Annulus Seal Utilizing Energized Discrete Soft Interfacial Sealing Elements

Abstract

A seal assembly for sealing an annulus between inner and outer wellhead members comprises an energizer ring having inner and outer legs separated by a slot, formed of a high strength elastic material and having a central axis and an inner diameter seal ring formed of an inelastic material located on an inner side of the inner leg for creating a seal between the inner wellhead member the energizer. An outer diameter seal ring formed of an inelastic material is located on an outer side of the outer leg for creating a seal between the energizer and the outer wellhead member. The seal assembly may have an initial radial dimension from inner surface of the inner diameter seal ring to an outer surface of the outer diameter seal ring that is adapted to be greater than a radial width of the annulus, causing the legs to deflect towards each other when inserted in the annulus.

1 . A seal assembly for sealing an annulus between inner and outer wellhead members, the seal assembly comprising:
 an energizer ring having inner and outer legs separated by a slot, formed of a high strength elastic material and having a central axis;   an inner diameter seal ring formed of an inelastic material located on an inner side of the inner leg for creating a seal between the inner wellhead member and the energizer; and   an outer diameter seal ring formed of an inelastic material located on an outer side of the outer leg for creating a seal between the energizer and the outer wellhead member.   
     
     
         2 . The seal assembly of  claim 1 , wherein the seal assembly has an initial radial dimension from inner surface of the inner diameter seal ring to an outer surface of the outer diameter seal ring that is adapted to be greater than a radial width of the annulus, causing the legs of the energizer to deflect towards each other when inserted in the annulus. 
     
     
         3 . The seal assembly of  claim 1  further comprising a plurality of anti-extrusion devices for restricting an axial dimension of each of the seal rings when the seal assembly is set. 
     
     
         4 . The seal assembly of  claim 3 , wherein the anti-extrusion devices comprises:
 an annular band on the inner side of the inner leg and protruding inward from the inner leg;   an annular band on the outer side of the outer leg and protruding outward from the outer leg;   an annular recess in each of the bands; and wherein   each of the seal rings is located in one of the recesses and radially protrudes therefrom prior to setting of the seal assembly.   
     
     
         5 . The seal assembly of  claim 4 , wherein prior to setting of the seal assembly, an axial dimension of each annular recess is greater than an axial dimension of each seal ring. 
     
     
         6 . The seal assembly of  claim 4 , wherein the annular bands are adapted to contact the inner and outer wellhead members when the seal ring assembly is set. 
     
     
         7 . The seal assembly of  claim 3 , wherein the anti-extrusion devices comprise a pair of wedge rings, the wedge rings having a mating wedge surface that causes one of the wedge rings to slide radially inward and the other to slide radially outward. 
     
     
         8 . The seal assembly of  claim 3 , wherein the anti-extrusion device comprises:
 an inner wedge ring having an inner wedge ring surface;   an outer wedge ring having an outer wedge ring surface; and   inner and outer wedge surfaces on a base of the energizer that slidingly engage the inner wedge ring surface and the outer wedge ring surface during setting of the seal assembly to convey the wedge rings apart from each other.   
     
     
         9 . The seal assembly of  claim 1 , further comprising:
 a second energizer ring having inner and outer legs facing in an opposite direction to said first mentioned energizer ring.   
     
     
         10 . The seal assembly of  claim 1 , wherein the inner diameter seal ring and the outer diameter seal ring are formed of an inelastic material selected from a group consisting of lead, tin, silver, gold, tantalum, virgin polytetrafluoroethylene, filled polytetrafluoroethylene, polyetheretherketone, or compression molded graphite. 
     
     
         11 . A wellhead assembly comprising:
 an outer wellhead member having a bore and an axis;   an inner wellhead member located in the bore and defining an annulus between the inner and outer wellhead members;   an energizer ring having inner and outer legs separated by a slot, formed of an elastic material and having a central axis;   an inner diameter seal ring formed of an inelastic material located on an inner side of the inner leg for creating a seal between the inner wellhead member and the energizer;   an outer diameter seal ring formed of an inelastic material located on an outer side of the outer leg for creating a seal between the energizer and the outer wellhead member; wherein   the legs deflect towards each other when inserted in the annulus, causing the seal rings to radially deform.   
     
     
         12 . The wellhead assembly of  claim 11  further comprising a plurality of anti-extrusion devices for restricting an axial dimension of each of the seal rings when set in the annulus. 
     
     
         13 . The wellhead assembly of  claim 12 , wherein the anti-extrusion devices comprise:
 an annular band on the inner side of the inner leg and protruding inward from the inner leg;   an annular band on the outer side of the outer leg and protruding outward from the outer leg;   an annular recess in each of the bands; and wherein   prior to setting of the seal assembly, each of the seal rings is located in one of the recesses and radially protrudes therefrom, and an axial dimension of each annular recess is greater than an axial dimension of each seal ring.   
     
     
         14 . An apparatus for sealing an annulus between inner and outer wellhead members, the seal assembly comprising:
 a first energizer ring having inner and outer legs separated by a slot, formed of a high strength elastic material and having a central axis;   a second energizer ring having inner and outer legs facing in an opposite direction to the first energizer ring;   an inner diameter seal ring formed of an inelastic material located on an inner side of each of the inner legs for creating a seal between the inner wellhead member and the energizers;   an outer diameter seal ring formed of an inelastic material located on an outer side of each of the outer legs for creating a seal between the energizers and the outer wellhead member; and   a plurality of anti-extrusion devices for restricting an axial dimension of each of the seal rings when the seal assembly is set.   
     
     
         15 . The apparatus of  claim 14 , wherein when a force is applied in an axial direction to set the apparatus in the annulus, the inner seal rings move inward to abut the inner wellhead member and the outer seal rings move outward to abut the outer wellhead member. 
     
     
         16 . The apparatus of  claim 15 , wherein the anti extrusion devices comprise:
 an inner wedge ring having an inner wedge ring surface;   an outer wedge ring having an outer wedge ring surface;   inner and outer wedge surfaces on a base of each energizer that slidingly engage the inner wedge ring surface and the outer wedge ring surface during setting of the apparatus to convey the wedge rings apart from each other.   
     
     
         17 . A method for sealing an annulus between inner and outer wellhead members, the method comprising the steps of:
 (a) positioning an energizer within the annulus, the energizer ring having inner and outer legs separated by a slot, formed of an elastic material and having a central axis;   (b) creating a seal between the inner wellhead member and the energizer with an inner diameter seal ring formed of an inelastic material located on an inner side of the inner leg; and   (c) creating a seal between the energizer and the outer wellhead member with an outer diameter seal ring formed of an inelastic material located on an outer side of the outer leg.   
     
     
         18 . The method of  claim 17 , wherein steps (b) and (c) further comprise applying sufficient force to the energizer to deflect the legs of the energizer towards each other by elastic deformation and cause plastic deformation of the inner diameter seal ring and outer diameter seal ring. 
     
     
         19 . The method of  claim 17 , wherein steps (b) and (c) further comprise providing a fluid under pressure within the slot to apply a radial force on the legs and cause plastic deformation of the inner diameter seal ring and outer diameter seal ring. 
     
     
         20 . The method of  claim 17  further comprising the step of limiting the axial expansion of the inner diameter seal ring and the outer diameter seal ring with an anti-extrusion device. 
     
     
         21 . The method of  claim 20 , wherein the step of limiting the axial expansion of the inner diameter seal ring and the outer diameter seal ring is performed by an annular band on the inner side of the inner leg and protruding inward from the inner leg and an annular band on the outer side of the outer leg and protruding outward from the outer leg, wherein an annular recess is formed in each of the bands and wherein prior to setting of the seal assembly: each of the seal rings is located in one of the recesses and radially protrudes therefrom; and an axial dimension of each annular recess is greater than an axial dimension of each seal ring.