Heat treat production fixture

Abstract

A method for manufacturing a metal structure (130) for use in a downhole assembly comprises plastically deforming at least a portion of the metal structure (130); and heating at least the deformed portion of the metal structure to a temperature below its critical and/or transformation temperature. An assembly for performing the method comprises a production fixture (370) configured to receive the metal structure (130), wherein the production fixture is adapted to undergo heating to a temperature below and/or up to the critical and/or transformation temperature of the metal structure. By heating at least the deformed portion of the metal structure to a temperature below its critical and/or transformation temperature, the metal structure may undergo stress relief, which may help prevent undesirable movement of deformed portion, e.g. collet fingers of a catching apparatus, against the direction of deformation after impact(s) and/or shock(s) from moving objects, in use.

Claims

1. A method for manufacturing a metallic catching apparatus for use in catching an object in a downhole assembly, the method comprising: forming a cylindrical portion at or near a first end of the catching apparatus; forming a plurality of radially moveable seat members arranged circumferentially around a longitudinal axis, the seat members being provided at or near a second end of the catching apparatus; forming a plurality of fingers which extend between the cylindrical portion and the seat members, wherein the fingers and associated seat members define a plurality of collet fingers; plastically deforming at least a portion of the collet fingers; and heating at least the deformed portion of the collet fingers to a temperature below a critical and/or transformation temperature of the material forming the collet fingers.

2. The method according to claim 1, comprising providing or arranging the catching apparatus on a production fixture.

3. The method according to claim 2, wherein the production fixture comprises a mandrel.

4. The method according to claim 2, wherein the production fixture defines a cylindrical outer surface, and/or a tapered profile outer surface.

5. The method according to claim 2, wherein plastically deforming at least the portion of the collet fingers comprises forcing the catching apparatus onto the production fixture.

6. The method according to claim 2, comprising securing and/or fixing the catching apparatus to the production fixture.

7. The method according to claim 6, wherein securing and/or fixing the catching apparatus to the production fixture comprises use of a housing configured to contact at least a portion of an outer surface of the catching apparatus.

8. The method according to claim 7, comprising securing and/or fixing the housing to the production fixture.

9. The method according to claim 1, wherein heating comprises heating at least the deformed portion of the collet fingers to the temperature in the range of at least one of: 10-100 C. below the critical and/or transformation temperature; 20-90 C. below the critical and/or transformation temperature; 40-80 C. below the critical and/or transformation temperature; and 50 C. below the critical and/or transformation temperature.

10. The method according to claim 1, wherein heating comprises heating at least the deformed portion of the collet fingers to the temperature in the range of 450550 C.

11. The method according to claim 1, wherein the catching apparatus comprises steel.

12. The method according to claim 1, wherein heating comprises heating at least the deformed portion of the collet fingers for a period of time sufficient to remove a predetermined level of stress in said deformed portion.

13. The method according to claim 1, wherein heating comprises heating at least the deformed portion of the collet fingers at a predetermined level of the temperature for at least one of: at least 1 hour; at least 2 hours; at least 4 hours; and at least 24 hours.

14. The method according to claim 1, wherein heating comprises heating the entire catching apparatus.

15. The method according to claim 14, comprising providing or arranging the catching apparatus on a production fixture and providing the catching apparatus in position on the production fixture in a heating apparatus.

16. The method according to claim 15, comprising providing the catching apparatus, the production fixture, and the housing in the heating apparatus.

17. The method according to claim 1, comprising cooling at least the deformed portion of the collet fingers.

18. The method according to claim 17, wherein cooling comprises cooling at least the deformed portion of the collet fingers at a predetermined temperature.

19. The method according to claim 17, wherein cooling comprises regulating and/or controlling the cooling of at least the deformed portion of the collect fingers so as to avoid and/or minimize stress resulting from temperature change.

20. The method according to claim 1, comprising hardening at least a portion of the catching apparatus.

21. The method according to claim 1, comprising gas nitriding at least a portion of the catching apparatus.

22. The method according to claim 20, wherein the hardened and/or nitride layer has a thickness in the region of approximately 0.012-0.020 (0.3-0.5 mm).

23. The method according to claim 20, wherein the hardened and/or nitride layer has a hardness of at least one of: 550 HV; and between 550 HV10 and 750 HV10.

24. The method according to claim 21, comprising injecting ammonia gas into a heating apparatus.

25. The method according to claim 1, wherein heating comprises simultaneously heating at least the deformed portion of the collet fingers, to the temperature below the critical and/or transformation temperature, and hardening at least a portion of the catching apparatus.

26. An assembly for manufacturing a metallic catching apparatus according to the method of claim 1 for use in a downhole assembly.

27. A metallic catching apparatus manufactured according to the method of claim 1 for use in a downhole assembly.

28. The method according to claim 1, comprising plastically deforming each collet finger from an initial retracted position into an extended position, such that, in use, the collet fingers are moveable to their retracted position to catch the object.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 a side view of a metal structure according to an embodiment of the present invention, in the form of a ball catching apparatus in a downhole assembly, in an extended or plastically deformed configuration;

(3) FIG. 2A a side view of a metal structure according to an alternative embodiment of the present invention, in the form of a ball catching apparatus in a downhole assembly, in an extended or plastically deformed configuration;

(4) FIG. 2B the metal structure of FIG. 2A in a retracted or pre-deformation (catching) configuration.

(5) FIGS. 3A to 3D are perspective views of the metal structure of FIG. 1, shown in different stages of manufacture;

(6) FIG. 4 is a cross-sectional view of a production fixture for manufacturing a metal structure, according to an embodiment of the present invention; and

(7) FIG. 5 is a schematic representation of a heating apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF DRAWINGS

(8) A portion of a downhole tool, generally identified by reference number 100, is illustrated in FIG. 1. In the present embodiment the downhole tool 100 is for use in treating, for example fracturing, a subterranean formation. The tool 100 comprises a housing 110 which defines a plurality of ports 111 (only one visible on FIG. 1). A valve sleeve 120 is mounted within the housing 110 and is shown in a closed position in FIG. 1, in which the ports 111 are closed and sealed via o-rings 112. When in this initial closed position the valve sleeve 120 is pinned to the housing 110 via shear pin 113. The sleeve 120 comprises a plurality of sleeve ports 121.

(9) A catching apparatus 130, according to an embodiment of the present invention, is mounted within the housing 110 on a downhole side of the valve sleeve 120. The catching apparatus 130 is provided, generally, in the form of a collet-type sleeve, and comprises a tubular body 131 and a plurality of collet fingers 132 which extend axially from the tubular body 131. Each finger 132 carries at a distal end thereof a respective seat member 133. The catching apparatus 130 defines a longitudinal axis 134, which is coincident with the longitudinal axis of the tool 100, and the fingers 132 and seat members 133 are circumferentially distributed around the axis 134. The fingers 132 are deflectable by bending in a longitudinal direction to permit the seat members 133 to be selectively moved radially into and out of a central bore or passage 115 defined by the catching apparatus 130.

(10) In the configuration shown in FIG. 1, the seat members are positioned in an outwardly deformed or radially extended position, received within a recess 116 provided in the housing 110, and thus removed from the central bore 115. Accordingly, any object passing through the tool 100 will not be caught by the catching apparatus 130. For example, a passing object may continue past the tool 100 to perform some operation further downhole, for example within a deeper tool. In this respect, the catching apparatus 130 may be considered to be presented in a free configuration in FIG. 1.

(11) An activator sleeve 140 is located downhole of the catching apparatus 130, wherein said sleeve 140 defines an activation surface 141 and a step profile 142. In the configuration shown in FIG. 1 the activator sleeve 140 is secured to the housing 110 via a number of shear screws 143, and covers an annular recess 144.

(12) FIG. 2A shows a portion of a downhole tool 200, generally similar to the downhole tool 100 of FIG. 1, like part being denoted by like numerals, but incremented by 100.

(13) Whereas in FIG. 1, adjacent the seat members 133 of adjacent collet fingers 132 define substantially straight or longitudinally extending contact surfaces 135 when in an retracted or catching configuration, the seat members 233 of adjacent collet fingers 232 of the catching apparatus 230 of FIG. 2A define a contact surface 235 comprising circumferentially extending meshing or overlapping surfaces.

(14) In other embodiments, the catching apparatus 130,230 may comprise contact surfaces having alternative profiles, such as waved, toothed, or the like.

(15) The downhole tool 200 is shown in FIG. 2B in an initial activated configuration. Specifically, the shear screw 213 has been sheared and the valve sleeve 220 has been axially moved in a downhole direction to open the ports 211 and permit fluid communication outwardly from the tool 200. The valve sleeve 220 may be moved by any suitable actuator, such as via a piston. In some embodiments the valve sleeve may be moved or actuated by an indexing sleeve, such as a collet sleeve disclosed in WO 2011/117601 and/or WO 2011/117602.

(16) During actuation the valve sleeve 220 acts upon the catching apparatus 230, causing the apparatus 230 to also move axially downhole within the housing 210, driving the seat members 233 out of the recess 216 and onto the activation surface 241 of the activator sleeve 240. Relative movement of the catching apparatus 230 and activator sleeve 240 is arrested upon engagement of the seat members 233 against the step profile 242. Thus, the seat members 233 are positioned radially inwardly in a retracted configuration, and into the central bore 215 of the apparatus 230. Such a configuration of the apparatus 230 may define a catching configuration. That is, any object, such as a ball 250 (shown in broken outline) of appropriate dimension passing through the tool 200 will engage and seat against the seat members 233, thus becoming caught.

(17) In the exemplary embodiment shown, the ball 250 may function to block the tool 200 and establish a flow diversion such that substantially all fluid may be diverted outwardly through the ports 211, for example to fracture a surrounding formation. Further, in some embodiments the ball 250 may have previously operated a system, such as an indexing system, to initially move the valve sleeve 220 and/or catching apparatus 230.

(18) Reference is now made to FIGS. 3A to 3D which provide perspective views of the catching apparatus 130 in sequential stages of manufacture.

(19) A cylindrical metal component 130a is provided as in FIG. 3A, and the catching apparatus 130 is initially machined as a complete component to the form illustrated in FIG. 3B. The catching apparatus 130 includes an uphole tubular portion 131 having a number of ports 135.

(20) The seat members 133 are initially formed as a complete annular structure 133a, in the form that the seat members 133 adopt when positioned radially inwardly to catch a ball. The collet fingers 132 are provided as longitudinal ribs 132a which extend, at a slight inward taper, from the uphole tubular portion 131 to the complete annular structure 133a. The ribs 132a define slots 136 therebetween.

(21) Once formed in this way the annular structure 133a is divided by wire cutting to form the individual seat members 133, as illustrated in FIG. 3C.

(22) Following this division, the individual seat members 133 and associated collet fingers 132 are plastically deformed radially outwardly, to the form shown in FIG. 3D. This step is described below in more detail.

(23) Referring now to FIG. 4, there is shown a production fixture, generally denoted 370, according to an embodiment of the present invention. In this embodiment, the production fixture 370 is configured to receive the catching apparatus 130 of FIG. 3C.

(24) The production fixture 370 comprises a mandrel 371. In this embodiment the mandrel 371 comprises a hollow core. However, in other embodiments, the mandrel may have other constructions, e.g. may be solid.

(25) The catching apparatus 130 is slid onto the mandrel 371. An upper portion of the catching apparatus 130, e.g. a portion comprising the tubular portion 131, is positioned near an upper portion 372 of the mandrel 371. The upper portion of the mandrel defines a substantially cylindrical outer surface. The mandrel 371 also comprises a tapered portion 373 which defines a substantially conical or frusto-conical outer surface. As the catching apparatus 130 is slid onto the mandrel 371, the seat members 133 engage the tapered portion 373 and are forced radially outwardly, thus deforming the collet fingers 132. If the stress on the fingers exceeds the elastic limit or yield point of the metal from which they are made, then plastic deformation occurs. Unlike elastic deformation, where a material will return to its original shape when the applied stress is removed, plastic deformation involves applying a level of stress beyond the yield point of the material, thereby causing permanent deformation.

(26) As shown on FIG. 4, the production fixture 370 comprises a housing 375. The housing 375 is configured to engage with the catching apparatus 130 and to secure the catching apparatus 130 onto the mandrel 371. In this embodiment, the production fixture 370 comprises screws 376 to secure the catching apparatus 130 to the mandrel 371. The housing 375 comprises apertures 377 arranged to allow insertions of screws 376 through the housing 375. The screws are inserted though the slots 136 between fingers 132 of the catching apparatus 130. The mandrel 371 may also comprises apertures (not shown) for receiving the screws 376, thus securing the housing 375 to the mandrel 371, thereby ensuring secure engagement of the catching apparatus 130 between the mandrel 371 and the housing 375.

(27) The mandrel 371, housing 375, and screws 376 are made of a metal suitable to be heated and to withstand a predetermined temperature up to the critical and/or transformation temperature of the catching apparatus 130.

(28) According to a method of the present invention, at least a deformed portion of the catching apparatus 130 is heated to a temperature below its critical and/or transformation temperature in order to relieve stress within the deformed portion. In the present embodiment, the production fixture 370, including the catching apparatus 130 fixed to the production fixture 370, is heated.

(29) An embodiment of a suitable apparatus 400 for performing stress relief according to the present invention is shown in FIG. 5. The production fixture 370, including the catching apparatus 130 fixed to the production fixture 370, is placed in oven or furnace 400. In this embodiment, the furnace 400 has several shelves 491,492,493. This allows a plurality of catching apparatus 130 to be placed simultaneously in the furnace 400, for improved productivity and/or for improved consistency within a batch.

(30) By heating the plastically deformed collet fingers 132 of the catching apparatus 130, to a temperature below its critical and/or transformation temperature, the metal structure undergoes stress relief. This, in turn, may help prevent undesirable subsequent movement of the plastically deformed collet fingers 132, against the direction of deformation, after impact(s) and/or shock(s) from moving objects, in use. Further, by maintaining temperature below the critical and/or transformation temperature of the metal, the method of the present invention does not significantly affect the crystallinity or structural integrity and/or properties of the metal.

(31) In this embodiment, the catching apparatus 130 is placed in a furnace 400 preheated at a predetermined temperature. In other embodiments, the catching apparatus may be placed in an unheated furnace, and the temperature of the furnace 400 may then be raised to a predetermined temperature.

(32) In this embodiment, the catching apparatus 130 is heated to a temperature in the range of 10-100 C., e.g. 20-90 C., e.g. 40-80 C., below its critical and/or transformation temperature. In one embodiment, the method comprises heating the catching apparatus 130 to a temperature approximately 50 C. below its critical and/or transformation temperature. In this embodiment, the catching apparatus 130 is made of steel. The catching apparatus 130 is heated to a temperature of 450-550 C. for approximately 96 hours.

(33) It will be appreciated that the critical and/or transformation temperature depends on the particular type of metal or metal alloy from which the catching apparatus 130 is made, and the skilled person would determine the desired heating temperature based on the known critical and/or transformation temperature for a particular metal or metal alloy.

(34) The catching apparatus 130 is left in the furnace 400 at the predetermined temperature below its critical and/or transformation temperature, for a predetermined amount of time, e.g. for a period of time sufficient to remove a predetermined level of stress in the catching apparatus 130. In one embodiment, the catching apparatus 130 is left in the furnace 400 at the predetermined temperature for a period of time sufficient to remove, e.g. at least 25%, at least 50%, at least 75%, or at least 90% of the stress caused by plastic deformation in the collet fingers 132. In this embodiment, the method comprises heating the catching apparatus 130 at the predetermined temperature for approximately 96 hours.

(35) In this embodiment, the method comprises hardening the catching apparatus 130. The method comprises injecting a nitrogen-containing gas, in this embodiment ammonia, in the furnace 400 via a gas injector 495. Without wishing to be bound by theory, it is understood that, when a nitrogen-containing gas, e.g. ammonia, comes into contact with the heated catching apparatus 130, nitrogen reacts with and diffuses into the surface of the metal apparatus, to form a nitride layer. By nitriding the catching apparatus 130 while heating the catching apparatus 130 to a temperature of approximately 50 C. below its critical and/or transformation temperature, e.g. to a temperature of 450-550 C., for approximately 96 hours, the method allows simultaneously relieving stress from at least the deformed portion of the steel catching apparatus 130, and hardening the surface of the catching apparatus 130. The method provides a nitride layer having a thickness in the region of approximately 0.012-0.020 (0.3-0.5 mm), and a hardness in the region of 550 HV10 and 750 HV10, as measured in accordance with ASTM E384.

(36) The catching apparatus 130 is then cooled.

(37) In one embodiment, the catching apparatus 130 is removed from the furnace 400, and left to cool at a predetermined temperature, e.g. at ambient temperature.

(38) In another embodiment, the catching apparatus 130 is cooled in a controlled manner by lowering the temperature of the furnace following a predetermined temperature profile, e.g. by cooling the metal structure at a predetermined rate.