Wellhead seal

Abstract: An improved wellhead seal for sealing across the annular space between the exterior of a hanger and the interior of a wellhead housing 16 comprises a seal ring 12 with upper and lower rims 22, 20, resilient metal lips 34, 36 on the interior of said lower rim for engaging the exterior of the hanger, gripping and sealing elements 38 on the exterior of the upper rim, multiple camming surfaces 40 on the interior of the upper rim, and an actuating ring 14 having multiple camming surfaces 46 mating with the multiple camming surfaces on the upper rim so that downward movement of the actuating ring 14 cams the gripping and sealing elements 38 on the upper rim 22 into tight metal-to-metal sealing engagement with the housing interior sealing surface. The sealing may be accomplished directly between the exterior of a hanger rim or by a seal ring positioned between the hanger rim and the interior housing surface.

Description: This invention relates to wellhead seals. Wellhead seals are used to seal across the annular space between the exterior of a hanger and the interior of a wellhead housing in which the hanger is supported. Many types of seals have been used in the past. Such seals have included resilient annular members which are positioned within the annular space and compressed axially to expand them into sealing engagement with the surfaces defining the interior and exterior of the annular space, such as disclosed in U.S. Patent No. 3,797,864. Other seals include metal members having lips urged into engagement with the inner and outer sealing surfaces as shown in U.S. Patent Nos. 2,405,152; 2,746,486; 4,131,287; and 4,178,020. GB-A-2180016 also describes a casing hanger seal of this type. US-A-4131287 describes a seal for sealing in the annular space between a wellhead housing and a casing hanger. The seal comprises a body having upper and lower pairs of sealing lips. The sealing lips can be forced outwardly into sealing engagement with the hanger and wellhead housing by means of upper and lower sealing rings which are moved into the space between each pair of clips. Some seals have utilised a combination of resilient and metal seals such as illustrated by U.S. Patent Nos. 4,488,740 and 4,550,782. Additionally seals have been provided which utilise a resilient or metal seal which is mechanically wedged or cammed into sealing engagement with the walls of the annular space in a well bore. Other seal structures have included threaded or roughened sealing surfaces, such as wickers, which provide a positive metal-to-metal seal. U.S. Patent No. 4,595,053 is an example of these two types of seals. According to the present invention there is provided an annular wellhead seal for sealing between the interior surface of the wellhead housing and the exterior of a hanger within the housing, said housing having an internal landing seat and an internal sealing surface above the landing seat and said hanger having an external landing shoulder for engaging the internal landing seat when the hanger has been landed within the housing, and an external upwardly facing shoulder, said seal comprising a sealing ring adapted to be landed on the hanger external shoulder so that it can seal between the interior of the wellhead housing and the exterior of the hanger, and an actuating ring for moving the sealing ring to its sealing position, projections being formed on one of said sealing ring external surface or said housing internal sealing surface, and said sealing ring including internal sealing means for sealing against the exterior of the hanger, and said actuating ring having camming means which, when said actuating ring is moved downwardly, are operable to cam said sealing ring outwardly so that said projections are caused to bite into the other surface to provide a gripping and sealing engagement therebetween, characterised in that the sealing ring has a central body with an inner upwardly facing shoulder, an upper outer rim extending above the central body, and a lower rim extending below the central body, said shoulder defining an annular surface extending substantially from the outer rim to the central bore of the sealing ring body, and wherein the lower rim has the internal sealing means and the actuating ring is positioned within the upper rim and is operable to cam outwardly the upper rim to provide said gripping and said sealing engagement. The invention will be described now by way of example only, with particular reference to the accompanying drawings. In the drawings: FIGURE 1 is a partial sectional view of the improved annular wellhead seal as it is being run into a wellhead for subsequent landing within the annular space across which is it to seal. FIGURE 2 is another partial sectional view of the improved wellhead seal after it has been landed and prior to energisation. FIGURE 3 is another partial sectional view of the improved wellhead seal after it has been moved into tight sealing engagement across the annular space. FIGURE 4 is a partial sectional view of a modified form of the improved annular wellhead seal of the present invention. Description of the Preferred Embodiment Improved seal assembly 10 of the present invention is shown in its running position in FIGURE 1. Seal assembly 10 includes seal ring 12 and actuating ring 14. As shown in FIGURE 1, seal assembly 10 is positioned within wellhead member 16 and is being lowered therein on a suitable running tool (not shown). Seal ring 12 includes annular body 18 having lower rim 20 extending downward from the inner portion of body 18 and upper rim 22 extending upward from the outer portion of body 18. Wiper 24 is positioned within groove 26 around the exterior of body 18 and is sufficiently large to engage the interior of wellhead member 16 as seal assembly 10 is being lowered therein. Lower rim 20 includes groove 28 on the lower portion of its interior surface with wiper 30 being positioned therein and being sufficiently large to wipe the outer sealing surface of the hanger against which seal assembly 10 is to seal. Spaced above groove 28 is seal area 32 having sealing lips 34 and 36. Both of lips 34 and 36 extend inwardly with upper lip 34 extending upwardly and inwardly and lower lip 36 extending downwardly and inwardly. The outer diameter of lips 34 and 36 is sufficiently small to ensure proper sealing against the exterior of the hanger against which seal assembly 10 is to seal. Upper rim 22 includes external teeth or gripping and sealing elements or serrations 38 and internal multiple upward facing camming surfaces 40. Serrations 38 are intended to include small parallel grooves with pointed projections between the grooves. The inner edges of camming surfaces 40 terminate at flat cylindrical surfaces 40a and the outer edges of camming surfaces 40 terminate at flat cylindrical surfaces 40b so that camming surfaces 40 and cylindrical surfaces 40a and 40b form a toothed profile 40c with recesses 40d. Upper rim 22 extending upwardly from the outer portion of annular body 18 provides shoulder 42 on the upper part of body 18 within rim 22. Actuating ring 14 is annular in shape and includes inner tapered landing seat 44 on which a subsequent well member could be landed, external multiple downward facing camming surfaces 46 which mate with the camming surfaces 40 on the interior of upper rim 22. The outer edges of camming surfaces 46 terminate at flat cylindrical surfaces 46a and the inner edges of camming surfaces 46 terminate at flat cylindrical surfaces 46b so that camming surfaces 46 and cylindrical surfaces 46a and 46b form a toothed profile 46c with recesses 46d. In running position, actuating ring 14 is in its upper position, as shown in FIGURE 1, and in such position its lower surface 48 is spaced above shoulder 42 on body 18 and camming surfaces 40 and 46 are in contact. Toothed profiles 40c of upper rim 22 are located in recesses 46d of actuating ring 14 and toothed profiles 46c of actuating ring 14 are located in recesses 40d of upper rim 22 so that toothed profiles 40c and 46c are interlocked. This spacing between surfaces 42 and 48 should be sufficient to allow full travel of actuating ring 14 in its downward setting movement as hereinafter described. Actuating ring 14 includes an outwardly extending flange 50 at its upper end above surfaces 46 and the lower surface of flange 50 is also spaced above the upper end of upper rim 22 by a sufficient distance to allow full setting movement of actuating ring 14. Actuating ring 14 also includes preparation for receiving the suitable running tool (not shown). As shown in FIGURE 2, sealing assembly 10 is landed in annular space 52 between the interior of wellhead member 16 and the exterior of hanger 54 above upwardly facing shoulder 56 of hanger 54. Hanger 54 is landed upon in wellhead member 16 with downwardly facing shoulder 57 of hanger 54 being in supporting contact with upwardly facing shoulder 58 of wellhead member 16 and includes the usual mud slots 55 which allow circulation of cement or other well fluids prior to the landing of seal assembly 10 in annular space 52. With seal assembly 10 landed in annular space 52 as shown in FIGURE 2 the lower end of lower rim 20 is in engagement with shoulder 56 on hanger 54. In this position, wiper 30 in its downward movement has wiped external sealing surface 60 of hanger 54 free of trash, mud and all other materials which would interfere with proper sealing of lips 34 and 36 against sealing surface 60. Also, wiper 24 has wiped interior sealing surface 62 of wellhead member or housing 16 free of trash, mud and all other materials which would interfere with proper sealing of gripping teeth 38 to sealing surface 62. With seal assembly 10 in the position shown in FIGURE 2, it is ready for the engagement of gripping teeth 38 of upper rim 22 with sealing surface 62 of wellhead member 16. Actuating ring 14 is moved downward by a suitable tool (not shown) so that its exterior camming surfaces 46 move downward on camming surfaces 40 of upper rim 22 to wedge gripping teeth 38 into tight gripping and sealing engagement with sealing surface 62. In this position as shown in FIGURE 3, actuating ring 14 has moved to its lower position with its lower surface 48 engaging shoulder 42 on the upper portion of seal body 18 and also with the lower surface of flange 50 in engagement with the upper surface of rim 22. These two engagements between actuating ring 14 and seal ring 12 provide suitable stops for the downward movement of actuating ring 14 at a position when maximun force has been exerted on upper rim 22 to ensure positive deformation of sealing surface 62 by gripping teeth 38. Also, lower inner surface 49 of actuator 14 engages upper surface 54a of hanger 54. These engagements provide a transfer of the load of a hanger which is subsequently landed on landing seat 44. This load is then transferred through actuating ring 14 and rim 22 into housing 16, through actuating ring 14, shoulders 42 and 48, hanger 54 and seat 58 into housing 16 and through actuating ring 14, shoulder 54a and seat 58 into housing 16. Cylindrical surfaces 46a of actuating ring 14 have also been moved downward to become in tight contact with cylindrical surfaces 40b of upper rim 22 and thereby eliminate any tendency of actuating ring 14 to move upward in relation to seal ring 12. Also, sealing by lips 34 and 36 against sealing surface 60 is complete and is enhanced by the configuration of the lips. Fluid pressure from the interior of hanger 54 acts on exterior surface 34a of upper lip 34 to urge lip 34 into tight sealing engagement with surface 60 of hanger 54. In a similar manner fluid pressure from the exterior of hanger 54 acts on exterior surface 36a of lower lip 36 to urge lip 36 into tight engagement with surface 60 of hanger 54. Such pressure urging of lips 34 and 36 towards surface 60 increases as the pressure increases. As can be seen in FIGURE 1, lips 34 and 36 protrude inward from surface 20 and as such are able to compensate for eccentricity between wellhead member 16 and hanger 54 and still sealingly engage surface 60. It should be noted that the exterior surface 61 of lower rim 20 is spaced substantially from the interior surface 62 of wellhead housing 16. This provides a space for the trash and mud which is wiped from surface 62 by wiper 24 so that such trash and mud cannot interfere with the sealing operations of seal assembly 10. Sealing assembly 10 is retrievable from its sealing position in annular space 52 by lifting actuating ring 14 with a suitable well tool (not shown) which can engage lower surface 48 which is spaced from the upper end of hanger 54 or running tool preparation. Lifting of actuating ring 14 moves its camming surfaces 46 upwardly to release the force exterted on upper rim 22. When actuating ring 14 reaches its upper position as shown in FIGURES 1 and 2, the toothed profiles on actuating ring 14 and upper rim 22 again become interlocked to transmit the lifting force to seal ring 12. This upward force is sufficient to cause a release of the gripping engagement of gripping teeth 38 with sealing surface 62 to allow completion of the retrieval of seal assembly 10. Sometimes well debris, such as gravel or clay, becomes deposited on upwardly facing shoulder 58 of wellhead member 16 and prevents downwardly facing shoulder 57 of hanger 54 from contacting shoulder 58. Pressure subsequently present in the interior of hanger 54 may crush the debris and cause hanger 54 to move downward relative to wellhead member 16 and sealing assembly 10. Since sealing lips 34 and 36 are not firmly locked to hanger seal surface 60, such relative vertical movement between the sealing lips and surface 60 does not compromise the sealing engagement of the lips 34 and 36. It should be recognized in the preferred embodiment of FIGURES 1, 2 and 3 that the Brinell hardness of seal assembly 10 in the area of serrations 38 is preferably greater than the Brinell hardness of surface 62 of wellhead member 16 so that serrations 38 will bite into surface 62 when actuating ring 14 is moved downward. In some situations it may be preferable to place serrations at the appropriate location on surface 62 rather than on seal assembly 10. In such a situation it would be preferable to have the serration area of the wellhead member a higher Brinell hardness than the smooth exterior surface of the seal assembly. It should be noted that in most wellhead sealing situations, the condition of the sealing surface on the exterior of the hanger is known to be satisfactory while the condition of the sealing surface of the interior of the wellhead housing is unpredictable. The present invention provides an improved metal-to-metal seal against both such surfaces. Another modified form of the present invention is shown in FIGURE 4 wherein seal assembly 110 is energized by exterior tapered surface 146 of actuating ring 114 engaging interior tapered surface 140 of upper rim 122 to urge upper rim 122 into sealing engagement with the interior surface of wellhead member 116. Shear pin 123 is inserted in hole 125 through rim 122 and into energizing ring 114 to retain seal assembly 110 in an unenergized position until shoulder 57 engages upwardly facing shoulder 58 of wellhead member 116.

Claims: An annular wellhead seal for sealing between the interior surface of the wellhead housing (16) and the exterior of a hanger (54) within the housing, said housing (16) having an internal landing seat (58) and an internal sealing surface (62) above the landing seat and said hanger (54) having an external landing shoulder (57) for engaging the internal landing seat (58) when the hanger has been landed within the housing, and an external upwardly facing shoulder (56), said seal comprising a sealing ring (12) adapted to be landed on the hanger external shoulder (56) so that it can seal between the interior of the wellhead housing and the exterior of the hanger, and an actuating ring (14) for moving the sealing ring to its sealing position, projections (38) being formed on one of said sealing ring external surface or said housing internal sealing surface (62), and said sealing ring including internal sealing means (34, 36) for sealing against the exterior of the hanger, and said actuating ring (14) having camming means (46) which, when said actuating ring is moved downwardly, are operable to cam said sealing ring outwardly so that said projections (38) are caused to bite into the other surface to provide a gripping and sealing engagement therebetween, characterised in that the sealing ring (12) has a central body with an inner upwardly facing shoulder (42), an upper outer rim (22) extending above the central body, and a lower rim (20) extending below the central body, said inner upwardly facing shoulder (42) defining an annular surface extending substantially from the upper outer rim (22) to the central bore of the sealing ring body, and wherein the lower rim (20) has the internal sealing means (34, 36) and the actuating ring is positioned within the upper rim and is operable to cam outwardly the upper outer rim (22) to provide said gripping and said sealing engagement. An annular wellhead seal according to claim 1, wherein said projections (38) are positioned on the exterior of the upper rim (22). An annular wellhead seal according to claim 1 or claim 2, wherein said camming means (46) are between the interior of said sealing ring (12) and the exterior of said actuating ring (14). An annular wellhead seal according to any preceding claim, wherein said internal sealing means (34, 36) includes a resilient sealing ring positioned for sealing against the exterior of said hanger. An annular wellhead seal according claim 4, wherein said internal sealing means includes an upper metal sealing lip (34) extending upwardly and inwardly, and a lower metal sealing lip (36) extending downwardly and inwardly, said upper and lower metal sealing lips being sized to provide sealing engagement with the exterior of said hanger. An annular wellhead seal according to claim 1, wherein said projections (38) include a plurality of teeth. An annular wellhead seal according to claim 1, wherein said camming means (46) includes a plurality of camming surfaces (40) on the interior of said sealing ring (12) and a plurality of coacting camming surfaces (46) on the exterior of the actuating ring (14). An annular wellhead seal according to claim 1, wherein said coming means includes a tapered surface (146) on the exterior of the actuating ring (114) which engages a tapered surface (140) on the interior of the upper rim (122). An annular wellhead seal according to any preceding claim wherein said inner upwardly facing shoulder (42) acts as a limit to the downward travel of the actuating ring (14). An annular wellhead seal according to any preceding claim, including a wiper (24) carried by said seal ring (12) on its exterior below said upper rim (22) for wiping trash, mud, and other material from the sealing surface against which said upper rim is to seal. An annular wellhead seal according to any preceding claim, including a wiper (30) carried by the lower rim (20) for wiping trash, mud and other material from the sealing surface against which the lower rim is to seal.

Inventors: CASSITY THOMAS G, GULLION STEVEN D, CASSITY, THOMAS G., GULLION, STEVEN D.
Applicants: COOPER IND INC, COOPER INDUSTRIES INC.
Application year: 1988
Main classification: E21B33
IPC codes: E21B33, F16J15