Abstract:
A connection is established between a pin connector and a box connector defined on a pair of tubular members such as casing segments in the field of oil and gas recovery. The pin connector and box connector include features for the protection of metallic-sealing surfaces during assembly, disassembly, transport and handling of the tubular members. The pin connector includes a stabbing flank with an inwardly tapered annular flank surface thereon, and an alignment protrusion extending outward with respect to the pin-side metallic sealing surface in a direction normal to a cone angle defined by the inwardly tapered annular flank surface. The alignment protrusion engages internal surfaces of the box connector to concentrically align the pin connector with the box connector, and thereby protects the metallic sealing surfaces from damage that might otherwise result from collisions between the pin connector and the box connector.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/907,687, titled “Alignment Guide Feature for Metal to Metal Seal Protection on Mechanical Connections and Couplings” filed Nov. 22, 2013, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to connecting tubular members, e.g., in the field of oil and as recovery. In particular, the disclosure relates to the alignment and connection of adjacent tubular members within a wellbore, e.g., the installation of a casing segment into a wellbore to form a fluid seal with an adjacent casing segment. 
         [0004]    2. Brief Description of Related Art 
         [0005]    A variety of wellbore operations include the connection of adjacent tubular members such as pipe, drill string, riser sections, casing segments, and the like. Some of the joints established between the tubular members can employ metal-to-metal seals to form fluid-tight connections. Often, the tubular members include sealing surfaces that are integral with the metallic structure of the tubular members. Such integral seals can be formed more rapidly, and at a lower cost, than distinct metal or elastomeric seal components. Distinct seal components must be placed between the tubular members during make-up or assembled to one or both of the tubular members before being lowered into the wellbore. One challenge of working with integral metal-to-metal seals is preventing damage to the surface finish on the sealing surfaces, and thereby facilitating effective formation of fluid-tight connections. 
         [0006]    Tubular members, and the oilfield equipment used to transport and handle the tubular members, are often large and cumbersome. Thus, assembling tubular members to one another without causing damage to the sealing surfaces can be difficult. For example, due to the large masses of the tubular members and oilfield equipment, even low-speed collisions can produce sufficient force to damage the sealing surfaces while attempting to land or align a tubular member. Therefore, stab guides, shields, protective coatings or other additional protectors are often provided to protect the metal-to-metal sealing surfaces. These protectors add cost and, depending on the protector design, can be dislodged from a tubular member and lost. In some eases, removal of these protectors can be required where they interfere with the final stages of assembly, such as the final rotation(s) of a threaded in connector after being stabbed into a box connector of an adjacent tubular member. The removal of these protectors can slow the assembly process and leave the sealing surfaces exposed during a stage of assembly where the sealing surfaces are at risk. 
         [0007]    In light of the above, a demand exists for protecting the metal-to-metal sealing surfaces on tubular members without the need to provide distinct protectors. Also, recognizable is a demand for protecting the sealing surfaces during final makeup after the pin and box connectors are stabbed together. 
       SUMMARY OF THE INVENTION 
       [0008]    A tubular connection is described having features for the protection of sealing surfaces defined on a pair of tubular members. In some cases, both the sealing surfaces and the protective features can be integral to the geometry and/or the metallic structure of the tubular members, in some eases, the protective features operate to concentrically align the tubular members and thereby protect the sealing surfaces from collisions. Protection of the sealing surfaces can facilitate the establishment of a fluid-tight seal between the tubular members. 
         [0009]    According to one aspect of the invention, a tubular connection includes a first tubular member having box connector defined at an upper end thereof. The box connector defines a first longitudinal axis and includes threads or other internal mating features along an internal surface thereof. A box-side metallic sealing surface is defined on the internal surface below the internal mating features. The tubular connection also includes a second tubular member having as pin connector defined at a lower end thereof. The pin connector defines a second longitudinal axis and includes threads or other external mating features defined along an external surface thereof, which are operable to engage the internal mating features of the box connector to couple the first and second tubular members to one another. The pin connector further includes a stabbing flank defined on the external surface below the external mating features. The stabbing flank includes an annular flank surface that is tapered radially inwardly in a direction toward the lower end of the pin to define a cone angle with respect to the second longitudinal axis. A pin-side metallic sealing surface is defined on the annular flank surface, which is operable to engage the box-side metallic sealing surface to form a fluid seal therewith when the external mating features are engaged with the internal mating features. The stabbing flank also includes an alignment protrusion extending outward with respect to the pin-side metallic sealing surface in a direction normal to the cone angle. The alignment protrusion is defined below the pin-side metallic sealing surface such that the alignment protrusion is operable to engage the internal mating features of the box connector to concentrically align the pin connector with the box connector and urge the pin-side metallic sealing surface radially inward and away from the internal mating features when the pin connector is stabbed into the box connector. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment, thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only preferred embodiments of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0011]      FIG. 1  is a partial, cross-sectional view of first and second tubular members in a decoupled and misaligned configuration occurring prior to coupling the second tubular member to the first tubular member in accordance with an example embodiment of the present disclosure. 
           [0012]      FIG. 2  is an enlarged view of the area of interest identified in  FIG. 1  illustrating an alignment protrusion and a metallic sealing surface defined on the second tubular member that facilitate metal-to-metal sealing with a metallic sealing surface on the first tubular member. 
           [0013]      FIG. 3  is a partial, cross-sectional view of the first and second tubular members of  FIG. 1  in a fully connected configuration. 
           [0014]      FIG. 4  is an enlarged view of the area of interest identified in  FIG. 3  illustrating the metallic sealing surface of  FIG. 2  in sealing engagement with one another. 
           [0015]      FIGS. 5-7  are cross-sectional views of an alternate embodiment of an alignment protrusion and metallic sealing surface similar to those of  FIG. 2  (on a reverse lateral side of the first and second tubular components), which collectively illustrate a sequence for coupling a second tubular member to a first tubular member. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. 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 an 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, and the prime notation, if used, indicates similar elements in alternative embodiments. 
         [0017]    Referring to  FIG. 1 , a first tubular member  10  and a second tubular member  12  comprise sections of casing for completing a wellbore (not shown). In other embodiments, first and second tubular members  10 ,  12  comprise other wellbore components such as wellhead housing components, tubing string sections, pipe, riser sections, drill string sections, etc. The first tubular member  10  includes a box connector  14  at an upper end thereof, and the second tubular member  12  includes a pin connector  16  at a lower end thereof. The box connecter  14  and the pin connector  16  are operable to engage one another to couple the first and second tubular members  10 ,  12  to one another. The relative positions described in this specification, such as “above” or “below” or for description only. The components described can be used in any orientation. 
         [0018]    First and second tubular members  10 ,  12  are depicted in a decoupled and misaligned configuration. The box connector  14  defines a first longitudinal, axis “A1” that is obliquely arranged with respect to a second longitudinal axis “A2” defined by the pin connector  16 . The oblique Or misaligned arrangement, of the longitudinal axes “A1” and “A2” typically occurs in wellbore operations such as stabbing, e.g., during make-up and break-out of the first and second tubular members  10 ,  12 . As one skilled in the art will recognize, this misalignment can lead to galling at a leading end  20  of pin connector  16 , particularly when pin connector  16  and box connector  14  are constructed of similar materials. Galling can compromise a metal-to-metal seal formed between first and second tubular members  10 ,  12  when in a fully made-up configuration as described, in greater detail below. 
         [0019]    The box connector  14  includes internal mating features  22  defined along an annular internal surface  24  thereof. In the illustrated embodiment, internal mating features  22  are helical threads constructed of the same metallic structure of a body of first tubular member  10 . In other embodiments, internal mating features are parallel grooves or other structures for engaging pin connector  16  to thereby couple first and second tubular members  10 ,  12  to one another. 
         [0020]    A box-side metallic sealing surface  26  is defined on the internal surface  24  below the internal mating features  22 . As recognized by those skilled in the art, a box-side metallic sealing surface  26  disposed below the mating features  22  others protection to the box-side metallic sealing surface  26  due to the recessed location. In other embodiments, box-side metallic sealing surface  26  is disposed at other locations within box connector  14 . Box-side metallic sealing surface  26  can exhibit a surface finish that is more highly polished than the surrounding metal surfaces of the internal surface  24 . In some embodiments, the box-side metallic scaling surface  26  can exhibit a surface roughness of about 3 μm while the surrounding surfaces of internal surface  24  have a surface roughness of about 8 μm or higher. In some embodiments, box-side metallic sealing surface  26  can be attached to internal surface  24 , by welding or as an inlay positioned in and protruding from a groove (not shown). In other embodiments, the box-side metallic scaling surface  26  is a polished portion of the metallic structure of the body of first tubular member  10 . 
         [0021]    The pin connector  16  includes external mating features  30  defined along an outer external surface  32  thereof. The external mating features  30  are operable to engage the internal mating features  22  of the box connector  14  to couple the first and second tubular members  10 ,  12  to one another. The pin connector  16  further includes a stabbing flank  36  defined on the external surface  32  below the external mating features  30 . The stabbing flank  36  is defined at the leading end  20 , and leads the pin connector  16  through the internal mating features  22  as the pin connector  16  is stabbed into the box connector  14 . 
         [0022]    Referring to  FIG. 2 , the stabbing flank  36  at the leading end  20  of pin  16  engages mating features  22  of box  14  as second tubular member  12  is lowered into position for engagement with first tubular member  10 . The stabbing flank  36  includes an annular flank surface  40  that is tapered radially inwardly in a direction toward the lower end surface  42  of the pin connector. A cone angle “α” with respect to the second longitudinal axis “A2” is defined by the tapered annular flank surface  40 . In some embodiments, the cone angle “α” is in the range of about 8 degrees to about 16 degrees, and in some embodiments, the cone angle “α” is about 12 degrees. 
         [0023]    An alignment protrusion  44  extends outward with respect to the annular flank surface  40  and a pin-side metallic sealing surface  48  in a direction normal to the cone angle cone angle “α.” The alignment protrusion  44  engages internal mating features  22  of box connector  14  as second tubular member  12  is lowered into position, and thereby operates to concentrically align the pin connector  16  with the box connector  14 . In the illustrated embodiment, all protrusion  44  is a bulbous or curved feature to facilitate guiding or urging pin connector  16  toward a concentrically aligned arrangement with box connector  14  as the alignment protrusion  44  is axially lowered through mating features  22 . 
         [0024]    The pin-side metallic sealing surface  48  provided on stabbing flank  36  can be formed by any of the mechanisms described above the forming box-side metallic sealing surface  26 . The pin-side metallic sealing surface  48  is disposed on pin connector  16  above the alignment protrusion  30 . Thus, the pin-side metallic sealing surface  48  is protected from damage by the engagement of alignment feature  30  with mating features  22  or other wellbore surfaces encountered by leading end  20  of pin  16  as second tubular member  12  is lowered into position within box connector  14 . 
         [0025]    An annular groove  50  extending radially inward from the annular flank surface  40  is defined on stabbing flank  36 . The annular groove  50  extends inward in a direction normal to the cone angle “α.” At least a portion of pin-side metallic sealing surface  48  is disposed within the annular groove  50  further protecting the pin-side metallic sealing surface  48 . In the illustrated embodiment, pin-side metallic sealing surface  48  has an upper margin disposed within the annular groove  50  and a lower margin on the tapered annular funk surface  40 . Because pin-side metallic sealing surface  48  is located at the transition between annular groove  50  and annular flank surface  40 , the pin-side sealing surface  48  has a generally convex shape. The geometry of annular groove  50 , and the relationship of the annular groove  50  with pin-side sealing surface  48  is described in greater detail in commonly owned, U.S. patent application Ser. No. 13/606,302, entitled PROTECTED INTEGRAL METAL TO METAL SEAL, filed Sep. 7, 2012 to Pallini et al., which is hereby incorporated by reference herein. 
         [0026]    Referring to  FIGS. 3 and 4 , first and second tubular members  10 ,  12  are depicted in a fully coupled or made-up configuration. The lower end surface  42  of pin connector  16  rests on an axial compression shoulder  52  defined within the box connector  14 . Axial compression shoulder  52  faces generally upwardly, and slopes downward in a radially outward direction. Axial compression shoulder  52  defines a secondary load shoulder, while a primary load shoulder  54  is defined at an upper end  56  of box connector  14 . Alignment protrusion  44  extends axially beyond lower end surface  42  to define a lower-most point on pin connector  16 . The alignment protrusion  44  is received within an annular relief groove  60  defined in the box connector  14  below axial compression shoulder  52 . The alignment protrusion  44  is substantially spaced from the internal surface  24  of the box connector  14  when received within the annular relief groove  60 . The annular relief groove  60  ensures that no axial or radial loads are transferred through the alignment protrusion  44  when the fully made-up configuration is achieved. Annular relief groove  60  thus permits proper engagement of pin connector  16  with box connector  44 , even in the event that the alignment protrusion  44  is damaged and deformed. 
         [0027]    When the lower end surface  42  rests on axial compression shoulder  52 , pin-side metallic sealing surface  48  is axially aligned with box-side metallic sealing surface  26 . A minimum inner diameter of the box-side metallic scaling surface  26  is less than any portion of annular interior surface  24  above the box-side metallic sealing surface  26 . The minimum inner diameter of the box-side metallic sealing surface  26  can be less than a maximum outer diameter of the pin-side metallic sealing surface prior to achieving the fully made-up configuration depicted. Thus, an interference fit can be established when the box-side metallic sealing surface  26  and the pin-side metallic sealing surface  48  are axially aligned and the fully made-up configuration is achieved. The interference fit causes deformation of one or both of the metallic sealing surfaces  26 ,  48  to form an effective fluid seal between the box and pin connectors  12 ,  14 . The deformation can be fully elastic permitting repeatable assembly and disassembly of the box and pin connectors  12 ,  14  to establish the fluid seal multiple times. Alternately, the deformation may be plastic or permanent. An effective metal-to-metal seal can be established between metallic sealing surfaces  26 ,  48  since the pin-side metallic sealing surface  48  is protected and does not engage annular internal surface  24  until being concentrically and axially aligned with box-side metallic scaling surface  26  and first and second tubular members  10 ,  12  are in the fully made-up configuration. 
         [0028]    In one example embodiment of operation, second tubular member  12  is lowered in a generally axial direction toward first tubular member  10  until the stabbing flank  36  of pin connector  16  enters the box connector  14 . Any misalignment between the first and second tubular members  10 ,  12  can cause an impact between the alignment protrusion  44  and internal mating features  22  or other portions of annular internal surface  24 . The engagement of the alignment protrusion  44  with the annular internal surface  24  together with the axial movement between the first and second tubular members  10 ,  12  urges the pin-side metallic sealing surface  48  radially inward and away from the internal mating features  22 . Thus, the pin-side metallic sealing surface  48  is protected from impact. 
         [0029]    When the pin connector  16  is advanced sufficiently to permit the external mating features  30  to engage the internal mating features  22 , the second tubular member  12  can be rotated about longitudinal axis “A2” to threadingly engage the pin connector  16  with box connector. Galling and deformation of alignment protrusion  44  by engagement with internal surface  44  during this rotation does not damage or adversely influence the ability of metallic sealing surfaces  26 ,  48  to form an effective seal. The rotation continues until the alignment protrusion  44  disengages the internal surface  24  and moves into annular relief groove  60  and metallic sealing surfaces  26 ,  48  engage one another. The rotation and corresponding axial motion of second tubular member  12  can continue, thereby elastically or plastically deforming the metallic sealing surfaces  26 ,  48  to form an effective fluid seal, until the lower end surface  42  of pin in connector  16  engages the axial compression shoulder  52 . 
         [0030]    Referring now to  FIGS. 5-7 , an alternate embodiment of a threaded connection can be established between first and second tubular members  110 ,  112 , which respectively define as box connector  114  and pin connector  116 . A leading end  120  of pin connector  116  defines a thread stabbing flank  136 , which is straightly tapered inwardly toward a lower end surface  142  at angle “θ” with respect to a longitudinal axis (see “A2” in  FIG. 1 ). An upper portion  136   a  and a lower portion  136   b  of thread stabbing hank  136  are axially divided by a concave surface or annular groove  150 . Upper and lower portions  136   a,    136   b  are both disposed at the angle “θ,” such that annular groove  150  can be machined into a conically tapered stabbing flank surface in a manufacturing process as understood ID the art. A pin-side metallic sealing surface  148  is disposed axially between upper and lower portions  136   a,    136   b  within annular groove  150 . Pin side metallic sealing surface  148  is not necessarily concave itself, but is protectively disposed. within the concavity defined by annular groove  150 . 
         [0031]    A sacrificial alignment protrusion  144  is defined at the transition between annular groove  150  and the lower portion  136   b  of the thread stabbing flank  136 . Since lower portion  136   b  of thread stabbing flank  136  tapers radially inwardly below sacrificial alignment protrusion  144 , and since annular groove  150  is disposed above sacrificial alignment feature  144 , a local maximum radial dimension is defined at sacrificial alignment protrusion  144 . Sacrificial alignment protrusion  144  protrudes in a direction normal to tapered thread stabbing flank  136  with respect to the pin-side metallic sealing surface  148 . A sacrificial flat  158  is defined within the box connector  114 . Sacrificial flat  158  can be a generally cylindrical surface disposed axially between a convex box-side metallic sealing surface  126  and an annular relief groove  160 . Sacrificial flat  158  is positioned for engagement with sacrificial alignment protrusion  144  (see  FIG. 6  as pin connector  116  and box connector  114  are axially approximated. 
         [0032]    As illustrated in  FIG. 5 , second tubular member  112  is axially approximated with first tubular member  110  to a position wherein corresponding mating features  122 ,  130  begin to engage one another, and the sacrificial alignment protrusion  144  begins to engage sacrificial fiat  158 . The pin-side metallic sealing surface  148  is disposed axially between external mating features  130  and the sacrificial alignment profusion  144 , and the box-side metallic sealing surface  126  is disposed axially between the internal mating features  122  and the sacrificial flat  158 . Thus, the metallic sealing surfaces  126 ,  148  are radially supported on opposing axial sides thereof. 
         [0033]    As illustrated in  FIG. 6 , sacrificial alignment protrusion  144  is engaged with sacrificial flat  158  with further axial approximation of second tubular member  112  to guide second tubular member  112  into a central radial position where longitudinal axes A1, A2 ( FIG. 1 ) are aligned. In embodiments where the corresponding mating features  122 ,  130  are helical threads, further axial approximation is accompanied by rotational motion. The engagement of sacrificial alignment protrusion  144  with sacrificial flat  158  during this rotation operates to prevent wear of pin-side metallic sealing surface  148 . Galling and deformation of sacrificial alignment protrusion  144  and sacrificial flat  158  during this rotational engagement does not damage or adversely influence the ability of metallic sealing surfaces  126 ,  148  to form an effective seal. 
         [0034]    In some embodiments, alignment protrusion  144  remains engaged with sacrificial flat  158  as metallic sealing surfaces  126 ,  148  begin engagement with one another and deform to form a fluid seal. However, as illustrated in  FIG. 7 , alignment protrusion  144  disengages sacrificial flat  158  prior to second tubular member  112  landing on axial compression shoulder  152 . This disengagement allows metallic sealing surfaces  126 ,  148  to form an interference fit between first and second tubular members  110 ,  112 , thereby ensuring a leak-free seal therebetween. 
         [0035]    As one skilled in the art will appreciate, alignment protrusions  44 ,  144  eliminate a need for cumbersome and expensive external stab guides. Since metallic, sealing surfaces  26 ,  48 ,  126 ,  148  are protected by sacrificial alignment protrusions  44 ,  144 , a repeatable seal can be formed as metallic sealing surfaces  26 ,  48 ,  126 ,  148  are disengaged and reengaged with one another. Additionally, alignment feature  44 ,  144  may be provided on other wellhead components that are made-up by axial approximation. 
         [0036]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.