Abstract:
A pipe connection includes a tubular box having an internal threaded section extending from a rim, and a nose receptacle area joining the threaded section. A box seal surface is formed on the nose receptacle area. A tubular pin has a nose area extending from a pin end, and an external threaded section joining the nose area, the external threaded section mating with the internal threaded section. An annular groove is formed. on the nose area between the pin end and the external threaded section. A pin seal surface is located at least partially in the groove for engaging the box seal surface to form a metal to metal sealing engagement.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates in general to tubular connectors, and in particular to sealing surfaces for forming a seal between a box connector and a pin connector. 
         [0003]    2. Brief Description of Related Art 
         [0004]    Tubular members are connected to each other for various wellbore operations. The tubular members can be, for example, pipe, drill string, riser sections, casing, and the like. Some of the joints between tubular members can use integral metal-to-metal seals to form a fluid-tight seal between adjacent members. Such integral seals can be employed more rapidly, and at a lower cost, than separate seals that are placed between tubing members during makeup. A disadvantage of integral metal-to-metal seals is that they require high surface finishes and, thus, can tolerate very little damage and still work effectively. 
         [0005]    Oilfield equipment is large and cumbersome which can make gentle handling difficult. For example, large tubular members must be transported, positioned, and joined together using heavy equipment. Movement of the equipment and the tubular members themselves can cause damage to the sealing surfaces. Even a low-speed contact between a tubular member and another piece of equipment can cause damage because the large mass, even moving at a very low velocity, can create enough force to damage a seal. Therefore, metal-to-metal seal elements must be protected by additional protectors which add cost and, depending on the protector design, can be lost or removed, thus allowing the metal-to-metal seal to be exposed to damage. Therefore, it is desirable to protect a sealing surface without requiring additional protectors. Also, protection of the sealing surfaces is needed during final make up after the pin and box are stabbed together. 
       SUMMARY OF THE INVENTION 
       [0006]    A tubular connection has a tubular box having an internal threaded section extending from a rim, and a nose receptacle area joining the threaded section. A box seal surface is formed in the nose receptacle area. A tubular pin has a nose area extending from a pin end, and an external threaded section joining the nose area, the external threaded section mating with the internal threaded section. An annular groove is located on the nose area between the pin end and the external threaded section. A pin seal surface has a recessed portion located in the groove that engages the box seal surface to form a metal to metal sealing engagement. 
         [0007]    In one embodiment, prior to engagement of the pin with the box, a maximum outer diameter of the pin seal surface is greater than a minimum inner diameter of the box seal surface, causing deformation of the pin seal surface and the box seal surface when in engagement with each other. In one embodiment, the pin seal surface has an exposed portion located on the nose area, the recessed and exposed portions joining each other to define a rounded convex surface. 
         [0008]    The groove defines for the nose area a first nose section extending from the pin end to the groove, and a second nose section extending from the groove to the pin threaded section. The pin seal surface is located at a junction of the groove with the first nose section. The first nose section may be conical at the junction. The second nose section may also be conical. An angle of the second nose section relative to an axis of the pin may be the same as an angle of the first nose section to the axis at the junction. 
         [0009]    At least a portion of the box seal surface may be cylindrical. A conical lead-in surface may extend to the cylindrical portion. 
         [0010]    The first nose section from the pin end to the pin seal surface may be spaced radially apart from the nose receptacle when the pin is made up with the box. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    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 a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0012]      FIG. 1  is a partially sectional isometric view of a connection between tubular members according to an embodiment of the invention. 
           [0013]      FIG. 2  is an enlarged sectional view of the pin member of  FIG. 1 . 
           [0014]      FIG. 3  is an enlarged sectional view of the box member of  FIG. 1 . 
           [0015]      FIG. 4  is a sectional side view of the seal interface of the connection between tubular members of  FIG. 1 . 
           [0016]      FIG. 5  is a sectional side view of the tubular members of  FIG. 1 , showing the pin in an axially offset position during makeup with the box. 
           [0017]      FIG. 5   a  is an enlarged sectional view of a portion of the tubular members of  FIG. 5 , showing the pin axially and angularly offset from the box as the pin is stabbed into the box. 
           [0018]      FIG. 5   b  is an enlarged sectional view similar to  FIG. 5   a,  but showing the pin axially offset but angularly aligned with the box. 
           [0019]      FIG. 5   c  is an enlarged sectional view similar to  FIGS. 5   a  and  5   b,  but showing angularly misaligned with the box a different angle than in  FIG. 5   a.    
           [0020]      FIG. 6  is a sectional side view of the tubular members of  FIG. 1  showing an example of the pin member in contact with. threads during makeup. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    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 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, and the prime notation, if used, indicates similar elements in alternative embodiments. 
         [0022]    Referring to  FIG. 1 , the tubular connection or pipe joint  100  of a pin member (“pin”)  102  and box member (“box”)  106  is shown. Pin  102  is a connector on tubular member  104 , and box  106  is a connector on tubular member  108 . Tubular members  104  and  108  can be any type of tubular member including, for example, pipe, riser sections, drill string sections, and casing. Tubular members  104  and  108  can each have connectors at each end such as pin  102  atone end and box  106  at the other end. Pin  102  has an external thread  110  that extends downward from pin cylindrical body  114  toward a pin end  112 . A pin nose area  121  extends from pin end  112  to external thread  110 . In a similar manner, box  106  has a cooperative internal thread  116  and extends from a rim or box end  118  to a box bore  120 . For description purposes, it is assumed that pin  102  is pointing downward such that pin end  112  is the lowermost portion of pin  102 , and box  106  is pointing upward such that box end  118  is the uppermost portion of box  106 . 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. 
         [0023]    Referring also to  FIG. 2  and  FIG. 6 , an enlarged view of a lower portion of pin  102  is shown. Pin  102  is a connector on an end of tubular member  104  ( FIG. 1 ). Pin nose area  121  may have a conical alignment or nose surface  124  extending upward from pin end  112  to a nose cylindrical surface  122 . Nose cylindrical surface  122  joins conical alignment surface  124  and extends upward to external threads  110 . Cylindrical surface  122  is concentric relative to relative to pin axis  128 . All or part of conical alignment surface  124  may be at a same angle  126  relative to pin axis  128 . A curved recess or annular groove  136  is located on nose conical alignment surface  124 . Groove  136  is located is located a selected distance above pin end  112 , dividing alignment surface  124  into a lower conical alignment surface  124   a  and an upper conical alignment surface  124   b.    
         [0024]    A pin seal surface  132  has a portion located partially in groove  136  and partially on lower conical alignment surface  124   b.  As illustrated in  FIGS. 4 and 6 , the recessed portion  132   a  of seal surface  132  located in groove  136  is conical with a diameter increasing in a downward direction. The exposed portion  132   b  of seal surface  132 , which is located on lower alignment surface  124   b,  is also conical but has a diameter that decreases in a downward direction. Portions  132   a  and  132   b  define a rounded convex seal surface. Exposed portion.  132   b  can be a portion of alignment surface  124   b  that is flush with alignment surface  124   b,  thus extending at the same angle  126  relative to pin axis  128 . Alternately exposed pin. seal surface  132   b  can protrude outward from alignment surface  124   b.  Pin seal surface  132 , groove  136  and alignment surface  124  are a monolith part. in other embodiments, pin seal surface  132  can be an inlay of a dissimilar material on groove  136  and alignment surface  124   b.  Pin seal surface  132  can be polished to a smoother finish than other portions of groove  136  and lower alignment surface  124   b,  or pin seal surface  132  can have the same surface finish as other portions of alignment surface  124   b  and groove  136 . 
         [0025]    Groove  136  may have a continuously curved concave shape as shown. Recessed pin seal surface  132   a  has an upper margin that is located about half-way between the base of groove  136  and the lower edge of groove  136 . Because pin seal surface  132  is located at the transition from lower alignment surface  124   b  to groove  136 , pin seal surface  132  has a generally convex shape. The outer diameter of pin seal surface  132  at its upper margin within groove  136  is less than the outer diameter of pin seal surface  132  where groove  136  joins lower alignment surface  124   b.  The outer diameter of pin seal surface  132  at its lower margin on lower alignment surface  124   b  may be the same or less than the outer diameter of seal surface  132  at its upper margin within groove  136 . 
         [0026]    Referring to  FIG. 3 , an enlarged view of box  106  is shown. Box  106  is a cylindrical connector on an end of tubular member  108  ( FIG. 1 ). A nose receptacle area  140  extends downward from internal thread  116 . Nose receptacle area  140  may have a cylindrical section  139  extending downward from internal thread  116  a selected distance. In this example, an upper conical alignment section  141   a  joins and extends downward from nose receptacle cylindrical section  139 . Also, in this example, an upper conical lead-in section  143   a  extends downward at a lesser angle from upper alignment section  141   a.  A. lower conical lead-in section  143   b  extends downward at a lesser angle from upper lead-in section  143   b.  A cylindrical box seal surface  142  joins and extends downward from lower lead-in section  143   b.  In this example, box seal surface  142  joins a conical lower alignment surface  141   b  that extends to a shoulder  145  that is in a plane perpendicular to the axis of box  108 . Upper and lower alignment surfaces  141   a,    141   b  are illustrated as being at the same conical angle and same conical surface, except being separated by lead-in surfaces  143   a,    143   b  and box seal surface  142 . Lead-in surface  143   a,    1423   b  and box seal surface  142  are located radially inward from a line extending between the conical alignment surfaces  141   a,    141   b  at the same angle as conical alignment surfaces  141   a,    141   b.  Although shown as straight separate conical surfaces, alignment surfaces  141   a,    141   b  and lead-in surfaces  143   a,    143   b  may blend together and have a variety of shapes. Also, box seal surface  142  may be other than cylindrical, such as a rounded, convex contoured surface. 
         [0027]    Box seal surface  142  can be axially located such that when external thread  110  of pin  102  engages internal thread  116  of box  106 , and pin  102  ( FIG. 2 ) is tightened to a predetermined position or predetermined amount of torque, pin seal surface  132  ( FIGS. 2 ,  4 ) is axially aligned with box seal surface  142 . Pin  102  is in a sealing position when pin  102  is tightened. into box  106  such that pin seal surface  132  engages box seal surface  142 , as best shown in  FIG. 4 . 
         [0028]    Box seal surface  142  can be attached to nose receptacle  140  by, for example, welding or as an inlay positioned in and protruding from a groove (not shown). Box seal surface  142  can be polished to have a smoother surface finish than other portions of nose receptacle  140 . In some embodiments, box seal surface  142  can have a generally convex cross section. The minimum inner diameter of box seal surface  142  is less than any portion of nose receptacle  140  located. above it. The inner diameter of box seal surface  142  can be smaller than the outer diameter of pin seal surface  132  prior to making up pin  102  with box  106 . The difference in diameters causes an interference fit, as illustrated in  FIG. 4  by the hatch marks. The interference fit causes deformation of both pin seal surface  132  and box seal surface  142 . The deformation may be elastic, allowing the connector to be broken out and made-up more than one time. Alternately, the deformation may be plastic or permanent. The amount of deformation due to the interference fit may be very slight and is highly exaggerated in  FIG. 4 . 
         [0029]    Referring to  FIG. 4 , as pin  102  moves into the sealing position, pin seal surface  132  conforms to and seals against box seal surface  142 . Both recessed pin seal surface  132   a  and exposed seal surface  132   b  sealingly engage box seal surface  142 . When in the fully sealed position of  FIG. 4 , box lower alignment surface  141   b  is radially spaced from pin lower alignment surface  124   b,  creating a gap. Also, box upper alignment surface  141   a  is radially spaced from pin upper alignment surface  141   a.    
         [0030]    Referring to  FIGS. 5 ,  5   a,    5   b,  and  5   c,  during make-up, tubular member  104  can inadvertently be offset from and angularly out of alignment with tubular member  108 , such that elements of pin  102  contact various portions of the interior of box  106  before being aligned and threadingly engaging box  106 , A chamfer  144  can be located at box end  118 , and can be used to guide pin  102  into concentric alignment with box  106 . As shown in  FIG. 5 , the exposed portion of pin seal  132  is likely to contact chamfer  144  during insertion. The impact and subsequent sliding engagement can result in damage to the surfaces in contact. The recessed portion  132   a  ( FIGS. 4 and 6 ) of seal surface  132 , however, does not contact any portion of box  106  during insertion, until pin  102  is in the sealing position. Even if pin  102  is angularly misaligned as shown in  FIGS. 5   a  and  5   c,  the recessed portion of seal surface  132  will not contact any portion of the interior of box  106 . 
         [0031]      FIG. 6  illustrates a condition during stab-in wherein pin lower alignment surface  124   b  contacts internal thread  116  of box  106 . The recessed portion  132   a  of the pin seal surface is prevented from contacting internal thread  116  because it is located within groove  136 . As nose area  121  of pin  102  contacts inner diameter surfaces of box  106 , recessed pin seal surface  132   a  is isolated from contacting internal surfaces of box  106 . Referring back to  FIG. 1 , when tubular member  104  is concentrically aligned with tubular member  108 , external thread  110  can engage internal thread  116 , thereby axially advancing pin  102  into box  106 . Continued axial advancement results in pin seal surface  132  being axially and concentrically aligned with box seal surface  142 , resulting in inward deformation of pin seal surface  132  and outward deflection of box seal surface  142 . 
         [0032]    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.