Vibration isolation coupling for reducing high frequency torsional vibrations in a drill string

Abstract

A vibration isolation coupling for isolating torsional vibrations in a drill string includes a first coupling portion including a first annular wall having an outer surface and an inner surface defining a first central bore portion, and a second coupling portion disposed within the first central bore portion. The second coupling portion includes a second annular wall having an outer surface section and an inner surface section defining a second central bore portion, and a plurality of connecting elements extending from the inner surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the inner surface of the second annular wall.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 899,354, filed September 12, 2019, U.S. Provisional Application Serial No. 62 / 899,291, filed September 12, 2019, U.S. Provisional Application Serial No. 62 / 899,331, filed September 12, 2019, and U.S. Provisional Application Serial No. 62 / 899,332, filed September 12, 2019, the entire disclosures of which are incorporated herein by reference. BACKGROUND

[0003] Drill holes are drilled deep underground for many applications, such as carbon dioxide sequestration, geothermal production, and oil and gas exploration and production. In all of these applications, drill holes are drilled so that they pass through materials (e.g., gas or fluid) contained in formations (e.g., sequestration tanks) located below the surface or allow access to the materials. Different types of tools and instruments can be set in the drill holes to perform various tasks and measurements.

[0004] In operation, downhole components can be subjected to vibrations, which can impact operational efficiency. For example, severe vibrations in a 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 vibrations can take the form of stick / slip vibrations and high frequency torsional oscillations (HFTOs). HFTO vibrations typically occur at frequencies higher than 50 Hz and can be localized to a small portion of the drill string. Typically, HFTOs have high amplitudes at the drill bit. The effects produced by such vibrations 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

[0005] A vibration isolation coupling for isolating torsional vibrations in a drill string is disclosed, the vibration isolation coupling comprising a first coupling portion and a second coupling portion, the first coupling portion comprising a first annular wall having an outer surface and an inner surface defining a first central bore portion, the second coupling portion disposed within the first central bore portion. The second coupling portion comprises a second annular wall having an outer surface section and an inner surface section defining a second central bore portion, and a plurality of connecting elements extending from the inner surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the inner surface of the second annular wall.

[0006] Also disclosed is a method of isolating torsional vibrations from a portion of a drill string connected to another portion of the drill string by a vibration isolation coupling having a first coupling portion connected to a second coupling portion by a plurality of connector elements. The method includes introducing torsional vibrations into the first coupling portion, transmitting the torsional vibrations into the plurality of connector elements extending from an inner surface section of the second coupling portion, through an annular wall of the second coupling portion to an inner surface of the first coupling portion, and isolating the transmission of the torsional vibrations from the first coupling portion to the second coupling portion by elastic bending of the plurality of connector elements. BRIEF DESCRIPTION OF DRAWINGS

[0007] The following description should not be read as limiting in any way. With reference to the drawings, like elements are indicated by like reference numbers throughout:

[0008] Figure 1 A resource exploration and recovery system including a vibration isolation coupling is shown according to one example embodiment;

[0009] Figure 2A A bottom hole assembly (BHA) geometry without a vibration isolation coupling is shown;

[0010] Figure 2B A high frequency torsional oscillation (HFTO) mode without a vibration isolation coupling is shown;

[0011] Figure 3A A BHA geometry with a vibration isolation coupling is shown according to one example aspect;

[0012] Figure 3B A HFTO mode with a vibration isolation coupling is shown according to one example embodiment;

[0013] Figure 4 A planar glass view of a vibration isolation coupling is shown according to one example aspect;

[0014] Figure 5 A cross-sectional view of a vibration isolation coupling taken along line 5-5 is shown according to one aspect of one example embodiment; Figure 4

[0015] Figure 6 A plurality of connector elements joining a first coupling portion and a second coupling portion of a vibration isolation coupling is shown according to one example aspect;

[0016] Figure 7 A cross-sectional view of a vibration isolation coupling taken along line 7-7 is shown according to one aspect of one example embodiment; Figure 4 ​a cross-sectional end view of the vibration isolation coupler; and

[0017] Figure 8 a cross-sectional end view of the vibration isolation coupler is shown. Figure 4 a cross-sectional end view of the vibration isolation coupler is shown. DETAILED DESCRIPTION

[0018] A detailed description of one or more embodiments of the devices and methods disclosed herein is presented with reference to the accompanying drawings.

[0019] Figure 1 A schematic diagram of a resource detection and recovery system for performing downhole operations is shown. As shown, the resource detection and recovery system takes the form of a drilling system 10. The drilling system 10 includes a conventional derrick 11 erected on a floor 12 that supports a rotary table 14 that is rotated at a desired rotational speed by a prime mover, such as an electric motor (not shown). The drilling system 10 also includes a drill string 20 and downhole assembly having a drill string tubular 22, such as a drill pipe, extending through the rotary table 14 and into a borehole 26 having an annular wall 27 extending into a geological formation 28. The drill string 20 can be a directional drill string and include a deflection device, a drilling motor, and / or a steering unit such as shown at 29. A fragmentation tool 30, such as a drill bit, is attached to an end of the drill string 20. The fragmentation tool 30 forms part of a bottom hole assembly (BHA) 32. The fragmentation tool 30 is operated to fragment the geological formation when rotated to form the borehole 26. The drill string 20 is coupled to surface equipment, such as a system for lifting, rotating, and / or pushing (including but not limited to) a drawworks 33 through a crown block 43 via a kelly joint 35, a swivel 38, and a line 39. In some embodiments, the surface equipment can include a top drive (not shown). During drilling operations, the drawworks 33 is operated to control the weight on bit, which affects the rate of penetration. Operation of the drawworks 33 is well known in the art and thus is not described in detail herein.

[0020] During drilling operations, a suitable drilling fluid 45 (also referred to as "mud") from a source or mud pit 48 is circulated by a mud pump 50 under pressure through the drill string 20 and the borehole (including the borehole of the BHA). The drilling fluid 41 enters the drill string 20 via a desurger 56, a flow line 58, and a kelly cock 35. The drilling fluid 41 exits at the bottom 60 of the borehole 26 through an opening in the disintegrating tool 30. The drilling fluid 41 is circulated up the wellbore through an annular space 64 between the drill string 20 and the annular wall 27 (borehole wall) of the borehole 26, and is returned to the mud pit 48 via a return line 68. A sensor SI in the flow line 58 provides information about the flow rate of the fluid. A surface torque sensor S2 and a sensor S3 associated with the drill string 20 provide information about the torque and rotational speed, respectively, of the drilling tubular 22. In addition, one or more sensors (not shown) associated with the line 39 are used to provide hook load data for the drill string 20 and other desired parameters related to the drilling of the borehole 26. The drilling system 10 can also include one or more downhole sensors 70 positioned on the drill string 20 and / or the BHA 32.

[0021] In some applications, the disintegrating tool 30 is rotated by rotating the drilling tubular 22. However, in other applications, a drilling motor (not shown) such as a mud motor can form a part of the BHA 32 and can be operated to rotate the disintegrating tool 30 and / or to augment 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 disintegrating tool 30 into the formation 28 depends to a large extent on the weight on bit and the bit rotational speed.

[0022] The surface control unit 80 receives signals from the downhole sensors 70 and equipment via transducers 83 such as pressure transducers placed in the flow line 58, as well as from the sensors SI, S2, S3, hook load sensors, RPM sensors, torque sensors, and any other sensors. The surface control unit 80 processes such signals in accordance with programmed instructions. The surface control unit 80 can display on a display / monitor 85 desired drilling parameters and other information used by the operator at the rig site to control the drilling operation. The surface control unit 80 includes a computer, memory for storing data, computer programs, models, and algorithms accessible to the processor in the computer, a recorder such as a tape unit, memory unit, etc. for recording data, and other peripherals. The surface control unit 80 can also include simulation models used by the computer to process data in accordance with programmed instructions. The surface control unit 80 can be responsive to user commands entered through suitable devices such as a keyboard. The surface control unit 80 is adapted to activate an alarm 87 in the event of certain unsafe or undesirable operating conditions.

[0023] BHA 32 also includes other sensors and devices or tools for providing various measurements related to formation 28 and for drilling out borehole 26 along a desired path. Such devices can include devices for measuring formation resistivity proximate and / or ahead of fracturing tool 30, gamma ray devices for measuring formation gamma ray intensity, and devices for determining inclination, azimuth, and position of drilling tubular 22. Other devices such as logging-while-drilling (LWD) devices (indicated generally at 90, such as devices for measuring formation porosity, permeability, density, rock properties, fluid properties, etc.) can be placed at suitable locations in BHA 32 for providing information useful for evaluating formation 28 of borehole 26. Such devices can include, but are not limited to, temperature measurement tools, pressure measurement tools, borehole diameter measurement tools (e.g., calipers), acoustic tools, nuclear tools, nuclear magnetic resonance tools, and formation testing and sampling tools.

[0024] The above-described devices transmit data to downhole telemetry system 92, which in turn transmits received data up the wellbore to surface control unit 80. Downhole telemetry system 92 also receives signals and data from surface control unit 80 and transmits such received signals and data to appropriate downhole devices. In one aspect, a mud pulse telemetry system can be used to communicate data between downhole sensors (indicated generally at 94, disposed on drill string 20) and devices and surface equipment during drilling operations. Transducer 83, placed in fluid line 58 (e.g., a mud supply line), detects mud pulses in response to data transmitted by downhole telemetry system 92. Transducer 83 generates electrical signals in response to mud pressure variations and transmits such signals to surface control unit 80 via conductor 96.

[0025] In other aspects, any other suitable telemetry system can be used for bidirectional data communication (e.g., downlink and uplink) between the surface and BHA 32, including but not limited to acoustic telemetry systems, electromagnetic telemetry systems, optical telemetry systems, wired pipe telemetry systems that can utilize wireless couplers or repeaters in the drill string or borehole. A wired pipe telemetry system can be constructed by connecting drill pipe sections, where each pipe section includes a data communication link (such as an electrical wire) extending along the pipe. Data connections between pipe sections 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 direct coupling methods. In the case where coiled tubing is used as drilling tubular 22, the data communication link can extend along the side of the coiled tubing.

[0026] The drilling system 10 relates to those drilling systems that utilize a drill pipe to convey the BHA 32 into the borehole 26, where the weight on bit is typically controlled from the surface by controlling the operation of the drawworks 33. However, a large number of current drilling systems, particularly those used to drill highly deviated boreholes and horizontal boreholes, utilize coiled tubing to convey the drilling assembly downhole. In such applications, a pusher (not separately labeled) can be deployed in the drill string 20 to provide the desired force on the fracturing tool 30. Additionally, when coiled tubing is employed, the tubing is not rotated by a rotary table, but rather is injected into the borehole by a suitable injector, while a downhole motor such as a drilling motor (not shown) rotates the fracturing tool 30. For offshore drilling, an offshore rig or vessel can be used to support the drilling equipment, including the drill string.

[0027] Still referring to Figure 1 A resistivity tool 100 can be provided that includes, for example, a plurality of antennas, including, for example, a transmitter 104a or 104b or and a receiver 108a or 108b. Resistivity can be one formation property of interest in making drilling decisions. Those skilled in the art will appreciate that other formation property tools can be used with or instead of the resistivity tool 100.

[0028] Liner drilling can be a configuration or operation for providing a fracturing device that has several advantages over conventional drilling and thus is becoming more attractive in the oil and gas industry. One example of such a configuration is shown and described in commonly owned U.S. Patent No. 9,004,195, entitled “Apparatus and Method for Drilling a Borehole, Setting a Liner and Cementing the Borehole During a Single Trip,” which is incorporated herein by reference in its entirety. Importantly, while the rate of penetration is relatively low, the time to align the liner with the target is reduced because the liner is being run in while the borehole is being drilled. This can be beneficial in swelling formations where the contraction of the borehole can hinder installation of the liner. Moreover, using a liner to drill in a depleted and unstable reservoir can minimize the risk of sticking the pipe or drill string due to borehole collapse.

[0029] While Figure 1are shown and described with respect to drilling operations, but those skilled in the art will appreciate that similar constructions can be used to perform different downhole operations, albeit with different components. For example, as is known in the art, completion, wireline, wireline pipe, liner drilling, underreaming, coiled tubing, reentry, and / or other constructions can be used. Moreover, production configurations can be employed for extracting material from and / or injecting material into a formation. Thus, the present disclosure is not limited to drilling operations, but can be used for any appropriate or desired downhole operation(s).

[0030] Severe vibrations in the drill string and bottom hole assembly during drilling operations can be caused by cutting forces at the drill bit or mass imbalances in downhole tools such as drilling motors. Such vibrations can result in reduced rate of penetration, reduced wellbore quality, reduced quality of measurements made by tools of the bottom hole assembly, and can result in downhole component wear, fatigue, and / or failure. As understood by those skilled in the art, there are different vibrations, such as lateral, axial, and torsional vibrations. For example, stick / slip and high frequency torsional oscillation (“HFTO”) of the entire drilling system are both types of torsional vibrations. The terms “vibration,” “oscillation,” and “fluctuation” are used in the same broad sense of repeated and / or periodic motion or periodic deviation of the mean (such as mean position, mean velocity, and mean acceleration). In particular, 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, harmonic, and statistical deviations.

[0031] Torsional vibrations can be excited by a self-excitation mechanism that occurs as a result of the interaction of the drill bit or any other cutting structure, such as an underreamer bit, with the formation. The main difference between stick / slip and HFTO is the frequency and typical modal shape: for example, critical HFTO has a frequency that is typically higher than 50 Hz, compared to stick / slip torsional vibrations that typically have a frequency lower than 1 Hz. Typically, critical HFTO can be in the range between 50 Hz and 500 Hz. Criteria to identify the critical HFTO mode are described in Andreas Hohl et al., Journal of Sound and Vibration, 342 (2015), 290-302. The critical HFTO mode, critical frequency, and critical modal shape can also be referred to as undesired HFTO mode, undesired frequency, and undesired modal shape. Moreover, the excited modal shape of stick / slip is typically the first modal shape of the entire drilling system, whereas the modal shape of HFTO can be high order and typically localized to a smaller portion of the drilling system and relatively high in amplitude at the excitation point, which can be the drill bit or any other cutting structure, such as an underreamer bit, or any contact between the drilling system and the formation (e.g., achieved by stabilizers).

[0032] Due to the high frequency of the vibrations, HFTO corresponds to high acceleration and torque values along the BHA or at only a portion of the BHA. Those skilled in the art will appreciate that for torsional motion, one of acceleration, force, and torque always accompanies the other two. In this sense, acceleration, force, and torque are equivalent in the sense that none of these can occur without the other two. The loads of high frequency vibrations can have a negative impact on the efficiency, reliability, and / or durability of the electronic and mechanical components of the BHA. Embodiments provided herein are directed to providing a vibration isolation coupler 140 to mitigate HFTO. The vibration isolation coupler 140 is a modular tool that can be installed at various locations above, below, or within the BHA 32. For example, the vibration isolation coupler 140 can be installed above the drill bit. In a directional drill string (directional BHA). In a directional drill string (directional BHA), a steering unit 29 can be located above the drill bit. The steering unit 29 is located near the drill bit in order to deflect the drilling direction of the drill bit. In a BHA with a steering unit, it is desirable to position the vibration isolation coupler 140 above the steering unit. Above the vibration isolation coupler 140, one or more formation evaluation tools can be placed.

[0033] The fragmentation tool 30 represents the point of excitation of HFTO. Without the vibration isolation coupler placed in the BHA, the fragmentation tool 30 will excite HFTO at undesirable frequencies along the entire BHA. The vibration isolation coupler 140 isolates the propagation of HFTO excited in the portion of the BHA above the vibration isolation coupler 140 from the portion of the BHA below the vibration isolation BHA. The vibration isolation coupler 140 limits the excitation of HFTO by the cutting forces at the drill bit 30 to the BHA below the vibration isolation coupler 140. Due to the design of the vibration isolation coupler 140, the torsional dynamics of the BHA are modified to allow the undesirable HFTO modal shapes to have significant amplitude only in the portion of the BHA below the vibration isolation coupler 140.

[0034] The vibration isolation coupler 140 in the BHA allows the portion of the BHA below the vibration isolation coupler 140 to oscillate (HFTO) by isolating the oscillations from the portion of the BHA above the vibration isolation coupler. In addition, the vibration isolation coupler 140 changes the number of undesirable HFTO modes excited. In a BHA with the vibration isolation coupler 140, a smaller number of undesirable HFTO modes are excited. The vibration isolation coupler 140 acts as a mechanical low-pass filter for HFTO and includes an isolation frequency (natural frequency or first resonant frequency).

[0035] The isolation effect is caused by the significantly smaller isolation frequency of the vibration isolation coupling compared to the HFTO frequencies excited at the drill bit or at any other cutting structure in the BHA. The smaller isolation frequency can be achieved by using a vibration isolation coupling with a sufficiently small torsional stiffness. The small torsional stiffness of the vibration isolation coupling will isolate the mass located below from the mass located above in terms of the torsional degree of freedom for frequencies above the isolation frequency. The HFTO modes excited at the drill bit at frequencies above the isolation frequency are isolated from the part of the BHA located above the vibration isolation coupling 140. The term "small torsional stiffness" refers to a ratio between the bending stiffness and the torsional stiffness (Bending Stiffness / Torsional Stiffness (BST / TST)) greater than 10, greater than 15, greater than 20, greater than 30, greater than 40, or greater than 50.

[0036] In one embodiment, the desired isolation frequency of the vibration isolation coupling in the downhole assembly is between 10 Hz and 200 Hz. In another embodiment, the isolation frequency can be between 10 Hz and 100 Hz. In yet another embodiment, the isolation frequency can be between 20 Hz and 50 Hz. In yet another embodiment, an isolation frequency of 30 Hz reduces the isolation of undesired HFTO modes (e.g., HFTO modes in the range between 50 Hz and 500 Hz).

[0037] The isolation frequency of the vibration isolation coupling depends on the torsional spring constant (proportional to the torsional stiffness) of the vibration isolation coupling and the oscillating mass below the vibration isolation coupling. In one embodiment, positioning the vibration isolation coupling 140 above the steering unit 29 and the fragmentation tool 30 provides a sufficiently high oscillating mass (inertial mass) to achieve an isolation frequency of about 30 Hz. A smaller mass (e.g., only the drill bit) results in an isolation frequency higher than 30 Hz, e.g., 100 Hz to 200 Hz. The BHA components located near the fragmentation tool 30 are designed to withstand high levels of vibration (axial, lateral, and torsional).

[0038] An isolation frequency of 30 Hz limits the undesired HFTO modes and associated torque loads and angular acceleration loads acting on the steering unit 29 and the drill bit 30 to only a few critical HFTO modes. As shown in FIG. 2, at or near an isolation frequency of 30 Hz, there are also other modes with a higher likelihood of occurrence that are not considered undesired. A higher isolation frequency will result in more undesired HFTO modes excited in the part of the BHA located below the vibration isolation coupling 140, which can result in damage in the steering unit 29 or the fragmentation tool 30.

[0039] In one embodiment, the lower portion of the BHA (e.g., the portion of the BHA below the vibration isolation coupling 140) is decoupled (isolated) from the upper portion of the BHA (e.g., the portion of the BHA above the vibration isolation coupling 140) according to the HFTO. In alternative embodiments, undesirable HFTO modes can be excited in the portion of the BHA located in the vibration isolation coupling 140, for example by the under-reamer. In this case, the vibration isolation coupling 140 isolates the portion of the BHA below the vibration isolation coupling 140 from the undesirable HFTO modes. In a BHA with a vibration isolation coupling as described herein, the undesirable HFTO mode shape amplitude above the vibration isolation coupling 140 (the portion of the BHA without HFTO excitation) is relatively low compared to the HFTO mode shape amplitude below the vibration isolation coupling 140 (the portion of the BHA with HFTO excitation).

[0040] Figure 2A and Figure 2B The geometry of a reference BHA (4.75" tool size) in a drill string without a vibration isolation coupling is shown, showing six exemplary undesirable HFTO mode shapes with respective frequencies (f) between 119.4 Hz and 357.6 Hz. The parameter S c is an indicator of the likelihood of occurrence of a HFTO mode shape. The HFTO mode shape amplitude indicates the location of the torsional vibration energy in the BHA section of the drill string.

[0041] Figure 3A and Figure 3B The geometry of a reference BHA in a drill string with a vibration isolation coupling placed above the fracturing tool 30 and the steering unit 29 is shown according to one exemplary embodiment. The incorporation of the vibration isolation coupling 140 results in a lower number of undesirable HFTO modes in the frequency range of 50 Hz to 500 Hz. There are also other modes of the vibration isolation coupling 140 with high likelihood of occurrence at or near the isolation frequency (30 Hz) of the vibration isolation coupling 140. However, these HFTO modes with small frequencies (about 30 Hz) are considered less undesirable due to their small frequencies and small amplitudes (compared to the amplitudes occurring along the BHA in the reference BHA without a vibration isolation coupling (Figure 2)).

[0042] Figure 3 shows that the HFTO is concentrated at the fragmentation tool 30 and the steering unit 29. The HFTO modal shape amplitude above the vibration isolation coupler 140 is smaller compared to the amplitude of the corresponding modal shape vibration below the vibration isolation coupler 140. The HFTO modal shapes present in the upper part of the reference BHA without vibration isolation coupler do not excite in the BHA with vibration isolation coupler due to varying torsional dynamics or appear with significantly smaller HFTO modal shape amplitudes. Therefore, FE tools or MWD tools including highly sophisticated electronics (PCBA, ceramic material including multi-chip modules (MCM)), sensors, connectors, wires, hydraulic devices and / or mechanical devices located above the vibration isolation coupler are exposed to reduced torsional dynamic loads resulting in higher quality downhole measurement data (especially imaging data) and enhanced downhole tool reliability.

[0043] It is preferred that the vibration isolation coupler 140 is built as short as possible to keep the FE tool close to the drill bit. In one embodiment, the vibration isolation coupler 140 as described herein can be shorter than about 10 m. In another embodiment, the vibration isolation coupler 140 can be shorter than about 5 m. In yet another exemplary embodiment, the vibration isolation coupler 140 can be shorter than about 2 m. In yet another exemplary embodiment, the vibration isolation coupler 140 can be shorter than about 1.5 m. In yet another exemplary embodiment, the vibration isolation coupler 140 can be shorter than about 1.2 m. In yet another exemplary embodiment, the vibration isolation coupler 140 can be shorter than about 1.1 m. Furthermore, in another exemplary embodiment, the vibration isolation coupler 140 can be shorter than about 1 m. Additionally, in another example, the vibration isolation coupler 140 can be shorter than about 0.5 m.

[0044] To achieve the desired isolation properties, the vibration isolation coupler 140 has a small torsional stiffness (torsional softness) to isolate the HFTO. At the same time, the vibration isolation coupler must have a high bending stiffness to facilitate the steering behavior of the directional BHA (i.e. the steering unit). Different designs for the vibration isolation coupler are presented herein to achieve the desired mechanical properties to balance the trade-off between torsional softness and bending stiffness while keeping the mechanical stresses below acceptable limits. The mechanical stresses are induced by axial loads (weight on bit (WOB)), torque applied by surface equipment (drill string rotation), dynamic bending and vibrations (lateral, axial, torsional) of the borehole turn.

[0045] The vibration isolation coupler is preferably integrally formed in only one piece or can be formed from very few components. The vibration isolation coupler integrally formed without connections such as threaded, welded or otherwise formed connections is less prone to tool failure. Modern manufacturing methods such as additive manufacturing have the opportunity to get vibration isolation couplers formed as an integral part with complex shapes.

[0046] The bending stiffness of the vibration isolation couplings described herein is not achieved by including a housing having a high bending stiffness. The vibration isolation couplings as described herein do not include bearings or other elements having surfaces that move relative to each other. As such, the vibration isolation couplings do not include or utilize frictional forces or frictional surfaces. In this context, friction also includes viscous friction (viscous forces). The vibration isolation couplings as described herein do not use frictional surfaces or viscous friction to dissipate rotational energy. The vibration isolation couplings do not include wear due to frictional forces. It should be mentioned that the vibration isolation couplings only isolate high frequency torsional oscillations. Rotational (non-oscillatory or continuous rotation) imparted by the rotary table is transmitted from the BHA above the vibration isolation couplings to the BHA below the vibration isolation couplings. Although the vibration isolation couplings isolate HFTO, the BHA above and below the vibration isolation couplings are rotatably coupled.

[0047] According to the exemplary embodiment shown in FIGS. 2 to Figure 5 The vibration isolation couplings 140 include a first connector 144, which can take the form of a box thread connector 146, and a second connector 148, which can take the form of a pin thread connector 150, according to the exemplary embodiment shown in FIGS. 2 to 4. A first coupler portion 154 is connected to the second connector 148, and a second coupler portion 156 is coupled to the first connector 144. As will be described in detail herein, the second coupler portion extends within and is concentric with the first coupler portion 154. Further, the first coupler portion 154 is operatively connected to the second coupler portion 156 by a plurality of connecting elements, generally indicated at 159, as described in additional detail herein. The connecting elements 159 can be integrally formed with the first coupler portion 154 and the second coupler portion 156. Alternatively, the connecting elements 159 can be joined to the first coupler portion 154 and the second coupler portion 156 by welding. A seal 160 can be disposed between the first coupler portion 154 and the second coupler portion 156. The seal 160 can be formed of various materials, such as rubber, elastomer, or metal. Further, the seal 160 can allow a controlled amount of leakage between the first coupler portion 154 and the second coupler portion 156.

[0048] It should be mentioned that the connecting elements 159 can have a length, as shown in FIG. 4, that is less than the length of the first coupler portion 154 and the second coupler portion 156. As such, the connecting elements 159 can be shorter than the first coupler portion 154 and the second coupler portion 156. Alternatively, the connecting elements 159 can have a length that is greater than the length of the first coupler portion 154 and the second coupler portion 156. As such, the connecting elements 159 can be longer than the first coupler portion 154 and the second coupler portion 156. Figures 4 to 7The connecting elements 159 can have different shapes as shown in the figures. In an exemplary embodiment, the connecting elements 159 can have a cross-section comprising an I-shape, a figure-8 shape, a circular (elliptical, round) shape, or can comprise a hollow profile. The connecting elements 159 can not all have the same dimensions. Furthermore, the extension in axial direction can vary from one connecting element to another. The extension in radial direction can vary from one connecting element to another. As used herein, the axial direction refers to the direction parallel to the longitudinal axis A (Fig. 2) of the vibration isolation coupling 140, and the radial direction R (Fig. 2) herein refers to the direction perpendicular to the longitudinal axis A. The circumferential direction C Figure 5 ) refers to the tangential direction perpendicular to the longitudinal axis A. The angle a Figure 5 ) refers to the angle around the longitudinal axis A.

[0049] As shown in Figs. 2 and 3, the first connector 144 can comprise a female threaded connector 146 and the second connector 148 can comprise a pin threaded connector 150. The first connector 144 and the second connector 148 can be joined to the first coupling portion 154 and the second coupling portion 156, respectively, by stud welding. The first coupling portion 154 and the second coupling portion 156 are connected by a plurality of connecting elements 159 and form the vibration isolation portion 151 of the vibration isolation coupling 140. Thus, the first connector 144 and the second connector 148 can be joined to the vibration isolation portion 151 of the vibration isolation coupling 140 by stud welding. The weld 165 indicates the stud welding between the female threaded connector 146 and the second coupling portion 156, and the weld 167 indicates the stud welding between the pin threaded connector 150 and the first coupling portion 154. Alternatively, the female threaded connector 146 and the pin threaded connector 150 can be integral with the first coupling portion 154 and the second coupling portion 156, respectively, or joined by a different technique such as by friction welding, laser beam welding or electron beam welding.

[0050] According to one exemplary aspect, the first coupling portion 154 comprises a first tubular portion 162 having a first annular wall 164 with an outer surface 166 and an inner surface 168 defining a first central bore 170. The first annular wall 164 comprises a first end portion 172 and an opposite second end portion 173. The second coupling portion 156 comprises a second tubular portion 171 having a second annular wall 180 comprising an outer surface section 182 and an inner surface section 184 defining a second central bore 186. In one embodiment, the second central bore 186 can provide a passage for the flow of drilling fluid through the drill string 20. The second annular wall 180 comprises a first end portion 187 and an opposite second end portion 188. The first connector 144 is coupled to the first end portion 187 of the second coupling portion 156, and the second connector 148 is coupled to the second end portion 173 of the first coupling portion 154.

[0051] The inner surface 168 of the first annular wall 164 is spaced apart from the outer surface 182 of the second annular wall 180. In one embodiment, the inner surface 168 is spaced apart from the outer surface 182 by a distance of about 1 mm. In an alternative embodiment, the inner surface 168 is spaced apart from the outer surface 182 by a distance of about 0.1 mm to 0.9 mm. In yet another exemplary aspect, the inner surface 168 is spaced apart from the outer surface 182 by a distance of about 1 mm to 2 mm. In yet another exemplary aspect, the inner surface 168 is spaced apart from the outer surface 182 by a distance of about 2 mm to 10 mm. In yet another exemplary aspect, the inner surface 168 is spaced apart from the outer surface 182 by a distance of greater than about 10 mm.

[0052] According to one exemplary aspect, the second coupler portion 156 includes a first plurality of axially spaced apart openings 190a and 190b extending from the outer surface 182 through the second annular wall 180 to the inner surface 184 fluidly connecting the first central bore 170 and the second central bore 186. It should be appreciated that while shown as axially spaced apart, the openings 190a and 190b can be circumferentially spaced apart or can be both axially and circumferentially spaced apart. The second coupler portion 156 further includes a second plurality of axially spaced apart openings 193a and 193b axially and circumferentially offset relative to the axially spaced apart openings 190a and 190b, a third plurality of axially spaced apart openings 196a and 196b axially and circumferentially offset relative to the openings 190a / 190b and 193a / 193b, and a fourth plurality of axially spaced apart openings 198a and 198b axially and circumferentially offset relative to the openings 190a / 190b, 193a / 193b, and 196a / 196b. The number and location of the axially spaced apart openings can vary. In one embodiment, the first plurality of axially spaced apart openings, the second plurality of axially spaced apart openings, the third plurality of axially spaced apart openings, and the fourth plurality of axially spaced apart openings are circumferentially offset 90° relative to one another.

[0053] Further in accordance with one example embodiment, the plurality of connecting elements 159 includes a first plurality of connecting elements 207a and 207b, a second plurality of connecting elements 209a and 209b, a third plurality of connecting elements 212a and 212b, and a fourth plurality of connecting elements 214a and 214b. The connecting elements 207a and 207b extend from the inner surface 168 of the first coupler portion 154 through corresponding ones of the first plurality of axially spaced openings 190a and 190b and engage the inner surface 184 of the second coupler portion 156. The connecting elements 209a and 209b extend from the inner surface 168 through corresponding ones of the second plurality of axially spaced openings 193a and 193b and engage the inner surface 184. The connecting elements 212a and 212b extend from the inner surface 168 through corresponding ones of the third plurality of axially spaced openings 196a and 196b and engage the inner surface 184. The connecting elements 214a and 214b extend from the inner surface 168 through corresponding ones of the fourth plurality of axially spaced openings 198a and 198b and engage the inner surface 184.

[0054] In one embodiment, the first coupler portion 154 is formed of a first material, the second coupler portion 156 is formed of a second material, and the plurality of connecting elements 159 is formed of a third material. In one example aspect, the first material, the second material, the third material, and the fourth material are substantially the same. In another example aspect, the first coupler portion 154, the second coupler portion 156, and the plurality of connecting elements 159 are integrally formed. That is, the first coupler portion 154, the second coupler portion 156, and the plurality of connecting elements 159 are formed as a single unitary component, such as by additive manufacturing. However, it should be appreciated that the first material, the second material, and the third material can be different and other manufacturing techniques can be employed. For example, the individual components can be connected by welding, brazing, threading, clamping, or other joining methods. Other manufacturing methods can include precision casting.

[0055] The materials used to form the vibration isolation coupler 140 can be steel, high strength steel, titanium, titanium alloy, nickel, or nickel alloy (e.g., Inconel®). The materials used can have different material properties, such as modulus of elasticity, shear modulus, strength, density. In yet another embodiment, different portions of the vibration isolation coupler can be formed of different materials to meet the modulus of elasticity or shear modulus requirements or corrosion requirements. Modern additive manufacturing techniques are capable of combining different materials within one unitary component.

[0056] It should also be appreciated that the elastic bending of the connecting elements 159 can provide a selected amount of bending flexibility between the first and second coupler portions 154, 156. Further, it should be appreciated that the downhole components positioned downhole of the vibration isolation coupler 140 have a moment of inertia when rotating or oscillating (vibrating). The moment of inertia of the downhole components positioned downhole of the vibration isolation coupler 140 together with the elastic bending (bending flexibility) provided by the connecting elements 159 establishes a first torsional resonance derived from equation (1.1):

[0057]

[0058] where f = frequency [1 / s], I = moment of inertia [kgm2], k = torsional spring constant [Nm / rad] e.g. less than 100 Hz. It should be appreciated that the moment of inertia can also include a contribution from the moment of inertia of the vibration isolation coupler.

[0059] Accordingly, the vibration isolation coupler 140 isolates (decouples) vibrations between the first and second coupler portions 154, 156 at frequencies above the first torsional resonance.

[0060] According to one exemplary aspect, a load can be introduced into the vibration isolation coupler 140 through the first connector 144. The load can represent a torsional load, an axial load, and or a bending load. In one embodiment, the load can be imparted to the first connector 144 through the rotary table 14 and / or the drawworks 33. When a torsional load (drilling torque or bit torque) is applied between the first connector 144 and the pin and box connector 150, the plurality of connecting elements 159 form a torsionally flexible coupling between the first and second coupler portions 154, 156. Accordingly, the plurality of connecting elements 159 are subjected to bending and allow angular movement (angular a Figure 5 )) of the first coupler portion 154 relative to the second coupler portion 156.

[0061] When a bending moment is applied between the first and second connectors 144, 148, the plurality of connecting elements 159 are subjected to push-pull forces, utilize their entire cross section with a uniform distribution of stresses, and thus represent a rather rigid coupling for bending between the first and second coupler portions 154, 156. Upon axial loading, the plurality of connecting elements 159 bend along their large moment of inertia, thereby experiencing low stresses and low deformations compared thereto.

[0062] Further in accordance with one exemplary aspect, the plurality of connecting elements 159 can deform when a torque is applied on the first and second connectors 144, 148. Once a predetermined torque level is reached, one or more of the plurality of connecting elements 159 can come into contact with an opening surface of a corresponding one of the axial spaced openings 190a / 190b, 193a / 193b, 196a / 196b, and 198a / 198b. In this case, the opening surface forms a twist end stop, as indicated at 224. The twist end stop 224 limits further deflection and stress in the plurality of connecting elements 159. The twist end stop 224 can be used to apply a high static torque, for example, to release a situation where a hole component is stuck under the isolator. The twist end stop 224 can take a variety of forms, such as shown at 224a, where like reference numerals indicate corresponding parts in separate views. Figure 5 Figure 6

[0063] In Figure 8 , the twist end stop 224 is separate from the plurality of connecting elements 159. The separation of the twist end stop 224 from the connecting elements 159 prevents potential damage to the plurality of connecting elements 159 when they hit the opening surface (e.g., twist end stop 224). The twist end stop 224 can engage (stop) under torsion of the vibration isolation coupling 140 before the connecting elements 159 hit the opening surface (not separately labeled) of the twist end stop 224. Another reason for separating the twist end stop 224 from the connecting elements 159 is separation of functions.

[0064] The function of the plurality of connecting elements 159 is to isolate the HFTO. When the plurality of connecting elements 159 are bent and come into contact with, for example, the surfaces of the openings 190a / 190b, 193a / 193b, 196a / 196b, as a result of a torque (drilling torque) applied from, for example, the surface, it is not possible to cause further bending as a result of the HFTO and the vibration isolation coupling 140 will lose its isolation function. The twist end stop 224 engages before the plurality of connecting elements hit the surfaces of the openings 190a / 190b, 193a / 193b, 196a / 196b to maintain the function of the vibration isolation coupling 140 while limiting its maximum torsion angle as a result of a high torque.

[0065] A typical torsion of the vibration isolation coupling 140 as a result of surface torque (drilling torque) can be a torsion angle of about 10°. A typical torsion of the vibration isolation coupling 140 as a result of HFTO can be a torsion angle of about 15°. The torsion angle refers to as Figure 7 ​​The angle a is shown. The twist angle refers to the rotation of the first coupler portion 154 relative to the second coupler portion 156. In alternative embodiments, the twist angle due to drilling torque can be between about 5° and about 30°. In another embodiment, the twist angle can be between about 7° and about 20°. In yet another exemplary embodiment, the twist angle can be between about 8° and about 15°. The twist angle due to HFTO can also be between about 5° and about 50°; between about 8° and about 30°, and between about 10° and about 20°.

[0066] The drilling torque applied by the rotary table is transmitted to the drill bit through the vibration isolation coupler 140. The plurality of connecting elements 159 flex, but do not hit the surfaces of the openings 190a / 190b, 193a / 193b, 196a / 196b. Due to the drilling process and the cutting forces acting on the fragmentation tool 30, HFTO can be superimposed on the rotation applied by the rotary table at the location of the fragmentation tool 30 and propagate along the BHA. The oscillatory bending of the plurality of connecting elements 159 occurs in a direction perpendicular to the longitudinal axis A of the vibration isolation coupler 140. For HFTO modes having a frequency at and above the first resonance frequency of the vibration isolation coupler 140, the bending of the plurality of connecting elements 159 decreases along the longitudinal axis A from the second connector 148 to the first connector 144.

[0067] If the vibration isolation coupler 140 completely isolates the HFTO, no HFTO is transmitted to the first connector 144. The isolation of the HFTO between the second connector 148 and the first connector 144 is achieved by the torsional softness of the vibration isolation portion 140, which allows the second coupler portion 148 to rotate relative to the first coupler portion 146. In alternative embodiments, the input of HFTO can occur at the first connector 144. This can occur when, for example, HFTO is generated closer to the first connector 144 than the second connector 148 by a reaming drill located above the vibration isolation coupler 140. Up the wellbore in this disclosure is the end of the vibration isolation coupler 140 located closer to the surface.

[0068] The desired length of the vibration isolation coupler 140 is shorter than 1 m. A suitable thickness of the first and second walls 164, 180 can be 10 mm. In embodiments, the wall thickness can be between about 5 mm and about 9 mm. In another exemplary aspect, the wall thickness can be between about 11 mm and about 20 mm. In yet another exemplary aspect, the wall thickness can be between about 20 mm and about 50 mm. The wall thickness of the first annular wall 164 can be different from the wall thickness of the second annular wall 180. The shape and size can vary between the plurality of connecting elements 159. It should be mentioned that the term "length" in the present disclosure refers to the extension along the longitudinal axis A of the vibration isolation coupler, the terms "width" and "height" refer to the extension along 2 radial directions, wherein the two radial directions are perpendicular to each other. The number of connecting elements is not limited to Figures 4 to 7 eight as shown in Fig. 1.

[0069] A first portion of the plurality of connecting elements is oriented in parallel. A second portion of the plurality of connecting elements can be oriented perpendicular to the first portion of the plurality of connecting elements 159. In alternative embodiments, angles other than 90° between portions of the plurality of connecting elements 159 are envisaged. For example, the first portion of the plurality of connecting elements can be at an angle between about 1° and about 120° with respect to the second portion of the plurality of connecting elements. In another exemplary aspect, the first portion of the plurality of connecting elements can be at an angle between about 10° and about 90° with respect to the second portion of the plurality of connecting elements. In another exemplary aspect, the first portion of the plurality of connecting elements can be at an angle between about 10° and about 45° with respect to the second portion of the plurality of connecting elements. In yet another exemplary aspect, the first portion of the plurality of connecting elements can be at an angle between about 45° and about 90° with respect to the second portion of the plurality of connecting elements.

[0070] In one exemplary aspect, it should be understood that only two connecting elements can be used. In another embodiment, between 3 and 50 connecting elements can be used. In yet another embodiment, a significantly larger number of connecting elements can be used. For example, the vibration isolation coupler 140 can be formed with more than 1000 connecting elements. In this case, the connecting elements 159 will be oriented between the inner surface 168 of the first coupler portion and the inner surface 184 of the second coupler portion, thereby forming a spoke-like pattern. In case of a spoke-like pattern configuration, the angle between adjacent connecting elements can be 5° or less.

[0071] At this time, it should be understood that the vibration isolation coupling isolates vibrations from, for example, the fracturing device propagating up the wellbore. The fracturing device 30 is located below the vibration isolation coupling 140 and closer to the second connector 148 than the first connector 144. Vibration can be uncoupled (isolated) by the plurality of connecting elements 159 such that the amplitude above the vibration isolation coupling 140 can be significantly less than the amplitude below the vibration isolation coupling 140. In one exemplary embodiment, torsional vibrations with a frequency higher than the first natural frequency of a simplified alternative mechanical system, represented by the moment of inertia of the BHA section 250 (including the fracturing device) below the vibration isolation coupling 140 and the torsional spring constant (proportional to torsional stiffness) of the plurality of connecting elements 159, will be prevented. The BHA section 250 can include the drill bit 30 and the steering unit 29. The first natural frequency of the simplified alternative mechanical system can be calculated by the equation given in Equation 1.1:

[0072] The vibration isolation of the vibration isolation coupling 140 is caused by a significantly smaller (first) natural frequency (e.g., 30 Hz) than the critical excitation frequency of the HFTO, a cut-off frequency, compared to a mechanical low-pass filter. Typical values of the cut-off frequency of the mechanical system can be 10 Hz, 50 Hz, 100 Hz, or 200 Hz, selected according to the expected undesirable HFTO frequencies excited within the BHA. The cut-off frequency can be adjusted by the torsional stiffness of the connecting elements (or the torsional spring constant of the vibration isolation coupling) or the moment of inertia of the components placed below the vibration isolation coupling 140, for example, by adding or removing BHA sections, such as drill pipe, heavy weight drill pipe, or flexible pipe, below the coupling.

[0073] In addition to reducing vibrations, the vibration isolation coupling can also serve as a conduit for the drilling fluid. Typically, the pressure of the drilling fluid at the center of the tool is higher than the pressure in the annulus. The center of the tool fluid passage is connected to the inner bore of the drill string and the inner bore of the BHA, while the annulus is the way back for the drilling fluid towards the surface. The bore pressure is increased at least by the pressure loss caused by the nozzles in the fracturing device and / or the dynamic pressure drop of the fluid flowing through the downhole tools (BHA sections) below the isolation coupling and their surroundings. As shown in FIGS. 2-3, there can be a (small) flow passage at the seal 160 between the bore fluid and the annulus. By providing gaps at the seal 160 and setting their size appropriately (e.g., 0.1 mm), the fluid leakage through these gaps can have a controlled and tolerable flow. The controlled leakage of fluid flow then does not require expensive and delicate seals that seal under rotation and / or oscillation. Other options, not explicitly detailed here, can include labyrinth seals, elastomer seals, gap seals, magnetic seals, bellows seals, or other sealing elements (collectively referred to as 160 in FIGS. 3 and 4). Figure 5 As shown in FIGS. 2-3, there can be a (small) flow passage at the seal 160 between the bore fluid and the annulus. By providing gaps at the seal 160 and setting their size appropriately (e.g., 0.1 mm), the fluid leakage through these gaps can have a controlled and tolerable flow. The controlled leakage of fluid flow then does not require expensive and delicate seals that seal under rotation and / or oscillation. Other options, not explicitly detailed here, can include labyrinth seals, elastomer seals, gap seals, magnetic seals, bellows seals, or other sealing elements (collectively referred to as 160 in FIGS. 3 and 4). Figure 4 As shown in FIGS. 2-3, there can be a (small) flow passage at the seal 160 between the bore fluid and the annulus. By providing gaps at the seal 160 and setting their size appropriately (e.g., 0.1 mm), the fluid leakage through these gaps can have a controlled and tolerable flow. The controlled leakage of fluid flow then does not require expensive and delicate seals that seal under rotation and / or oscillation. Other options, not explicitly detailed here, can include labyrinth seals, elastomer seals, gap seals, magnetic seals, bellows seals, or other sealing elements (collectively referred to as 160 in FIGS. 3 and 4).

[0074] The vibration isolation coupler 140 can also accommodate passage of control signals by providing a passageway for conductors (shown as 260 in FIG. 2). Such passageway of conductors 260 allows for the passage of electrical conductors or optical conductors, wires, or cables through the vibration isolation coupler 140 for the transmission of power and / or communication (e.g., power line bus) from above the downhole component to below the downhole component through the vibration isolation coupler 140 and vice versa. The electrical conductors can, for example, extend through the first connector 144, the second annular wall 180, one or more of the plurality of connecting elements 159, the first annular wall 164, and transition into the second connector 148. The passageway of conductors 260 can terminate in a modular electrical connector, which in turn can take the form of electrical contacts, such as contact rings placed in the annular recess 270, sliding contacts, inductive connections, or resonant electromagnetic coupling devices positioned at the connectors 150 and 146.

[0075] It should be appreciated that other connector types are also possible. Moreover, it should be appreciated that the conductors 200 can terminate in a central connector (not shown) located in the central bore (not individually labeled) of the first connector 144 and the second connector 148. The central bore (also referred to as an inner bore) is fluidly connected to the inner bore of the BHA and the drill string and provides a passageway for drilling fluid.

[0076] The bending of the plurality of connecting elements 159 induces mechanical stresses in portions of the vibration isolation coupler 140. These stresses are mainly located at locations with sharp edges, for example in the areas where the connecting elements are attached to the inner surface 168 of the first annular wall 164 and to the inner surface 184 of the second annular wall 180. To reduce the mechanical stresses in these areas, transitions with a defined radius are formed during the manufacturing process, for example in the areas of the connecting elements 159 shown in FIG. 3. Figure 7 are generally exemplarily indicated by 280.

[0077] In alternative embodiments, a three-center curve can be formed instead of a single radius. Similar strategies can be used for the first load transfer ring 285 located at the first end portion 187 of the second annular wall 180 and / or the second load transfer ring 287 located at the second end portion 173 of the first annular wall 164. A radius corner 290 can be formed at the transition between the second annular wall 180 and the first load transfer ring 285. A corresponding radius corner can be formed at the transition between the first annular wall 164 and the second load transfer ring 287. The load transfer rings 285 / 287 transfer loads, such as axial loads, bending loads, torsional loads, from and to the first and second connectors 144, 148. In alternative embodiments, a three-center curve can be formed instead of a single radius. Finite element simulation (FE simulation, FE modeling) can be used to model the vibration isolation coupling, where different portions of the vibration isolation coupling 140 have different material properties and dimensions (e.g., number and size of the plurality of connecting elements 159, length of the vibration isolation portion 151) to optimize and fine-tune the ratio of bending stiffness to torsional stiffness (BST / TST) as much as possible, for example, a ratio greater than 15.

[0078] Some embodiments of the foregoing disclosure are illustrated below:

[0079] Embodiment 1. A vibration isolation coupling for isolating torsional vibrations in a drill string, comprising: a first coupler portion comprising a first annular wall having an outer surface and an inner surface defining a first central bore portion; a second coupler portion disposed within the first central bore portion, the second coupler portion comprising a second annular wall having an outer surface section and an inner surface section defining a second central bore portion; and a plurality of connecting elements extending from the inner surface of the first annular wall through the second annular wall past the second central bore portion and connecting with the inner surface of the second annular wall.

[0080] Embodiment 2. The vibration isolation coupling of any preceding embodiment, wherein the second coupler portion comprises a plurality of axially spaced openings extending through the second annular wall from the outer surface section of the second annular wall to the inner surface section of the second annular wall.

[0081] Embodiment 3. The vibration isolation coupling of any preceding embodiment, wherein the plurality of axially spaced openings comprises a first plurality of axially spaced openings, a second plurality of axially spaced openings circumferentially offset relative to the first plurality of axially spaced openings, a third plurality of axially spaced openings circumferentially offset from the first plurality of axially spaced openings and the second plurality of axially spaced openings.

[0082] Embodiment 4. The vibration isolation coupling of any preceding embodiment, further comprising: a conductor extending through at least one of the plurality of connecting elements.

[0083] Embodiment 5. The vibration isolation coupling of any preceding embodiment, wherein an outer surface of the second annular wall is spaced apart from an inner surface of the first annular wall.

[0084] Embodiment 6. The vibration isolation coupling of any preceding embodiment, further comprising: a seal disposed between the first coupling portion and the second coupling portion.

[0085] Embodiment 7. The vibration isolation coupling of any preceding embodiment, wherein the first coupling portion comprises a first tubular portion and the second coupling portion comprises a second tubular portion, the first tubular portion, the second tubular portion, and the plurality of connecting elements are formed from a same material.

[0086] Embodiment 8. The vibration isolation coupling of any preceding embodiment, wherein the first coupling portion comprises a first tubular portion and the second coupling portion comprises a second tubular portion, the first tubular portion and the second tubular portion are formed from a first material, and the plurality of connecting elements are formed from a second material different from the first material.

[0087] Embodiment 9. The vibration isolation coupling of any preceding embodiment, wherein the plurality of connecting elements are integrally formed with the first coupling portion and the second coupling portion.

[0088] Embodiment 10. The vibration isolation coupling of any preceding embodiment, wherein the second coupling portion is concentric with the first coupling portion.

[0089] Embodiment 11. The vibration isolation coupling of any preceding embodiment, wherein the first annular wall comprises a first end portion and a second end portion, and the second annular wall comprises a first end portion and a second end portion, the first end portion of the second annular wall supports the first connector, and the second end portion of the first annular wall supports the second connector.

[0090] Embodiment 12. The vibration isolation coupling of any preceding embodiment, wherein the first connector comprises a female threaded connector and the second connector comprises a pin connector.

[0091] Embodiment 13. The vibration isolation coupling of any preceding embodiment, further comprising the first connector and the second connector, wherein the first connector is connected to the second annular wall by a weld and the second connector is connected to the first annular wall by a weld.

[0092] Embodiment 14. The vibration isolation coupling of any preceding embodiment, wherein the vibration isolation coupling comprises a torsional spring constant that defines a torsional resonance frequency that is less than 100 Hz, whereby vibrations between the first coupling portion and the second coupling portion having a frequency higher than about the torsional resonance frequency are isolated.

[0093] Embodiment 15. The vibration isolation coupling of any preceding embodiment, wherein the vibration isolation coupling isolates torsional vibrations through elastic bending of the plurality of connecting elements.

[0094] Embodiment 16. A method of isolating torsional vibrations from a portion of a drill string connected to another portion of the drill string through a vibration isolation coupling having a first coupling portion connected to a second coupling portion through a plurality of connecting elements, the method comprising: introducing torsional vibrations into the first coupling portion; transmitting the torsional vibrations into the plurality of connecting elements extending from an inner surface section of the second coupling portion, through an annular wall of the second coupling portion to an inner surface of the first coupling portion; and isolating the transmission of the torsional vibrations from the first coupling portion to the second coupling portion through elastic bending of the plurality of connecting elements.

[0095] Embodiment 17. The method of any preceding embodiment, wherein isolating the torsional vibrations comprises elastically bending the plurality of connecting elements in a direction perpendicular to a longitudinal axis of the vibration isolation coupling.

[0096] Embodiment 18. The method of any preceding embodiment, further comprising: limiting a torsional angle of the second coupling portion relative to the first coupling portion through at least one torsional end stop.

[0097] Embodiment 19. The method of any preceding embodiment, further comprising: flowing a drilling fluid through the vibration isolation coupling.

[0098] Embodiment 20. The method of any preceding embodiment, further comprising: selecting a torsional stiffness of the vibration isolation coupling to have a torsional resonance frequency of the vibration isolation coupling that is less than 100 Hz; and selecting a moment of inertia of a section of the drill string positioned below the vibration isolation coupling to have a moment of inertia of the torsional resonance frequency of the vibration isolation coupling; and isolating torsional vibrations between the first coupling portion and the second coupling portion having a frequency higher than about the torsional resonance frequency.

[0099] The terms“about” and“substantially” are intended to include a degree of error, based on the equipment available at the time of submission, associated with a particular measurement. For example,“about” and / or“substantially” can include a range of ± 8% or 5%, or 2% of a given value.

[0100] In the context of describing the application (particularly in the context of the appended claims), the use of the terms “a,” “an,” and “the” and similar referents is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the use of the terms “first,” “second,” etc., do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

[0101] The teachings of the present disclosure can be used in a variety of well operations. These operations can involve treating a formation, fluids residing in the formation, a wellbore, and / or equipment in the wellbore, such as production tubulars, with one or more treatment agents. The 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, cementing agents, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers, and the like. Exemplary well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water injection, cementing, and the like.

[0102] While the application has been described with reference to one or more example embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the application. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the application without departing from the essential scope thereof. Therefore, it is intended that the application not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this application, but that the application will include all embodiments falling within the scope of the claims. Also, in the drawings and the specification, there have been disclosed exemplary embodiments of the application and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, otherwise, the scope of the application thus not to be construed as being limited to the specific embodiments set forth herein but to include all embodiments falling within the scope of the claims.

Claims

1. A vibration isolation coupling (140) for isolating torsional vibrations in a drill string (20), comprising: a first coupling portion (154) including a first annular wall (164) having an outer surface (166) and an inner surface (168) defining a first central bore (170) portion; a second coupling portion (156) disposed within the first central bore (170) portion, the second coupling portion (156) including a second annular wall (180) having an outer surface segment (182) and an inner surface segment (184) defining a second central bore (186) portion; and a plurality of connecting elements (159) extending from the inner surface (168) of the first annular wall (164) through the second annular wall (180) over the second central bore (186) portion and connecting with the inner surface segment (184) of the second annular wall (180); wherein the vibration isolation coupling (140) isolates torsional vibrations by elastic bending of the plurality of connecting elements (159).

2. The vibration isolation coupling (140) of claim 1, wherein the second coupling portion (156) includes a plurality of axially spaced openings (190a, 190b, 193a, 193b, 196a, 196b, 198a, 198b) extending from the outer surface segment (182) of the second annular wall (180) through the second annular wall (180) to the inner surface segment (184) of the second annular wall (180).

3. The vibration isolation coupling (140) of claim 2, wherein the plurality of axially spaced openings (190a, 190b, 193a, 193b, 196a, 196b, 198a, 198b) includes a first plurality of axially spaced openings (190a, 190b), a second plurality of axially spaced openings (193a, 193b) circumferentially offset relative to the first plurality of axially spaced openings (190a, 190b), a third plurality of axially spaced openings (196a, 196b) circumferentially offset from the first plurality of axially spaced openings (190a, 190b) and the second plurality of axially spaced openings (193a, 193b).

4. The vibration isolation coupling (140) of claim 2, further comprising: a conductor (260) extending through at least one of the plurality of connecting elements (159).

5. The vibration isolation coupling (140) of claim 1, wherein the outer surface segment (182) of the second annular wall (180) is spaced apart from the inner surface (168) of the first annular wall (164).

6. The vibration isolation coupling (140) of claim 1, further comprising: a seal (160) disposed between the first coupling portion (154) and the second coupling portion (156).

7. The vibration isolation coupling (140) of claim 1, wherein the first coupling portion (154) comprises a first tubular portion (162) and the second coupling portion (156) comprises a second tubular portion (171), the first tubular portion (162), the second tubular portion (171), and the plurality of connecting elements (159) being formed of the same material.

8. The vibration isolation coupling (140) of claim 1, wherein the first coupling portion (154) comprises a first tubular portion (162) and the second coupling portion (156) comprises a second tubular portion (171), the first tubular portion (162) and the second tubular portion (171) being formed of a first material, and the plurality of connecting elements (159) being formed of a second material different from the first material.

9. The vibration isolation coupling (140) of claim 1, wherein the plurality of connecting elements (159) are integrally formed with the first coupling portion (154) and the second coupling portion (156).

10. The vibration isolation coupling (140) of claim 1, wherein the second coupling portion (156) is concentric with the first coupling portion (154).

11. The vibration isolation coupling (140) of claim 1, further comprising a first connector (144) and a second connector (148), wherein the first connector (144) is welded to the second annular wall (180) and the second connector (148) is welded to the first annular wall (164).

12. The vibration isolation coupling (140) of claim 1, wherein the vibration isolation coupling (140) comprises a torsional spring constant defining a torsional resonance frequency less than 100 Hz, whereby vibrations between the first coupling portion (154) and the second coupling portion (156) having a frequency higher than the torsional resonance frequency are isolated.

13. A method of isolating torsional vibrations from a portion of a drill string (20) connected to another portion of the drill string (20) by a vibration isolation coupling (140) according to any one of claims 1 to 12 having a first coupling portion (154) connected to a second coupling portion (156) by a plurality of connecting elements (159), the method comprising: introducing the torsional vibrations into the first coupling portion (154); transmitting the torsional vibrations into the plurality of connecting elements; and isolating the transmission of the torsional vibrations from the first coupling portion (154) to the second coupling portion (156) by elastic bending of the plurality of connecting elements (159). ​ 14. The method according to claim 13, wherein isolating torsional vibrations comprises elastically bending the plurality of connecting elements (159) in a direction perpendicular to a longitudinal axis of the vibration isolation coupling (140).

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