Patent Grant
8960276
This invention relates to a wellhead seal device for sealing an annular space between tubular members, for example for sealing the annular space formed in a central bore of vertically aligned upper and lower wellhead members adjacent the rough outer wall of a tubular casing extending through the lower wellhead member and ending in the upper wellhead member. The invention also relates to a wellhead assembly sealed with the wellhead seal device, and to a method of sealing a wellhead with the wellhead seal device.
A tubular casing string, termed “casing” is used when drilling wells to support the drill hole against collapse. Casing is hung with a casing hanger, or is otherwise supported such as with a casing slip assembly, within the central bore of a pressure-containing wellhead member called a casing head. A “primary seal” is formed between the casing head and the rough outer wall of the casing to prevent fluid flow between the outside of the casing and the casing head. The casing may extend upwardly from the casing head to a cut upper end, which is then contained within a pressure-containing wellhead member called a tubing head. The casing and tubing heads are connected at mating surfaces in a pressure tight connection. A string of production tubing is supported by the tubing head, to extend concentrically within the casing. The production tubing acts as a conduit for the oil, gas or water of the well. To seal the contents of the well from the primary seal between the casing and the casing head, one or more additional seals are used above the primary seal, between the tubing head and the casing. These one or more additional seals are termed “secondary seals”.
Metal seals are favoured to provide an extreme temperature, high pressure metal-to-metal barrier seal between metal surfaces in wellhead environments. When the metal sealing surfaces are machine finished surfaces, a large number of metal-to-metal seal designs may be used, such as an interference fit between tapered, machined metal surfaces. However, when the metal seal is to an un-machined or otherwise rough outer surface of a casing, it is more difficult to make a metal seal. The following patents show exemplary secondary seals to a rough casing: U.S. Pat. No. 4,646,845 to Boeker; U.S. Pat. No. 4,718,679 to Vyvial; U.S. Pat. No. 4,771,832 to Bridges; U.S. Pat. No. 4,911,245 to Adamek et al.; U.S. Pat. No. 5,158,326 to Anderson et al. and U.S. Pat. No. 5,183,268 to Wong et al.
Most metal seals to a rough casing have been made in wellheads in which considerable pressure may be exerted to energize the metal seal through the use of flanged connections between the wellhead members. However, for threaded unions between wellhead members, metal seals are more difficult to achieve, since the limited force which is applied to make the threaded connection may not be sufficient to energize the seal. In a threaded union, the wellhead members are held together by a threaded nut or collar that is tightened to a required torque using a wrench or a hammer. One exemplary threaded union is shown in U.S. Pat. No. Publication 2008/0185156 to Rodgers et al., in which a threaded collar between a tubing head and a casing head includes a set of left-hand threads and a set of right-hand threads to connect to the outer threads on the tubing and casing heads.
Thus, one disadvantage of most prior-art threaded unions is that they rely on elastomeric seals, and not metal seals, to achieve a pressure containing, fluid-tight joint between wellhead members. However, flanged connections between wellhead members are expensive to construct and time-consuming to assemble in the field. As the oil industry continues to move toward producing hydrocarbons at a lower cost, there is considerable interest in wellhead equipment that can be quickly assembled and disassembled. Threaded unions are much quicker and less expensive than flange connections to construct. However, reliable high-pressure metal-to-metal seals with a threaded unions continues to be a problem area for the industry.
In one broad embodiment, there is provided a wellhead seal device for sealing an annular space formed between an outer tubular member and an inner tubular member, such as a casing head and a casing. The wellhead seal device includes an annular metal sealing sleeve having a lower portion and an upper portion. The upper portion forms a neck portion extending upwardly from the lower portion. The lower portion is adapted to be supported in the annular space. The neck portion has an inner surface adapted to be spaced from the inner tubular member to form an inner sealing annulus. A first metal seal ring is provided having an outer conical surface and being adapted to fit around the inner tubular member within the inner sealing annulus supported by the lower portion adjacent the inner tubular member. A first wedge ring is provided which is adapted to fit around the inner tubular member above the first metal seal ring and having an inner cam surface to engage the conical surface of the first metal seal ring within the inner sealing annulus. A first retaining ring is included and is adapted to be retained in and to close the inner sealing annulus around the inner tubular member above the first wedge ring. The first retaining ring forms a plurality of first vertical threaded ports extending there through for alignment with the first wedge ring. A plurality of first threaded seal energizing members is provided, each being adapted to be threaded through the first vertical threaded ports to push downwardly on the first wedge ring such that the first metal seal ring is compressed radially inwardly to form an inner metal seal to the inner tubular member and thus seal the inner sealing annulus.
The neck portion of the annular metal sealing sleeve may be formed with an outer surface adapted to be spaced from the outer tubular member to form an outer sealing annulus to seal to the inner wall of the outer tubular member. A second metal seal ring is provided with an inner conical surface and adapted to fit around the neck portion within the outer sealing annulus supported by the lower portion adjacent the outer tubular member. A second wedge ring is provided, adapted to fit around the neck portion above the second metal seal ring and having an outer cam surface to engage the conical surface of the second metal seal ring within the outer sealing annulus. A second retaining ring is provided, adapted to be retained in and to close the outer sealing annulus around the neck portion above the first wedge ring. The second retaining ring forms a plurality of second vertical threaded ports extending there through for alignment with the second wedge ring. A plurality of second threaded seal energizing members adapted to be threaded through the second vertical threaded ports is included to push downwardly on the second wedge ring such that the second metal seal ring is compressed radially inwardly to form an outer metal seal to the outer tubular member and thus seal the outer sealing annulus.
The wellhead seal device may be provided to seal the annular space formed between a central bore of vertically aligned upper and lower wellhead members and a rough casing. For example, the upper wellhead member may be a tubing head, and the lower wellhead member may be a casing head. However, the seal device might be accommodated in other wellhead members. The seal device has the advantage of providing, at its lower sealing portion, a primary seal to the rough casing, and a seal to the central bore of the lower wellhead member (ex. casing head), while providing at its upper sealing portion, an external metal seal to the central bore of the upper wellhead member (ex. tubing head), and an internal, secondary metal seal to the rough casing. The seal device includes an annular metal sealing sleeve configured to provide elastomeric or other seals at its lower sealing portion. The upper sealing portion of the annular metal sealing sleeve is configured to allow a secondary metal seal to the rough casing to be energized from above, with a downward force, prior to installing the upper wellhead member. This allows the wellhead seal device to be used in a wellhead with a threaded union between the lower and upper wellhead members (ex. casing head and the tubing head).
The outer surface of the casing, which is formed by rolling, is a rough un-finished surface, with large diametric tolerance. Thus, it takes a large force to energize a seal to this casing surface. However, the central bore of the upper and lower wellhead members typically have machine finished surfaces and tight tolerances, so seals to these surfaces require less force to energize. In one embodiment of the wellhead seal device, the primary and secondary seals to the rough casing are separated from the seals to the finished surfaces of the upper and lower wellhead members. As well, the primary and the secondary seals to the casing are both made by separate surfaces of the one seal device. By separating the seals in the manner, and by configuring the seal device such that the primary and secondary seals to the rough casing are energized from above, without the upper wellhead member yet in place, for example using vertical threaded seal energizing members, sufficient force can be applied to energize a secondary metal seal to the rough casing. A threaded connection between the upper and lower wellhead members can thereafter be made without concern for the primary and secondary seals to the rough casing. The seal device may alternatively be used with flanged or other wellhead connections, but it has the advantage of being able to form a secondary metal seal to the casing in a wellhead which uses a threaded connection.
Broadly stated, there is provided a wellhead seal device for sealing the annular space formed in a central bore extending through vertically aligned upper and lower wellhead members adjacent the rough outer wall of a tubular casing, the casing extending through the lower wellhead member and having an upper end in the upper wellhead member. The wellhead seal device includes an annular metal sealing sleeve having an upper portion integral with a lower portion. The lower portion has an inner bore adapted to provide an inner seal to the casing, and an outer surface adapted to provide an outer seal to the lower wellhead member. The upper portion is configured to extend upwardly from the lower portion into the central bore of the upper wellhead member. An outer tapered surface on the upper portion is adapted to form an external metal seal to a conical central bore section at a lower end of the upper wellhead member. An inner surface of the upper portion is adapted to be spaced from the casing in the upper wellhead member to form a sealing annulus. A metal seal ring having an outer conical surface is adapted to fit around the casing within the sealing annulus supported by the lower portion adjacent the casing. A wedge ring, adapted to fit around the casing above the metal seal ring, has an inner cam surface to engage the outer conical surface of the metal seal ring within the sealing annulus. A retaining ring is adapted to be retained in and to close the sealing annulus of the upper portion around the casing above the wedge ring. The retaining ring forms a plurality of vertical threaded ports extending there through for alignment with the wedge ring. A plurality of threaded seal energizing members are adapted to be threaded through the threaded ports to push downwardly on the wedge ring such that the metal seal ring is compressed radially inwardly to form an internal metal seal to the casing and thus seal the sealing annulus. The downward action on the wedge ring also transfers downward force to the lower portion to energize the inner and outer seals.
Also provided is a wellhead assembly including an upper wellhead member vertically aligned and connected above a lower wellhead member and forming a central bore to accommodate a tubular casing extending through the lower wellhead member and ending with an upper end in the upper wellhead member, such that an annular space is formed between the central bore of the upper and lower wellhead members and the outer wall of the casing. The wellhead assembly further includes one of the above-described wellhead seal devices positioned in sealing relationship in the annular space and providing seals to the central bore in each of the upper and lower wellhead members and seals to the outer wall of the casing in each of the upper and lower wellhead members.
There is also provided a method of sealing an annular space formed between an inner tubular member and an outer tubular member. The method includes:
providing an annular metal sealing sleeve having a lower portion and an upper portion, the upper portion forming a neck portion extending upwardly from the lower portion, the lower portion being adapted to be vertically supported in the annular space, and the neck portion having an inner surface adapted to be spaced from the inner tubular member to form an inner sealing annulus;
installing the annular metal sealing sleeve in a vertically supported manner in the annular space;
installing a first metal seal ring in a supported manner in the inner sealing annulus; and
applying a downward force within the inner sealing annulus such that the first metal seal ring is compressed radially inwardly to form an inner metal seal to the inner tubular member.
Broadly stated, there is also provided a method of sealing an annular space formed in a central bore extending through vertically aligned upper and lower wellhead members adjacent an outer wall of a tubular casing, the casing extending through the lower wellhead member and having an upper end in the upper wellhead member. The method includes:
a. providing an annular metal sealing sleeve having an upper sealing portion and a lower sealing portion, the lower sealing portion having an inner bore adapted to form an inner seal to the casing and an outer surface adapted to form an outer seal to the central bore of the lower wellhead member, and the upper sealing portion having an outer tapered surface adapted to form an external metal seal to a conical central bore section at a lower end of the upper wellhead member, and an inner surface adapted to be spaced from the casing in the upper wellhead member to form a sealing annulus to accommodate an internal metal seal to the casing;
b. installing the metal sealing sleeve in the annular space of the lower wellhead member;
c. installing a metal seal ring in a supported manner in the sealing annulus;
d. applying a downward force within the sealing annulus such that the metal seal ring is compressed radially inwardly to form the internal metal seal to the casing, and to energize the inner and outer seals of the lower sealing portion; and
e. connecting the upper wellhead member above the lower wellhead member such that the outer tapered surface of the upper sealing portion forms the external metal seal to the conical central bore section of the upper wellhead member.
Also provided is a method of sealing an annular space formed in a central bore extending through vertically aligned upper and lower wellhead members adjacent a rough outer wall of a tubular casing, the casing extending through the lower wellhead member and having an upper end in the upper wellhead member. The method includes:
a. installing one of the above-described annular metal sealing sleeves in the annular space of the lower wellhead member;
b. installing the metal seal ring in the sealing annulus such that it is supported against downward movement by the lower portion of the metal sealing sleeve;
c. installing the wedge ring above the metal seal ring;
d. installing the retaining ring in the upper portion of the metal sealing sleeve;
e. threading the threaded seal energizing members into the threaded ports in the retaining ring to press downwardly on the wedge ring and to compress the metal seal ring radially inwardly to form the internal metal seal to the casing and thus seal the sealing annulus, and to also transfer downward force to the lower portion to energize the inner and outer seals; and
f. connecting the upper wellhead member above the lower wellhead member such that the outer tapered surface of the upper portion of the metal sealing sleeve forms the external metal seal to the conical central bore section at the lower end of the upper wellhead member.
The wellhead seal device has the advantage of allowing for testing each of the seals formed by the seal device, for example through one or more test ports formed through the tubing head and through the metal sealing sleeve to communicate with the seals.
Having reference to
When the casing head 12 and the tubing head 14 are connected together in a vertically aligned manner, a central bore 32 extends through the casing head 12 and a central bore 33 extends through the tubing head 14. The central bores 32, 33 communicate with each other to accommodate a tubular casing 34 (i.e., an inner tubular member). The bores 32, 33 are profiled by machining to accommodate or support conventional components, guides, landing shoulders and the like, as is known in the industry. The upper portion of the central bore 33 of the tubing head 14 is shown formed with a profile 33a to support a conventional tubing hanger. The central bore 32 of the casing head 12 is shown profiled to support a casing hanger, such as a slip assembly 40. The casing head 12 is sealed at its lower end 57 to a surface casing 36, for example with an O-ring 37 held in a circumferential groove 38. Lower external welds 39 may be included between the casing head 12 and the surface casing 36. The slip assembly 40 is supported on landing shoulder 42 in the central bore 32 of the casing head 12. The slip assembly 40 includes an outer slip housing 44 supported on landing shoulder 42, and forming a tapered bowl 44a at its inner bore. A plurality of wedge shaped segmented slips 46 are supported by the slip housing 44. The slips 46 are formed with inwardly projecting teeth 48 on their inner gripping surface to grip the rough outer wall 50 of the casing 34, thus enabling the slip assembly 40 to engage and suspend the casing 34. The casing 34 extends upwardly into the central bore 33 of the tubing head 14 such that the upper end 52 of the casing 34 is located above the lower end 54 of the tubing head 14. An annular space S is formed between the communicating central bores 32, 33 and an upper portion of the outer wall 50 of the casing 34. This annular space S is sealed by the seal device 10, as described more fully below.
In the embodiment of
The upper portion 64 of the sealing sleeve 60 extends upwardly from the lower portion 62, and forms an outer tapered surface 74 adapted to form an external metal seal to the conical central bore section 76 at the lower end of the central bore 33 of the tubing head 14. The outer tapered surface 74 is slightly larger diametrically than the diameter of the conical central bore section 76 of the tubing head 14 so as to form an interference fit when the tubing head 14 is lowered over the seal device 10. Spaced apart circumferential grooves 78, 80 are formed above and below the tapered surface 74 of the upper portion 64. These grooves 78, 80 increase the resiliency of the upper portion 64, allowing it to flex slightly inwardly to form the metal seal when the tubing head 14 is connected above the casing head 12. The grooves 78, 80 also allow for seals, for example O-rings (not shown) to be included on this external metal sealing surface.
The inner surface 82 of the upper portion 64 is formed recessed relative to the central bore 63 of the lower portion 62, such that the inner surface 82 is spaced from the outer wall 50 of the casing 34. This forms a sealing annulus A between the upper portion 64 and the casing 34. The sealing annulus A accommodates an internal metal seal to the rough outer wall 50 of the casing 34 within the tubing head 14, as described below. At the base of the sealing annulus A, above the lower portion 62, a reduced diameter section 86, adjacent the casing 34 is preferably formed to accommodate the internal metal seal to the casing 34.
A metal seal ring 88 is installed in the reduced diameter section 86 so as to be supported against downward vertical movement by the lower portion 62 of the metal sealing sleeve 60. The metal seal ring 88 is formed with an outer conical surface 90. The inner surface (i.e., inner bore) of the metal seal ring 88 is formed with inwardly projecting ribs, ridges, serrations or ribs (i.e., projections) 92 to seal to the casing 34. A wedge ring 94 is positioned in the reduced diameter section 86 around the casing 34 above the metal seal ring 88. The wedge ring 94 has an upper portion which forms a lip 96 which extends inwardly to the casing 34 to form a central bore adjacent the outer wall 50 of the casing 34. The lower portion of the wedge ring 94 is spaced from the metal seal ring 88 and provides a mating cam surface 97 at its inner surface to slide over the outer conical surface 90 of the metal seal ring 88. The metal seal ring 88 and the lower portion of the wedge ring 94 have a combined radial thickness which is slightly oversized compared to the radial dimension of the reduced diameter section 86. In this manner, downward force applied to the upper surface of the wedge ring 94 transfers a sliding cam force on the metal seal ring 88, causing the metal seal ring 88 to be radially compressed inwardly to form a metal seal to the outer wall 50 of the casing 34.
A retaining ring 98 is retained within the upper portion 64 of the sealing sleeve 60. The retaining ring 98 has multiple functions, including closing the sealing annulus A above the metal seal ring 88, supporting the upper portion 64 of the sealing sleeve 60 (ex. to form the external seal to the tubing head 14, and to withstand high internal pressure without collapse), and providing a means to energize the metal seal ring 88 prior to installing the tubing head 14. The inner surface 82 of the upper portion 64 of the metal sealing sleeve 60 is preferably threaded to receive and retain a retaining ring 98 within the sealing annulus A. The retaining ring 98 is threaded on its outer peripheral surface. The retaining ring 98 is formed with a central bore 100 to accommodate the casing 34. An upper inwardly extending lip 102 on the retaining ring 98 may be included to extend over and to protect the upper end 52 of the casing 34 once the retaining ring 98 is threaded in place. A plurality of threaded cap screws 104 (or other threaded seal energizing members such as threaded screws or bolts/nuts) extend through vertical threaded ports 106 and are aligned with the wedge ring 94, such that downward threading of the cap screws 104 forces the wedge ring 94 downwardly to energize the metal seal ring 88. The retaining ring 98 preferably includes a circumferential groove 107 at its outer surface to serve as a relief groove on its threaded outer surface.
The lower portion 62 is preferably formed with one or more test ports 108, 108a extending there through to a location above the primary seal 72. In the illustrated embodiment, two communicating test ports 108, 108a are shown, which allow for bleeding out during testing. These test ports 108, 108a allow for testing of the seals to the casing 34 (i.e., seals 72 and 88), before installing the tubing head 14. Thus, the seal device 10 allows one to check the integrity of the seals to the rough outer surface of the casing 34, before installing further wellhead members.
One or more test ports 110, 112 are formed through the tubing head 14 as shown in
It will be understood that the metal sealing sleeve 60, retaining ring 98, wedge ring 94 and metal seal ring 88 are each formed for tight fitting relationships with each other and with the casing 34 to fully close and seal the sealing annulus A along the outer wall 50 of the casing 34. These four components 60, 98, 94, 88, when fully installed and connected together around the casing 34, provide a single wellhead seal device which forms both the primary seal and the secondary seal to the rough outer wall of the casing 34.
It will be apparent from the above description that there is provided a method in which the seal device 10 is installed in the casing head 12 prior to connecting the tubing head 14 with the threaded collar 16. In this way, the secondary seal to the casing 34 can be formed as a reliable metal seal with a sufficient seal energizing force being supplied through threaded seal energizing members, such as the cap screws 104. The tubing head 14 is thereafter connected to the casing head 12 using a threaded connection, such as the threaded collar 16, without damaging the seals to the casing 34. Alternate connections between the casing and tubing heads 12, 14 may be used, but the seal device 10 has the advantage of allowing for a secondary metal seal to be made to the casing in a wellhead which uses a threaded connection between the heads 12, 14.
In
A first retaining ring 160 is retained within the neck portion 132 to close the inner sealing annulus 144 above the first metal sealing ring 148. The inner surface 140 of the neck portion 132 is preferably threaded to receive and retain the first retaining ring 160 within the inner sealing annulus 144. The first retaining ring 160 is threaded on its outer peripheral surface. The first retaining ring 160 is formed with a central bore 162 to accommodate the inner tubular member 126. A plurality of first threaded cap screws 164 (or other threaded seal energizing members such as bolts/nuts) extend through first vertical threaded ports 166 in the first retaining ring 160 and are aligned with the first wedge ring 154, such that downward threading of the first cap screws 164 forces the first wedge ring 154 downwardly to energize the first metal seal ring 148, and thus seal the inner sealing annulus 144.
The neck portion 132 is preferably formed with an outer surface 168 which is recessed from the inner wall 169 of the outer tubular member 124 to form an outer sealing annulus 170. A reduced radius section 172 is formed at the base of the outer sealing annulus 170. A second metal seal ring 174 and a second wedge ring 176 are accommodated in the reduced radius section 172. The second metal seal ring 174 has an inner conical surface 178, and projections 180 are formed on the outer peripheral surface. The second wedge ring 176 has an upper portion forming a lip 182 which extends outwardly to the outer tubular member 124. The lower portion of the second wedge ring 176 is spaced from the second metal seal ring 174 and provides a mating cam surface 184 at its outer surface to slide over the inner conical surface 178 of the second metal seal ring 174. The second metal seal ring 174 and the lower portion of the second wedge ring 176 have a combined radial thickness which is slightly oversized compared to the radial dimension of the reduced diameter section 172. In this manner, downward force applied to the upper surface of the second wedge ring 176 transfers a sliding cam force on the second metal seal ring 174, causing the second metal seal ring 174 to be radially compressed outwardly to form the outer metal seal to the inner wall 169 of the outer tubular member 124.
A second retaining ring 188 is retained within the neck portion 132 to close the outer sealing annulus 170 above the second metal sealing ring 174. The outer surface 168 of the neck portion 132 is preferably threaded to receive and retain the second retaining ring 188 within the outer sealing annulus 170. The second retaining ring 188 is threaded on its inner surface. The second retaining ring 188 is formed with an outer peripheral surface to accommodate the outer tubular member 124. A plurality of second threaded cap screws 190 (or other threaded seal energizing members such as bolts/nuts) extend through second vertical threaded ports 192 and are aligned with the second wedge ring 176, such that downward threading of the second cap screws 190 forces the second wedge ring 176 downwardly to energize the second metal seal ring 174, and thus seal the outer sealing annulus 170.
This further embodiment provides a method of sealing the annular space 122 formed between the inner tubular member 126 and the outer tubular member 124, with an inner metal seal to the inner tubular member 126. The annular metal sealing sleeve 128 is installed in a vertically supported manner in the annular space 122, for example on the landing shoulder 135. The sealing sleeve 128 may be alternatively supported, for example as shown in
As used herein and in the claims, the word “comprising” is used in its non-limiting sense to mean that items following the word in the sentence are included and that items not specifically mentioned are not excluded. The use of the indefinite article “a” in the claims before an element means that one of the elements is specified, but does not specifically exclude others of the elements being present, unless the context clearly requires that there be one and only one of the elements.
All references mentioned in this specification are indicative of the level of skill in the art of this invention. All references are herein incorporated by reference in their entirety to the same extent as if each reference was specifically and individually indicated to be incorporated by reference. However, if any inconsistency arises between a cited reference and the present disclosure, the present disclosure takes precedence. Some references provided herein are incorporated by reference herein to provide details concerning the state of the art prior to the filing of this application, other references may be cited to provide additional or alternative device elements, additional or alternative materials, additional or alternative methods of analysis or application of the invention.
The terms and expressions used are, unless otherwise defined herein, used as terms of description and not limitation. There is no intention, in using such terms and expressions, of excluding equivalents of the features illustrated and described, it being recognized that the scope of the invention is defined and limited only by the claims which follow. Although the description herein contains many specifics, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the embodiments of the invention.
One of ordinary skill in the art will appreciate that elements and materials other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such elements and materials are intended to be included in this invention. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.
This application claims priority from U.S. Provisional Patent Application No. 61/385,299 filed Sep. 22, 2010, which is incorporated by reference herein to the extent that there is no inconsistency with the present disclosure.
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| Number | Date | Country | |
|---|---|---|---|
| 20120067597 A1 | Mar 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61385299 | Sep 2010 | US |
