CROSS REFERENCE PARAGRAPH

[0001] This application claims the benefit of U.S. Provisional Application No. 63/374,980, entitled " THROUGH-ROTARY CENTRALIZER," filed September 8, 2022, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND

[0002] The present invention relates to a through-rotary centralizer for downhole operations. This may include a wireline tool string, such as a powered wireline milling string for various milling or other rotary applications, including removing debris or obstructions. The through-rotary centralizer has a sleeve with an opening through its center that allows a shaft or mandrel to rotate through the sleeve opening, thus providing power to a bit or other tool on the downhole side of the through-rotary centralizer. The sleeve may have extendable centralizing arms that can pass through downhole tubing, such as casing, and extend to grasp the inner wall of the tubing, thereby centralizing the tool string within the tubing.

[0003] A milling string (also referred to as a milling tool or milling toolstring) may be used for numerous downhole operations, including removing debris and scale buildups, tubing restrictions, and plugs. The milling string’s rotating drill bit engages an obstruction to remove it. It is desired to center the drill bit within a tubular during such operations so that the bit engages the desired area within the tubular and not the tubular itself or any components within the tubular. The drill bit may be moved away from the centerline of the tubular by torque from the drill bit, the obstruction, or if the milling string is not perfectly vertical, such as in a deviated wellbore. A centralizer assists with keeping the bit centered within the tubular by engaging the inner surface of the tubular and holding the bit within the center. The centralizer ideally is located in close proximity to the bit.

[0004] Various types of centralizers are known, but none can rotatably transmit torque or rotation through their center as disclosed and described in the current inventions. Examples of prior centralizers include slipover centralizers, inline centralizers, and integral centralizers.

[0005] A slipover centralizer may be a hollow cylinder mounted around the circumference of milling string. The outside diameter of a slipover centralizer is selected to be smaller than the narrowest tubular that the milling string is intended to pass through. Otherwise, the milling string cannot be lowered to the desired areas downhole. A slipover centralizer is fixedly mounted to the milling string, such as with a bolt or set screw. This type of centralizer thus has a fixed outer diameter that cannot adjust as it moves downhole and rotates with the milling string.

[0006] An in-line centralizer is installed as one of the components in the milling string. It may be installed using threads located at each end that match the threads of adjacent milling string components. One example of this type of stabilizer includes bowsprings that can compress inwards to fit through a tubular. The bowsprings may have a coil spring attached to each end of the bowsprings to assist with pushing the bowsprings outwards, thus applying additional force to the inside surface of the tubular for centralizing. Because this stabilizer is mounted “in line,” it rotates with the milling string.

[0007] An integral centralizer is part of the milling string and may include collapsible bowsprings that extend and contract as the milling string is lowered through a tubular. This type of stabilizer rotates with the milling string as it is fixedly mounted to the string.

[0008] A centralizer provides more effective centralization of the drill bit or other downhole tool if the centralizer is located close to the bit. The above examples of prior centralizers typically are not installed adjacent to the bit. If such a centralizer was installed adjacent to the bit on the rotating portion of the bit tool, the centralizer itself would rotate along with the bit, which also is not a desired feature of a centralizer due to wear or damage that the centralizer could cause to the inside of the tubular or components therein.

[0009] As a result, a need exists for devices, systems, and methods directed to a through- rotary centralizer that is rotatably mounted to the milling string, can be mounted proximate the drill bit, can pass through the desired wellbore tubing, can centralize a tool string within the tubing, and transmits power or torque through the center of the centralizer.

SUMMARY

[0010] Examples described herein include devices, systems and methods for a through- rotary centralizer for downhole operations, such as providing centralization and torque for a bit or other rotary tool. The through-rotary centralizer may be installed proximate the downhole end of the rotary tool, such as proximate a drill bit. The through-rotary centralizer has a mandrel, a sleeve rotatably mounted around the mandrel, a floating hub slidably mounted around the sleeve, and centralizing arms mounted to the sleeve and/or floating hub. The centralizing arms are able to extend and contract, in part due to the floating hub’s ability to slide along the sleeve. The centralizing arms may be bendable or articulating to provide extension and contraction. The centralizing arms exert outward force against a wellbore tubular, such as casing, thereby providing centering force for the rotary tool.

[001 1] The centralizing arms may be bowsprings or bar linkages. The centralizer may include a second floating hub wherein each end of the centralizing arms is attached to one of the floating hubs. Coil springs may be installed around the sleeve to provide centralization force for the centralizing arms. For example, coil springs may be configured such that they press against the floating hubs in a direction that will in turn push the centralizing arms outwards.

[0012] The centralizing force of the through-rotary centralizer may be varied through known variations of the components used in the centralizer. For example, the strength of the bowsprings, the number of centralizing arms, the strength of the coil springs, and the number of coil springs.

[0013] The through-rotary centralizer also may be configured so that the centralizing arms can fully retract to minimize their diameter, which in turn allows the centralizer to pass through a tubular. For example, the mandrel may be sufficiently long to provide room for the centralizing arms to fully retract and the diameters of the mandrel and sleeve may be small enough to provide clearance for the centralizing arms to fully retract. The through-rotary centralizer also may be configured so that the centralizer is small enough to fit through the intended wellbore tubular.

[0014] In another example, the mandrel may include a longitudinal passage through its center, such as for allowing hydraulic fluid.

[0015] In another example, the through-rotary centralizer may be comprised of a mandrel, a sleeve rotatably mounted around the mandrel, and a cylinder or standoff mounted around the sleeve. The standoff is sized to be larger in diameter than the rotating tool, such as a bit, to provide centralization.

[0016] In another example, a through-rotary centralizer is part of a system that also includes a surface system. The surface system has a deployable cable attached to the tool string and controls the depth and operation of the tool string.

[0017] In another example, a through-rotary centralizer is used in methods for centralizing a downhole tool in a wellbore tubular. [0018] Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the examples, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. l is a side view of a well site where a through-rotary centralizer of the present invention may be used.

[0020] FIG. 2 is a side view of various types of wireline tools, including a milling tool.

[0021] FIG. 3 is a perspective view of a milling tool.

[0022] FIG. 4 is a cross sectional view of a through-rotary centralizer.

[0023] FIG. 5 is a cross sectional view of a through-rotary centralizer with a fixed standoff.

DESCRIPTION OF THE EXAMPLES

[0024] Reference will now be made in detail to the present examples, including examples illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0025] Examples described herein include devices, systems, and methods for a through- rotary centralizer. The centralizer may be installed near an operating tool, such as a drill bit, to keep the tool within the center of a tubular, provide torque to the operating tool, and avoid damaging the tubular or any other components therein. The through-rotary centralizer has centralizing arms that extend and hold the centralizer against the inner wall of a tubular. The centralizer has an inner mandrel that can rotate independently of the centralizing arms via a sleeve rotatably mounted around the mandrel. Rotary power (torque) to the tool is transmitted through the mandrel, which rotates, while not requiring the centralizing arms to rotate. However, the centralizing arms may articulate or move inwards and outwards to maintain force on the tubular wall as the through-rotary centralizer passes through varying diameter tubulars. The centralizing arms are attached at one end to a floating hub slidably mounted around the sleeve. Alternatively, the other ends of the centralizing arms may be attached to a second floating hub. Coil springs around the sleeve may also be included to provide additional centering force against the floating hubs, which in turn provides more centering force to the centralizing arms.

[0026] FIG. 1 shows an exemplary well site where a slot cutting tool of the present invention may be utilized. A formation 1 has a drilled and completed wellbore 2. A derrick 3 above ground may be used to raise and lower components into the wellbore 2 and otherwise assist with well operations.

[0027] A wireline surface system 4 at the ground level includes a wireline logging unit, a wireline depth control system 5 having a cable 6, and an electronic control system 7. The cable 6 is connected to a wireline tool string 8 that may be lowered downhole. The electronic control system 7 includes a processor 9, memory 10, storage 11, and display 12 that may be used to control various operations of the wireline surface system 4, send and receive data, and store data.

[0028] The wireline surface system 4 can deploy the cable 6, which in turn lowers the wireline tool string 8 deeper downhole. Conversely, the wireline surface system 4 can retract the cable 6 and raise the wireline tool string 8, including to the surface. The cable 6 is deployed or retracted by the wireline depth control system 5, such as by unwinding or winding the cable 6 around a spool that is driven by a motor.

[0029] The wireline logging unit communicates with the electronic control system 7 to send and receive data and control signals. For example, the wireline logging unit can communicate data received from the wireline tool string 8 to the electronic control system 7. The wireline logging unit likewise can communicate data and control signals received from the electronic control system 7 to the wireline tool string 8.

[0030] As shown in FIG. 2, the wireline tool string may be any number of down hole tools, such as a debris removal tool, milling tool 8, setting tool, shifting tool, or stroking tool. A through-rotary centralizer of the present invention may be used as part of a milling tool, as described herein. However, it should be appreciated that the inventions of the through-rotary centralizer may be used with any wireline tool where the ability to transmit rotating power or torque through a centralizer is desired.

[0031] A wireline tool string for milling may include a telemetry module 13, control module 14, and a milling tool that includes a tractor 15, and milling module 16. The telemetry module 13 and control module 14 send and receive data with the surface system 4, control equipment in the tool string, and have other computing capabilities for operating the tool string.

[0032] FIG. 3 shows an exemplary configuration of the milling tool with tractor 15 and milling module 16. The tractor 15 uses powered wheels or gears to guide the tool string along the well bore. The milling module 16 may include a power cartridge, a weight-on-bit mechanism, a rotary mechanism, and a bit 17 or other rotary device that interacts with the wellbore or something in it. The bit could of any type, such as a scale-milling bit or metalmilling bit. Alternatively, the end of a tool used with the present invention may utilize a brush, cutter, underreamer, hone, or any other implement that would benefit from centralization or positioning within a wellbore tubular.

[0033] In operation, the tool string with milling tool 8 is lowered into the wellbore using the wireline surface system 4. The tool string travels farther down hole as the surface system 4 deploys cable 6. The tractor 15 may also assist with lowering the tool string by mechanically grasping the inner surface of the wellbore tubular pulling the tool string farther down hole. This is particularly useful in regions where the tubular is not vertical and instead in a deviated or sideway direction.

[0034] When the drill bit 17 nears the desired area of milling, the bit 17 is activated by applying rotation, thereby spinning the bit 17. The tool string is lowered so that the now spinning bit 17 contacts the desired area of milling, such as scale buildup or an obstruction, and the bit 17 is continually lowered until it passes through the end of the desired area of milling. It is desired to keep the bit 17 centered within the wellbore tubular so that the bit 17 only engages with material intended to be milled. Without centering, the bit may deviate within the tubular and cause damage to the inside of the tubular, connections between sections of the tubular, or any components in the wellbore.

[0035] To provide centering for the bit 17, FIG. 4 shows a cross sectional view of a through-rotary centralizer 18 of the present invention. The through-rotary centralizer 18 preferably is installed proximate the bit 17 but may be installed anywhere along the milling tool 8, such as between the tractor 15 and milling module 16. Although the centralizer 18 provides centering as described, it is also capable of transmitting torque to downhole tools.

[0036] The through-rotary centralizer 18 includes a mandrel 19 that is fixedly attached along or as part of the rotating mechanism that drives the drill bit 17. Thus, the mandrel 19 rotates as the bit 17 rotates. The mandrel 19 can be installed along the drill string in any variety of ways, such as threads or pins. The mandrel 19 may have a reduced diameter section to provide clearance within the wellbore tubular for centralizing arms, as explained in more detail below. In the example of FIG. 4, the mandrel 19 includes a portion that extends to contact the milling module 16 or bit 17.

[0037] A sleeve 20 is rotatably mounted around a portion of the mandrel 19. Rotation of the sleeve 20 around the mandrel 19 may be achieved by any known designs, including plain bearing, bushing sleeve, or bearings. For example, diamond bearings may be used where heavy debris might interfere with the rotation of the mandrel inside the sleeve. As power or torque is transmitted through the mandrel 19, the sleeve 20 is able to rotate independent of the mandrel 19 due to its rotatable installation.

[0038] Floating hubs 21, 22 are rotatably and slidably installed around the sleeve 20. As a result, the hubs 21, 22 are able to rotate around the sleeve 20 as well as move up and down along the length of the sleeve 20. The floating hubs 21, 22 may have bearings to reduce friction for sliding along the sleeve.

[0039] Centralizing arms are attached at each end to the floating hubs 21, 22. Any type of compressible or articulating arm may be used as a centralizing arm. As shown, the through- rotary centralizer 18 includes bowsprings 23 and 3-bar linkages 24, where the middle linkage of each 3-bar linkage 24 is attached to a bowspring 23. Each bowspring 23 is attached at each end to a floating hub 21. Likewise, each 3-bar linkage 24 is attached at each end to a floating hub 22.

[0040] Coil springs 25 are mounted around the sleeve 20 between the floating hubs 21 attached to the bowsprings 23 and end surfaces of the sleeve 20. Thus, the coil springs 25 remain captured on the sleeve 20 between the end surface of the sleeve 20 and floating hubs 21. As coil springs 25 are compressed, they provide force against floating hubs 21 as a hub 21 moves towards an end of the sleeve 20, such as if a bowspring 23 is compressed towards the centerline of the centralizer 18. Similarly, coil springs 26 are mounted around the sleeve 20 between floating hubs 22 attached to the 3-bar linkages 24. These coil springs 26 resist the motion of floating hubs 22 towards an end surface of the sleeve 20, such as if a 3-bar linkage is compressed towards the centerline of the centralizer 18. [0041] This configuration provides centering force for the drill bit 17. Because of the sliding movement of the floating hubs 21, 22, the bowsprings 23 and 3 bar linkages 24 may be compressed inwards towards the centerline of the centralizer 18. Specifically, as the bowsprings 23 and 3-bar linkages 24 are compressed, the floating hubs 21, 22 are able to move along the length of the sleeve 20, which allow the bowsprings 23 and 3 bar linkages 24 to compress towards the centerline of the centralizer 18. Therefore, when the centralizer is placed into a wellbore tubular, the centralizing arms (for example, the bowsprings 23 and 3 bar linkages 24 shown in FIG. 4) compress inwards so that the centralizer 18 can pass through the inside of a tubular. Although the centralizer 18 provides centering as described, it is also capable of transmitting torque to downhole tools.

[0042] As the centralizer 18 passes through narrower sections of tubular, the centralizing arms continue to compress towards the centerline of the centralizer 18. Conversely, the centralizing arms can expand as the centralizer 18 passes through wider sections of tubular. For example, the bowsprings 23 provide outward force for this expansion. The coil springs 25, 26 also provide outward expansion force by pressing against the floating hubs 21, 22.

[0043] The mandrel 19 may have a length sufficient to provide room for the bowsprings 23 and 3-bar linkages 24 to completely close or lay flat against the sleeve 20. Thus, when fully compressed, the centralizer 18 has a diameter small enough to fit through the entire portion of the tubular through which the drilling operations are to be performed. The centralizer 18 can be configured and sized to have a diameter less than or equal to the diameter of the bit 17. This can be achieved by the mandrel 19 and the sleeve 20 having diameters less than the bit 17 diameter, the sleeve having a reduced diameter section to provide clearance for the centralizing arms to compress to a diameter less than the bit 17, or the mandrel 19 having sufficient length to provide clearance for the centralizing arms. The length of the mandrel 19 may be varied to accommodate different standoff or centralizer configurations.

[0044] As the centralizing arms are compressed, the coil springs 25, 26, bowsprings 23, and 3-bar linkages 24 exert outward force against the inner wall of the tubular. This outward force is created by the spring force of coil springs 25, 26 against the floating hubs 21, 22 and the bowsprings 23 under bending force from being compressed downhole. This outward force and displacement of the centralizing arms provides centering force for the drill bit 17.

[0045] Because the sleeve 20 can rotate independently of the mandrel 19, the centralizing arms hold the centralizer 18 within a tubular without rotating while the torque is carried through the mandrel inside them. In this manner, the centralizer 18 can be configured to transmit torque. In operation, the centralizing arms expand and contract as the through-rotary centralizer passes through narrower or wider diameter portions of tubular. The centralizing arms exert outward forward against the inner walls of tubular to hold the centralizer in the center of the tubular, thereby providing centering of the drill bit 17. At the same time, the mandrel is free to rotate and provide rotational power to the tool downhole, such as the rotating bit 17. Thus, the centralizing arms do not rotate much, if at all, relative to the tubular, as the rotating tool operates. This is advantageous because the through-rotary centralizer may be installed proximate the bit 17 for improved centralization.

[0046] Many alternatives of the above embodiments may be used to achieve centralization under the present inventions. The centralizer 18 may use any number of centralizing arms. Thus, the number of bowsprings 23 or 3-bar linkages 24 may be varied depending on the application. The centralizer 18 may use a 4-bar linkage instead of a 3-bar linkage. The centralizer 18 could use only bowsprings 23 without any bar linkages or bar linkages without any bowsprings 23. The bowsprings 23 could close to the sides of the mandrel

19 instead of against it. The bowsprings 23 could rotate out instead of translating out.

[0047] The centralizer 18 could utilize a single floating hub instead of a hub at each end of a centralizing arm. Thus, one end of the centralizing arm would be fixedly attached to the sleeve and the other end of the centralizing arm would be attached to the single floating hub. As a centralizing arm is compressed or expanded, the single floating hub can travel along the sleeve 20 to provide room for the centralizing arm to compress or expand. This configuration could employ any number or types of centralizing arms attached to the single floating hub.

[0048] The centralizer 18 could utilize stiffer bowsprings 23 to provide more centering strength or less stiff bowsprings if less centering force is sufficient for the application. The stiffness of the bowsprings 23 can be varied based upon material, length, thickness, width, shape, or any other ways to vary the strength of a spring.

[0049] The centralizer 18 could omit coil springs 25, 26 entirely. This embodiment may be used where the centralizing arms, such as bowsprings 23, independently provide sufficient outward force against the tubular that the additional force provided by the coil springs 25, 26 is not necessary to provide the desired centralization. For example, the bowsprings 23 may have sufficient stiffness that they provide sufficient centering of the drill bit 17 without coil springs 25, 26.

[0050] In another alternative, the coil springs could be arranged such that they provide force against floating hubs 21, 22 under tension rather than compression. For example, coil springs could be arranged between floating hubs 21, 22 rather than between hubs and an end of the sleeve 20. In this configuration, as a centralizing arm is compressed and the floating hub moves down the sleeve 20, the coil springs are expanded in length. Due to this coil spring expansion, the coil springs exert a pulling force on the hub, which in turn exerts an outward force by the centralizing arm against the tubular to provide centralization.

[0051] Alternatively, the centralizing arms could be actively actuated, such as by hydraulic force, rather than relying on the spring force of coil springs 25, 26 or bowsprings 23.

[0052] As shown in FIG. 4, the mandrel 19 could include a passage through its center, such as to provide a hydraulic fluid passage. Hydraulic fluid may be used to operate or control a tool on the downhole side of the centralizer 18, such as a tubing cutter.

[0053] In another alternative, a mechanism could be placed between the mandrel 19 and sleeve 20 that would only allow the sleeve to rotate in one direction. This configuration would allow normal rotary motion for a drill bit 17 while also providing a secondary function, such as a disconnect, when the motion of the mandrel 19 is reversed.

[0054] As shown in FIG. 5, centralizing arms could be replaced by a simple standoff 28. As with the embodiments of FIG. 4, the sleeve 20 is rotatably mounted around the mandrel 19. The standoff 28 is fixedly mounted onto the sleeve 20. Thus, the sleeve 20 and standoff 28 are free to rotate independently of the mandrel 19. The outer diameter of the standoff 28 may be varied depending on the application, such as the inner diameter of the tubular. A standoff 28 embodiment may be useful if a large expansion ratio is not required or where there is insufficient room for a slip-over centralizer.

[0055] Other examples of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. Though some of the described methods have been presented as a series of steps, it should be appreciated that one or more steps can occur simultaneously, in an overlapping fashion, or in a different order. The order of steps presented are only illustrative of the possibilities and those steps can be executed or performed in any suitable fashion. Moreover, the various features of the examples described here are not mutually exclusive. Rather any feature of any example described here can be incorporated into any other suitable example. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.