Wicker profile for enhancing lockdown capacity of a wellhead annulus seal assembly

Abstract

A wellhead assembly comprises an outer tubular wellhead member with a bore having an axis and a concentric inner seal surface, an inner tubular wellhead member for receiving an annular seal landed within the outer tubular wellhead member defining a seal pocket between them, the inner tubular member having a concentric outer seal surface, and a plurality of circumferentially extending, parallel wickers formed in at least one of the seal surfaces of the outer tubular and on the outer surface of the inner tubular. A profile of at least one of the wickers differs from a profile of at least some of the other wicker.

1 . A wellhead assembly comprising:
 an outer tubular wellhead member with a bore having an axis and a concentric inner seal surface;   an inner tubular wellhead member for receiving an annular seal landed within the outer tubular wellhead member defining a seal pocket between them, the inner tubular member having a concentric outer seal surface;   a plurality of circumferentially extending, parallel wickers formed in at least one of the seal surfaces of the outer tubular and on the outer surface of the inner tubular; wherein   a profile of at least one of the wickers differs from a profile of at least some of the other wickers.   
     
     
         2 . The assembly of  claim 1 , further comprising an annular seal that is adapted to be disposed within the seal pocket and to be urged against the wickers on the outer tubular and the inner tubular to create a seal and to resist upward motion of the inner tubular relative to the outer tubular and wherein the plurality of wickers are adapted to deform a surface of the annular seal. 
     
     
         3 . The assembly of  claim 1 , wherein the wickers on said at least one of the seal surfaces are located in a bottom region of the seal pocket, a middle region of the seal pocket which is above the bottom region, and a top region of the seal pocket which is above the middle region, and wherein the profiles of the wickers in each of the regions differs from the profiles in each of the other regions. 
     
     
         4 . The assembly of  claim 3 , wherein:
 the profile of the wickers in the bottom region are substantially similar to each other;   the profile of the wickers in the middle region are substantially similar to each other; and   the profile of the wickers in the top region are substantially similar to each other.   
     
     
         5 . The assembly of  claim 3 , wherein:
 the wickers are formed of a material;   the profile of the wickers in the bottom region are different than the profile of the wickers in the middle region and the top region; and   the profile of the wickers in the middle region are different than the profile of the wickers in the top region.   
     
     
         6 . The assembly of  claim 3 , wherein:
 the wickers in the bottom region have more material on a top flank of each wicker than on a bottom flank of each wicker;   the profile of the wickers in the middle region are symmetrical about a mid plane of each wicker; and   the wickers in the top region have more material on the bottom flank of each wicker than on the top flank of each wicker.   
     
     
         7 . The assembly of  claim 3 , wherein:
 the wickers in the bottom region have a tilted mid plane symmetrically dividing each wicker in half, the tilted mid plane being inclined relative to a normal plane perpendicular to the axis, resulting in more material below the normal plane in each wicker; and   the wickers in the top region have a tilted mid plane symmetrically dividing each wicker in half, the tilted mid plane being inclined relative to a normal plane perpendicular to the axis, resulting in more material above the normal plane in each wicker.   
     
     
         8 . The assembly of  claim 3 , wherein:
 the wickers have a mid-plane passing through a crest of each wicker that is normal to the axis; and   the wickers in the top region and in the bottom region are asymmetrical about their respective mid-plane.   
     
     
         9 . The assembly of  claim 1 , wherein the wickers have a mid-plane passing through a crest of each wicker that is normal to the axis, and some of the wickers are asymmetrical about their respective mid-plane. 
     
     
         10 . The assembly of  claim 1 , wherein the wickers have an aspect ratio of less than 1.0. 
     
     
         11 . A wellhead assembly comprising:
 an outer tubular wellhead member with a bore having an axis and a concentric inner seal surface;   an inner tubular wellhead member for receiving an annular seal landed within the outer tubular wellhead member defining a seal pocket between them, the inner tubular member having a concentric outer seal surface;   a plurality of circumferentially extending, parallel wickers formed of a material in at least one of the seal surfaces of the outer tubular and on the outer surface of the inner tubular; wherein   the wickers have a mid plane passing through a crest of each wicker dividing each wicker substantially in half, and a normal plane passing through the crest and perpendicular to the axis; and   the material above the normal plane of at least one of the wickers does not equal the material below the normal plane of such at least one wicker.   
     
     
         12 . The assembly of  claim 11 , wherein at least one wicker has a mid plane inclined relative to the normal plane, resulting in more material below the normal plane in each such wicker than above. 
     
     
         13 . The assembly of  claim 11 , wherein at least one wicker has a mid plane inclined relative to the normal plane, resulting in more material above the normal plane in each such wicker than below. 
     
     
         14 . The assembly of  claim 11 , wherein the mid plane and normal plane of each wicker are parallel to each other and a profile of at least one wicker is asymmetrical about its mid plane. 
     
     
         15 . The assembly of  claim 14 , wherein:
 an upper flank and a lower flank of at least one wicker are at the same an g le relative to the axis;   the mid plane bisects a base of such wicker equidistant from a top and a bottom of the base of such wicker; and   there is more material above the mid plane than below.   
     
     
         16 . The assembly of  claim 14 , wherein:
 an upper flank and a lower flank of at least one wicker are at the same angle relative to the axis;   the mid plane bisects a base of such wicker equidistant from a top and a bottom of the base of such wicker; and   there is more material below the mid plane than above.   
     
     
         17 . The assembly of  claim 11 , wherein:
 at least one wicker has a mid plane inclined relative to the normal plane, resulting in more material below the normal plane in each such wicker than above; and   at least one wicker has a mid plane inclined relative to the normal plane, resulting in more material above the normal plane in each such wicker than below.   
     
     
         18 . The assembly of  claim 17 , wherein the wickers are symmetrical about the mid plane and asymmetrical about the normal plane. 
     
     
         19 . A wellhead assembly comprising:
 an outer tubular wellhead member with a bore having an axis and a concentric inner seal surface;   an inner tubular wellhead member for receiving an annular seal landed within the outer tubular wellhead member defining a seal pocket between them, the inner tubular member having a concentric outer seal surface;   a plurality of circumferentially extending, parallel wickers formed in at least one of the seal surfaces of the outer tubular and on the outer surface of the inner tubular, each adjacent wicker being separated by a valley and having:
 a wicker radial width measured from the base of the valley to a crest; 
 an axial length dimension measured as the distance between the base of the valley on either side of such wicker; and wherein 
 the wicker radial width of at least one wicker is equal to no more than the axial length dimension. 
   
     
     
         20 . The assembly of  claim 19 , wherein the valley between the wickers comprises a curved surface having a radius of at least 0.04 inches.