U.S. patent application number 09/775118 was filed with the patent office on 2001-11-29 for water ingress seal for tapered seals.
Invention is credited to Johnson, Ready Joseph.
Application Number | 20010045711 09/775118 |
Document ID | / |
Family ID | 49165419 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045711 |
Kind Code |
A1 |
Johnson, Ready Joseph |
November 29, 2001 |
Water ingress seal for tapered seals
Abstract
A wellhead housing includes a metal seal with a ring portion and
a rib portion. The ring portion includes two frustoconical surfaces
for mating with tapered surfaces of a wellhead connector and the
wellhead housing. Two conical, metal-to-metal seals are created
where the ring portions of the seal engage the tapered surfaces of
the wellhead connector and housing. These metal-to-metal seals
contain internal pressure within the wellhead. Two legs extend
outward from the rib portion. An upward-facing foot surface at the
end of the top leg engages the wellhead connector, while a
downward-facing foot surface at the end of the bottom leg engages
the wellhead housing. A metal-to-metal seal created between each
foot surface and the corresponding tubular member resists external
pressure to prevent water ingress into the joint.
Inventors: |
Johnson, Ready Joseph;
(Houston, TX) |
Correspondence
Address: |
James E. Bradley
BRACEWELL & PATTERSON LLP
711 Louisiana Street, Suite 2700
Houston
TX
77002-2781
US
|
Family ID: |
49165419 |
Appl. No.: |
09/775118 |
Filed: |
February 1, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60183183 |
Feb 17, 2000 |
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Current U.S.
Class: |
277/608 |
Current CPC
Class: |
E21B 33/038 20130101;
F16L 17/08 20130101; F16L 25/0018 20130101 |
Class at
Publication: |
277/608 |
International
Class: |
H02G 015/04 |
Claims
I claim:
1. A tubular joint comprising: a first tubular member having a
bore, a tapered inner end surface, and a shoulder surface which is
generally perpendicular to the bore; a second tubular member having
a bore, a tapered inner end surface, and a shoulder surface which
is generally perpendicular to the bore, said second tubular member
connected with first tubular member in an end-to-end orientation; a
metal annular seal having a first tapered sealing surface that
sealingly engages the tapered inner end surface of the first
tubular member, a second tapered sealing surface that sealingly
engages the tapered inner end surface of the second tubular member;
and the annular seal having metal first and second ingress seal
surfaces located between the shoulder surface of the first and
second tubular members, the first and second ingress seal surfaces
being biased in opposite directions to sealingly engage the
shoulder surface of each tubular member.
2. The tubular joint of claim 1, wherein the annular seal comprises
a ring portion containing the first and second tapered sealing
surfaces and a rib portion, the rib portion extending radially
outward from the ring portion relative to an axis of the tubular
members, each of the first and second ingress sealing surfaces
extending radially outward from the rib portion.
3. The tubular joint of claim 1 wherein the ingress seal surfaces
comprise two legs which extend generally radially outward from the
first and second tapered sealing surfaces relative to an axis of
the tubular member.
4. The tubular joint of claim 1 wherein the annular seal comprises
a ring portion containing the first and second tapered sealing
surfaces and a rib portion, the rib portion extending radially
outward from the ring portion relative to an axis of the tubular
members, the first and second ingress sealing surfaces comprising a
pair of legs joined to and extending radially outward from the rib
portion relative to an axis of the tubular members.
5. The tubular joint of claim 1 wherein the annular seal comprises
a ring portion containing the first and second tapered sealing
surfaces, a rib portion extending radially outward from the ring
portion relative to an axis of the tubular members, and a pair of
legs joined to and extending radially outward from the rib portion
relative to an axis of the tubular members, the first and second
ingress sealing surfaces comprising foot portions located on each
leg that sealingly engage one of the shoulder surfaces of each of
the tubular members.
6. The tubular joint of claim 5 wherein the two legs diverge apart
from each other in a radially outward direction before the annular
seal is installed, and wherein installation of the seal causes the
two legs to deflect, so that the feet move toward each other.
7. A seal for sealing between first and second tubular members, the
first and second tubular members adapted to be connected in
end-to-end orientation and each having a bore, a tapered inner end
surface, and a shoulder surface which is generally perpendicular to
the bore, the seal comprising: a metal seal ring having first and
second tapered sealing surfaces adapted to sealingly engage the
tapered inner end surfaces of the first and second tubular members;
a rib portion extending radially outward from the ring portion
relative to an axis of the first and second tubular members; and a
pair of seal legs extending generally radially outward from the rib
portion relative to an axis of the first and second tubular
members, each of the seal legs having an ingress seal portion which
is adapted to sealingly engage one of the shoulder surfaces of one
of the tubular members.
8. The seal of claim 7 wherein each seal leg comprises a foot
portion that is adapted to sealingly engage one shoulder surface of
one of the tubular members.
9. The seal of claim 7 wherein the two seal legs diverge apart from
each other in a radially outward direction before the seal is
installed between the first and second tubular members, and wherein
installation of the seal is adapted to cause the two seal legs to
deflect so that the seal legs move toward each other.
10. The seal of claim 7 wherein each leg has an upper surface and a
lower surface, the ingress seal portion of the first leg being
located on the upper surface and the ingress seal portion of the
second leg being located on the lower surface, the upper surface of
the first leg and the lower surface of the second leg having a
recessed portion located radially inward of the ingress seal
portion of each leg relative to an axis of the seal ring.
11. A subsea wellhead assembly, comprising: a wellhead housing
having a bore, a tapered inner end surface, and a shoulder surface
which is generally perpendicular to the bore; a wellhead connector
having a bore, a tapered inner end surface, and a shoulder surface
which is generally perpendicular to the bore, said wellhead
connector being connected to the wellhead housing in end-to-end
orientation; and a metal annular seal having ring portion and a rib
portion, the ring portion having an upper tapered sealing surface
that sealingly engages the tapered inner end surface of the
wellhead connector and a lower tapered sealing surface that
sealingly engages the tapered inner end surface of the wellhead
housing, and the rib portion having upper and lower legs extending
generally radially outward from the rib portion relative to an axis
of the wellhead housing and wellhead connector, each upper and
lower leg having an upper surface and a lower surface, the upper
leg having on its upper surface a foot portion which sealingly
engages the shoulder surface of the wellhead connector, the lower
leg having on its lower surface a foot portion which sealingly
engages the shoulder surface of the wellhead housing.
12. The subsea wellhead assembly of claim 11 wherein the upper leg
has on its upper surface a recessed portion located radially inward
of the foot portion, and wherein the lower leg has on its lower
surface a recessed portion located radially inward of the foot
portion.
Description
[0001] This application claims the benefits of Provisional Patent
Application Ser. No. 60/183,183, filed Feb. 17, 2000.
TECHNICAL FIELD
[0002] This invention relates to a seal for a subsea well system.
More particularly, this invention relates to a tapered wellhead
seal having provisions to prevent water ingress into the well.
BACKGROUND OF THE INVENTION
[0003] In subsea oil and gas well systems, a wellhead connector is
installed onto the wellhead housing at the sea floor. For sealing
between the wellhead connector and the wellhead housing, an annular
gasket or seal is positioned between the connector and the housing.
U.S. Pat. No. 4,474,381 dated Oct. 2, 1984 discloses a tubular
joint with a metal seal ring positioned between internal tapered
surfaces on the tubular members. This type of seal is for sealing
against internal pressure within the tubular members.
[0004] Advances in offshore drilling technology have made it
possible to drill in deeper water than ever before. As drilling
depths increase, so does the water pressure at the sea floor. New
seals had to be designed to withstand the increased external
pressure when the internal pressure is lower than the external
pressure. U.S. Pat. No. 5,839,765 dated Nov. 24, 1998 discloses a
metal seal ring which creates a metal-to-metal seal against
internal pressure within the tubular members. A pair of O-ring
seals mounted to the seal rib creates a secondary seal to prevent
the ingress of sea water into the joint. O-ring seals have also
been used on the outer sides of the primary seal surfaces to
prevent ingress of sea water.
[0005] Although the secondary O-ring seal represents an improvement
over the prior art, further improvements are desired. O-ring seals
are prone to deteriorate in the environment of a subsea wellhead.
Replacing a seal on a gasket of a connector would be difficult and
expensive. It is desirable to provide a seal which can seal against
internal and external pressures without requiring the use of
elastomers.
SUMMARY OF THE INVENTION
[0006] The present invention relates to an improved seal for a
subsea wellhead connector. The seal of the invention includes a
metal seal with a ring portion and a rib portion. The rib portion
extends radially outward from the ring portion. The ring portion
includes two frustoconical surfaces for mating with tapered
surfaces of the wellhead connector and wellhead housing. Two
conical, metal-to-metal seals are created where the ring portions
of the seal engage the tapered surfaces of the wellhead connector
and housing. These metal-to-metal seals are the primary seals to
contain internal pressure within the wellhead.
[0007] In a preferred embodiment, two legs extend outward from the
rib portion. An upward-facing foot surface at the end of the upper
leg engages the wellhead connector, while a downward-facing foot
surface at the end of the lower leg engages the wellhead housing. A
metal-to-metal seal is created between each foot surface and the
corresponding tubular member. These seals resist external pressure
to prevent water ingress into the joint.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional detail of a seal constructed in
accordance with this invention, shown installed.
[0009] FIG. 2 is a sectional detail of the seal of FIG. 1, shown
prior to installation.
DETAILED DESCRIPTION OF THE INVENTION
[0010] Referring first to FIG. 1, a generally cylindrical subsea
wellhead housing 10 has a bore 12 and extends upward from the sea
floor. Housing 10 has an upward facing shoulder 14 generally
perpendicular to bore 12 and a conical primary seal surface 16 on
its inner diameter, extending from shoulder 14 downward and inward
into bore 12. Between conical primary seal surface 16 and shoulder
14 is a cylindrical transition surface 18. Cylindrical transition
surface 18 is concentric with bore 12 at a larger diameter, and
intersects orthogonally with shoulder 14.
[0011] A wellhead connector 20 is adapted to connect to wellhead
housing 10, and has a downward facing shoulder 28. A conical
primary seal surface 24 and cylindrical transitional surface 26 on
the inner diameter of connector 20 substantially mirrors seal
surface 16 and transitional surface 18.
[0012] A metal tapered seal 32 is adapted to seal against primary
seal surfaces 16,24 and position between upwardly facing shoulder
14 and downwardly facing shoulder 28. Seal 32 has a ring portion 34
with an upper tapered surface 36 and lower tapered surface 38 on
its outer diameter. Upper and lower tapered surfaces 36, 38 each
have approximately the same slope as upper seal surface 16 and
lower seal surface 24 respectively. The diameter of seal ring 32 is
such that tapered surfaces 36, 38 interferingly engage conical
surfaces 16, 24. The interference causes elastic deformation of
tapered seal 32 when connector 20 is landed on wellhead housing 10
and seals tapered seal 32 to connector 20 and housing 10. Seal 32
contains pressure within wellhead housing 10 and connector 20.
[0013] Seal ring 32 has a rib portion 40 which extends radially
outward from ring portion 34. Upper and lower transition surfaces
42, 44 reside on ring portion 34 to either side of rib 40 and are
generally parallel with transitional surfaces 18,26 of connector 20
and housing 10. Rib portion 40 is sized to fit in between upwardly
facing shoulder 14 and downwardly facing shoulder 28.
[0014] In a preferred embodiment, rib portion 40 has an ingress
seal 46 on its outer diameter. Ingress seal 46 comprises two legs
48 which are either formed from or attached to rib portion 40. Legs
48 are biased apart, one upward and one downward, and form
generally a V-shape in relation to one another. The crotch 50 of
the V-shape is curved rather than sharp to eliminate stress
raisers. Each leg 48 has a recess on its outer surface, forming a
foot 52 at the leg's end.
[0015] Unrestrained, feet 52 reside above and below rib 40 (FIG.
2); however, when connector 20 is landed on housing 10 it bends
legs 48 to be almost parallel, and feet 52 press tightly against
wellhead shoulder 14 and connector shoulder 28 (FIG. 1) and form a
seal preventing water from leaking into bore 12. Rib 40 serves as a
positive stop to limit the downward movement of connector 20. As
water fills in between downward facing connector shoulder 28 and
upward facing wellhead shoulder 14, the hydrostatic pressure of the
water applies a force between legs 48, causing feet 52 to press
more tightly against surfaces 14 and 28 and further energize
ingress seal 46. If connector 20 and wellhead housing 10 separate
slightly due to bending forces on the riser, feet 52 still press
against downwardly facing shoulder 28 and upward facing surface 14
to maintain the seal.
[0016] The seal of the invention has several advantages. The
metal-to-metal ingress seals effectively prevent seawater from
entering the joint when the external pressure exceeds the internal
pressure. Unlike elastomer seals, the metal-to-metal ingress seals
do not deteriorate when used in the environment of a subsea
wellhead. The durability of the seal of the invention reduces the
likelihood that a seal will require replacement.
[0017] Though the invention is discussed in the context of a subsea
wellhead and a wellhead connector, it would be clear to one skilled
in the art that this invention is applicable to virtually any
connection employing a tapered seal, for example the juncture of
two hubs. Additionally, while the invention has been shown in only
one of its forms, it should be apparent to those skilled in the art
that it is not so limited, but is susceptible to various changes
without departing from the scope of the invention.
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