Abstract:
An adjustable casing sub having an outer housing, an inner housing insertable into the outer housing, and a ratcheting system for coupling the inner housing within the outer housing. An annulus is between a portion of the inner and outer housing, the annulus including an inwardly tapered section. A metal faced seal is disposed in the annulus, wherein the metal faced seal includes a sliding surface and a compressive sealing surface. The sliding surface may include a malleable inlay and the compressive sealing surface may include a spring like element. Moreover, the metal faced seal radial thickness is greater than the inwardly tapered section radial thickness.

Description:
BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The device described herein relates generally to the production of oil and gas. More specifically, the device described herein relates to a sealing assembly for use in an adjustable casing sub. 
         [0003]    2. Description of Related Art 
         [0004]    Some offshore platforms have a production tree or trees above the sea surface on the platform. In this configuration, a casing string extends from the platform housing to a subsea wellhead housing disposed on the seafloor. Production casing inserted within the wellbore is supported on the subsea floor by a hanger in the subsea housing. The casing string between the subsea and surface wellhead housings is tensioned to prevent flexure that may be caused by thermal expansion from heated wellbore fluids or vibration from applied side loads. Additionally, the string length or height is typically adjusted to seat or land the upper casing within a surface hanger. 
         [0005]    A sub assembly can be attached to the casing string and used to tension the casing string and adjust its length. The sub assemblies typically comprise a pair of mated housings that in response to an applied force are mechanically retractable in length The adjustable sub assemblies connect inline within the string or on its upper end and when retracted impart a tension force on the casing string and by its retraction, shortening the casing string length. 
       SUMMARY OF INVENTION 
       [0006]    The present disclosure includes a tubular assembly extending between a platform and a subsea wellhead. In an embodiment the tubular assembly includes a casing string connected to the subsea wellhead and an adjustable casing sub coupled between the casing string and the platform. The adjustable casing sub comprises an outer housing, an inner housing selectively insertable within the outer housing, and an annulus formed between the inner and outer housings. At least one of the housings has a seal surface in the annulus. A seal is provided that moves from an initial “clearance” position to a sealing position in the annulus adjacent the seal surface. The seal may have a metal face, the face having an interfering diameter with the seal surface causing radial deformation of the seal as it moves axially within the annulus. Also included is a seal energizing system. 
         [0007]    The metal face may be a ductile metal and may be one of a silver coated metal, a eutectic alloy, an indium alloy, and combinations thereof. The compressive sealing surface may be a spring like element. The seal on a side opposite the metal face can include a resilient cantilevered member having a sealing surface on its free end that engages the other side of the housing. In one embodiment, the seal face is in sealing contact with the outer housing inner circumference. A plurality of seal elements of a soft ductile metal may be included on the seal face. The housing surface may include a transition circumscribing an axis of the adjustable casing sub, the transition defining a change in diameter of the housing, wherein on one side of the transition a clearance exists between the seal and the housing, and the other side of the transition defines the seal surface where the seal is put into interfering and sealing engagement with the seal surface. The transition may be on the outer diameter of the inner housing, or on the inner diameter of the outer housing. 
         [0008]    The seal, in one embodiment, has an elongate height aligned with the casing sub axis, the seal face comprising bands of ductile metal inlays coaxially circumscribing the body outer surface, the inlays in sliding contact with the outer housing inner surface, and the seal has an opposite side containing a sealing surface disposed on the end of a spring like cantilever member, the elastic deformable sealing surface compressively engagable with the outer circumference of the inner housing. 
         [0009]    Also disclosed herein is a well production apparatus comprising a first housing and a second housing coaxially and telescopingly engaged with the first housing with an improved seal between the housings. The seal comprises a radial seal body circumscribing an axis, the body having an elongate section aligned with the axis, elastically deformable cantilevered arms extending from the respective ends of the elongate section, sealing members extending from the end of the cantilevered arms configured for sealing engagement with one of the housings on a first side of the seal body, and a plurality of ductile metal inlays on a side of the seal body opposite to the first side. A transition is formed on one of the housings defining a transition to a sealing surface on the housing. The seal body is radially stretched when in contact with the sealing surface to put the seal members in sealing contact with the sealing surface. 
         [0010]    The present disclosure also include an adjustable casing sub, the sub including an upper end mechanically couplable to a platform, a lower end mechanically couplable to a casing string, a first housing, a second housing, wherein the housings are telescopingly insertable within one another, an energizing sleeve provided within one of the housings, elongated splines formed on the energizing sleeve inner diameter for rotating the energizing sleeve, a change in diameter radially circumscribing one of the housings defining a transition from a clearance portion to a sealing surface on the housing, a radial annulus between the first and second housing extending across the transition, and a radial seal disposed in the annulus and axially moveable therein, and the seal energized into sealing engagement with the sealing surface when urged past the transition from the clearance portion. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  is a side view of an offshore rig with a casing string extending to the seafloor, the casing string having an adjustable casing sub. 
           [0013]      FIG. 2  is a side cutaway view of an embodiment of an adjustable casing sub. 
           [0014]      FIG. 3  is a side cross sectional view of a seal for an adjustable casing sub prior to being energized. 
           [0015]      FIG. 4  is a side cross sectional view of the seal of  FIG. 3  after being energized. 
           [0016]      FIG. 5  is a side cross sectional view of an embodiment of a seal for use in an adjustable casing sub. 
           [0017]      FIG. 6  is a side cross sectional view of an embodiment of a seal for an adjustable casing sub prior to being energized. 
           [0018]      FIG. 7  is a side cross sectional view of the seal of  FIG. 6  after being energized. 
       
    
    
       [0019]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0020]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0021]    The device described herein provides a metal seal for use in an adjustable casing sub. The metal seal includes a compressible surface having a ductile metal insert that is also lubricating when axially sliding along an opposing sealing surface. The seal may also include an elastically deformable member on the opposing side of the compressible surface that elastically deforms under a compressive load, and due to its elasticity imparts a sealing force on its respective sealing surface. 
         [0022]    With reference now to  FIG. 1 , an example of an offshore rig  20  is provided in a side view. The offshore rig  20  comprises a platform  22  situated above the level of the sea  21  with a derrick structure  24  attached to the top of the platform  22 . Support legs  26  extend from the bottom of the platform and attach on the sea floor  28 . A subsea wellhead  30  is formed over a wellbore  31 . A tieback casing string  34  extends upward from the subsea wellhead and is coupled with a surface wellhead  32  that is within the platform  22  of the offshore rig  20 . In line with the casing string  34  is an adjustable casing sub  36 . As is known, insertion of the adjustable casing sub  36  can adjust the length of the casing string  34  to a predetermined length and can also tension the casing string  34 . 
         [0023]    A partial cross-sectional view of an example of an adjustable casing sub  40  is shown in  FIG. 2 . The adjustable casing sub comprises a generally annular inner housing body  42  that partially coaxially extends into an outer sleeve  50 . The outer sleeve  50  is an annular member with its inner diameter roughly equal to the outer diameter of the inner housing body  42 . These respective dimensions allow insertion and telescoping coaxial movement of the inner housing body  42  within the outer sleeve  50 . A ratchet ring housing  46  is attached to the lower terminal end of the outer sleeve  50 . The ratchet ring housing  46 , which is also annular, coaxially circumscribes a portion of the inner housing body  42  below the terminal end of the outer sleeve  50 . Teeth  48  are provided on the inner circumference of the ratchet ring housing  46  on its lower skirt section. A ratchet ring  44  is formed on the outer circumference of the inner housing body  42  and profiled on its outer surface with teeth corresponding to the teeth  48  on the ratchet ring housing  46 . The combination of ratchet ring housing  46  and ratchet ring  44  comprise a ratchet assembly  47  that permits movement of the ratchet ring housing  46  downward or away from the outer sleeve  50  while preventing upward movement of the ratchet ring housing  46 . 
         [0024]    An annular traveling sleeve  54  is coaxially affixed within a portion of the outer sleeve  50 . The traveling sleeve  54  is profiled on its inner circumference and at its lower end, in the embodiment illustrated the profiles comprise elongated torque splines  52 . The splines  52  extend generally parallel to the axis A X  of the adjustable casing sub  40 . Also coaxially disposed within the outer sleeve  50  is an annular fixed sleeve  51  having an outer diameter less than the inner diameter of the traveling sleeve  54 . The dimensions of the fixed sleeve  51  and the outer sleeve  50  form an annulus  49  therebetween. Threads  55  are formed on the outer circumference of the upper end of the traveling sleeve  54 , and corresponding threads  53  are formed on the outer diameter of the fixed sleeve  51 . 
         [0025]    The respective inner and outer diameters of the inner housing body  42  in the outer sleeve  50  form a housing annulus  45  between these two members. The annulus  45  is an annular void with a seal assembly  59  disposed therein. The seal assembly  59  includes a metal sealing face in contact with one of either the inner or outer housings to seal the coupling connection between the inner housing body  42  and outer sleeve  50 . The embodiment of  FIG. 2  also illustrates an energizing sleeve  56  for urging the seal assembly  59  into an energized sealing configuration. 
         [0026]      FIG. 3  provides a side cross-sectional view of an embodiment of a seal assembly. In this figure, the lower end of the traveling sleeve  54  connects to the energizing sleeve  56  via a locking element  58 . In this embodiment, the locking element  58  comprises a split ring compressed into respective channels formed in the traveling sleeve  54  and the energizing sleeve  56 . The energizing sleeve  56  is illustrated as a ring-like member extending around the lower circumference of the traveling sleeve  54 . A sealing element  57  may optionally be provided in a space between the outer surface of the energizing sleeve  56  and the inner radius of the outer sleeve  50 . In this embodiment, the energizing sleeve  56  outer diameter is substantially the same as the outer sleeve  50  inner diameter. The energizing sleeve  56  and outer sleeve  50  are in sliding contact. 
         [0027]    The energizing sleeve  56  lower portion terminates in an inwardly directed lip  63  that extends away from the outer sleeve  50 . An inner housing nut  61  is shown coaxially adjacent within the lower portion of the energizing sleeve  56 . The inner housing nut  61  is a largely annular member having a shoulder formed on its upper end that extends outward toward the outer sleeve  50  to form a cooperating surface with the lip  63  on the lower end of the energizing sleeve  56 . The lower terminal end of the inner housing nut is threadingly coupled to the upper terminal end of the inner housing body  42 . A shear pin  60  radially extends inward from the energizing sleeve  56  outer diameter to the inner housing nut outer diameter. The shear pin  60  is disposed below the point where the lip  63  and the shoulder  65  are coupled. 
         [0028]    An annular seal pocket  64  is shown radially disposed between the outer diameter of the inner housing body  42  and the inner circumference of the outer sleeve  50 . The annular seal pocket  64  axially extends on one end from the outer sleeve  50  to a radial ledge  43  in the inner housing body  42  radially extending outward to the inner radius of the outer sleeve  50 . An optional ring seal  69  is shown disposed in the annular seal pocket  64  adjacent the radial ledge  43 . A seal  62  is shown positioned within the annular seal pocket  64 ; a side cross-sectional view of an embodiment of the seal  62  is illustrated in  FIG. 5 . The seal  62  of  FIG. 5  comprises a seal body  66 , cantilever members  68  shown on an inner diameter, and metal inlays  74  depicted on an outer surface of the seal  62 . The body  66  has an elongate height with respect to its thickness, and in the embodiment of  FIG. 3  the elongate portion is largely parallel to the axis of the adjustable casing sub  40 . The cantilever members  68  comprise elongate cantilever legs  70  having sealing members  72  on their free end. The sealing members  72  face away from the body  66 . 
         [0029]    The body  66  and cantilever members  68  may be comprised of materials such as stainless steel, titanium, or any elastically deformable material capable of withstanding an applied distributed force without permanently deforming. In one example of use, the force is about 40,000 lbf/in 2 , and another embodiment the force is about 30,000 lbf/in 2 , and yet another embodiment the force is about 25,000 lbf/in 2 . The metal inlays  74  are comprised of a soft ductile metal plastically deformable upon applied sealing loads. Moreover, the inlays  74  should compress when the seal  62  placed in sealing engagement. In one optional embodiment, the metal inlays  74  also provide lubricity such that when sliding across an opposing sealing surface the resultant coefficient of friction is less than that if the metal inlay  74  were made from a less ductile or harder material. Examples of soft metal candidates include lead, copper, silver, gold, zinc, and alloys thereof. The inlays  74  can comprise all soft metal, or be a harder material having a film, coating, or plating comprising a soft metal. 
         [0030]    Referring again to  FIG. 3 , a transition  67  on the inner housing body  42  identifies a change in diameter of the inner housing body  42 . Preferably, the inner housing body  42  outer diameter between the transition  67  and the energizing sleeve  56  does not exceed the seal  62  inner diameter. This allows clearance for the seal  62  when in the portion of the annular seal pocket  64  between the transition  67  and the energizing sleeve  56 . The annular seal pocket  64  cross-section or thickness reduces between the transition  67  and the radial ledge  43 . As seen in  FIG. 4 , the dimensional change in the annular seal pocket  64  at the transition  67  results in an interference fit when moving the seal  62  between the transition  67  and the radial ledge  43 . The interference fit energizes the seal  62  when it is urged into the portion of the annular seal pocket  64  between the transition  67  and the radial ledge  43 . When the seal  62  is in the interference position the body  66  is radially stretched. The increased inner housing body  42  diameter past the transition  67  contacts the sealing members  72  to elastically deform the cantilever legs  70 . The elastic deformation produces an opposing sealing force between the sealing members  72  and the inner housing body  42  outer circumference to form a seal between these two surfaces. Additionally, the increased inner housing body  42  diameter also radially urges the inlays  74  against the outer sleeve  50  inner circumference. This plastically deforms the inlays  74  to form a sealing surface between the metal inlays  74  and the outer sleeve  50 . 
         [0031]    Radially stretching the seal  62  around the increased diameter of the inner housing body  42  effectively increases the seal diameter to actively engage the mating seal surface on the seal  62  inner and outer diameters. Optionally, the side of the seal  62  having the metal inlay  74  and the side having the cantilever  68  may be reversed such that the metal inlays  74  are in contact with the outer circumference of the inner housing body  42  and the cantilevers  68  and their respective sealing members  72  are in contact with the outer sleeve  50  inner circumference. 
         [0032]    With respect to the adjustable casing sub  40 , the seal  62  may be energized prior to or after tensioning. In one example of use, the casing sub  40  is secured on its lower end to the casing string  34  and an upper portion of the casing sub  40  is attached to a section having a hanger to be landed within the surface wellhead  32 . After engaging the ratchet ring housing  46  over the ratchet ring  44 , the casing string is further tensioned by an inserted running or torque tool (not shown) within the casing string and in engagement with the torque splines  52 . The tool rotates the torque splines  52  and traveling sleeve  54  counter-clockwise engaging the threads  55  on the traveling sleeve  54  with the threads  53  on the outer sleeve  50 . Energizing ring  56  does not rotate with the traveling sleeve  54 . Since the traveling sleeve  54  is coupled with the inner housing body  42 , as previously described, upwardly moving the traveling sleeve  54  pulls the inner housing body  42  upward to tension the casing string. When a desired amount of tension in the string has been reached the running tool rotation may be reversed, thereby downwardly motivating the traveling sleeve  54  within the outer housing  50  to set or energize the seal  62 . 
         [0033]    The locking interaction between the ratchet ring  44  and the ratchet ring housing  46  prevents inner housing body  42  movement relative to the outer sleeve  50  when downwardly motivating the traveling sleeve  54 . Instead, continued downward force will fracture the shear pin  60 , thereby allowing energizing sleeve  56  downward movement with respect to the inner housing nut  61  without rotation. As previously noted, traveling sleeve  54  upward movement does not apply a shear force to the shear pin  60  due to the inner locking connection between the lip  63  and shoulder  65 . Continued downward movement of the energizing sleeve  56  urges the seal  62  within the annulus  64  below the transition  67 , as shown in side view in  FIG. 4 . Whether or not the step of energizing the seal  62  occurs prior to tensioning the casing string or after tensioning, at some point a sliding action will occur between the seal  62  and a sealing surface of either the outer sleeve  50  or the inner housing body  42 . Accordingly, the ductile and lubricating effect of the metal inlay is operative in either scenario of operation. 
         [0034]    The cantilever member is not limited to the embodiment illustrated in the figures, but can include any elastically deformable configuration. In addition to being radially stretched, the seal can be radially compressed to affect the energizing configuration. One of the advantages of the device described herein is the use of metal sealing without the need for any elastomer. 
         [0035]      FIGS. 6 and 7  provide a side view of an alternative example of a seal for use in an adjustable casing sub. In this embodiment the seal is integral with either an inner or an outer housing. With reference now to  FIG. 6 , a portion of the inner housing body includes a seal assembly  76  where the seal assembly includes a mid-section  78  and inlays  80  disposed on one side of the mid-section  78 . The outer housing includes an outer housing seal surface  82  with a radial transition  84  formed along a portion of the sealing surface  82 . Additionally, the mid-section  78  of the seal assembly  76  is thicker than the housing. In  FIG. 7 , the inner housing body  42  has been coaxially telescopingly inserted within the outer sleeve  50 , and the mid-section  78  has slid past the transition  84  and into a reduced diameter portion. Moving the seal assembly  76  below the transition  84  produces a compressive and sealing contact between the seal assembly  76  and the outer housing seal surface  82 . Accordingly, in this configuration, an energized sealing surface between an inner housing and an outer housing can be formed integral with the step of tensioning within an adjustable casing sub. 
         [0036]    It should be pointed out that in the configuration illustrated in  FIGS. 6 and 7 , the seal is not limited to being placed on the inner housing, but can be situated on the outer sleeve  50 . When made part of the inner housing body  42  the sealing surface is radially compressed when put into the energizing situation. Conversely, when the seal is disposed on the outer sleeve it is radially expanded during sealing. The sliding seal being radially compressed or expanded generates stored energy that imparts an increased contact stress that is sufficient to create a metal-to-metal seal. Accordingly, embodiments exist wherein the metal seal has a bearing stress of between 5,000 pounds per square inch and 30,000 pounds per square inch. Based on particular applications, however, this sealing stress can be increased. 
         [0037]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.