EXPANDABLE METAL-TO-METAL SEAL

BACKGROUND

In the hydrocarbon recovery arts, seals are endlessly used to effect working conditions supportive of desired production fluid recovery. In recent years engineering and development dollars have been spent attempting to improve both pressure holding capacity and longevity. One type of seal receiving significant interest is a metal-to-metal seal due to the fact that of many types metal seals exhibit high temperature tolerance, high-pressure capability, robust chemical resistance, and high durability.

Although there are many types of seals that utilize metal as a sealing structure, those receiving the most attention contemporaneously with the filing of this document are heavier wall metal seals that are deformed in order to bring them into contact with another structure in a manner where a seal is created against that other structure. While such seals do indeed provide all of the above noted benefits with respect to metal-to-metal seals, recovery sometimes can be difficult. Such seals experience a high degree work hardening when they are set and because of this work hardening experience loss of resilience. This is of course an issue with respect to stretching a seal out to retrieve it from the wellbore.

SUMMARY

A seal includes a seal body having a bridge; at least one leg extending from the bridge; and at least one concentrated deformation area of the at least one leg, at least that area being at least one of polished and annealed after machining.

A method for improving durability of a plastically deformed metal-to-metal seal includes identifying one or more portions of the seal that experience a threshold deformation in use; and treating one or more of the identified portions with at least one of a polishing process and an annealing process after machining.

A method for making a metal-to-metal seal includes annealing a blank material; machining the blank material into a machined piece; and at least one of polishing and annealing the machined piece.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alike in the several Figures:

FIG. 1 is a schematic view of one embodiment of a seal disclosed herein in a run in condition;

FIG. 2 is a schematic view of the embodiment of FIG. 1 illustrated in a set position;

FIGS. 3A-3F represent sequential views of the seal of FIG. 1 withdrawing from the set position during retrieval;

DETAILED DESCRIPTION

Initially it is to be understood that the seal created as disclosed herein performs better in one respect due to its teardrop cross sectional shape. The shape itself helps to absorb backlash in the setting force and therefore renders the seal more reliable. This is described in more detail in connection with one embodiment of a seal that forms the stated shape. It is also to be understood that although the drawings hereof illustrate a seal that bows radially outwardly, the components can easily be reversed such that the seal will bow radially inwardly such that the seal will be formed against a tubular radially inwardly disposed of the seal device rather than radially outwardly of the seal device as specifically illustrated.

Referring to FIG. 1, an embodiment of a seal 10 in accordance with this disclosure is illustrated. The seal 10 comprises a seal body 12 having a first end ring 14 and a second end ring 16. Seal body 12 comprises a seal bridge 18 and first and second seal legs 20 and 22. The legs terminate at roots 36 and 38. Seal 10 further includes configurations capable of causing the seal body to collapse axially into a set position such as, for example, two gauge rings 24 and 26, each disposed in operable communication with one end of the seal body 12. While gauge rings are specifically disclosed, the terms as used herein are intended to convey any configuration capable of loading the seal body 12 to set the seal 10 and to be instrumental in retrieving the seal 10. This “operable communication” as noted is, in one embodiment, a fixed connection to each end ring 14 and 16, respectively, while in other embodiments it can float. The fixed connection as illustrated is adjacent roots 36 and 38. The gauge rings 24 and 26 are also in supportive communication with the legs 20 and 22, respectively. As can be readily seen in FIG. 1, each gauge ring includes an angled surface identified by the numerals 28 and 30, respectively. The surfaces 28 and 30 are roughly parallel to the legs 20 and 22 although not in contact therewith prior to the setting sequence for the seal 10. These surfaces 28 and 30 come in contact with the legs 20 and 22 during the setting sequence to support the same as will be better appreciated after exposure to the operation section of this document.

Also visible in FIG. 1 are two radiuses 32 and 34 provided one on each of gauge rings 24 and 26, respectively. The radiuses, in one embodiment, are in a range of about 0.13 to about 0.16 inch. While a wider range is also operable, it has been found that the range of about 0.13 to about 0.16 is effective in minimizing stress in the seal body 12 during setting. This is also the purpose for which the angled surfaces 28 and 30 are provided. The angle of the surfaces 28 and 30 is selected to coincide with the angle of legs 20 and 22 as noted above in order to support these structures thereby preventing significant bending thereof during setting of the seal 10. Angles for surfaces 28 and 30 range in particular embodiments from about 45 degrees to about 90 degrees. As illustrated, the angles are both about 60 degrees. The range indicated has been found to work well though it is to be appreciated that angles outside the exemplary range are also contemplated but may not reduce stress in legs 20 and 22 to the extent of the reduction found in the identified range.

The prevention of bending reduces work hardening effects that would otherwise be experienced in these locations. Such reduction in work hardening effectively equates to more residual elasticity in the material of the seal in locations of the seal (legs and roots) that will be subject to bending stresses upon retrieval of the seal. During setting of the seal the bending stress is localized in the bridge 18 and in retrieval, bending stress is localized in the legs and roots. Generally, materials that are somewhat ductile can be bent at least once without breaking, work hardening, of course, building within the material during this and any subsequent bending stress. Since in the disclosed seal, the configuration ensures that bending is experienced substantially only once in each localized area of the seal 12, the likelihood of each localized area enduring sufficient stress to rupture is dramatically reduced. The protective action of the surfaces 28 and 30 extends to both the legs 20 and 22 and leg roots 36 and 38, respectively. By avoiding stress in these structures during setting of the seal 10, the ability to retrieve the seal 10, without suffering a rupture of the seal, is facilitated. It is further noted that in the seal 10, nowhere is there a sharp bend of the material of the seal body 12. Rather, all bends are gradual thereby spreading the stress over a broader area of the seal material. This avoids point stresses that generally create weaknesses in the seal both while being initially deformed and certainly while being retrieved. As such, embodiments of the invention alleviate the problem found in the prior art as noted above.

One last point that should be made prior to a discussion of actuation of an exemplary seal 10 is that seal body 12 is a machined part in one embodiment such that there are no, or extremely little, residual stresses in the body 12 in the position shown in FIG. 1. Little residual stress in the seal body 12 prior to deformation in use is a benefit as this helps to minimize the magnitude of stresses experienced by the body 12 during setting. As the purpose of this configuration is the reduction in initial stress of the body 12, it is noted that an alternate arrangement is that body 12 could be a preformed and stress relieved component for some applications or even a molded component for some applications. Again, the important thing is that the position illustrated at the roots 36 and 38 is a position of the seal body 12 that should exist prior to setting of the seal, with very little residual stress. Further, stress is not introduced into roots 36 and 38 during the setting of the seal 10 due to the configuration of the gauge rings thereby retaining elasticity of the material of the body 12 in the legs and the roots. This is to the operator's advantage during retrieval of the seal 10, as noted above.

Referring now to FIGS. 1 and 2 simultaneously, setting of seal 10 is illustrated. Seal 10 is set through the application of an axial load resulting in the space between the gauge rings diminishing. This can be effected in a number of ways including: 1) by causing at least one of the gauge rings to move toward the other of the gauge rings while the “other” gauge ring is stationary; 2) to cause one ring to move toward the “other” ring while the other ring moves away from the one ring more slowly than the one ring is moving toward the other ring; or 3) to cause one ring to move toward the other ring while the other ring is moving towards the one ring. For illustrative purposes, the drawings and description herein are directed to an embodiment where gauge ring 24 is moved while gauge ring 26 remains stationary through, for example, operable contact with an anchoring mechanism (not shown).

Due to the shape of body 12, one will appreciate that axial shortening thereof will necessarily cause the body 12 to bulge outwardly. What may not be immediately appreciated from the drawings, however, is the action of gauge rings 24 and 26 on the process. As gauge rings 24 and 26 are moved so that they are closer to one another, surfaces 28 and 30 come into contact with legs 20 and 22, respectively. As contact is made in this location, the legs 20 and 22 are substantially supported such that they and the roots 36 and 38 from which the legs extend experience very little bending stress while the seal 10 is being set. Since the distance between gauge rings 24 and 26 is still being reduced, however, the seal body 12 must necessarily still react. Due to the supported condition of legs 20 and 22, a great majority of the bending stress in the body 12 is concentrated in the bridge 18. The stress in bridge 18 causes it to bow outwardly until it makes contact with an inside surface 40 of a tubular in which the seal 10 is being set. Once contact is made at surface 40, a load useful for creating the desired seal begins to build. As gauge rings 24 and 26 continue to be urged into closer proximity with one another it will become apparent that radiuses 32 and 34 are also important to reducing stress in the seal body 12. In the position of FIG. 2, it will be easily appreciated that were the radiuses to be significantly sharper, much higher stress would be experienced by the seal body 12 at the contact point with such radiuses. It has been determined by the inventors hereof that a radius range of from about 0.13 inches to about 0.16 inches produces a desirably low stress in the seal body 12.

It is to be appreciated from FIG. 2 that the bridge 18 is deformed such that over an axial length thereof, more than 180 degrees of repositionment is represented. In other words, the bridge 18 is deformed from relatively flat to beyond U-shaped. In the illustrated embodiment of FIG. 2, it will be appreciated that the bridge is nearly a closed teardrop shape 44. In the condition illustrated in FIG. 2 substantial sealing force is applied to surface 40 such the pressure may be held in either direction relative to seal 10. Important to notice as well is that because of the teardrop shape of bridge 18, backlash in the setting system is better absorbed than in prior art sealing systems. This is because with a reduction in the sealing force at gauge rings 24 and 26 move slightly away from each other. When this occurs elastic resilience in the bridge 18 will tend to straighten the two sides 46 and 48 of the teardrop shape 44. This will tend to increase loading at interface 50 with surface 40 rather than to reduce loading at interface 50 which would have been common in the prior art.

Referring now to FIGS. 3a through 3f retrieval of seal 10 is illustrated in sequence. It is important to note in this sequence of drawings the relative positions of the legs 20 and 22 versus the teardrop shape 44 as they are illustrated in FIGS. 3b and 3c. Upon review of these figures it will become apparent to one of ordinary skill in the art that the teardrop shape 44 is maintained substantially intact while the legs 20 and 22 and the roots 36 and 38 are subjected to tensile bending stress and experience a greater degree of movement. This is beneficial since as noted above the legs and roots are protected from bending stress during initial setting of this seal. Therefore they have significantly greater elasticity than the bridge 18, which has been work hardened, at this stage in use of the seal 10. With reference to FIG. 3d, it can be ascertained that he bridge 18 has begun to reopen but it is also important to note that the interface 50 has come out of contact with surface 40 by a significant margin at this point in the retrieval process. While more bending stress is being added to bridge 18 at this point in the process a rupture is less likely to create a problem. Moving on to FIGS. 3e and 3f the seal has already been substantially withdrawn and again rupture at this point is less damaging. It will also be appreciated by the reader at legs 20 and 22 and roots 36 and 38 are now significantly deformed but because this deformation is the first bending stress experienced by those components, they are highly likely to survive that stress.

In order to further enhance survivability of the seal when it undergoes retrieval stress, it has been discovered by the inventors hereof that one or both of a second annealing process and a polishing process applied to areas of the seal particularly stressed will substantially improve retrieval results without rupture of the seal. Areas of the seal that are subject to stresses that induce significant work hardening and predispose the seal to rupture are identified through various means such as Finite Element Analysis (FEA) studies, skilled observations, and experience, for example. One or more of these identified areas may be treated with at least one of the polishing and annealing processes noted. In some instances, one or more of the identified areas will be treated with both processes. Further, in some embodiments, the entire seal will be treated with one or both of the noted processes in order to avoid the need for identifying specific areas of the seal that would benefit from treatment. Annealing is to be performed on a machined piece created by machining of a blank. The annealing process includes in one embodiment using a vacuum annealing process employing a contact thermocouple at about 1800 degrees Fahrenheit for about one hour and a fast (gas) cool. Polishing comprises removing fine machining grooves with a sand paper or crocus cloth, for example. The polishing process is then finished utilizing a 320 grit of finer sandpaper or equivalent. In one particular embodiment of a seal a blank is machined to within about 0.2 inch of minimum outside dimension and maximum inside dimension. The rough machined part is then heat treated using a contact thermocouple for about one hour at about 1800 degrees Fahrenheit and then oil quenched or fan cooled. The part is then finish machined. After finish machining either the whole part or one or more identified areas is one or more of annealed and polished as noted above.

The foregoing description might be reasonably understood to relate to only a symmetrically positioned seal. It is to be appreciated however that depending upon the type of movement utilized during the setting process it is sometimes advantageous to prepare the seal 10 as a non-symmetrical device. More specifically, and utilizing one-gauge-ring movement as an example, if gauge ring 24 is moved toward gauge ring 26 while gauge ring 26 is held in a stationary position it is reasonably likely that the teardrop shape 44 will contact the inside surface 40 (at interface 50) before the seal 10 is fully set. While it is subtle in the drawings utilized to exemplify the invention, careful consideration of the illustrated position of interface 50 relative to a centerline of the seal 10 will show that it is offset in the direction of gauge ring 24. This is because of the contact with surface 40 prior to fully setting of the seal 10. Once contact is made at interface 50, the positioning of side 48 is relatively fixed and the positioning of side 46 will continue to change. Side 46 will deflect under the impetus of gauge ring 24 to have a greater curvature than that of side 48. Because it is desirable to promote symmetry as much as practicable in teardrop 44 it may be desirable in certain applications to vary a thickness of the seal body 12 over its length. More specifically is possible to utilize thickness of seal body 12 to encourage early deformation in some portions of the seal body 12 and delayed deformation in other portions of the seal body 12. Generally speaking in order to enhance symmetry in the teardrop 44 a lesser thickness at the more relatively fixed end of seal body 12 will allow side 48 to more readily deform into a desirable position. Likewise, while the angles of the angled surfaces 28 and 30 and the radiuses 32 and 34 need not be symmetrical and in some applications may be better operable by being disparate. It is further to be understood that although the disclosure hereinabove describes an embodiment where each component is mirrored on both axial ends of the seal 10, albeit not necessarily with the identical dimensions or shapes, the teardrop shape can still be created with asset of the identified components on but one axial side of the seal 10 with the other side being simply attached to a carrier component.

While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.

EXPANDABLE METAL-TO-METAL SEAL

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