Shear collar having upper and lower sub bodies with longitudinally aligned shear connector

Abstract

The disclosure relates to a shear collar system having upper and lower sub bodies with a longitudinally aligned shear connector. The upper and lower sub bodies have corresponding torque lugs that provide mating surfaces between the upper and lower sub bodies via a slip-fit. The shear collar includes an internal shear pin aligned with a longitudinal axis of the assembled system.

Description

SHEAR COLLAR HAVING UPPER AND LOWER SUB BODIES WITH LONGITUDINALLY ALIGNED SHEAR CONNECTORCROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application Serial No. 63 / 626,960, filed January 30, 2024, the entire content of which is herein incorporated by reference.FIELD

[0002] The disclosure relates to a shear collar system having upper and lower sub bodies with a longitudinally aligned shear connector. The upper and lower sub bodies have corresponding torque lugs that provide mating surfaces between the upper and lower sub bodies via a slip-fit. The shear collar includes an internal shear pin aligned with a longitudinal axis of the assembled system.BACKGROUND

[0003] A shear collar is a device used on a production string where separation is a requirement should a downhole device become difficult or impossible to retrieve. In a submersible pump application for example, equipment often becomes lodged due to sedimentation, corrosion or fouling (e.g. asphaltene adhesion) with the inner bore of the steel casing of the well. Removal of the production string or sucker rod is required in order to apply a remedy in removal of such equipment. That is, the production string or sucker rod must be detached from the submersible pump in order that other equipment can be placed in the well to enable the pump removal and any required remedy.

[0004] Present design technologies utilize some form of shear pin or screw application that provides a point of weakness in the production string at a desired point. Typically, a number of shear planes introduced through the solid wall of an upper or lower sub provide a resistance to an axial load introduced by pulling on that production / sucker rod string from surface but that will fail when an axial load above a threshold is applied.

[0005] One problem is that when high torque loads are applied the shearing system will fail. That is, and as downhole sub have relatively small diameters, a desired torque shear strength may be difficult to incorporate within a shear collar whilst enabling a desired axial shear strength.

[0006] As a result, and in the field, production string loads can inadvertently exceed shear systems, particularly if the drill string is torqued / rotated, resulting in unwanted failure of the shear collar. Most often, the failure is the inability to shear off the collar sub assembly.

[0007] One method to overcome this limitation is to make use of a forced interface within torque lugs that reduce torque loads. As described in Canadian patent 2855128 (23 June 2014) and US patent 9605493 (28 March 2017), a torque lug is a geometry used to enable rotation of the production string which is often an advantage when landing equipment during the final stages of completion. As shown in Figures 1 and 2, a torque lug has a forced fit interface between upper and lower subs of a sucker rod shear collar where mating torque flats enable the rotational loads to be delivered to the production string but not to the shear pins. Thus, shearing of the shear pins can only be affected by an axial load.

[0008] That is, by providing an interference fit at the torque flats, a rotational load considerably greater than the shear capacity of a set of the shear pins makes high rotational loads possible.

[0009] I n these systems, assembly of the shear collars can only be done at the factory as heavy equipment such as a bench arbor or hydraulic press is required to press shear collars together. Moreover, once this type of collar is used, it cannot be re-used, and is discarded.

[0010] In view of the foregoing, there is a need for improved shear collars that address various problems of past systems including enabling re-use of the system.SUMMARY

[0011] In accordance with the disclosure, shear collar system is described, the shear collar system having: an upper sub having an upper sub body configured with an upper sub connector to connect to drill string components, an upper sub bore and at least one upper sub torque lug; a lower sub having a lower sub body configured with a lower sub connector to connect to drill string components, a lower sub bore and at least one lower sub torque lug; a shear pin configured to connect to the upper sub body within the upper sub bore and within the lower subbore wherein each of the upper sub and lower sub are configured to connect to each other via the upper and lower sub torque lugs and the shear pin, upper sub bore and lower sub bore are configured for the shear pin to connect the lower sub and upper sub with each other.

[0012] In various embodiments,• the shear pin is a threaded shear pin having a shear plane substantially perpendicular to a longitudinal axis of the shear pin and where the shear plane is a zone of weakness.• the upper sub bore and lower sub bore are threaded and configured to engage with the threaded shear pin.• the system includes a lock collar configured to thread to the shear pin, the lock collar having a flange for seating against a lock nut surface within the lower sub body.• the lock collar includes at least one tool engagement surface for engagement with a tightening tool.• the upper sub body engages with the lower sub body and the upper and lower sub torque lugs engage with a slip-fit.• each of the upper sub, lower sub and shear pin have a liquid nitration finish.• each of the upper sub, lower sub and shear pin have a zinc phosphate finish.• the shear pin has a narrowed neck region defining the shear plane.• the shear mechanism is a collet having a plurality of collet fingers each having a flange configured for engagement within a corresponding lower sub groove of on the lower sub. each collet finger flange has a contact surface with a groove contact surface within the lower sub groove and where the contact surface is greater than zero degrees with respect to a transverse cross-section plane.the shear mechanism includes a pin and a plurality of balls and ball springs configured to engage with a ball groove on the pin and where the ball springs are configured to compress the balls within the ball groove.• the ball springs are secured within channels within the lower sub and locked within the channels with set screws.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Various objects, features and advantages of the disclosure will be apparent from the following description of particular embodiments, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments. Similar reference numerals indicate similar components.Figures 1 and 2 are isometric and cross-sectional perspective views respectively of a shear collar in accordance with the prior art.Figure 3, 3A and 4 are isometric, exploded and cross-sectional perspective views respectively of a shear collar in accordance with one embodiment the disclosure.Figures 5A-5B are cross-sectional / transparent and end views of a shear collar design in accordance with one embodiment of the disclosure.Figures 6A-6B are cross-sectional / transparent and end views of a lower sub in accordance with one embodiment of the disclosure.Figures 7A-7D are cross-sectional / transparent, side and end views of an upper sub in accordance with one embodiment of the disclosure.Figures 8A-8C are cross-sectional / transparent, end and isometric / transparent views of a lock collar in accordance with one embodiment of the disclosure.Figures 9A-9B are side and end views of a threaded shear pin in accordance with one embodiment of the disclosure.Figures 10A-10C are side, exploded and isometric / transparent views of a shear collar having a spring collet shear mechanism in accordance with one embodiment of the disclosure.Figures 11A-11C are side, exploded and isometric / transparent views of a shear collar having a ball and spring shear mechanism in accordance with one embodiment of the disclosure.DETAILED DESCRIPTION

[0014] With reference to figures 3 to 9, a shear collar system 10 is described having an upper sub 10a and a lower sub 10b configured to connect via slip-fit torque lugs 11 , shear mechanism such as a shear pin or stud 12 and lock collar 18 (or collet or ball / spring system). This assembly, forming the shear collar system, may be connected to other components of a downhole string (not shown). The shear collar system 10 is configured to enable the separation of the upper sub from the lower sub under high axial loads.

[0015] Within this description, terms such as “upper”, “lower”, “uphole” and “downhole” are used to describe the general orientation of components in use and as a general descriptor of the relative position of different components on a string that may be assembled for use within a well. The terms are intended to provide an understanding of orientation and relative position of components but not necessarily as a definitive position as understood by those skilled in the art.

[0016] As shown in Figures 1 and 2, a prior art shear collar 5 having upper 5a and lower 5b subs are shown. In this system, the upper sub includes upper pin threads 5h to enable connection of the shear collar 5 to other components of a downhole string assembly. The upper sub includes a pin body shaft 5k for insertion into the lower sub 5b. The lower sub 5b includes lower pin threads 5j to enable connection of the shear collar 5 to other components of the downhole string. The lower sub is hollow to receive pin body shaft 5k. Each of the upper and lower subs include a number of torque flats 6 having a forced interface that when forced together, enable upper and lower shear pins 5f and 5h to be inserted through the pin shaft 5k and lower sub 5b. The shear pins define / have shear planes 5e, 5g that are substantially parallel to a longitudinal axis of the shear collar.

[0017] As described above, the shear pins may be sheared under axial load, i.e. under load parallel to the shear planes 5e, 5g. Importantly, in order to effect shearing, the majority of force required to effect longitudinal shearing and separation of the upper and lower sub is consumed by overcoming the interference-fit at the torque lugs 6.

[0018] As shown in Figures 3-9, a first embodiment of an improved shear collar system 10 having a shear pin / stud 12 and lock collar 18 is described. The shear collar system 10 is referred to herein as a threaded shear pin shear collar (TSPC). The TSPC includes an upper sub 10a and lower sub 10b. Other embodiments are described with reference to Figures 10A- 10C and 11A-11C.

[0019] The upper sub includes upper pin threads 10h having a diameter D1 to enable connection of the TSPC to other components of a downhole string as is known to those skilled in the art. The lower sub 10b includes lower pin threads 10j having an internal diameter D3 to enable connection of the TSPC 10 to other components of a string as is known to those skilled in the art.

[0020] Each of the upper and lower subs 10a, 10b include torque flats 11 having a slip-fit interface that enables the upper and lower subs to be manually engaged with one another and interior components enabling threaded shear pin 12 to engage and lock the upper and lower subs together as will be explained below.

[0021] The structure and interconnection of each of the upper sub 10a, lower sub 10b and threaded pin 12 with lock collar 18 are further described with reference to Figures 3-9.

[0022] The upper sub (US) has US body 15 having diameter D2 downhole of threads 10h. US body 15 has threaded upper bore 15a sized to receive the threaded shear pin 12. US body 15 includes flange 15b having external torque lugs 11 and mating surface 15c for engagement with a corresponding mating surface 16c on the lower sub.

[0023] The lower sub (LS) has LS body 16 having a diameter substantially equal to diameter D2. LS body 16 has LS bore 16a having an internal diameter D5 sized to receive lock collar 18 and threaded shear pin 12. LS body includes flange 16b having internal torque lugs 11 and mating surface 16c for engagement with the corresponding mating surface 15c in the upper sub.

[0024] LS bore 16a includes mating surface 17 configured to receive and engage with flange 18a of lock collar 18 that may be tightened by engaging a tool (not shown) within tool bores 18b.

[0025] The TSPC is generally assembled according to the following representative steps. It is understood that the following steps may be performed in various alternate orders to achieve a similar assembly with the appropriate tension / loads being applied to the various mating surfaces: a) Threaded shear pin 12 is inserted into US bore 15a and threaded a sufficient distance for rated loads. b) The upper and lower subs are aligned and moved together over the threaded shear pin such that the torque surfaces 11 of each sub engage with each other. c) Lock collar 18 is inserted with LS bore 18a over threaded shear pin and tightened via tool bores 18b such that lock nut flange 18a engages tightly against mating surface 17. d) The assembled TSPC may be connected to other drill string components.Threaded Shear Pin

[0026] The threaded shear pin 12 includes a shear plane (shown as 12c in Figure 5A) generally perpendicular to the longitudinal axis of the TSPC that is rated to fail at the shear plane under a designed axial load. As such the threaded shear pin may have a neck 12a being a section of reduced diameter D6 that minimizes the cross-sectional area of metal at a desired point in the threaded shear pin.

[0027] The threaded shear pin 12 and lock collar 18 may be tightened by simple shop tools and will include any additional mating surfaces (e.g. tool bores 18b) required to engage with specific assembly tools.

[0028] In operation, if shearing is required, an appropriate axial load is applied to the string to initiate failure at the shear plane thus causing separation of the upper and lower subs.

[0029] When recovered to surface, the sheared threaded shear pin can be removed from both the upper and lower subs and the upper and lower subs reassembled with a new threaded shear pin.

[0030] Importantly, the TSPC enables field servicing as the TSPC can be reassembled with a new threaded shear pin and simple tools as compared to past systems that required machine presses to engage the interference-fit torque lugs.

[0031] In addition, different threaded shear pins can be readily configured having different materials and / or shear failure strengths / parameters thus providing flexibility to operators during completion design and / or removal operations.Alternate Designs

[0032] With reference to Figures 10A-10C and 11A-11C, alternate designs of a shear pin mechanism are shown. Figures 10A-10C show a spring collet design and Figures 11A-11C show a ball and spring design.

[0033] In each case, the US and LS are substantially similar to the systems as described above but differ in terms of the means of engagement of the shear mechanism within the LS.

[0034] As shown in Figures 10A and 10B, finger collet 100 is configured to connect the US and LS. The finger collet has a threaded uphole portion as above and slotted collet fingers 100a each having outer flanges / nubbins 100b that are configured to engage with groove 101 on the LS. In this embodiment, the shear collar is assembled in the same manner as described above wherein the finger collet is screwed into the US until the point where the individual fingers / nubbins 100b engage within the groove 101.

[0035] Resistance to string tensile load is from outward radial deflection of the slotted collet fingers. The combination of the spring pressure of the collect fingers and contact angle of each finger collet flange / nubbin 100b within groove 101 determines the shear load to separate the LS from the US. Importantly, the contact angle is greater than 0 degrees to the transverse cross section such that separation can occur without shearing off the nubbins. That is, the combination of the contact angle and spring pressure (e.g. a 5-degree offset angle) can enable separation once an pre-determined axial load is reached. The idea here is that the collet finger spring load is amplified by a sharp incline, hence a large axial load but known force is required for separation.

[0036] Other mechanisms such as bow springs with nubbins or dog-latches may be configured as the means of engaging the shear mechanism with the LS.

[0037] Figures 11A-11C show another embodiment having a number of circumferentially distributed balls 110b, springs 110a and set-screws 110 configured to engage within one or more grooves 111a, 111b on the shear pin that are secured within threaded bores 110c.

[0038] This design operates similarly to the finger collet design where the balls 110b are similar to flanges / nubbins as above and the spring pressure set by the springs and set-screws determines the axial load to enable US and LS separation. That is, semi-circular grooves 111a, 111 b have a step height that must be overcome in order for separation to occur.

[0039] Other systems such as a key and keyway system (not shown) could be employed.

[0040] Ideally, any system enables ready calculation and consistency in manufacturing to ensure that the shear load required for separation is at a desired threshold and within a known range.Other Design Features

[0041] The TSPC may be designed in a number of diameters to meet production string requirements.

[0042] Various materials, component finishes and geometries can be adjusted for specific applications.

[0043] In one embodiment, a liquid nitration finish is used to impart hardness as well as reduction of downhole corrosion by removing carbon steel from oxidation. As liquid nitration is an absorption process, a liquid nitration finish cannot be peeled off or damaged by impingement.

[0044] In another embodiment, a zinc phosphate finish is used to minimize surface damage such as scrapping, denting, and / or spalling that can occur during running in hole (RIH) operations.

[0045] Importantly, the neck of the preferential shear plane 12c in addition to material selection, can accurately dial in a host of shear strengths dictated by the hole design.

[0046] Although the present technology has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the technology.

Claims

CLAIMS1 . A shear collar system comprising: an upper sub having an upper sub body configured with an upper sub connector to connect to drill string components, an upper sub bore and at least one upper sub torque lug; a lower sub having a lower sub body configured with a lower sub connector to connect to drill string components, a lower sub bore and at least one lower sub torque lug; a shear mechanism configured to connect to the upper sub body within the upper sub bore and within the lower sub bore wherein each of the upper sub and lower sub are configured to connect to each other via the upper and lower sub torque lugs and the shear mechanism, upper sub bore and lower sub bore are configured for the shear mechanism to connect the lower sub and upper sub with each other.

2. The shear collar system as in claim 1 where the shear mechanism is a threaded shear pin having a shear plane substantially perpendicular to a longitudinal axis of the shear pin and where the shear plane is a zone of weakness.

3. The shear collar system as in claim 2 where the upper sub bore and lower sub bore are threaded and configured to engage with the threaded shear pin.

4. The shear collar system as in claim 3 further comprising a lock collar configured to thread to the shear pin, the lock collar having a flange for seating against a lock nut surface within the lower sub body.

5. The shear collar system as in claim 4 wherein the lock collar includes at least one tool engagement surface for engagement with a tightening tool.

6. The shear collar system as in any one of claims 1 -5 wherein the upper sub body engages with the lower sub body and the upper and lower sub torque lugs engage with a slip-fit.

7. The shear collar system as in claim 1 where the shear mechanism is a collet having a plurality of collet fingers each having a flange configured for engagement within a corresponding lower sub groove of on the lower sub.

8. The shear collar system as in claim 7 where each collet finger flange has a contact surface with a groove contact surface within the lower sub groove and where contact surface is greater than zero degrees with respect to a transverse cross-section plane.

9. The shear collar system as in claim 1 where the shear mechanism includes a pin and a plurality of balls and ball springs configured to engage with a ball groove on the pin and where the ball springs are configured to compress the balls within the ball groove.

10. The shear collar system as in claim 9 where the ball springs are secured within channels within the lower sub and locked within the channels with set screws.11 . The shear collar system as in any one of claims 1-10 wherein each of the upper sub, lower sub and shear mechanism have a liquid nitration finish.

12. The shear collar system as in any one of claims 1-10 wherein each of the upper sub, lower sub and shear mechanism have a zinc phosphate finish.

13. The shear collar system as in any one of claims 2-6 wherein the shear pin has a narrowed neck region defining the shear plane.

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