WELLHEAD ANNULAR SEAL

Abstract: An improved annular seal 10 and hanger 14 which are to be installed in a wellhead housing 12. The annular seal assembly 10 includes seal ring 42 having a central body with upper outer rim 66, upper inner rim 64, lower outer rim 70 and lower inner rim 68 extending from the central body, an upper wedge ring 46, a lower wedge ring 44 and means 50 connecting the rings to allow setting movement thereof, and means releasably securing the assembled rings to the hanger for running into the wellhead housing. Each of the rims includes an outer sealing lip 72, the outer sealing lips having a free diameter less than the diameter of the lower wedge ring so that the sealing lips are protected during running of the hanger into the wellhead housing. Means are provided for moving the wedge rings into the space between the rims of the seal ring for urging the sealing lips into sealing engagement with the interior sealing surface of the housing.

Description: Background The present invention relates to an improved annular seal assembly for use in sealing across the annulus between a wellhead housing and a hanger supported therein. Wellhead seals have long been used to seal between the hanger and the housing in which it is supported. An example of a prior art wellhead seal is disclosed in U. S. Patent No. 3,797,864 which provides an elastomeric ring positioned between metal end pieces having arms extending onto the inner and outer end portions of the elastomeric seal ring and means for compressing the seal axially to cause it to expand radially into sealing engagement with the inner and outer sealing surfaces. Another type of wellhead annular seal is disclosed in U. S. Patent No. 4,595,063 which seal includes inner and outer seal rings positioned on inner and outer surfaces of a sleeve and a U-shaped actuator which engages the ends of the seal ring to create a compression in them by virtue of relative movement between the actuator and the sleeve. U. S. Patent No. 4,471,965 discloses another type of seal in which an H-shaped member having arms with rounded sealing ends thereon is used for sealing across an annulus. U. S. Patent No. 4,178,020 discloses an H-shaped seal member with opposed wedge rings for use in a slip joint to lock the components together and provide an irreversible metal-to-metal seal. A U-shaped seal which is wedged inward and outward into sealing engagement with the inner and outer walls of an annulus is disclosed in U. S. Patent No. 4,595,053. A resilient packing ring which has upper and lower legs which are actuated by wedges is disclosed in U. S. Patent No. 1,905,122. Another wellhead annulus sealing assembly is disclosed in U. S. Patent No. 4,131,287. This structure includes a seal ring with two upper and two lower arms which forced into sealing position by upper and lower wedges. The assembly is connected into an assembly by bolts which extend through the wedges and into the seal ring. Another prior art assembly is described in US-A-4353560. The seal assembly described in this document has a sealing ring with flared upper and lower flanges. The ring can be sandwiched between upper and lower rings to urge the flanges into contact with spaced annular sealing surfaces. According to the present invention there is provided a wellhead structure having an annular seal assembly for sealing across the annular space between a wellhead housing and a hanger positioned within the housing, said seal assembly comprising an annular seal ring having at least an inner and an outer rim, said inner and outer rim being spaced apart radially, wedging means having a portion which can project into the space between said rims and being wider than said space so that when it is moved fully into the space between the rims it wedges the rims outwardly for sealing engagement with inner and outer surfaces, means coacting with the seal rim and wedging means to retain them in their assembled position and an actuating ring for moving said wedging means, that each rim extending axially from a body portion and has a surface engaging sealing portion near its axial extremity, said wedging means when moved fully into the space between said rims acting to wedge the surface engaging sealing portion outwardly for sealing engagement with the inner and outer surfaces of said housing and hanger, characterised in that the free outer diameter of the sealing portions of the outer rim is less than the outer diameter of the wedging means and the seal includes means for releasably securing said annular seal to said hanger until said rims have been wedged to their sealing position, said securing means then releasing to allow movement of the annular seal along said hanger to a position in which the rim sealing portions contact sealing surfaces on the hanger and wellhead housing. In embodiments in accordance with the present invention outer sealing lips of the rims which have a free diameter less than the diameter of the lower energizing ring are protected during running of the hanger into the wellhead housing. The invention will be described now by way of example only, with particular reference to the accompanying drawings. In the drawings: FIGURE 1 shows a metal annular seal being run into a wellhead housing on a hanger. FIGURE 2 is a detailed sectional view of a seal as the hanger is landed in its position within the wellhead housing. FIGURE 3 is another detailed sectional view of the seal in its prestressed partially set position. FIGURE 4 is another detailed sectional view of the seal in its set position. FIGURE 5 is a detailed sectional view of a modified form of seal as landed. Description of the Preferred Embodiment Annular seal assembly 10 is utilized in a wellhead to seal across the annulus between the interior of wellhead housing 12 and the exterior of tubular hanger 14. Hanger 14 is landed with its outer shoulder 16 on internal seat 18 of housing 12. The interior of housing 12 above seat 18 includes latching groove 20, groove 22 with sealing surface 25 between such grooves 20 and 22, tapered ridge 24 on the upper end of groove 22 with its interior being sealing surface 26 and inner surface 28 above ridge 24 which inner surface 28 has the same diameter as the diameter of groove 22. Sealing surfaces 25 and 26 are at the same diameter. The exterior of hanger 14 above shoulder 16 is recessed at 30 to provide shoulder 32 on which latching means, such as split latching ring 34 is supported, second recess 36 providing shoulder 38 at the level of the upper part of latching ring 34 and the upper exterior of hanger 14 includes threads 40. Improved seal assembly 10 includes annular seal 42, lower wedge ring 44, upper wedge ring 46, actuating ring 48 and means 50 for retaining seal assembly 10 as assembled. Such means 50 includes cap screws 52 and 53 which extend through wedge rings 44 and 46 and thread into holes 52a and 53a in the central portion of seal 42. Cap screw threaded holes 52a and 53a must not be in communication with one another. In some situations it may be preferred to radially stagger holes 52a and 53a rather than have them radially aligned as shown in the drawings. Seal assembly 10 when assembled is installed on the exterior of hanger 14 in the position shown in FIGURES 1 and 2 and shear pin 54, which extends through lower wedge ring 44, prevents inadvertent downward movement of lower wedge ring 44 with respect to hanger 14. Actuating ring 48 is threaded onto threads 40 on the exterior of hanger 14. Sleeve 56 is integral with lower wedge ring 44 and extends downwardly into position so that its lower tapered surface 58 which tapers downwardly and inwardly is in engagement with upper tapered surface 60 of split latching ring 34. Annular seal 42 includes central ring 62 with upper inner and outer rims 64 and 66 and lower inner and outer rims 68 and 70 extending therefrom. The ends of each of the rims 64, 66, 68 and 70 are formed into arcuate lips 72. Lips 72 on outer rims 66 and 70 are curved to present a curved convex surface for sealing against sealing surfaces 25 and 26 on the interior of housing 12 as hereinafter set forth. Lips 72 on inner rims 64 and 68 are curved to present a curved convex surface for sealing against sealing surface 73 on the exterior of hanger 14 above shear pin 54. The interengagement between actuating ring 48 and upper wedge ring 46 for the lifting of annular seal 10 is provided by retainer ring 74 which is secured within the upper interior of upper wedge ring 46 by a plurality of set screws 76. Lower surface 78 of retainer ring 74 is positioned above outer shoulder 80 on actuating ring 48. The upper rim 82 of actuating ring 46 is provided with slots 84 which can be engaged by a suitable tool (not shown) to cause rotation of actuating ring 48 with respect to hanger 14. Bearing ring 81 is interposed between the lower surface of actuating ring 48 and shoulder 83 which forms the upper interior surface of upper wedge ring 46. Upper wedge ring 46 includes a plurality of bores 86 extending therethrough to receive cap screws 53 and counterbores 88 which are sufficiently large to receive the heads of cap screws 53. Lower wedge ring 44 includes a plurality of bores 90 extending therethrough to receive cap screws 52 and counterbores 92 which are sufficiently large to receive the heads of cap screws 52 as shown in FIGURE 2. Control lines 94 extend through hanger 14 to the subsurface safety control valves (not shown). In the running position as shown in FIGURES 1 and 2, outer lips 72 have a diameter less that the outer diameter of wedge rings 44 and 46. Inner lips 72 are in sealing engagement with sealing surface 73. The outer surface of both wedge rings 44 and 46 have a reduced diameter at their ends which are in engagement with the interior of lips 72 on outer rims 66 and 70. In this structure the wedge rings 44 and 46 serve to support rims 66 and 70 during running without causing them to be wedged outward from their desired free position. After hanger 14 has landed with its shoulder 16 seated on seat 18, a suitable tool (not shown), which could be the running tool, is engaged within slots 84 in upper rim 82 of actuating ring 48 and is rotated to cause the threading of ring 48 downward on threads 40 of hanger 14. This downward movement causes wedge rings 44 and 46 to be moved inward into annular seal 42 to the position shown in FIGURE 3. It should be noted in this position that lips 72 on rims 66 and 70 have been wedged outward but are at a level so that they are adjacent upper surface 28 and groove 22. In this manner rims 66 and 70 are effectively prestressed prior to being set. The movement of the wedge rings 44 and 46 into the space between the rims also causes inner rims 64 and 68 to be wedged into tighter engagement with sealing surface 73. Further movement of actuating ring 48 causes the shearing of shear pin 54. This allows further downward movement of annular seal 10 to move sleeve 56 behind latching ring 34 so that it moves into groove 20 and secures hanger 14 in its seated position as shown in FIGURE 4. Additionally, lips 72 on rims 66 and 70 are moved into tight sealing engagement with surfaces 26 and 25, respectively to complete the setting of annular seal 10 into position forming a tight metal-to-metal sealing engagement across the annular space between the hanger 14 and the interior of the housing 12. The modified form of the seal illustrated in FIGURE 5, is substantially the same as the form previously discussed and for that reason, the numbering of components which are not changed are kept the same with the addition of the prefix 1. Sealing assembly 110 is supported on hanger 114 with actuating ring 148 threaded onto the external threads 140 on hanger 114 and shear pin 154 releasably secures lower wedge ring 144 to hanger 114. Cap screws 153 provide the means 150 for retaining the components of seal assembly 110 together by extending through upper wedge ring 146 and threading into annular seal 142. Annular seal 142 includes upper inner and outer rims 164 and 166 but the lower rims shown in the previous embodiment are omitted Annular seal 142 includes sleeve 156 since the omission of the lower rims eliminates the need for the lower wedge ring. The operation of modified sealing assembly 110 is similar to sealing assembly 10 except that the lower rims are eliminated. With the prestressing of upper rims 164 and 166, additional movement of actuator ring 148 causes shearing of shear pins 154 and sleeve 156 moves downward within latching ring 134 to force it outward into latching engagement within latching groove 120 on the interior of housing 112. This effectively latches hanger 114 in its landed position within housing 112. The outer diameter of rim 166 is less than the diameter of central ring 162 of seal 142 and the diameter of upper wedge ring 146 to ensure that there is no possibility of the rims catching on the interior of the bore through which they are run before landing on housing seat 118. An additional change in this modified form of the invention is the interior profile of housing 112 which includes only sealing surface 126 and against which lip 172 of rim 166 seals. The setting of the modified form of the invention is as described above with the lips 172 of rims 164 and 166 being initially wedged outwardly and when they are in their outermost positions, the force increases against shear pin 154 until it shears allowing the assembly to move downwardly to set split latching ring 134 within groove 120. This final downward movement brings both lips 172 into sealing engagement with sealing surface 126 and sealing surface 173 to complete the metal-to-metal seal across the annulus between the exterior of hanger 114 and the interior of housing 112.

Claims: A wellhead structure having an annular seal assembly (10) for sealing across the annular space between a wellhead housing (12) and a hanger (14) positioned within the housing, said seal assembly (10) comprising an annular seal ring (43) having at least an inner and an outer rim (64, 66), said inner and outer rim being spaced apart radially, wedging means (46) having a portion which can project into the space between said rims (64, 66) and being wider than said space so that when it is moved fully into the space between the rims (64, 66) it wedges the rims outwardly for sealing engagement with inner and outer surfaces, means (50) coacting with the seal rim (42) and wedging means (46) to retain them in their assembled position and an actuating ring (48) for moving said wedging means (46), each rim (64, 66) extending axially from a body portion (42) and has a surface engaging sealing portion (72) near its axial extremity, said wedging means (46) when moved fully into the space between said rims acting to wedge the surface engaging sealing portion (72) outwardly for sealing engagement with the inner and outer surfaces of said housing and hanger, characterised in that the free outer diameter of the sealing portions (72) of the outer rim (66) is less than the outer diameter of the wedging means (46) and the seal includes means (54) for releasably securing said annular seal (42) to said hanger (14) until said rims (64, 66) have been wedged to their sealing position, said securing means (54) then releasing to allow movement of the annular seal (42) along said hanger to a position in which the rim sealing portions (72) contact sealing surfaces on the hanger (14) and wellhead housing (12). A wellhead structure according to claim 1 wherein said seal ring (42) has two pairs of rims (64, 66; 68, 70), one pair (64, 66) extending axially upwardly and the other pair (68, 70) extending axially downwardly, and each pair of rims having an associated wedging means (46, 44). A wellhead structure according to claim 1, or claim 2, wherein said wellhead housing (12) has an internal landing seat (18), at least one sealing surface (26) above said landing seat, and an upper surface (28) above said sealing surface having a diameter greater than that of said second sealing surface, and said hanger (14) has an outer lower landing shoulder (16), which when landed is in engagement with said internal landing seat (18) in said wellhead housing, an upwardly facing external shoulder (38) above said landing seat, external threads (40) on the upper exterior of said hanger and a sealing surface (73) between said external shoulder and said threads. A wellhead structure according to claims 2 and 3, wherein said means (54) releasably securing said lower wedge ring (44) to said hanger (14) with sufficient strength to allow completion of setting movement of said wedge rings (44, 46) into said seal ring (42) responsive to movement of said actuating ring (48) without releasing said securing means, said securing means (54) then releasing responsive to continued movement of said actuating ring (48) following completion of the setting movement of said wedge rings into said seal ring. A wellhead structure according to any preceding claim, wherein said releasable securing means includes a shear pin (54) extending through said wedging means (44, 46) and into said hanger (14). A wellhead structure according to any preceding claim, wherein said coacting means includes at least one cap screw (53) extending through said wedging means (44, 46) and threading into said seal ring to retain said wedging means without restricting the setting movement of said wedging means into said seal ring (42). A wellhead structure according to claim 1, wherein said seal assembly includes an H-shaped seal ring (42) with upper and lower inner and outer rims (64, 66; 68, 70) with sealing lips (72) on the ends of each of said rims. A wellhead structure according to claim 2, wherein said actuating ring (48) moves an upper wedge ring (46) fully between said upper seal ring rims (64, 66) to wedge said upper seal ring rims apart into tight metal-to-metal sealing engagement with the walls of said hanger and wellhead housing, and moves a lower wedge ring (44) fully between said lower seal ring rims (68, 70) to wedge said lower seal ring rims apart into tight metal-to-metal sealing engagement with the walls of said hanger and wellhead housing.

Inventors: SMITH, JERRY D., SZYMCZAK, EDWARD J.
Applicants: COOPER INDUSTRIES INC.
Application year: 1988
Main classification: E21B33
IPC codes: E21B33