during the operation of downhole systems;

[0023] Figure 10 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0024] Figure 11 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0025] Figure 12 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0026] Figure 13 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0027] Figure 14 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0028] Figure 15 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0029] Figure 16 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0030] Figure 17 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0031] Figure 18 This is a schematic diagram of a damping system according to one embodiment of the present disclosure;

[0032] Figure 19This is a schematic diagram of a damping system according to one embodiment of the present disclosure; and

[0033] Figure 20 This is a schematic diagram illustrating the effect of modal damping ratio on local vibration amplitude;

[0034] Figure 21 This is a schematic diagram of a downhole tool with a damping system;

[0035] Figure 22 yes Figure 21 A cross-sectional view of the downhole tools;

[0036] Figure 23 This is a set of graphs showing the mode shapes and standardized damping of the damper for various BHA modes according to one embodiment of the present disclosure;

[0037] Figures 24A to 24C This is a schematic diagram of the placement of a single damper element downhole according to an embodiment of this disclosure;

[0038] Figure 25 This is a set of graphs showing the mode shapes and standardized damping of the damper for various BHA modes according to one embodiment of the present disclosure;

[0039] Figure 26A This is a schematic diagram of a downhole string according to one embodiment of the present disclosure, the downhole string having a modal-mode tuning element and a damper element mounted on the downhole string;

[0040] Figure 26B A modal mode modified or tuned by incorporating a modal-mode tuning element is shown according to one embodiment of the present disclosure;

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

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

[0043] Figure 29A This is a schematic diagram of an example of a modal-mode tuning element according to one embodiment of the present disclosure; and

[0044] Figure 29B This is a schematic diagram of an exemplary assembled downhole string according to one embodiment of the present disclosure, the exemplary assembled downhole string having modal-mode tuning elements and damper element sub-joints. Detailed Implementation

[0045] Figure 1A schematic diagram of a system for performing downhole operations is shown. As shown, the system is a drilling system 10, which includes a drill string 20 having a drilling assembly 90 (also referred to as a bottom hole assembly (BHA)) delivered in a borehole 26 penetrating the formation 60. The drilling system 10 includes a conventional derrick 11 erected on a base plate 12 supporting a rotary table 14, which is rotated at a desired rotational speed by a prime mover (such as an electric motor (not shown)). The drill string 20 includes a drilling tubing 22, such as a drill pipe, extending downwards from the rotary table 14 into the borehole 26. A fracturing device 50 (such as a drill tip (also referred to as a “drill bit”) attached to the end of the BHA 90) fractures the geological formation as it rotates to drill the borehole 26. The drill string 20 is connected to surface equipment, such as a system for lifting, rotating, and / or pushing (including but not limited to) the winch 30 via pulley 23 through the square drill pipe joint 21, swivel 28, and line 29. In some embodiments, the surface equipment may include a top drive (not shown). During drilling operations, the winch 30 is operated to control the pressure on the drill bit, which affects the drilling rate. The operation of the winch 30 is well known in the art and will not be described in detail herein.

[0046] During drilling operations, suitable drilling fluid 31 (also referred to as “mud”) from the source or mud pit 32 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 wave eliminator 36, a fluid line 38, and a kerb 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 upwards along the wellbore through the annular gap 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 velocity. 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. Additionally, one or more sensors (not shown) associated with line 29 are used to provide information about the hook load on the drill string 20 and other desired parameters related to drilling of the borehole 26. The system may also include one or more downhole sensors 70 positioned on the drill string 20 and / or BHA 90.

[0047] In some applications, the fracturing device 50 is rotated solely by rotating the drill string 22. However, in other applications, a drill motor 55 (e.g., a mud motor) housed within the drilling assembly 90 is used to rotate the fracturing 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 fracturing device 50 into the formation 60 depends largely on the pressure on the drill bit and the drill bit rotation speed. Figure 1In one aspect of the implementation, a drilling motor 55 is coupled to a fracturing device 50 via a drive shaft (not shown) disposed in a bearing assembly 57. The drilling motor 55 rotates the fracturing device 50 as drilling fluid 31 passes under pressure through it. The bearing assembly 57 supports the radial and axial forces on the fracturing device 50, the downward thrust of the drilling motor, and the reactive upward load from the applied drilling pressure. A stabilizer 58, coupled to the bearing assembly 57 and / or other suitable locations, acts as a centralizer for the drilling assembly 90 or a portion thereof.

[0048] The surface control unit 40 receives signals from downhole sensors 70 and equipment via transducers 43, such as pressure transducers, placed in fluid lines 38, and 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 desired drilling parameters and other information used by operators at the drilling rig site to control drilling operations on a display / monitor 42. The surface control unit 40 includes a computer; a memory for storing processor-accessible data, computer programs, models, and algorithms; 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 via a suitable device (such as a keyboard). The surface control unit 40 is adapted to activate an alarm 44 in the event of certain unsafe or undesirable operating conditions.

[0049] Drilling assembly 90 also includes other sensors and devices or tools for providing various measurements related to the formation surrounding the borehole and for drilling the borehole 26 along a desired path. Such devices may include equipment for measuring formation resistivity near and / or in front of the drill bit, gamma-ray equipment for measuring formation gamma-ray intensity, and equipment for determining the drill string inclination, azimuth, and position. A formation resistivity tool 64, fabricated according to the embodiments described herein, can be coupled at any suitable location (including above the lower initiator assembly 62) to estimate or determine the formation resistivity near or in front of the fracturing device 50 or at other suitable locations. Inclinometer 74 and gamma-ray equipment 76 may be suitably positioned to determine the inclination and formation gamma-ray intensity of the BHA, respectively. Any suitable inclinometer and gamma-ray equipment may be used. Additionally, an azimuth device (not shown) such as a magnetometer or gyroscope may be used to determine the drill string azimuth. Such devices are known in the art and therefore will not be described in detail herein. In the exemplary configuration described above, the drilling motor 55 transmits power to the fracturing device 50 via a shaft that also allows drilling fluid to be transferred from the drilling motor 55 to the fracturing device 50. In an alternative embodiment of the drill string 20, the drilling motor 55 may be coupled below the resistivity measuring device 64 or at any other suitable location.

[0050] Still referencing Figure 1 Other logging-while-drilling (LWD) devices (generally designated as 77 here), such as devices for measuring formation porosity, permeability, density, rock properties, fluid properties, etc., may be placed in appropriate locations within the drilling assembly 90 to provide information for assessing the subsurface formation along the borehole 26. Such devices may include, but are not limited to, temperature measuring tools, pressure measuring tools, borehole diameter measuring tools (e.g., calipers), acoustic tools, nuclear tools, nuclear magnetic resonance tools, and formation testing and sampling tools.

[0051] The aforementioned equipment transmits data to a downhole telemetry system 72, which in turn transmits the received data upwards along the wellbore to a 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 sensor 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 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 a signal via a conductor 45 to the surface control unit 40. In other respects, any other suitable telemetry system may be used for two-way data communication (e.g., downlink and uplink) between the ground and BHA 90. These telemetry systems include, but are not limited to, acoustic telemetry systems, electromagnetic telemetry systems, optical telemetry systems, and wired telemetry systems, which may utilize wireless couplers or repeaters within the drill string or borehole. A wired telemetry system can be constructed by connecting drill pipe segments, each segment including a data communication link (such as an electrical wire) extending along the pipe. Data connections between segments can be made by any suitable method, including but not limited to hard electrical or optical connections, inductive, capacitive, resonant coupling (such as electromagnetic resonant coupling), or directional coupling methods. When coiled tubing is used as drill pipe 22, the data communication link may extend along the side of the coiled tubing.

[0052] The drilling systems described so far relate to those that utilize drill tubing to deliver drilling assemblies 90 into the borehole 26, where pressure on the drill bit is typically controlled from the surface by controlling the operation of a winch. However, a large number of current drilling systems, particularly those used for drilling highly skewed and horizontal boreholes, utilize coiled tubing to deliver drilling assemblies downhole. In such applications, thrusters are sometimes deployed in the drill string to provide the desired force at the drill bit. Additionally, when coiled tubing is used, the tubing is not rotated via a rotary table, but rather injected into the borehole via a suitable injector, while a downhole motor (such as drilling motor 55) rotates the fracturing equipment 50. For offshore drilling, offshore drilling rigs or vessels are used to support the drilling equipment, including the drill string.

[0053] Still referencing Figure 1 A resistivity tool 64 may be provided, which includes, for example, multiple 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 understand that other formation property tools may be used in conjunction with or in place of the resistivity tool 64.

[0054] Tail-end drilling can be a configuration or operation used to provide fracturing equipment and is becoming increasingly attractive in the oil and gas industry due to several advantages compared to 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,” the entire contents of which are incorporated herein by reference. Importantly, despite the relatively low drilling rate, the time required to align the tail-end with the target is reduced because it is run into the borehole simultaneously. This can be beneficial in expanding formations where borehole contraction can hinder tail-end installation. Furthermore, using tail-end drilling in depleted and unstable oil formations minimizes the risk of casing or drill string jamming due to borehole collapse.

[0055] although Figure 1 This disclosure pertains to drilling operations, but those skilled in the art will understand that, despite the different components, similar configurations can be used to perform various downhole operations. For example, as known in the art, cabled, wireline, tailpipe drilling, reaming, coiled tubing, and / or other configurations can be used. Furthermore, production configurations can be employed for extracting materials from and / or injecting materials into the formation. Therefore, this disclosure is not limited to drilling operations but can be applied to any suitable or desired one or more downhole operations.

[0056] Severe vibrations in the drill string and bottomhole 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 reduced drilling rates, decreased quality of measurements performed by the tools in the bottomhole assembly, and wear, fatigue, and / or failure of downhole components. As those skilled in the art will understand, different types of vibration exist, such as lateral vibration, axial vibration, and torsional vibration. For example, viscous / slippage and high-frequency torsional oscillations (“HFTO”) throughout the drilling system are types of torsional vibration. The terms “vibration,” “oscillation,” and “fluctuation” are used in the same broad sense as repetitive and / or periodic movements or periodic deviations from average values ​​(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 can include all kinds of deviations, such as, but not limited to, periodic deviations, harmonic deviations, and statistical deviations. Torsional vibrations can be induced by self-excitation mechanisms arising from the interaction of the drill bit or any other cutting structure (such as a reamer bit) with the formation. The main difference between low-frequency torsional oscillations (such as viscous / slip) and HFTO is the frequency and typical mode shape: for example, HFTO typically has a frequency above 50 Hz compared to low-frequency torsional vibrations, which typically have frequencies below 1 Hz. Furthermore, the excited mode shape of low-frequency torsional vibrations or viscous / slip is usually the first mode shape of the entire drilling system, while the mode shape of HFTO can be higher order and is usually confined to a smaller part of the drilling system with 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 (e.g., achieved by a stabilizer).

[0057] Due to the high frequency of the 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. In this sense, acceleration, force, and torque are equivalent in that none of them would occur without the other two. The load of high-frequency vibration can negatively impact 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 downhole systems to mitigate HFTO. In some embodiments of this disclosure, torsional vibration damping can be activated if a threshold value for a measured characteristic (such as torsional vibration amplitude or frequency) is achieved within the system.

[0058] According to the non-limiting embodiments provided herein, a vibration damper, or simply a damper (also referred to as a damping system, such as a torsional vibration damping system) in the context of this disclosure, may be based on a friction damper. For example, according to some embodiments, the damper may include one or more damper elements, which may be included in a damper element short joint. Friction between two parts within the damper element (such as two interacting bodies in the damper element) can dissipate energy and reduce the level of torsional oscillations, thus mitigating potential damage caused by high-frequency vibrations. Preferably, the energy dissipation of the damper is at least equal to the HFTO energy input caused by the drill bit-rock interaction.

[0059] The friction damper described herein can cause significant energy dissipation and thus reduce torsional vibration. When two components or interacting bodies are in contact with each other and move relative to each other, friction acts in the opposite direction to the relative velocities of the contact surfaces of these components or interacting bodies. Friction causes energy dissipation.

[0060] Figure 2 Figure 200 is an illustrative curve of a typical curve of friction or torque between two interacting bodies against relative velocity v (e.g., relative rotational speed). The two interacting bodies have contact surfaces and a force component F perpendicular to the contact surfaces that engage the two interacting bodies. N Figure 200 illustrates the correlation between frictional force or torque and velocity weakening behavior (e.g., frictional characteristics of cutting) between two interacting subjects. At higher relative velocities (v>0) between the two interacting subjects, the frictional force or torque exhibits different values ​​as shown by point 202. Decreasing the relative velocity will result in an increase in frictional force or torque (also known as velocity weakening characteristics). When the relative velocity is zero, the frictional force or torque reaches its maximum value. Maximum frictional force is also known as static friction, adhesive friction, or viscous friction.

[0061] Typically, frictional force F R Depends on the normal force, as in equation F R =μ·F N As described in the text, the coefficient of friction is μ. Generally speaking, the coefficient of friction μ is a function of velocity. In this paper, the normal force can also correspond to the undulation of excited vibrations in the normal direction. When the relative velocity between two interacting bodies is zero (v = 0), the static friction force F S With normal force component F N The relevant equation is F. S =μ0·F NThe static friction coefficient is μ0. When the relative velocity between two interacting bodies is not zero (v≠0), the friction coefficient is called the dynamic friction coefficient μ. If the relative velocity further decreases to a negative value (i.e., if the direction of relative motion of the two interacting bodies switches to the opposite direction), the frictional force or torque switches to the opposite direction and has a high absolute value at point 204 in graph 200, corresponding to the step from a positive maximum to a negative minimum. That is, the relationship between frictional force and velocity shows the sign change at the point where the velocity changes sign and is discontinuous at point 204 in graph 200. Velocity weakening is a well-known effect between frictionally connected interacting bodies. The velocity weakening characteristic of contact force or torque is considered a potential root cause of viscosity / slippage. Velocity weakening can also be achieved by utilizing a dispersed fluid with higher viscosity at lower relative velocities and lower viscosity at higher relative velocities. The same effect can be achieved by forcing the dispersed fluid through a relatively small channel, since the flow resistance is relatively high or low at low or high relative velocities, respectively.

[0062] refer to Figures 8A to 8B , Figure 8A The measured torsional acceleration of the downhole system versus time is shown. Figure 8A During the 5-second measurement time shown, Figure 8A An oscillating torsional acceleration with an average acceleration of approximately 0g is shown, which is superimposed with an oscillating torsional acceleration having a relatively low amplitude between approximately 0s and 3s and a relatively high amplitude of up to 100g between approximately 3s and 5s. Figure 8B It shows the relationship with Figure 8A The corresponding rotational speed within the same time period. According to Figure 8A , Figure 8B The average velocity v0 is shown (in) Figure 8B (Indicated by line v0), this average speed is relatively constant at approximately 190 revolutions per minute. This average speed is determined by... Figure 8A The relatively low and high acceleration amplitudes in the oscillating rotational velocity are superimposed, with a relatively low amplitude between approximately 0 s and 3 s and a relatively high amplitude between approximately 3 s and 5 s. Notably, even within the time period of approximately 3 s and 5 s, when the amplitude of the rotational velocity oscillation is relatively high, the oscillating rotational velocity does not cause a negative value in the rotational velocity.

[0063] Refer again Figure 2 Point 202 shows the average velocity of the two interacting entities, which corresponds to Figure 8B The average velocity v0 in the middle. Figure 2 In the schematic diagram, Figure 8BThe data corresponds to points with velocities that oscillate at a relatively high frequency around the average velocity v0 due to HTFO, which changes relatively slowly over time compared to HFTO. Therefore, it is shown that... Figure 8B The data points are at Figure 2 The curve moves back and forth on the positive branch, rarely or never reaching negative velocity values. Therefore, the corresponding frictional force or torque oscillates around the positive average frictional force or average frictional torque and is generally positive or only rarely negative. As discussed further below, point 202 shows the location where the positive average relative velocity corresponds to the static torque, and point 204 shows the advantageous point for frictional damping. It should be noted that the frictional force or torque between the drilling system and the borehole wall does not produce additional damping for the high-frequency oscillations in the system. This is because the average velocity of the relative velocity between the contact surfaces of the interacting subjects (e.g., the stabilizer and the borehole wall) is not so close to zero that the HFTO causes a sign change in the relative velocity of the two interacting subjects. Instead, the relative velocity between the two interacting subjects has a high average value at a certain distance from zero, which is large enough that the HFTO does not cause a sign change in the relative velocity of the two interacting subjects (e.g., by...). Figure 2 Point 202 is shown in the diagram.

[0064] As those skilled in the art will understand, Figure 2 The weakening characteristic of contact force or torque relative to relative velocity, as shown, results in energy being applied to the system to cause the relative movement of the interacting subjects to oscillate at an average velocity v0, which is high compared to the velocity of the oscillating movement. In this context, other examples of self-excited mechanisms, such as coupling between axial and torsional degrees of freedom, can induce similar characteristics.

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

[0066] Refer again Figure 2 Point 204 represents the favorable average velocity for frictional damping of small velocity fluctuations or oscillations other than the average velocity. For small fluctuations in relative movement between two interacting bodies, Figure 2 The discontinuity at point 204 and the sign change of the relative velocities of the interacting entities also cause a sudden sign change in the frictional force or torque. This sign change causes hysteresis, resulting in a large amount of dissipated energy. For example, comparing... Figure 5 and Figure 6 , Figure 5 and Figure 6 respectively with Figure 3 and Figure 4 It has a similar graph, but shows the case of zero average relative velocity with additional small velocity fluctuations or vibrations. Figure 6 The line below 600 corresponds to the product. The area of ​​the region is equal to the energy dissipated during a given time period, and in this case, it is positive. That is, in the region formed by... Figure 5 and Figure 6 In the case shown, energy is transferred from high-frequency oscillations to friction via frictional contact. (This is in contrast to the previous example.) Figure 3 and Figure 4 Compared to the cases shown, this effect is considerably higher and has the expected positive or negative sign. According to... Figure 2 , Figure 5 and Figure 6 The comparison also clearly shows that the dissipated energy depends significantly on v = 0 (i.e., Figure 2 The difference between the maximum and minimum frictional forces at position 204. When v = 0, the larger the difference between the maximum and minimum frictional forces, the higher the energy dissipation. Although Figures 3 to 4 By using speed weakening properties (such as Figure 2 The frictional force or torque is generated by the characteristics shown herein, but embodiments of this disclosure are not limited to this type of characteristic. The apparatus and methods disclosed herein will be effective for any type of characteristic, provided that the frictional force or torque undergoes a step with a sign change when the relative velocity between the two interacting bodies changes its sign.

[0067] Friction dampers according to some embodiments of this disclosure will now be described. Friction dampers are installed in drilling systems (such as...) Figure 1The drilling system 10 shown is on or in, and / or part of, the drilling system 10, such as part of a bottom hole assembly 90. The friction damper element is part of the friction damper and may include two interacting bodies, such as a first element and a second element having a frictional contact surface with the first element. The friction damper of this disclosure is arranged such that the average velocity of the first element is correlated with the rotational velocity of the drilling system on which the first element is mounted. For example, the first element may have an average velocity or rotational velocity similar to or the same as that of the drilling system, such that small undulating oscillations cause... Figure 2 The sign change or zero crossing of the relative velocity between the first and second elements at point 204.

[0068] It should be noted that the friction or torque between the drilling system and the borehole wall does not generate additional damping for high-frequency oscillations in the system. This is because the relative velocity between the contact surfaces (e.g., the stabilizer and the borehole) does not have a zero average value (e.g., Figure 2 Point 202 in the document). According to the embodiment described herein, the static friction between the first and second elements is set sufficiently high such that the first element can accelerate the second element (during rotation) to an average speed v0 with the same value as the drilling system. Therefore, the additional high-frequency oscillation is based on being equal to or close to... Figure 2 Point 204 in the middle Figure 2 The oscillations around the position in the middle introduce sliding between the first and second elements at positive or negative velocities. Inertial force F I Slippage occurs when the static friction force exceeds the coefficient of static friction between the two interacting bodies, which is expressed as the coefficient of static friction between the two bodies multiplied by the normal force: F I >μ0·F N According to the implementation scheme of this disclosure, the normal force F N (For example, caused by the contact and surface pressure of the contact surfaces between two interacting subjects) and the static friction coefficient μ0 are 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.

[0069] For example, turning Figure 7A schematic diagram of a damping system 700 according to one embodiment of the present disclosure is shown. 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 drilling fluid, such as drilling mud. The damping system 700 includes a first element 710 that is operatively coupled (e.g., fixedly coupled) or integral with the downhole system 702 to ensure that the first element 710 rotates at an average speed correlated with (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, wherein a contact surface 714 is located between the first element 710 and the second element 712.

[0070] Regarding friction, the difference between the minimum and maximum friction is positively correlated with the normal force and the static friction coefficient. Energy dissipation increases with friction and harmonic displacement, but only during the sliding phase. In the viscous phase, the relative displacement between the friction interfaces and the dissipated energy are zero. The upper amplitude limit of the viscous phase increases linearly with the normal force and friction coefficient at the contact interface. This is because one of the contacting elements... Under accelerated conditions, the reactive force at the contact interface can be caused by the moment of inertia J of the contacting entity. The torque M must be higher than the limit between viscosity and slip. H =F N μ H r. As used in this article, F N It is a normal force, and μ H is the effective coefficient of friction, and r is the effective or average radius of the frictional contact area. For complex frictional contact parts with interacting subjects, both adhesion and sliding can occur simultaneously. In this paper, the contact pressure can be optimized to achieve optimal damping and amplitude.

[0071] If the contact force is caused by displacement and spring elements, a similar mechanism applies. Acceleration of the contact area. This can be attributed to the excitation of a mode and depends on the corresponding mode shape, as described below relative to... Figure 9B Further discussion. Regarding an additional inertial mass (or simply an inertial element or mass within the context of this disclosure) with a moment of inertia J, as long as the contact interface is viscous, the acceleration... This is equal to the acceleration of the excited mode and the corresponding mode shape at the additional location.

[0072] The normal force and frictional 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 the amplitude between zero and the load limit, which is given, for example, by the design specifications of the tool and component. The limit can also be given as a percentage of the expected amplitude without a damper. The dissipated energy, comparable to the energy input (e.g., by forced excitation or self-excitation), is a measure of the damper's efficiency. Another measure is the equivalent damping provided to the system, which is proportional to the ratio of the energy dissipated during one cycle of harmonic vibration in the system to the potential energy during one cycle of 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 equivalent damping and negative damping can be directly compared. The damping force provided by the damper is nonlinear and strongly dependent on the amplitude.

[0073] like Figure 20 As shown, damping occurs during the viscous phase ( Figure 20 The left end of the curve (where the relative movement between the interacting entities is zero) is zero. If, as described above, the limit between the viscous and sliding stages is exceeded by the force transmitted through the contact interface, relative sliding motion causing energy dissipation occurs. Subsequently, the damping ratio provided by frictional damping increases to a maximum and then decreases to a minimum. The amplitude that will occur depends on the excitation, which can be described by the negative damping term. In this paper, as... Figure 20 The maximum value of the damping provided must be higher than the negative damping from the self-excited mechanism. The amplitude occurring in the so-called limiting cycle can be determined by the intersection of the negative damping ratio and the equivalent damping ratio provided by the friction damper.

[0074] This curve depends on various parameters. Advantageous is a high normal force but minimal amplitude during the sliding phase. In terms of inertial mass, this can be achieved with 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, a high relative displacement is advantageous compared to the amplitude of the mode shape at the contact point, for example, along the axial axis of the BHA. Therefore, optimal damper arrangement based on high amplitude or relative amplitude is important. This can be achieved using simulation results, as discussed below. Normal force and friction coefficient can be used to shift this curve to lower or higher amplitudes, but have little effect on the maximum damping value. If more than one friction damper is implemented, this will cause… Figure 20The superposition of similar curves is shown. Adjusting the normal force and coefficient of friction to achieve the same maximum amplitude benefits the overall damping achieved. Furthermore, a slight shift in the damping curve will result in a wider curve relative to the amplitude, which is advantageous for considering the effect of shifting the amplitude to the right of the maximum value. In this case, for a self-excited system, the amplitude will increase to an extremely high value, as indicated by negative damping. In this case, the amplitude needs to be shifted again to the left of the maximum value, for example, by moving away from the bottom or reducing the rotational speed of the system to a lower level. The amplitude in this context is expressed as shown below relative to... Figure 8B The average rotational speed indicated and discussed scales approximately linearly.

[0075] Refer again Figure 7 The tubing string 704 and therefore the downhole system 702 rotate at a speed of Rotation, the speed of which can be measured in revolutions per minute (RPM). The second element 712 is mounted on the first element 710. The normal force F between the first element 710 and the second element 712 can be selected or adjusted by adjusting the application and use of element 716. N The adjusting element 716 can be adjusted, for example via a thread, actuator, piezoelectric actuator, hydraulic actuator, and / or 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. For example, as Figure 7 As shown, the adjusting 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, this 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 system 712 and the inertial mass element is selected or defined to allow sliding motion and avoid self-locking.

[0076] The second element 712 has a moment of inertia J. When an HFTO occurs during the 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., the amplitude distribution defined along the dimensions of the drilling system, drill string, and / or BHA) and the amplitude of the mode (e.g., scaling the amplitude of the mode shape). Figure 8A and Figure 8B An exemplary result of this operation is shown in the figure. Figure 8A It is a graph of tangential (i.e., circumferential) acceleration measured at the drill bit, and Figure 8B That is the corresponding rotational speed.

[0077] Due to the tangential acceleration and inertia of the second element 712, a relative inertial force occurs between the second element 712 and the first element 710. If these inertial forces exceed the threshold between viscosity and slippage, i.e., if these inertial forces exceed the static friction between the first element 710 and the second element 710, relative motion will occur between elements 710 and 712, causing energy dissipation. In this arrangement, acceleration, the coefficient of static friction and / or the coefficient of dynamic 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 element 710 and the second element 712. High acceleration and moment of inertia increase the tendency to slip at the contact surface 714, thus causing higher energy dissipation and equivalent damping ratio provided by the damper.

[0078] Energy dissipation due to frictional movement between the first element 710 and the second element 712 will generate heat and wear on the first element 710 and / or the second element 712. To keep wear below an acceptable level, wear-resistant materials may be used for the first element 710 and / or the second element 712. For example, diamond or polycrystalline diamond composite sheets may be used for at least a portion of the first element 710 and / or the second element 712. Alternatively or additionally, coatings may help reduce wear caused by friction between the first element 710 and the second element 712. 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 may be made of materials with high thermal conductivity or high heat capacity, and / or may be in contact with materials with high thermal conductivity or high heat capacity.

[0079] 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 hot greases containing fats, greases, oils, epoxy resins, 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). In addition or alternatively, one or both of the first element 710 and the second element 712 may be in contact with a fluid (such as drilling fluid) configured to remove heat from the first element 710 and / or the second element 712 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 an acceptable limit, thereby reducing wear.

[0080] When the damping system 700 is arranged, a high normal force and / or static or dynamic friction coefficient will prevent relative sliding motion between the first element 710 and the second element 712, and in such cases, no energy is dissipated. In contrast, a low normal force and / or static or dynamic friction coefficient can result in low friction, and sliding will occur, but less energy will be dissipated. Furthermore, a low normal force and / or static or dynamic friction coefficient can cause friction at the outer surface of the second element 712 (e.g., between the second element 712 and the formation 708) to be higher than that between the first element 710 and the second element 712, resulting in a relative velocity between the first element 710 and the second element 712 that is not equal to or close to zero but falls within the range of the average velocity between the downhole system 702 and the formation 708. Therefore, the normal force and static or dynamic friction coefficient, as well as the arrangement of the damper elements relative to the excited modes and mode shapes (e.g., by using the adjusting element 716), can be adjusted to achieve optimized energy dissipation.

[0081] This can be achieved by adjusting the normal force F. N The static friction coefficient μ0, the dynamic friction coefficient μ, the arrangement of damper elements relative to the excited mode shape, or a combination thereof are used to achieve this. The normal force F can be adjusted in the following ways. N The positioning adjustment element 716 and / or the actuator generates a force on one of the first and second elements, with a component perpendicular to the contact surfaces of the first and second elements, thereby adjusting the pressure state around the first and second elements, or increasing or decreasing the area of ​​pressure application. For example, increasing the external pressure acting on the second element (such as mud pressure) will also increase the normal force F. N The pressure of the downhole mud can be adjusted by regulating the mud pump on the surface (e.g., Figure 1 This can be achieved using the mud pump 34 shown or other equipment (such as bypasses, valves, fluctuation suppressors) that affects mud pressure on the surface or downhole. The normal force can be adjusted to a harmonic with the same frequency as the natural frequency of the excited mode shape, and thus has a low normal force value for low acceleration of inertial mass and a high normal force value for low acceleration of inertial mass, and thus allows sliding motion with low acceleration values.

[0082] The normal force F can 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, for example, a force in an axial direction away from or towards the first element 710. The normal force F can also be applied in a controlled manner based on input received from the sensor. NThe adjustment is as follows. For example, a suitable sensor (not shown) can provide one or more parameter values ​​to the controller (not shown), which 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 can provide an increase or decrease in the normal force F. N The controller can provide instructions, for example, to reduce the normal force F if the temperature of one or both of the first element 710 and the second element 712 exceeds a threshold temperature. N The controller provides instructions to prevent damage to one or both of the first element 710 and the second element 712 due to high temperatures. 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 can provide an increase or decrease in the normal force F. N The instructions ensure optimal energy dissipation. The normal force F can be controlled by monitoring parameter values. N To achieve the desired result within a time period. For example, controllable normal force F N To provide optimal energy dissipation while keeping the temperature of one or both of the first element 710 and the second element 712 below a threshold during or during the drilling process.

[0083] Additionally, the static or dynamic coefficient of friction can be adjusted by using 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 thereof. The materials 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 materials capable of withstanding the friction generated between the first and second elements. The inertia, coefficient of friction, and expected acceleration amplitude (e.g., varying with mode shape and eigenfrequency) of the second element 712 are parameters that determine the dissipated energy and also need to be optimized. The critical mode shape and acceleration amplitude can be determined by measurement or calculation, or based on other known methods as understood by those skilled in the art. Examples are finite element analysis, transfer matrix method, or finite difference method, and modal analysis or analytical modes based thereon. It is optimal to place the friction damper where high relative displacement or acceleration is expected.

[0084] Now turning Figure 9A and Figure 9B An example of downhole system 900 and its corresponding modes is shown. Figure 9A This is a schematic diagram of the downhole system, showing how the mode shapes of the downhole system change with distance from the drill bit. Figure 9B It shows that it can be used Figure 9A An exemplary corresponding torsional oscillation mode shape excited during the operation of a downhole system. Figure 9A and Figure 9B The schematic diagram illustrates the potential location and arrangement of one or more components of the damping system on the downhole system 900.

[0085] like Figure 9A As schematically shown, the downhole system 900 includes various components with different diameters (and different masses, densities, configurations, etc.), and therefore, during rotation of the downhole system 900, these different components can induce various modes. Exemplary modes indicate where the highest amplitude will exist, which may require damping by applying a damping system. For example, as... Figure 9B As shown, mode shapes 902, 904, and 906 of a first torsional oscillation, a second torsional oscillation, and a third torsional oscillation of a downhole system 900 are illustrated. Based on knowledge of mode shapes 902, 904, and 906, the location of the first element of the damping system can be optimized. Damping may be required and / or implemented when the amplitudes of mode shapes 902, 904, and 906 are at their maximum values ​​(peak values). Therefore, two potential locations for attaching or mounting the damping system of this disclosure are exemplarily shown.

[0086] For example, the first damping position 908 is close to the drill bit of the downhole system 900 and primarily dampes the first and third torsional oscillations (corresponding to modes 902 and 906) and provides some damping for the second torsional oscillation (corresponding to mode 904). That is, the first damping position 908 is approximately at the peak of the third torsional oscillation (corresponding to mode 906), close to the peak of the first torsional oscillation mode 902, and approximately halfway to the peak of the second torsional oscillation mode 904.

[0087] The second damping position 910 is arranged to again primarily provide damping for the third torsional oscillation mode 906 and some damping for the first torsional oscillation mode 902. However, in the second damping position 910, damping of the second torsional oscillation mode 904 does not occur because the second torsional oscillation mode 904 is close to zero at the second damping position 910.

[0088] Despite Figure 9A and Figure 9B Only two locations are shown for arranging the damping system of this disclosure, but the implementation is not so limited. For example, any number and arrangement of damping systems can be installed along the downhole system to provide torsional vibration damping to the downhole system. Examples of preferred installation locations for the dampers are where one or more of the mode shapes are expected to exhibit high amplitudes.

[0089] Due to the high amplitude at the drill bit, a good location for a damper, for example, is close to or even inside 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, multiple bodies (multi-body) first or second elements (e.g., friction dampers) can be used, where each body has the same or different normal force, coefficient of friction, and moment of inertia. Such a multi-body element arrangement can be used, for example, if it is uncertain which mode shape and corresponding acceleration are expected at a given location along the downhole system.

[0090] For example, two or more component bodies can be used to dissipate energy by achieving different relative sliding motions between them. The multiple bodies of the first component can be selected and assembled using different static or dynamic coefficients of friction, angles between contact surfaces, and / or may have other mechanisms affecting the amount of friction and / or the transition between viscosity and sliding. Such configurations can be used to dampen several amplitude levels, excited mode shapes, and / or natural frequencies.

[0091] For example, turning Figure 10 A schematic diagram of a damping system 1000 according to one embodiment of the present disclosure is shown. The damping system 1000 can be compared with the above-described damping system. Figure 7 The damping system 1000 operates in a similar manner to that 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, mounted to the first element 1010 of 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, allowing them to operate independently of each other (e.g., move) or not to interact directly with each other. In this embodiment, the first body 1018 has a first static friction coefficient or dynamic friction coefficient μ1 and a first force F perpendicular to the first contact surface 1022. N1 The second body 1020 has a second static friction coefficient or dynamic friction coefficient μ2 and a second force F perpendicular to the second contact surface 1024. N2 Furthermore, 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 and the first normal force F... N1At least one of the first moment of inertia J1 is chosen to be different from the second static friction coefficient or dynamic friction coefficient μ2 and the second normal force F. N2 And the second moment of inertia J1. Therefore, the damping system 1000 can be configured to take into account multiple different mode shapes at essentially a single location along the downhole system 1002.

[0092] Turn now Figure 11 A schematic diagram of a damping system 1100 according to one embodiment of the present disclosure is shown. The damping system 1100 can operate in a manner similar to that shown and described above. However, in this embodiment, the second element 1112 installed to the first element 1110 of the downhole system 1102 is formed by a first body 1118, a second body 1120, and a third body 1128. The first body 1118 has a first contact surface 1122 between the first body 1118 and the first element 1110, the second body 1120 has a second contact surface 1124 between the second body 1120 and the first element 1110, and the third body 1128 has a third contact surface 1130 between the third body 1128 and the first element 1110. As shown, the third body 1128 is located between the first body 1118 and the second body 1120. In this embodiment, the three bodies 1118, 1120, and 1128 are in contact with each other, and therefore they can have a normal force and a static friction coefficient or a dynamic friction coefficient.

[0093] The contact between the three bodies 1118, 1120, and 1128 can be established, maintained, or supported by an elastic connecting element (such as a spring element) between two or more of the bodies 1118, 1120, and 1128. Alternatively, the first body 1118 may have a first static or dynamic coefficient of friction 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 dynamic friction coefficient μ2 and a second force F at the second contact surface 1124. N2 Furthermore, 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 .

[0094] Alternatively, the first body 1118 and the third body 1128 may have a fourth force F between them at the contact surface between the first body 1118 and the third body 1128. N13 and the fourth static friction coefficient or dynamic friction coefficient μ 13 Similarly, the third body 1128 and the second body 1120 may have a fifth force F between them at the contact surface between the third body 1128 and the second body 1120. N32 And the fifth static friction coefficient or dynamic friction coefficient μ32 .

[0095] Furthermore, 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 friction coefficient or dynamic friction coefficient μ1, μ2, μ3, μ 13 μ 32 Force F N1 F N2 F N3 F 13 F 32 The moments of inertia J1, J2, and J3 can be chosen to be different from each other, such that for at least a subrange of the 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 or dynamic friction coefficient and normal force between adjacent bodies can be selected to achieve different damping effects.

[0096] Although a limited number of embodiments and specific shapes, relative dimensions, and quantities of elements have been shown and described, those skilled in the art will understand that the damping system of this disclosure can take any configuration. For example, shape, size, geometry, radial arrangement, contact surfaces, number of bodies, etc., can be selected to achieve the desired damping effect. Although in Figure 11 In the arrangement shown, the first body 1118 and the second body 1120 are connected to each other through frictional contact with the third body 1128; however, such arrangement and description are not limiting. The connection between the first body 1118 and the second body 1120 can also be achieved by hydraulic, electrical, or mechanical coupling devices or mechanisms. For example, the mechanical coupling between the first body 1118 and the second body 1120 can be achieved by a rigid or elastic connection between the first body 1118 and the second body 1120.

[0097] Turn now Figure 12 A schematic diagram of a damping system 1200 according to one embodiment of the present disclosure is shown. The damping system 1200 can operate in a manner similar to that shown and described above. However, in this embodiment, a second element 1212 of the damping system 1200 is partially fixedly attached to or connected to a 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 frictional contact with the first element 1210 relative to the first element 1210). Figure 10The first element 1010 and the second element 1012 are in frictional contact (described).

[0098] Movable parts 1234 can have the ability to interact with Figure 9B The movable portion may be longer than one-tenth the distance between the maximum and minimum values ​​of any modal vibration mode 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 the distance between the maximum and minimum values ​​of any modal vibration mode that may have been calculated for a particular drilling assembly. In yet another example, in some embodiments, the movable portion may be longer than half the distance between the maximum and minimum values ​​of any modal vibration mode that may have been calculated for a particular drilling assembly. In yet another example, in some embodiments, the movable portion may be longer than the distance between the maximum and minimum values ​​of any modal vibration mode that may have been calculated for a particular drilling assembly.

[0099] Therefore, even if the exact location of the modal maximum or minimum may not be known during downhole deployment, it can be 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 a specific arrangement is used to illustrate, those skilled in the art will understand that other arrangements of the partially fixed first element are possible without departing from the scope of this disclosure. For example, in a non-limiting embodiment, the fixed portion may be located in a more central part of the first element, such that the first element has two movable portions (e.g., at opposite ends of the first element). Figure 12 As can be seen, the movable portion 1234 of the second element 1212 is quite elongated and can cover the modal vibration modes (such as) corresponding to the length of the movable portion 1234 of the second element 1212. Figure 9B Part of the modal modes 902, 904, 906. An elongated second element 1212 that is in frictional contact with the first element 1210 is preferable to a shorter second element because a shorter second element can be located in an undesirable portion of the modal mode, such as in a damped position 910 where the second modal mode 904 has little or even zero damping, as described above relative to... Figure 9B As explained, the use of the elongated second element 1212 ensures that at least a portion of the second element is located at a certain distance from a position where one or more of the modal modes are zero or at least close to zero. Figures 13 to 19 and Figures 21 to 22Further examples of elongated second elements that frictionally contact the first element are shown. In some embodiments, the elongated second element may be elastic, such 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 may have multiple contact points at multiple locations on the first element 1210.

[0100] In the above embodiments, and in the damping system according to this 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, the first element (or a portion thereof) moves relative to the second element, thus providing damping. That is, when the HFTO increases within the downhole system to above a predetermined threshold (e.g., a threshold for amplitude, distance, velocity, and / or acceleration), the damping system will operate automatically, and therefore the embodiments provided herein include passive damping systems. For example, embodiments include passive damping systems that operate automatically without utilizing additional energy, thus eliminating the need for additional energy.

[0101] Turn now Figure 13 A schematic diagram of a damping system 1300 according to one embodiment of the present disclosure is shown. In this embodiment, the damping system 1300 includes one or more elongated first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f, each elongated first element disposed within and in contact with a second element 1312. Each of the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f may be positioned in the axial tool direction (e.g., in relation to...). Figure 13 The cross-section shown has a length (vertical direction) and optionally fixed points, at which corresponding first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f are fixed to the second element 1312. For example, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, 1310f can be fixed at the corresponding upper end, middle portion, lower end, or multiple fixed 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. Furthermore, as... Figure 13As shown, the first elements 1310a, 1310b, 1310c, 1310d, 1310e, and 1310f may optionally be biased or engaged 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, and 1310f may be arranged and selected to have the same or different normal force, static friction coefficient or dynamic friction coefficient, and moment of inertia, thereby achieving various damping configurations.

[0102] 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, refer to Figure 14 A schematic diagram of a damping system 1400 according to an embodiment of the present disclosure is shown. 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 helical arrangement relative to the second element 1412. Thus, in some embodiments, the geometry or shape of the first element or a portion of the second element may change along its length relative to the second element, and such changes may also occur in the circumferential span around or relative to the second element and / or relative to the tool body or downhole system.

[0103] Turn now Figure 15 A schematic diagram of another damping system 1500 according to one embodiment of the present disclosure is shown. In the damping system 1500, a first element 1510 is a toothed (threaded) body that mates 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 provides 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. Furthermore, the movement of the first element 1510 in the axial or circumferential direction will also produce circumferential or axial movement in this configuration, respectively. Therefore, utilizing Figure 15 The arrangement shown allows axial vibration to be used to reduce torsional vibration or to dampen torsional vibration, and torsional vibration to be used to reduce axial vibration or to dampen axial vibration.

[0104] The locations where axial and torsional vibrations occur can differ. For example, while axial vibrations can be uniformly distributed along the drilling assembly, torsional vibrations can follow the patterns described above relative to... Figures 9A to 9B The modal vibration modes are discussed. Therefore, regardless of where the vibration occurs, Figure 15The configuration shown can be used to dampen torsional vibrations by using the movement of the first element 1510 relative to the second element 1512 caused by axial vibration (and vice versa). As shown, an optional fastening element 1540 (e.g., a bolt) can be used to adjust the contact pressure or normal force between the two elements 1510, 1512, thus adjusting the friction and / or other damping characteristics of the damping system 1500.

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

[0106] Turn now Figure 17 A schematic diagram of a damping system 1700 according to one embodiment of the present disclosure is shown. The damping system 1700 includes a first element 1710 frictionally attached or connected to a second element 1712, the second element being arranged as a rigid rod and fixedly connected (e.g., by welding, screwing, brazing, adhesion, etc.) to an outer tube 1714, such as a drill collar, at a fixed connection 1716. In one aspect, the rod may be a tube comprising electronic components, power supplies, storage media, batteries, microcontrollers, actuators, sensors, etc., susceptible to wear due to HFTO. That is, in one aspect, the second element 1712 may be a probe, such as a probe for measuring orientation information, including one or more of a gravimeter, gyroscope, and magnetometer. In this embodiment, the first element 1710 is arranged to frictionally contact the fixed rod structure of the second element 1712, and to move or oscillate relative to and along the fixed rod structure, thus providing damping as described in the embodiment of the present disclosure. While the first element 1710 is in Figure 17 The element 1710 is shown as relatively small compared to the damping system 1700, but this is not intended to be limiting in this respect. Therefore, the first element 1710 can be of any size and can have the same outer diameter as the damping system 1700. Furthermore, the position of the first element 1710 can be adjustable to move it closer to the maximum modal value, thereby optimizing damping reduction.

[0107] Turn now Figure 18 A schematic diagram of a damping system 1800 according to one embodiment of the present disclosure is shown. The damping system 1800 includes a first element 1810 that is frictionally movable along a second element 1812. In this embodiment, the first element 1810 is arranged to have an elastic spring element 1842 (such as a coil spring or other element or device) to engage the first element 1810 with the second element 1812, thus providing a restoring force when the first element 1810 has moved and deflected relative to the second element. This restoring force is directed to reduce the deflection of the first element 1810 relative to the second element 1812. In such embodiments, the elastic spring element 1842 may be arranged or tuned to the resonant and / or critical frequency (e.g., the lowest critical frequency) of the oscillating system including the first element 1810 and the elastic spring element 1842.

[0108] Turn now Figure 19 A schematic diagram of a damping system 1900 according to one embodiment of the present disclosure is shown. The damping system 1900 includes a first element 1910 that is frictionally movable about 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 The first end static friction coefficient or dynamic friction coefficient μ i and the first moment of inertia J i ), and has a second contact at the second end 1910b (e.g., the normal force F at the second end). Ni The second end static friction coefficient or dynamic friction coefficient μ i Second end moment of inertia 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 may have different physical characteristics. For example, one or both of the first end 1910a and the second end 1910b may have viscous contact / engagement, and one or both may have sliding contact / engagement. The arrangement / construction of the first end 1910a and the second end 1910b may be configured to provide damping as described in embodiments according to this disclosure.

[0109] Advantageously, the embodiments provided herein relate to systems for mitigating high-frequency torsional oscillations (HFTO) in downhole systems by applying a damping system mounted on a rotating drill string (e.g., the drill string). A 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 about the axis of the drill string). In some embodiments, a second element may be part of the drilling system or a bottomhole assembly and does not need to be a separately installed component or weight. The second element, or a portion thereof, is connected to the downhole system in such a way that 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) in the absence of HFTO. 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 remainder of the downhole system providing the functions described herein) and there is friction between the first and second elements.

[0110] As described above, the second element of the damping system is selected or configured such that when there is no vibration in the drill string (i.e., HFTO), the second element is frictionally connected to the first element via static friction. However, when vibration (HFTO) is present, the second element moves relative to the first element and as described above relative to... Figure 2 As described, the frictional contact between the first and second elements is reduced, allowing the second element to rotate (move) relative to the first element (and vice versa). During movement, the first and second elements dissipate energy, thereby mitigating HFTO. The damping system, particularly its first element, has a specific position, weight, external force, and size to achieve damping at one or more specific or predefined vibration modes / frequencies. As described herein, the first element is fixedly connected in the absence of HFTO vibration, but is subsequently able to move in the presence of certain accelerations (e.g., according to the HFTO mode), thus achieving HFTO damping through zero-crossing of 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 of the damper and the energy dissipated. For example, measurements of displacement, velocity, and / or acceleration near the contact point or surface of the two interacting bodies, in conjunction with force or torque sensors, can be used to estimate relative motion and calculate the 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 also be known without measurement. The dissipated energy can also be derived from temperature measurements. Such measurements can be transmitted to a controller or operator, allowing adjustment of parameters such as normal force and / or the coefficient of static or kinetic friction to achieve higher energy dissipation. For example, measured and / or calculated values ​​of displacement, velocity, acceleration, force, and / or temperature can be sent to a controller (such as a microcontroller) having a set of instructions stored in a storage medium, based on which the controller adjusts and / or controls at least one of the force and / or the coefficient of static or kinetic friction that engages the two interacting bodies. Preferably, the adjustment and / or control are performed during the drilling process to achieve optimal HFTO damping results.

[0112] Although the embodiments described herein have been described with reference to specific accompanying drawings, it should be understood that various changes may be made and equivalents may be substituted for elements therein without departing from the scope of this disclosure. Furthermore, many modifications will be made to adapt particular apparatus, situations, or materials to the teachings of this disclosure without departing from the scope of this disclosure. Therefore, it is contemplated that this disclosure is not limited to the specific embodiments disclosed, but rather will include all embodiments falling within the scope of the following description of the appended claims or possible embodiments.

[0113] Severe vibrations in the drill string and downhole assembly can be caused by cutting forces at the drill bit or mass imbalances in downhole tools (such as drill motors). Among other negative effects are reduced drilling rates, decreased measurement quality, and downhole malfunctions.

[0114] Different types of torsional vibrations exist. In the literature, torsional vibrations are mainly distinguished as viscous / slippage throughout the drilling system and high-frequency torsional oscillations (HFTO). Both are primarily excited by self-excitation mechanisms arising from the interaction between the drill bit and the formation. The main difference between viscous / slippage and HFTO is the frequency and typical mode shape: HFTO has frequencies above 50 Hz, compared to frequencies below 1 Hz for viscous / slippage. Furthermore, the excited mode shape of viscous / slippage is the first mode shape throughout the drilling system, while the mode shape of HFTO is typically confined to a small portion of the drilling system and has a relatively high amplitude at the drill bit.

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

[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 discuss the design principle that they believe is most suitable for damping caused by friction. Damping should be achieved by frictional force, wherein the operating point of the frictional force relative to the relative velocity must be... Figure 2 The area around point 204 is shown. This operating point experiences high energy dissipation due to the implementation of frictional hysteresis, while... Figure 2 Point 202 will cause energy 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 contact surfaces (e.g., the stabilizer and the borehole) does not have a zero average value. The two interacting bodies of a friction damper must have an average velocity or rotational velocity relative to each other that is small enough that the HFTO causes a sign change in the relative velocity of the two interacting bodies. 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 first and second elements of the damper. Sliding occurs when the inertial force exceeds the limit between viscosity and sliding (i.e., static friction): F R >μ0·F N (Where static friction equals the static friction coefficient multiplied by the normal force between the two contact surfaces). The normal force and / or the static or dynamic friction coefficient can be adjusted to achieve optimal or desired energy dissipation. Adjusting at least one of the normal force and the static or dynamic friction coefficient can improve energy dissipation caused by the damping system.

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

[0121] An equivalent can be used as the friction damper of this disclosure. A drill collar 2100 with a slot can be used, such as... Figure 21 and Figure 22 As shown. Figure 22 A cross-sectional view of a slotted drill collar 2100 is shown. In a non-limiting embodiment, the slotted drill collar 2100 has high flexibility or low stiffness and will cause higher deformation without the addition of a friction device 2102. Higher speed will cause higher centrifugal force, which will push the friction device 2102 into the slot under optimized normal force to allow for high frictional damping. Other factors that can be optimized in this configuration are the number and geometry of the slots and the geometry of the damper. The additional normal force can be provided by spring elements (such as those discussed above) Figure 22 (as shown), actuator and / or applied by centrifugal force.

[0122] The advantage of this principle is that the friction devices 2102 will be directly integrated into the force flow. The torsion of the drill collar caused by the excited HFTO mode and the corresponding mode shape will be partially supported by the friction devices 2102, which will move up and down during one cycle of vibration. The high relative motion, along with the optimized friction coefficient and normal force, will result in high energy dissipation.

[0123] The objective is to prevent an increase in the amplitude of the HFTO (in this case, represented by the tangential acceleration amplitude). The (modal) damping that must be added by friction dampers to each unstable torsional mode requires a higher energy input to the system. This energy input does not occur instantaneously but over multiple cycles until the worst-case amplitude (zero RPM at the drill bit) is reached.

[0124] According to this concept, a relatively short drill collar can be used because the friction damper utilizes relative motion along the distance from the drill bit. A high tangential acceleration amplitude is not required; only some deflection (“torsion”) of the drill collar is needed, which will be achieved in almost every place along the BHA. The drill collar and damper should have a mass-stiffness ratio (“impedance”) similar to that of the BHA. This will allow the mode shape to propagate in the friction drill collar. High damping will be achieved, which will alleviate the HFTO by adjusting the parameters discussed above (normal force due to springs, etc.). An advantage compared to other friction damper principles is that the friction device is directly applied to the force flow of the HFTO mode deflection. The relatively high relative velocity between the friction device and the drill collar will cause high energy dissipation.

[0125] The damper will be highly efficient and effective for various applications. HFTO (High-Frequency Friction Tolerance) causes high costs due to extensive repair and maintenance work, reliability issues accompanied by non-productive time, and a small market share. The proposed friction damper will operate both below (decoupling the HFTO) and above the motor. It can be installed in every location within the BHA (Body Harness), and if the mode shape propagates to that point, this will also be included in the arrangement above the BHA. If the mass and stiffness distributions are relatively similar, the mode shape will propagate throughout the entire BHA. The optimal arrangement can be determined, for example, by a torsional oscillation advisor, which allows for the calculation of critical HFTO modes and corresponding mode shapes.

[0126] Furthermore, as mentioned above, due to the high amplitude at the drill bit, one location of the damper, as described herein, can be within the drill bit. That is, according to some embodiments of this disclosure, the damper can be integrated into the drill bit or other fracturing device and become part of that drill bit or other fracturing device. In such embodiments, the distance to the drill bit is zero or substantially zero.

[0127] In some such embodiments, the damper may be formed by a mass or inertial element connected to the drill bit or tubing damper element solely by a damping force or damping torque. The damping force may be, for example, but not limited to, viscous damping, frictional damping, hydraulic damping, magnetic damping (e.g., eddy current damping), piezoelectric (shunt) damping, etc. In some such embodiments, the damper may be combined with a spring that will enable a tuned damper (e.g., a tuned friction damper). In these cases, the damper's resonant frequency will be tuned to the resonant frequency of the mode to be damped. The damper may be mounted anywhere in or on the BHA, except when installed inside or on the drill bit (i.e., at the end of the downhole tubing), and thus arranged close to the end of the downhole tubing.

[0128] As mentioned above, the placement of vibration damping equipment along the drill string affects vibration damping efficiency. Typical HFTO modes have several nodes and maxima along the BHA section of the drill string because these modes are high-order. Placing a vibration damper that responds to vibration amplitude at locations with low or no mode shape (node) amplitudes inside or on top of the BHA can result in inefficient damping of the corresponding mode. However, placing the damper at the local maxima of the mode to be damped produces higher damping for that mode, as described above.

[0129] According to some embodiments of this disclosure, drill string elements (hereinafter referred to as "modal-mode tuning elements") having a predetermined or selected length and / or diameter can be used to increase the local maximum amplitude at specific locations of modal modes (such as mass-normalized modal modes). Such amplification can increase the damping effect. That is, intentional and specific modifications to the drill string and / or BHA can enable control over the location and amplitude of the local maximum values ​​of modal modes (such as mass-normalized modal modes), thereby controlling and / or enhancing the damping effect, which can be achieved as described above in the case of including modal-mode tuning elements.

[0130] For example, through modeling or other software, modal tuning elements can be selected individually to achieve damper improvement or optimal positioning for a single BHA assembly. Such modeling or software can be used to achieve customized design properties of the modal tuning elements (e.g., dimensions such as length or diameter, material and / or mechanical properties such as stiffness, flexibility, weight, moment of inertia, density, or elastic modulus (shear and volumetric strain)) and positioning / location and / or positioning / positioning of one or more damping elements. Furthermore, in some embodiments, the software / modeling can be configured to draw from a pool of specific pre-configured modal tuning elements (e.g., such as...). Figure 29A (As shown) or a list can be selected for use in combination with one or more damping elements. Software / modeling can also be used to generate and optimize the pool of modal-mode tuned elements. In addition to customizing the length and diameter of the modal-mode tuned elements, density, shape, elastic modulus (shear and volumetric strain), and / or other parameters affecting the flexibility or inertia of the tubular column and / or BHA can be predetermined to control the local maximum amplitude.

[0131] HFTO damping and, in particular, the placement of devices for improving or optimizing HFTO damping are relatively new technologies. The basic theory is published in Hohl et al. (2015): “Derivation and experimental validation of ananalytical criterion for the identification of self-excited modes in drilling systems,” *Journal of Sound and Vibration*, 342, pp. 290–302, the full text of which is incorporated herein by reference. One approach to modal-mode tuning is to minimize vibrations at certain locations in the BHA and reduce excitability S. c(For example, the minimum slope of the torque characteristic for a slightly stable system) is disclosed in U.S. Patent No. 9,976,405, published May 22, 2018, entitled "Method to mitigate bit-induced vibrations by intentionally modifying mode shapes of drill strings by mass or stiffness changes," the contents of which are incorporated herein by reference. However, the artificial maximization of the amplitude of the mode shape at the actual location of the damping element is not disclosed. For example, the use of a modal-mode tuning element as provided herein can be used to amplify or even maximize the mode shape at a particular location, and thus make it possible to improve the efficiency of HFTO damping. Examples of modal-mode tuning elements may be combinations of both, such as torsional soft elements (e.g., flexure tubes) and / or high-inertia components (e.g., heavy-duty segments), or various lengths for amplifying the amplitude of the mode shape at the location of the damping element (e.g., the damping element described above and below).

[0132] Placing dampers at arbitrary locations along the drill string is one approach, but such arbitrary placement can lead to inefficient damping. Such arbitrary placement can be chosen based on specific BHA or other string properties / characteristics, allowing the dampers to be placed at locations feasible considering other string characteristics. This inefficient damping effect results in damping being significantly below its maximum value at most locations (e.g., at locations where the modal modes (such as the mass-normalized modal modes shown and described above) are not at their maximum values). This leads to essentially random positioning of the damping element, resulting in relatively low damping efficiency.

[0133] Besides positioning the damper at an inefficient location, there are typically more than one HFTO mode during drilling operations. Each mode has a corresponding characteristic frequency and mode shape, and different local maxima and minima (depending on wavelength). If more than one HFTO mode is likely to occur (which is often the case), it is preferable that all (or most) modes be adequately damped.

[0134] Figure 23 The diagram shows the mass-normalized mode shape (top plot) and normalized damping (normalized to the maximum damping value at distance = 0 from the drill bit) (bottom plot) of some exemplary BHA HFTO modes at distances from the drill bit. Figure 23The top curve plot shows that for this BHA, at least four modes are generated corresponding to frequencies of 162Hz, 216Hz, 270Hz, and 324Hz. The maximum and minimum values ​​of the four modes are located at different locations. For example, the first maximum value of the 324Hz mode is at a distance of approximately 10m from the drill bit, while the first maximum value of the 270Hz mode is at a distance of approximately 6m from the drill bit. As shown, except for the drill bit (distance 0), the damping varies with distance from the drill bit, but is always less than 25% of the maximum damping and is therefore quite small. Therefore, embodiments of this disclosure involve optimizing the placement of one or more dampers at effective locations along the top of the BHA or preferably at the top of the BHA to effectively dampen or reduce all BHA HTFO modes. For example, depending on the position of one or more dampers relative to the BHA (e.g., if one or more dampers are located outside the BHA or at the top or bottom of the BHA), it is advantageous to use damper elements or damper element shorts that do not have electrical connections and / or damper elements or damper element shorts that are not connected from the top wire of the damper element or damper element short to the bottom wire.

[0135] The embodiments of this disclosure relate to the placement of dampers and the tuning of mode shapes to obtain acceptable damping for all modes that may occur during drilling with a specific BHA equipment. To capture all potential mode shapes, the damper elements are not necessarily placed at the maximum position for each mode, but rather at positions exhibiting acceptable amplitudes for producing adequate damping of the mode shapes. Therefore, a trade-off is defined across all modes and locations, as well as the selection of applicable mode-mode tuning elements (e.g., flexible and heavyweight sections) to amplify local maxima and concentrate them at certain locations. Under assumptions of susceptibility or severity of certain modes, certain modes can be weighted to optimize the damping of selected or target modes.

[0136] Go to Figures 24A to 24C The diagram illustrates the placement of dampers on the drill string and / or BHA. Figures 24A to 24C This indicates the placement of a single damper in a single HFTO mode. However, it should be understood that the described process can be applied to any number of damper elements and modes. Figure 24A In this study, a random placement of the damper is employed, and this random placement achieves only about 20% of the maximum possible damping D at the optimal position of the damper in a non-optimal BHA (e.g., a BHA in which dimensions such as length or diameter, material and / or mechanical properties such as stiffness, flexibility, weight, moment of inertia, density, or elastic modulus (shear and volumetric strain), and location / position is not optimized). Although the modal mass-normalized deflection is only slightly less than 50% compared to the optimal positioning, the resulting damping is due to the positioning of mode i and position j (mass-normalized mode shape). The quadratic effect of the damping effect (D and) (Proportional) but significantly smaller. Such a relationship is described in U.S. Patent No. 9,976,405, which is combined above.

[0137] One method to optimize damper placement is to vary the lengths of various drill string elements near the damper. For example, by lengthening the tubing, the damper can be moved toward the maximum value of the mode shape. Figure 24B (as shown in the diagram), thus resulting in increased damping effect (i.e., optimal position within the initial BHA). The length of the element can be increased by including one or more modal-tuning elements in the string and / or replacing conventional string elements with modal-tuning elements. The resulting damping can achieve up to 100% efficiency (i.e., complete damping of a given HFTO mode attributable to the placement of the damper and modal-tuning / offset caused by the modal-tuning elements).

[0138] In addition to length variations, one or more modal-mode tuning elements can be used to alter the moment of inertia of the drill string. This allows for the localized increase of modal amplitudes by combining soft and high-inertia drill string components. Figure 24C The diagram illustrates the position of the damper within the BHA when the lengths and diameters of the two components are changed (i.e., replaced by modal-tuned elements). This position results in 140% of the maximum damping of the BHA without modal-tuned elements, relative to dimensions such as length or diameter, material and / or mechanical properties such as stiffness, flexibility, weight, moment of inertia, density, or elastic modulus (shear and volumetric strain), and without optimized positioning / location. In other words, using modal-tuned elements with specific component lengths and diameters for position optimization relative to a given modal maximum value, exceeding 100% of the maximum damping is possible.

[0139] The modal-mode tuning element disclosed herein can locally alter the properties of the drill string and / or BHA. The modal-mode tuning element can be used as an add-on to the drill string or as a replacement for typical drill string or BHA components. The modal-mode tuning element allows selection of diameter, length, density, elastic modulus, material, geometry, cross-sectional geometry, etc., to tune or shift the modal shape, and thus enables the use of dampers at specific locations to result in maximum damping efficiency. The use of the modal-mode tuning element can result in a change in the modal shape (e.g., amplitude) of one mode, several modes (e.g., for a critical mode), or all modes, and (e.g., at the drill bit) the entire mode, at the damper location. Furthermore, the use of the modal-mode tuning element can change the frequency of one mode, several modes, or all modes (e.g., the mode can become critical or non-critical). Furthermore, modal-mode tuning elements can alter the excitability of one, several, or all modes (e.g., a mode can become critical or non-critical). For example, a combination of a torsional soft modal-mode tuning element (e.g., a flexible tube) with high-inertia components of various lengths (e.g., heavy-duty sections) can amplify the amplitude of the modal at the location of the damping element.

[0140] For this reason, the optimization method of this disclosure can be used to determine the damping achieved by one or more dampers relative to various modes. By changing local components (e.g., replacing components with one or more mode-mode tuning elements), not only is the damping effect affected by placement, but also the excitability of the critical modes.

[0141] Optimization methods that can be employed according to embodiments of this disclosure may include analyzing / calculating / simulating (e.g., numerically simulating) one or more HFTO modes of the BHA or drilling system to determine the maximum value of the mode shape or damping efficiency. In a second step, dampers and / or mode-mode tuning elements with given characteristics may be selected. Such characteristics may include, but are not limited to, dimensions such as length or diameter, material properties and / or mechanical properties such as stiffness, flexibility, weight, moment of inertia, density, or elastic modulus (shear and volumetric strain). The location where the damper and / or mode-mode tuning element will be added to the BHA to produce a modified BHA will be selected. In a next step, the modified BHA will be analyzed / calculated / simulated (e.g., numerically simulating) to estimate one or more HFTO modes of the modified BHA in order to determine the maximum value of the modified mode shape or the modified damping efficiency. If the modified BHA meets the criteria (e.g., pre-selected criteria, such as thresholds related to maximum mode shape, excitability, modal derivative, damping efficiency, or the difference in amplitude between two mode shapes), then the modified BHA can be used to drill the borehole section into the formation. Otherwise, the modified BHA can be further modified by adding / removing / moving dampers and / or modal-mode tuning elements with given characteristics until the criteria are met. Therefore, the advantageous placement and selection of dampers and modal-mode tuning elements can be determined through an iterative process.

[0142] In additional or alternative embodiments, the favorable placement and selection of dampers and modal-mode tuning elements can be determined by (numerical) inversion methods. Such inversion methods may include, for example, automatic or semi-automatic inversion methods. Furthermore, in additional or alternative embodiments, the favorable placement and selection of dampers and modal-mode tuning elements can be determined by optimization methods, which may include, but are not limited to, gradient-based optimization. Such gradient-based optimization may include Neldermead. Other possible optimization methods include Monte Carlo simulation, Levonburg-Marquardt optimization, genetic algorithms, simulated annealing, minimum square algorithm, ant colony optimization algorithm, conjugate gradient method, Krylov subspace method, biconjugate gradient method, or any other optimization method as will be understood by those skilled in the art. The optimization criterion or penalty function is primarily set to maximize damping, but can be constrained optimization using geometric factors or a set of predefined modal-mode tuning elements or other constraints. Advantageously, a mode, several modes, or all modes can be weighted during optimization by a weighting factor or weighting function, for example, to determine the optimization criterion or penalty function. It should be understood that, for design applications / configurations, both modal-mode tuning and the location and effects of damping elements can be considered.

[0143] Turn now Figure 25 The diagram shows the mode shapes of four (4) modes and the normalized minimum damping. (The diagram is used to illustrate...) Figure 25In the configuration, one or more modal-mode tuning elements are used in the BHA to offset or change the location of the maximum value (e.g., with...). Figure 23 (Compared to the positions shown). Figure 25 As shown, at a distance of approximately 7.5 m from the drill bit, the minimum normalized damping of over 60% can be determined for all modes. Therefore, this location is ideal for dampers to stabilize all modes. That is, by using modal-mode tuning elements, the positions of the maximum values ​​for multiple different modes can be substantially aligned, allowing one damper (or several dampers) to reduce the HFTO of the string.

[0144] In addition, still refer to Figure 25 If two dampers are installed in the drill string instead of one, the position 18m from the drill bit can also be considered a good position due to the alignment of different maximum values. However, the minimum normalized damping at the new position (18m) can be small compared to the damping at the 7.5m position, and the combination of the two positions provides improved damping compared to a single damping system. Two modes (one at 218Hz and one at 263Hz) have high mode shape deflection at 7.5m, and two modes (160Hz and 317Hz) have high mode shape deflection at 18m. Therefore, placing the damper elements at 7.5m and 18m from the drill bit results in all modes being damped.

[0145] To enable modal tuning, one or more structural elements can be added to the drill string or BHA, or can be used to replace typical / conventional parts with modified parts as modal tuning elements. That is, by including one or more modal tuning elements, the tool string (i.e., drill string plus BHA) can be customized such that one or more maximum values ​​associated with HFTO can be offset in position, and multiple different maximum values ​​can be offset to or near a single location, allowing a single damper element to be used to dampen different modes or orders of HTTO. The modal tuning element may include, for example, a pipe section with selected or predetermined length, diameter, and / or geometry, attached to the drill string near the BHA. This modal tuning element can add additional weight and / or flexibility (or non-flexibility) to the drill string at the location where it is connected, thereby changing the maximum value of the system's HTTO (and offsetting that maximum value). Based on this offset, damper elements can be installed to dampen one or more selected HFTO modes.

[0146] Advantageously, modal tuning elements added to sections of the drill string, outside the BHA, at the BHA, in the middle, or above can be used to offset the position of the HFTO maximum and enable one or more damper elements to provide improved damping efficiency. The position of the modal tuning element relative to the BHA advantageously allows the use of modal tuning elements without electrical connections and / or modal tuning elements not connected from the top line to the bottom. The performance of the actual damper elements can be significantly increased by including modal tuning elements, which in turn can lead to the need for fewer damper elements. Furthermore, such optimization or increased efficiency can result in the use of smaller and / or cheaper damper elements and better damping across a wide range of modes.

[0147] It should be understood that embodiments of this disclosure do not merely relate to improving the position of the damper relative to a specific mode shape. That is, embodiments of this disclosure relate to altering the properties of drill string elements and / or compositions within or near the BHA. Such modifications improve the performance of the installed damper based on the positioning and modification of the mode shape (i.e., mode-mode tuning, adjustment, and / or offset). Improved damping (e.g., exceeding 100%) can be achieved for one or more HFTO modes by changing one or more characteristics or properties of the drill string (e.g., length, diameter, density, geometry, etc.).

[0148] Turning Figures 26A to 26B The illustration shows a downhole string 2600 with two dampers. Figure 26A This is a structural schematic diagram of a 2600mm downhole tubing string, and... Figure 26B The diagram illustrates a modified or tuned mode shape achieved by incorporating modal-mode tuning elements 2602. As shown in the figure, in this embodiment, two damper elements 2604 are illustrated, positioned at the maximum offset, allowing multiple HFTO modes to be damped by the damper elements 2604. In this illustration, the downhole string 2600 represents a sample BHA on which damper elements 2604 are mounted. The BHA is subjected to a critical vibration environment, and therefore damping of such vibrations is advantageous. For all BHA configurations, the maximum damping impact placement of the damper elements 2604 requires only a few modal-mode tuning elements 2602 (e.g., flexible and heavyweight sections).

[0149] According to some embodiments of this disclosure, a specific response to all HFTO modes can be permanently achieved by using certain components (e.g., modal-mode tuning elements, specific damper elements, isolator elements, etc.). For example, isolator elements are shown and described in co-owned U.S. Patent Application Publication No. 2019 / 0284882A1 entitled “Dampers for mitigation of downhole tool vibrations and vibration isolation device for downhole bottom hole assembly”, U.S. Provisional Patent Application No. 62 / 899,331 entitled “Vibration Isolating Coupler for Reducing HighFrequency Torsional Vibrations in a Drill String”, and U.S. Provisional Patent Application No. 62 / 899,332 entitled “Vibration Isolating Coupler for Attenuating Vibrations in a Drill String”, the entire contents of which are incorporated herein by reference. Furthermore, it should be understood that such modal-mode shifting and tuning are not limited to friction dampers. For example, according to some embodiments of this disclosure, a stiffness-based damping principle can be employed. The optimal location for stiffness-based damping does not depend on the amplitude of the mode shape, but rather on the derivative of the mode shape. Therefore, the difference between the amplitudes of the two modes (mode shape difference) can be considered for stiffness-based damping. The optimal solution for stiffness-based damping is at the nodes, because the relative displacement is greatest at these nodes.

[0150] As described above, in addition to increasing length and / or weight in the form of modal-mode tuning elements, the modal-mode tuning elements of this disclosure can provide other modifications to the tubing and / or BHA, such that the modal modes are shifted or tuned to specific locations, thereby enabling improvements in the efficiency of damper elements mounted on or in the tubing and / or BHA. For example, lengthening the tubing section can be used to increase the flexibility of the tubing, modified modes or geometries (other than simply changing the diameter), changes in density and / or modulus of elasticity can be made, or other properties of the tubing / BHA can be modified or customized to achieve the shift of the HFTO modal modes. Therefore, a combination of modal-mode tuning elements and damper elements can be used in downhole systems to improve the efficiency of HFTO damping and thus reduce tool vibration, and can reduce, avoid, or eliminate adverse shocks associated with tool vibration.

[0151] Turn now Figures 27 to 28A schematic diagram of damper elements 2700 and 2800 is shown. As described above, damper elements 2700 and 2800 are configured for mounting within the blades of a shredding device. Each damper element 2700 and 2800 includes a corresponding housing 2702 and 2802 for receiving and containing the components of the respective damper element 2700 and 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 and 2802 are configured for mounting into the blades of the shredding device (e.g., as shown in Figure 26).

[0152] Damping elements 2700 and 2800 each include mass elements 2704 and 2804 movably mounted within housings 2702 and 2802, respectively. Mass elements 2704 and 2804 are arranged between mounting elements 2706 and 2806 and contact elements 2708 and 2808. Mounting elements 2706 and 2806 are configured to apply forces toward contact elements 2708 and 2804 on the respective mass elements 2704 and 2804. Therefore, frictional contact can be achieved between the respective mass elements 2704 and 2804 and the contact elements 2708 and 2808. Mass elements 2704 and 2804 may be arranged within the respective housings 2702 and 2802 together with one or more limiting stops 2710 and 2810. Limiting stops 2710 and 2810 may include optional stiffness or hydraulic elements for damping the movement of mass elements 2704 and 2804.

[0153] Furthermore, limiting stops 2710 and 2810 prevent mass elements 2704 and 2804 from getting stuck in one edge of housings 2702 and 2802. Limiting stops 2710 and 2810 may be configured with springs or other elements to avoid damaging mass elements 2704 and 2804 and to push mass elements 2704 and 2804 toward a central or resting position relative to the housings. In some embodiments, optimizing the spring stiffness and / or clearance in housings 2702 and 2802 to allow movement of mass elements 2704 and 2804 within housings 2702 and 2802 may be advantageous. Damper elements 2700 and 2800 may be arranged as inserts (e.g., housings 2702 and 2802 are configured for mounting). Insertable damper elements 2700 and 2800 may be mounted such that mass elements 2704 and 2804 are positioned at a high radius relative to the axis of the drilling system to increase rotational inertia.

[0154] Mounting elements 2706, 2806 are configured to apply a normal force (e.g., a force perpendicular to mounting elements 2706, 2806 or mass elements 2704, 2804) to mass elements 2704, 2804. For example, mounting elements 2706, 2806 may be arranged as spring housings to press mass elements 2704, 2804 into contact with contact elements 2708, 2808. Furthermore, mounting elements 2706, 2806 and / or contact elements 2708, 2808 may be configured to control tangential movement of mass elements 2704, 2804 to enable damping of the HFTO. In some embodiments, mounting elements 2706, 2806 press mass elements 2704, 2804 into contact with contact elements 2708, 2808 to generate a frictional force. This frictional force may be applied, for example, by a material favorable to the coefficient of friction and the expected wear, which should be as low as possible.

[0155] According to embodiments of this disclosure, damping can be integrated into the drill bit or other locations along the string (e.g., at or in the BHA). Damping can be applied by any axial, tangential, and / or radial force or a corresponding torque capable of dissipating energy. In the case of the 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 the interaction between the drill bit and the rock. As described for frictional damping, contact surfaces with applied friction coefficients and normal forces can be optimized and / or selected to dampen one or more critical modes. In some embodiments, advantageous materials or designs can be employed 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 coefficient of friction or characteristics.

[0156] Another form of damping that can be employed is hydraulic damping. This hydraulic damping can be achieved through a system located within the drill bit inserts or arranged around the drill bit or fracturing equipment, or located in or along the BHA or downhole string. An example of a hydraulic damper is shown and described in co-owned U.S. Patent Application No. 62 / 899,291 entitled “Viscous Vibration Damping of Torsional Oscillation,” the entire contents of which are incorporated herein by reference. In some such embodiments, a viscous fluid (e.g., a viscous fluid in a chamber) can be arranged and installed in locations similar to those described above. In some such applications, the (shear) stress in the fluid between the inertial ring / mass and the drill bit / drilling system can be selected to achieve (damping) forces acting in the direction of tangential acceleration and associated harmonic shifts to dampen torsional oscillations such as HFTO. In the case of ring shear, the fluid provides a damping force between the inertial ring / mass and the drill bit. In this case, the ring may require a well-defined geometry with a closed housing and a potential gap between the ring and the housing. In hydraulic damping, the viscous damping force is sensitive to changes in the clearance and parameters of the viscous fluid. Therefore, temperature-insensitive or less temperature-sensitive fluids are preferred. Fluids with varying shear stresses that change with shear rate can be used to achieve advantageous behavior. Some such exemplary fluids include, but are not limited to, Newtonian fluids, expanding agents (e.g., shear-thickening fluids), pseudoplastics, Bingham plastics, Bingham pseudoplastic fluids, etc. Advantageously, solids can be added to the fluid to achieve dispersion behavior.

[0157] Furthermore, in some implementations, magnetic damping may be employed. Magnetic damping can be achieved using a permanent magnet (e.g., mounted on an inertial ring / mass) that allows movement relative to the coil and can be used to dampen the HFTO. Based on magnetic principles, the damping force characteristics are similar to hydraulic (e.g., eddy current) or frictional (hysteresis) forces. In some such configurations, the force will act in the direction of tangential acceleration or in any other direction capable of causing damping in the circumferential direction or the direction to be damped.

[0158] Furthermore, in some implementations, the piezoelectric damping principle can be employed to prevent torsional oscillations, such as HFTO at the drill bit or in the drill string. A piezoelectric material can be used, connected on one side to the inertial ring / mass and on the other side to a portion of the downhole string. The electrodes of the piezoelectric material can be connected to a circuit incorporating coils, resistors, and capacitors, or semi-active or active components. This combination of electrical components can be used to achieve favorable damping characteristics between the inertial ring / mass and the downhole string components. The circuit can be tuned to the system's natural frequency to act as a tuned damper (i.e., for one or more desired modes). If the piezoelectric stack deforms due to the relative forces between the inertial ring / mass and the downhole string components, the resistor can be arranged to directly dissipate energy. Additionally, the stiffness of the piezoelectric material and the inertial ring / mass can also be tuned to a specific frequency. The electrodes of the piezoelectric material can be arranged to dampen torsional vibrations. The direction of the damping force can differ from the direction of the electrodes using the favorable 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 the force), D 31 (orthogonal to the direction of the force) and D 15 (Shear stress). The arrangement of piezoelectric materials can be configured to optimize or control the connection between mechanical and electrical systems for specific modes or multiple mode shapes that are critical to HFTO. Furthermore, various different materials can be used to transmit mechanical forces or stresses or associated loads to electrical signals without departing from the scope of this disclosure.

[0159] Furthermore, internal damping and the forces of the resulting material can be used to reduce HFTO. That is, material damping can be passively achieved through the damping properties of highly damped materials. Some such materials include, but are not limited to, polymers, elastomers, rubbers, and 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 a greater damping effect.

[0160] Other damping configurations are possible without departing from the scope of this disclosure. For example, negative capacitors 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 illustrative and explanatory purposes and are not intended to be limiting. All damping principles described herein can be adjusted to act as tuned dampers by adding mechanical springs tuned to a specific frequency and by adding any type of damping. Furthermore, one or more damping principles (or other methods / mechanisms) described herein can be combined in a multi-principle configuration. For example, a ring damper or a tangential mass / inertia damper may be mounted within or attached to the blades of a fracturing device or mounted at other locations within the drill string. In addition, magnetic damping forces, hydraulic damping forces, frictional damping forces, piezoresistive damping forces, and material damping forces and principles can be combined to achieve robust damping effects, such as, for example, with respect to temperature.

[0161] As described above, one or more damper elements can be integrated into the drill bit or other fracturing equipment or integrated at other locations along the downhole string or BHA. For example, the drill bit damper can be positioned within or around the drill bit shank. In some configurations, the damper inertia ring can be lubricated by mud or covered by a sleeve design. In some configurations, a closed or uninterrupted ring can be used. In other configurations, a partial arcuate element can be assembled around the downhole string (e.g., where the ring cannot be assembled in any other way). In some such embodiments, two half-ring arcuate elements can be used. In other embodiments, depending on the specific configuration achieved, more than two ring arcuate elements can be used to form a complete hoop (circumference) structure or a structure smaller than a complete hoop (circumference).

[0162] In some implementations, a broken-ring structure may be employed, where discrete masses are arranged behind or adjacent to the drill bit's cutting edges. In another example, a complete ring structure may be arranged adjacent to the cutting edges, but the specific additional mass elements or features of the ring may be positioned relative to the specific cutting edge of the drill bit. One such example may have a relatively thick ring and a lower overall thickness at the location of the cutting edge to allow cuttings flow along the drill bit. Furthermore, such rings may be located at other locations along the downhole string (e.g., BHA).

[0163] In some embodiments, a limiting stop may be provided to prevent the inertia ring / mass from moving freely around the circumference of the drill bit. Such a limiting stop may be provided in embodiments where the mass or higher mass is located behind or adjacent to a specific cutting edge. In such cases, the limiting stop ensures that the inertia ring / mass remains in place relative to the cutting edge, or that the space in which the inertia ring / mass can move is restricted.

[0164] It should be understood that the friction damper element of this disclosure can employ radial and / or axial contact forces to achieve circumferential friction. Radial friction can be achieved through springs, pressure differentials, or through an elastic design of an inertial ring or ring segment that may have two or more housings, and can be prestressed. Axial normal force can be achieved through springs, pressure differentials, and / or the weight of the inertial ring / mass in a non-horizontal borehole. The material of the drill bit or other fracturing equipment can be steel or a matrix composite, etc. In some embodiments, bearings can be used in the radial direction to ensure movement of the inertial ring / mass. That is, bearings can be provided to support circumferential or tangential movement of the damper element. Axial bearings can be used to decouple the potential normal force spring stack from rotational movement.

[0165] In some embodiments, alternatively, the damper element, either from or in combination with a ring-shaped damper element, may be implemented in or on the blades, stabilizers, or other components of the downhole tubing of the fracturing equipment. In some such embodiments, the damper element may be mounted within a housing threaded into the blades or recesses, below a cover sleeve, or hatch cover. In some such configurations, one or more limiting stops may be provided to prevent the damper element from sticking or wedging into the edges or corners of the housing. Contact between the limiting stops and the mass of the damper may be achieved using springs or other biasing elements or structures. In some embodiments, the spring stiffness or clearance in the housing may be selected to allow the mass of the damper to move within the housing, and thus enable damping of vibrations, as described above.

[0166] Adjustable elements that alter the nature of the contact between contact elements in the downhole tubing can also be used. For example, the normal force can be adjusted in frictional contact. Furthermore, the efficiency of the normal force or damper can be measured by load and acceleration or other vibration measurement and sensing devices, and adjustments can be made based on these measurements.

[0167] Turn now Figures 29A to 29B This shows schematic diagrams of various types of modal-mode tuning elements. Figure 29A A set of exemplary modal-mode tuning elements 2902-2916 are shown, and Figure 29B A downhole string 2920 (e.g., BHA) is shown, having various modal-mode tuning elements 2922 mounted thereon (e.g., one or more of the exemplary modal-mode tuning elements 2902-2916) to tune or offset or reduce one or more maximum values ​​of the HFTO modes, and thus enabling such HFTO vibrations within the downhole string 2920 to be damped.

[0168] like Figure 29AAs shown, modal-mode tuners can have various sizes. Each of the modal-mode tuners 2902-2916 has a different length, and as shown, modal-mode tuners 2902 and 2904 have larger diameters and can be configured as weight-increased (i.e., heavy weight) modal-mode tuners. In contrast, modal-mode tuners 2906, 2908, 2910, 2912, 2914, and 2916 have narrower diameters and can provide flexibility (i.e., flexible tubing) to the tubing to which these modal-mode tuners are attached. Modal-mode tuners 2902-2916 can also differ in stiffness relative to torsional rigidity. Figure 29A The image also shows the damper element short connector 2918. Downhole tubing (such as...) Figure 29B The downhole string 2920 shown may be configured with one or more modal-mode tuning elements to offset one or more maximum values ​​of HFTO, and then to enable improved damping to be provided by the damper element short joint 2918.

[0169] like Figure 29B As shown, the downhole tubing 2920 includes a motor 2924 and one or more modal-mode tuning elements 2922 (these modal-mode tuning elements can be selected from, for example, from...). Figure 29A The diagram shows modal-mode tuning elements 2902-2916, damper element short connectors 2918, flexible stabilizing short connectors 2926, a set of drilling operation elements 2928 (e.g., measurement while drilling, logging while drilling, steering unit, etc.), and a fracturing device 2930 (e.g., drill bit) disposed at the end of the downhole string. Including modal-mode tuning elements 2922 in the downhole string 2920 allows tuning or shifting one or more maximum values ​​of HFTO, and thus reduces HFTO even when HFTO-sensitive elements are located within the BHA. Furthermore, including modal-mode tuning elements 2922 in the downhole string 2920 allows tuning or shifting one or more maximum values ​​of HFTO, such as optimizing the position of the damper element short connectors 2918 to dampen such vibrations.

[0170] Therefore, embodiments of this disclosure relate to positioning damping systems, such as annular dampers or tangential dampers, within or at other specific locations within / on / along the downhole string, such as at the drill bit or other fracturing equipment. Improved damping of HFTO or other vibration modes can be achieved by positioning the damping system at specific locations within / on / along the downhole string (e.g., in the steering unit, within the drill bit, or other locations). Furthermore, modal-mode tuning elements can be configured such that one or more damping elements can be placed at or near the end of the drill string, the end of the BHA, close to or within the drill bit (e.g., within 10m of the drill bit, such as within 5m of the drill bit, or even within 3m of the drill bit), at one or more maxima of one or more modal modes, or at one or more modal mode nodes, to effectively enable damping of one or more HFTO modes using a single damping element. That is, as described herein, the maximum values ​​of multiple different HFTO modes can be aligned (tuned) to achieve optimal placement of the damping element so that one or more HFTO modes are damped and thus reduce downhole system vibration.

[0171] Implementation Scheme 1: A system for damping high-frequency torsional oscillations (HFTO) in a downhole system, the downhole system comprising: a downhole drilling system configured at an end of the downhole system for operative connection to a drill bit; a damping system mounted on the downhole drilling system, the damping system including at least one damper element configured to damp at least one HFTO mode; and at least one modal-mode tuning element disposed on the drilling system, wherein the at least one modal-mode tuning element is configured and positioned on the drilling system to modify at least one of: the mode shape of the HFTO mode, the frequency of the HFTO mode, the excitability of the HFTO mode, and the damping efficiency of the at least one damper element.

[0172] Implementation Scheme 2: The system according to any of the foregoing embodiments, wherein the at least one modal-mode tuning element is configured and positioned on the drilling system to modify the mode shape of the HFTO mode at the location of the at least one damper element.

[0173] Implementation Scheme 3: The system according to any of the foregoing embodiments, wherein the at least one modal-mode tuning element is selected based on at least one of the following: the size of the at least one modal-mode tuning element, the material properties of the at least one modal-mode tuning element, and the mechanical properties of the at least one modal-mode tuning element.

[0174] Implementation Scheme 4: The system according to any of the foregoing embodiments, wherein the positioning of the at least one modal-mode tuning element on the drilling system is selected to modify at least one of the mode shape of the HFTO mode at the location of the at least one damper element and to optimize the damping efficiency of the at least one damper element.

[0175] Implementation Scheme 5: The system according to any of the foregoing embodiments further includes: a pool of modal-mode tuning elements, the at least one modal-mode tuning element being selected from the pool for arrangement on the drilling system.

[0176] Implementation Scheme 6: The system according to any of the foregoing implementation schemes, wherein the at least one modal-mode tuning element is selected for placement on the drilling system based on numerical simulations of the HFTO of at least a portion of the downhole system.

[0177] Implementation Scheme 7: The system according to any of the foregoing embodiments, wherein at least one of the at least one damper element and the at least one modal-mode tuning element is located and / or selected based on numerical inversion.

[0178] Implementation Scheme 8: The system according to any of the foregoing implementation schemes, wherein the damping system is at least one of a viscous damping system, a friction damping system, a hydraulic damping system, a magnetic damping system, and a piezoresistive damping system.

[0179] Implementation Scheme 9: The system according to any of the foregoing implementation schemes further includes: an isolator.

[0180] Implementation Scheme 10: The system according to any of the foregoing implementation schemes, wherein the at least one damper element is arranged within 10m of the drill bit.

[0181] Implementation Scheme 11: A method for damping high-frequency torsional oscillations (HFTO) in a downhole system, the method comprising: drilling into the Earth's subsurface using a downhole drilling system, wherein the downhole drilling system is operatively connected to a drill bit and includes a damping system having at least one damper element and at least one modal-mode tuning element disposed on the drilling system; configuring and positioning the at least one modal-mode tuning element on the drilling system to modify at least one of: the mode shape of the HFTO mode, the frequency of the HFTO mode, the excitability of the HFTO mode, and the damping efficiency of the at least one damper element; and damping the at least one HFTO mode using the at least one damper element.

[0182] Implementation Scheme 12: The method according to any of the foregoing embodiments, wherein the at least one modal-mode tuning element is configured and positioned on the drilling system to modify the mode shape of the HFTO mode at the location of the at least one damper element.

[0183] Implementation Scheme 13: The method according to any of the foregoing embodiments, further comprising: selecting the at least one modal-mode tuning element for arrangement in the drilling system based on at least one of the size of the at least one modal-mode tuning element, the material properties of the at least one modal-mode tuning element, and the mechanical properties of the at least one modal-mode tuning element.

[0184] Implementation Scheme 14: The method according to any of the foregoing embodiments, further comprising: selecting the location of the at least one modal-mode tuning element on the drilling system to modify the mode shape of the HFTO mode at the location of the at least one damper element and optimizing the damping efficiency of the at least one damper element.

[0185] Implementation Scheme 15: The method according to any of the preceding embodiments, further comprising: selecting the at least one modal-mode tuning element from the pool of modal-mode tuning elements for arrangement in the drilling system.

[0186] Implementation Scheme 16: The method according to any of the foregoing embodiments, further comprising: performing a numerical simulation of the HFTO of at least a portion of the downhole system; and selecting the at least one modal-mode tuning element for arrangement in the drilling system based on the numerical simulation of the HFTO of that portion of the downhole system.

[0187] Implementation Scheme 17: The method according to any of the preceding embodiments further includes: performing a numerical inversion; and locating and selecting at least one of the at least one damper element and the at least one modal-mode tuning element based on the numerical inversion.

[0188] Implementation Scheme 18: The method according to any of the preceding implementation schemes, wherein the damping system is at least one of a viscous damping system, a friction damping system, a hydraulic damping system, a magnetic damping system, and a piezoresistive damping system.

[0189] Implementation Scheme 19: The method according to any of the foregoing implementation schemes, wherein the downhole drilling system further includes: an isolator.

[0190] Implementation Scheme 20: The method according to any of the preceding embodiments, wherein the at least one damper element is arranged within 10m of the drill bit.

[0191] Implementation Scheme 21: A system for damping torsional oscillations in a downhole system, the system comprising: a drilling system including a bottom hole assembly disposed at an end of a drill string; at least one modal tuning element disposed on the drilling system, the at least one modal tuning element being configured to offset the position of one or more maximum values ​​of a high-frequency torsional oscillation (HFTO) mode; and a damping system disposed on the drilling system, the damping system including at least one damper element being arranged to be closer to the offset position of the one or more maximum values ​​than if the modal tuning element were not disposed on the drilling system.

[0192] Implementation Scheme 22: The system according to any of the foregoing implementation schemes, wherein the at least one modal-mode tuning element is a tube segment having at least one of the following: predefined dimensions such as predefined length or predefined diameter, material and / or predefined mechanical properties such as predefined stiffness, predefined flexibility, predefined weight, predefined moment of inertia, predefined density or predefined elastic modulus (shear and volumetric strain), and predefined positioning / location.

[0193] Implementation Scheme 23: The system according to any of the foregoing embodiments, wherein the damping system includes a damping element short joint that accommodates the at least one damper element.

[0194] Implementation Scheme 24: A system according to any of the foregoing implementation schemes, wherein the damping system is configured to provide at least one of viscous damping, frictional damping, hydraulic damping, piezoresistive damping, eddy current damping, and magnetic damping for the torsional oscillations of the drilling system.

[0195] Implementation Scheme 25: A method for damping torsional oscillations in a downhole system in a borehole, the method comprising: mounting at least one modal-mode tuning element on the drilling system, the at least one modal-mode tuning element being configured to offset the position of one or more maximum values ​​of a high-frequency torsional oscillation (HFTO) mode of the drilling system; and mounting a damping system on the drilling system, the damping system including at least one damper element arranged to be closer to the offset position of the maximum value than if the modal-mode tuning element were not mounted on the drilling system.

[0196] Implementation Scheme 26: The method according to any of the preceding embodiments, wherein the at least one modal-mode tuning element is a tube segment having at least one of the following: predefined dimensions such as predefined length or predefined diameter, material and / or predefined mechanical properties such as predefined stiffness, predefined flexibility, predefined weight, predefined moment of inertia, predefined density or predefined elastic modulus (shear and volumetric strain), and predefined positioning / location.

[0197] Implementation Scheme 27: The method according to any of the preceding embodiments, wherein the damping system includes a damping element short joint accommodating the at least one damper element.

[0198] Implementation Scheme 28: The method according to any of the preceding embodiments, wherein the damping system is configured to provide at least one of viscous damping, frictional damping, hydraulic damping, piezoresistive damping, eddy current damping and magnetic damping for the torsional oscillations of the drilling system.

[0199] To support the teachings herein, various analytical components, including digital and / or analog systems, may be used. For example, controllers, computer processing systems, and / or geological guidance systems as provided herein and / or used with the embodiments described herein may include digital and / or analog systems. These systems may have components such as processors, storage media, memories, inputs, outputs, communication links (e.g., wired, wireless, optical, or others), 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 manners well known in the art. It may be understood that these teachings may be implemented, but not necessarily, 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 disk drive), or any other type of media, which, when executed, cause a computer to perform 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 system designers, owners, users, or other such persons deem relevant. Processed data (such as the results of implemented methods) may be transmitted as signals via the processor output interface to a signal receiving device. The signal receiving device may be a display monitor or printer used to present the results to the user. Alternatively or otherwise, the signal receiving device may be a memory or storage medium. It should be understood that storing the results in memory or storage medium allows the memory or storage medium to be converted from a previous state (i.e., without results) to a new state (i.e., containing results). Furthermore, in some embodiments, if the results exceed a threshold, an alarm signal may be emitted from the processor to the user interface.

[0200] In addition, various other components may be included, and they may be required to provide 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 the aspects discussed herein or to support other functions beyond this disclosure.

[0201] In the context of describing the invention (particularly in the context of the appended claims), the terms “an,” “a,” and “the,” and similar designations, should be interpreted to cover both the singular and plural, unless otherwise specified herein or clearly contradicted by the context. Furthermore, it should be noted that the terms “first,” “second,” etc., used herein do not indicate any order, quantity, or importance, but are used to distinguish one element from another. The modifier “about,” used in conjunction with quantity, includes the stated value and has a meaning determined by the context (e.g., it includes the degree of error associated with a particular quantity of measurement).

[0202] It should be recognized that various components or technologies may provide certain necessary or beneficial functions or features. Therefore, these functions and features that may be required to support the appended claims and their variations are considered to be inherently included as part of the teachings herein and as part of this disclosure.

[0203] The teachings of this disclosure can be applied to a variety of well operations. These operations may involve treating a formation, fluids residing in the formation, boreholes, and / or equipment in the borehole, such as production tubing, with one or more treatment agents. Treatment agents can be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Exemplary treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, corrosion inhibitors, binders, permeability modifiers, drilling mud, emulsifiers, demulsifiers, tracers, flow improvers, etc. Exemplary well operations include, but are not limited to, hydraulic fracturing, production enhancement, tracer injection, cleaning, acidizing, steam injection, water injection, cementing, etc.

[0204] While the embodiments described herein have been described with reference to various implementations, it should be understood that various changes may be made and equivalents may be substituted for elements therein without departing from the scope of this disclosure. Furthermore, many modifications will be made to adapt particular instruments, situations, or materials to the teachings of this disclosure without departing from the scope of this disclosure. Therefore, it is contemplated that this disclosure is not limited to the specific embodiments disclosed as the best mode contemplated for achieving the described features, but rather that this disclosure will include all embodiments falling within the scope of the appended claims.

[0205] Therefore, the embodiments disclosed herein should not be considered as limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A system for damping high-frequency torsional oscillations (HFTO) in a downhole system (1002), said downhole system (1002) comprising: A drilling system (10) is configured at the end of the downhole system (1002) to be operatively connected to the drill bit; A damping system (700, 1000, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900), said damping system being mounted on said drilling system (10), said damping system (700, 1000, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900) comprising at least one damper element (2604, 2700, 2800) configured to damp at least one HFTO mode; and At least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is arranged on the drilling system (10). The at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is configured and positioned on the drilling system (10) to modify at least one of the following: the mode shape of the at least one HFTO mode, the frequency of the at least one HFTO mode, and the excitability of the at least one HFTO mode, to amplify the amplitude of the mode shape of the at least one HFTO mode at the location of the at least one damper element (2604, 2700, 2800).

2. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, wherein the at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is selected based on at least one of the following: the at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) The dimensions of the at least one modal-mode tuner (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922), the material properties of the at least one modal-mode tuner (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922), and the mechanical properties of the at least one modal-mode tuner (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922).

3. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, wherein the positioning of the at least one mode-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) on the drilling system (10) is selected to modify at least one of the mode shape of the at least one HFTO mode at the position of the at least one damper element (2604, 2700, 2800) and to optimize at least one of the damping efficiency of the at least one damper element (2604, 2700, 2800).

4. The system for damping high-frequency torsional oscillations (HFTO) in a downhole system (1002) according to claim 1, the system further comprising: A pool of modal-mode tuning elements (2602), wherein at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is selected from the pool for arrangement on the drilling system (10).

5. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, wherein the at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is selected based on numerical simulations of the HFTO of at least a portion of the downhole system (1002) for arrangement on the drilling system (10).

6. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 5, wherein at least one of the at least one damper element (2604, 2700, 2800) and the at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is located, configured, and / or selected based on numerical inversion.

7. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, wherein the damping system (700, 1000, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900) is at least one of a viscous damping system, a friction damping system, a hydraulic damping system, a magnetic damping system, and a piezoelectric damping system.

8. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, the system further comprising an isolator.

9. The system for damping high-frequency torsional oscillations (HFTO) of a downhole system (1002) according to claim 1, wherein at least one damper element (2604, 2700, 2800) is arranged within 10 m of the drill bit.

10. A method for damping high-frequency torsional oscillations (HFTO) in a downhole system (1002), the method comprising: Drilling into the Earth's subsurface is achieved using a drilling system (10), wherein the drilling system (10) is operatively connected to a drill bit and includes a damping system (700, 1000, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900) having at least one damper element (2604, 2700, 2800) and at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) arranged on the drilling system (10); The at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is configured and positioned on the drilling system (10) to modify at least one of the following: the mode shape of the HFTO mode, the frequency of the HFTO mode, and the excitability of the HFTO mode, to amplify the amplitude of the mode shape of the HFTO mode at the location of the at least one damper element (2604, 2700, 2800); as well as The HFTO mode is damped by using at least one damper element (2604, 2700, 2800).

11. The method according to claim 10, further comprising: The at least one modal-mode tuner (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is selected for arrangement in the drilling system (10) based on at least one of the dimensions of the at least one modal-mode tuner, the material properties of the at least one modal-mode tuner, and the mechanical properties of the at least one modal-mode tuner.

12. The method according to claim 10, further comprising: The position of at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) on the drilling system (10) is selected to optimize the damping efficiency of the at least one damper element (2604, 2700, 2800).

13. The method according to claim 10, further comprising: At least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is selected from the pool of modal-mode tuning elements (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) for arrangement in the drilling system (10).

14. The method according to claim 10, further comprising: Numerical simulations were performed on at least a portion of the HFTO of the downhole system (1002); as well as The numerical simulation of the HFTO based on at least a portion of the downhole system (1002) selects at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) for arrangement in the drilling system (10).

15. The method according to claim 14, further comprising: Perform numerical inversion; as well as Based on the numerical inversion, at least one of the at least one damper element (2604, 2700, 2800) and at least one of the at least one modal-mode tuning element (2602, 2902, 2904, 2906, 2908, 2910, 2912, 2922) is located and selected.

16. The method of claim 10, wherein, The damping system (700, 1000, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900) is at least one of a viscous damping system, a friction damping system, a hydraulic damping system, a magnetic damping system, or a piezoresistive damping system.

17. The method according to claim 10, wherein, The drilling system (10) also includes an isolator.

18. The method according to claim 10, wherein, At least one damper element (2604, 2700, 2800) is arranged within 10m of the drill bit.

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