U.S. patent application number 14/023370 was filed with the patent office on 2014-03-13 for freestanding hybrid riser system including a bottom configuration with a flexible pipe joint and a diverless pipe connector.
This patent application is currently assigned to Oil States Industries, Inc.. The applicant listed for this patent is Oil States Industries, Inc.. Invention is credited to Bao Duy Povloski.
Application Number | 20140069657 14/023370 |
Document ID | / |
Family ID | 49261761 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069657 |
Kind Code |
A1 |
Povloski; Bao Duy |
March 13, 2014 |
Freestanding Hybrid Riser System Including a Bottom Configuration
with a Flexible Pipe Joint and a Diverless Pipe Connector
Abstract
A freestanding hybrid riser system includes a steel pipe riser
having a bottom end anchored to a foundation on a seabed through a
flexible joint and a diverless pipe connector. A tube is mounted to
the foundation and connected to the diverless pipe connector for
providing a static connection to a subsea pipeline on the seabed
for a flow of fluid between the steel pipe and the subsea pipeline
and through the flexible pipe joint and through the diverless pipe
connector and through the tube. In a preferred implementation, the
flexible pipe joint includes alternate elastomer layers and metal
layers reinforcing the elastomer layers, and a receptacle of the
diverless connector is mounted on a foundation such as a suction
pile on the seabed, or a pile grouted in a bore in the seabed.
Inventors: |
Povloski; Bao Duy; (Katy,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Oil States Industries, Inc. |
Arlington |
TX |
US |
|
|
Assignee: |
Oil States Industries, Inc.
Arlington
TX
|
Family ID: |
49261761 |
Appl. No.: |
14/023370 |
Filed: |
September 10, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61699544 |
Sep 11, 2012 |
|
|
|
Current U.S.
Class: |
166/345 |
Current CPC
Class: |
E21B 17/015 20130101;
E21B 17/012 20130101; E21B 43/013 20130101; E21B 43/0107
20130101 |
Class at
Publication: |
166/345 |
International
Class: |
E21B 17/01 20060101
E21B017/01 |
Claims
1. A freestanding hybrid riser system comprising: a vertical steel
pipe having a top end and a bottom end; a floating tank coupled to
the top end of the vertical steel pipe for supporting the vertical
steel pipe; a flexible pipe joint; a diverless pipe connector
attached to the flexible pipe joint; a foundation mounted on a
seabed, and the bottom end of the vertical steel pipe being
anchored to the foundation through the flexible pipe joint and the
diverless pipe connector; and a tube mounted to the foundation and
connected to the diverless pipe connector for providing a static
connection to a subsea pipeline on the seabed for a flow of fluid
between the vertical steel pipe and the subsea pipeline and through
the flexible pipe joint and through the diverless pipe connector
and through the tube.
2. The freestanding hybrid riser system as claimed in claim 1,
wherein the flexible pipe joint includes alternate elastomer layers
and metal layers reinforcing the elastomer layers.
3. The freestanding hybrid riser system as claimed in claim 1,
wherein the flexible pipe joint has an upper end attached to the
bottom end of the vertical steel pipe, and the flexible pipe joint
has a lower end attached to the diverless pipe connector.
4. The freestanding hybrid riser system as claimed in claim 1,
wherein the flexible pipe joint has an upper end attached to the
bottom end of the vertical steel pipe, the diverless pipe connector
has a connector hub attached to a lower end of the flexible pipe
joint, and the diverless pipe connector has a connector receptacle
mounted to the foundation, and the tube has an upper end attached
to the connector receptacle and provides a vertical-to-horizontal
transition from the diverless pipe connector to the static
connection to the subsea pipeline.
5. The freestanding hybrid riser system as claimed in claim 1,
wherein the tube is a J-tube having an upper end attached to a
receptacle of the diverless pipe connector, and the J-tube has a
lower end for providing the static connection to the subsea
pipeline.
6. The freestanding hybrid riser system as claimed in claim 1,
wherein the foundation includes a suction pile, and the tube passes
through the suction pile.
7. The freestanding hybrid riser system as claimed in claim 1,
wherein the foundation includes a pile grouted in a bore in the
seabed, and the tube extends from a branch fitting mounted on top
of the pile.
8. A bottom configuration for a freestanding hybrid riser system,
the bottom configuration comprising: a flexible pipe joint; a
diverless pipe connector attached to the flexible pipe joint; and a
tube connected to the diverless pipe connector for providing a
vertical-to-horizontal transition from the diverless pipe connector
for conveying fluid when the fluid flows through the flexible pipe
joint and through the diverless pipe connector.
9. The bottom configuration for a freestanding hybrid riser system
as claimed in claim 8, wherein the flexible pipe joint includes
alternate elastomer layers and metal layers reinforcing the
elastomer layers.
10. The bottom configuration for a freestanding hybrid riser system
as claimed in claim 8, wherein the flexible pipe joint has an upper
end configured for attachment to a lower end of a vertical steel
pipe of a riser, and the diverless pipe connector has a hub
attached to a lower end of the flexible pipe joint, and the
diverless pipe connector has a receptacle configured for engaging
the diverless pipe connector hub, and the tube has an upper end
attached to the diverless pipe connector receptacle for conveying
the fluid when the diverless pipe connector hub is engaged in the
diverless pipe connector receptacle and fluid flows through the
flexible pipe joint, through the diverless pipe connector hub,
through the diverless pipe connector receptacle, and through the
tube.
11. The bottom configuration for a freestanding hybrid riser system
as claimed in claim 8, further comprising a suction pile upon which
the diverless pipe connector is mounted, and the tube passes
through the suction pile.
12. The bottom configuration for a freestanding hybrid riser system
as claimed in claim 8, further comprising a branch fitting upon
which the diverless pipe connector is mounted, and the branch
fitting has a first arm configured for attachment to an upper end
of a pile, and the branch fitting has a second arm attached to the
tube.
13. A method of installing a freestanding hybrid riser to assemble
a freestanding hybrid riser system, the freestanding hybrid riser
including a steel pipe having a top end and a bottom end, said
method comprising: (a) installing a foundation structure upon a
seabed, the foundation structure including a foundation on the
seabed and a tube mounted on the foundation for providing a static
connection to a subsea pipeline on the seabed; (b) orienting the
steel pipe over the foundation structure; and (c) engaging a
diverless pipe connector to anchor the bottom end of the steel pipe
to the foundation structure and to complete a connection between
the bottom end of the steel pipe and the foundation structure, the
connection including a flexible pipe joint and the diverless pipe
connector between the bottom end of the steel pipe and the tube for
a flow of fluid between the bottom end of the steel pipe and the
subsea pipeline, and through the flexible pipe joint, through the
diverless pipe connector, and through the tube.
14. The method as claimed in claim 13, which includes attaching a
first end of the flexible pipe joint to the bottom end of the steel
pipe, and wherein the engaging of the diverless pipe connector
mounts a second end of the flexible pipe joint to the foundation
structure.
15. The method as claimed in claim 14, wherein the second end of
the flexible pipe joint is terminated by a diverless pipe connector
hub, and a receptacle of the diverless pipe connector is mounted to
the foundation structure, and the method includes landing the hub
of the diverless pipe connector in the receptacle to mount the
second end of the flexible pipe joint to the foundation
structure.
16. The method as claimed in claim 15, wherein the receptacle for
the diverless pipe connector has an engagement mechanism for
locking the diverless pipe connector hub into a fixed engagement
position with respect to the receptacle, and the method further
includes orienting the steel pipe in a vertical position once the
diverless pipe connector hub has been landed into the receptacle,
and then actuating the engagement mechanism to lock the diverless
pipe connector hub into the fixed engagement position with respect
to the receptacle.
17. The method as claimed in claim 15, wherein the diverless pipe
connector hub becomes engaged with the receptacle when the
diverless pipe connector hub is landed into the receptacle, and the
method further includes thereafter increasing buoyancy of a
floating tank supporting the steel pipe in order to place the steel
pipe in a state of tension for stability.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of Bao Duy Povloski,
U.S. Provisional Application Ser. 61/699,544 filed Sep. 11, 2012,
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a freestanding hybrid riser
system (FHRS) having a bottom configuration including a flexible
pipe joint and a diverless pipe connector.
BACKGROUND OF THE INVENTION
[0003] A freestanding hybrid riser comprises a vertical steel pipe
supported at its top end by a floating tank, the pull from which
provides the system with stability. The floating tank is at a depth
at which the effects of surface currents and waves are
significantly attenuated. A length of pipe or flexible riser in a
double catenary connects the top of the vertical steel pipe to a
production platform. A tie bar or mooring connection provides a
link between the floating tank and the top of the vertical steel
pipe. The anchor or base for the riser typically is a suction pile
in the seabed, or a drilled steel pipe grouted to the seabed.
[0004] A freestanding hybrid riser system (FHRS) may be used for
the production (gathering) or export of oil or gas. The fluids
produced or exported pass through the vertical steel pipe, which
also performs the structural function of supporting the system. At
its bottom end the vertical steel pipe has a component which makes
a connection between the vertical steel pipe and a gathering or
export line. This component is a length of pipe located at the base
of the riser and made of steel, known as a rigid jumper, or a
length of a flexible line.
[0005] The basic architecture of the freestanding hybrid riser
system has been known for decades; for example, as described in
Panicker et al. U.S. Pat. No. 4,423,984, issued Jan. 3, 1984.
Panicker describes a freestanding hybrid riser system having a
vertical rigid section which extends from a base on the seabed to a
floating tank at a fixed position below the zone of turbulence that
exists near the surface of the water, and a flexible section, which
is comprised of flexible flowlines that extend in a catenary
configuration from the floating tank to a surface facility.
[0006] Recently there has been a trend towards extending free
standing risers from deep water (at least 1000 feet or 300 meters)
to ultradeep water (at least 5,000 feet or 1,500 meters). The
increasing depth raises problems of loading upon the foundation and
the jumper from the vertical steel pipe to the gathering or export
line. These problems are discussed in S. A. Halton et al., Hybrid
Riser Foundation Design and Optimization, OTC 17199, Offshore
Technology Conference, Houston, Tex., May 2-5, 2005, Offshore
Technology Conference Organization, Richardson, Tex. In deep water,
the axial tension from the riser upon the foundation can be
significant (70-1000 Te or 690-9800 kN). This tension must be
reliably reacted into the seabed over the life of the development.
Depending on the configuration of the selected foundation there may
be, in addition to axial tension, bending moments, shear loads, and
loads arising from flexure of rigid base jumper spools. The result
is a complex set of load conditions, which, when combined with
installation issues, can lead to a foundation system that is a
significant cost element in the overall riser system.
SUMMARY OF THE INVENTION
[0007] In accordance with a first aspect, the invention provides a
freestanding hybrid riser system. The freestanding hybrid riser
system includes a vertical steel pipe having a top end and a bottom
end, a floating tank coupled to the top end of the vertical steel
pipe for supporting the vertical steel pipe, a flexible pipe joint,
a diverless pipe connector attached to the flexible pipe joint, a
foundation mounted on a seabed, and a tube mounted to the
foundation. The bottom end of the vertical pipe is anchored to the
foundation through the flexible pipe joint and the diverless pipe
connector. The tube is connected to the diverless pipe connector
for providing a static connection to a subsea pipeline on the
seabed for a flow of fluid between the vertical steel pipe and the
subsea pipeline and through the flexible pipe joint and through the
diverless pipe connector and through the tube.
[0008] In a preferred implementation, the freestanding hybrid riser
system includes a vertical steel pipe having a top end and a bottom
end, a floating tank coupled to the top end of the vertical steel
pipe for supporting the vertical steel pipe, a flexible pipe joint
having an upper end attached to the bottom end of the vertical
steel pipe, a diverless pipe connector hub attached to a lower end
of the flexible pipe joint, a foundation mounted on a seabed, a
diverless pipe connector receptacle attached to the foundation and
engaging the diverless pipe connector hub, and a J-tube having an
upper end attached to the diverless pipe connector receptacle and a
lower end for providing a static connection to a subsea pipeline on
the seabed so that fluid may flow between the vertical steel pipe
and the subsea pipeline and through the flexible pipe joint,
through the diverless pipe connector hub, and through the
J-tube.
[0009] In accordance with a second aspect, the invention provides a
bottom configuration for a freestanding hybrid riser system. The
bottom configuration includes a flexible pipe joint, a diverless
pipe connector attached to the flexible pipe joint, and a tube
connected to the diverless pipe connector for conveying fluid when
the fluid flows thorough the flexible pipe joint and through the
diverless pipe connector and through the tube.
[0010] In a preferred implementation, the bottom configuration
includes a flexible pipe joint having an upper end for attachment
to a lower end of a vertical steel pipe of a riser, a diverless
pipe connector hub attached to a lower end of the flexible pipe
joint, a diverless pipe connector receptacle configured for
engaging the diverless pipe connector hub, and a J-tube having an
upper end attached to the diverless pipe connector receptacle for
conveying fluid when the diverless pipe connector hub is engaged in
the diverless pipe connector receptacle and fluid flows through the
flexible pipe joint, through the diverless pipe connector hub,
through the diverless pipe connector receptacle, and through the
J-tube.
[0011] In accordance with a final aspect, the invention provides a
method of installing a freestanding hybrid riser to assemble a
freestanding hybrid riser system. The freestanding hybrid riser
includes a steel pipe having a top end and a bottom end. The method
includes installing a foundation structure upon a seabed. The
foundation structure includes a foundation mounted on the seabed
and a tube mounted to the foundation and extending to a static
connection to a subsea pipeline on the seabed. The method further
includes orienting the bottom end of the steel pipe over the
foundation structure, and engaging a diverless pipe connector to
anchor the bottom end of the steel pipe to the foundation structure
and to complete a connection between the bottom end of the steel
pipe and the foundation structure. The connection includes a
flexible pipe joint and the diverless pipe connector between the
bottom end of the steel pipe and the tube for a flow of fluid
between the steel pipe and the subsea pipeline and through the
flexible pipe joint and through the diverless pipe connector and
through the tube.
[0012] A preferred implementation includes installing a foundation
structure upon a seabed, the foundation structure including a
receptacle for a diverless pipe connector, and a J-tube extending
from the receptacle to a stationary subsea pipeline end
termination, so that the J-tube provides a vertical-to-horizontal
transition from the receptacle to the subsea pipeline end
termination. The preferred implementation further includes
attaching a first end of a flexible pipe joint to a bottom end of a
steel pipe for the freestanding hybrid riser. The flexible pipe
joint has a second end terminated by a diverless pipe connector
hub. The preferred implementation further includes orienting the
steel pipe over the foundation structure, and landing the diverless
pipe connector hub into the receptacle to make a connection between
the diverless pipe connector hub and the receptacle for the flow of
fluid between the steel pipe and the subsea pipeline end
termination and through the flexible pipe joint, through the
diverless pipe connector hub, and through the J-tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Additional features and advantages of the invention will be
described below with reference to the drawings, in which:
[0014] FIG. 1 shows a conventional freestanding hybrid riser
system;
[0015] FIG. 2 shows a first example of a freestanding hybrid riser
system in accordance with the present invention;
[0016] FIG. 3 shows a second example of a freestanding hybrid riser
system in accordance with the present invention;
[0017] FIG. 4 is a flowchart of a method of installing a
freestanding hybrid riser to assemble the freestanding hybrid riser
system of FIG. 2 or FIG. 3;
[0018] FIG. 5 is an enlarged cross-section of the upper portion of
the diverless collet-style pipe connector introduced in FIG. 2,
shown in an open configuration
[0019] FIG. 6 shows the upper portion of the diverless collet-style
pipe connector of FIG. 5, shown in a closed configuration;
[0020] FIG. 7 is a cross-section view along section line 7-7 of
FIG. 8 of the upper portion of a diverless clamp-style pipe
connector, shown in an open configuration;
[0021] FIG. 8 is a top view of the diverless clamp-style pipe
connector, shown in a closed configuration;
[0022] FIG. 9 is an oblique view of components of the diverless
clamp-style pipe connector of FIGS. 7 and 8;
[0023] FIG. 10 is a cross-section view of a diverless collet-style
pipe connector having an elastomeric flexible pipe joint integrated
with the collet mechanism, shown in an open configuration;
[0024] FIG. 11 is a cross-section view of the diverless
collet-style pipe connector of FIG. 10, shown in a closed
configuration;
[0025] FIG. 12 shows an alternative arrangement, in which two
diverless collet-collet style pipe connectors having integral
flexible pipe joints are joined together;
[0026] FIG. 13 is a cross-section view of a diverless clamp-style
pipe connector with a flexible pipe joint located on the riser side
of the connection, shown in an open configuration;
[0027] FIG. 14 is a cross-section view of the diverless clamp-style
pipe connector of FIG. 13, shown in a closed configuration;
[0028] FIG. 15 is a cross-section view of a diverless clamp-style
pipe connector in a closed configuration joining two flexible pipe
joints, one on the riser side of the connection, and the other on
the foundation side of the connection;
[0029] FIG. 16 is a cross-section view of a diverless collet-style
pipe connector including a first flexible pipe joint on the riser
side of the connection, and joining a second flexible pipe joint on
the foundation side of the connection;
[0030] FIG. 17 shows a flange-type pipe connector connecting a
foundation structure to a horizontal rigid subsea pipeline;
[0031] FIG. 18 shows a diverless collet-style pipe connector
connecting a foundation structure to a horizontal rigid subsea
pipeline;
[0032] FIG. 19 shows a diverless collet-style pipe connector
connecting a foundation structure to a vertical rigid jumper;
[0033] FIG. 20 shows a diverless collet-style pipe connector
connecting a foundation structure to a horizontal flexible subsea
pipeline; and
[0034] FIG. 21 shows a diverless collet-style pipe connector
connecting a foundation structure to a vertical flexible
jumper.
[0035] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
in the drawings and will be described in detail. It should be
understood, however, that it is not intended to limit the invention
to the particular forms shown, but on the contrary, the intention
is to cover all modifications, equivalents, and alternatives
falling within the scope of the invention as defined by the
appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] With reference to FIG. 1, there is shown a conventional
freestanding hybrid riser system (FHRS) 10 in a deep water
environment. The freestanding hybrid riser 10 comprises a vertical
steel pipe 11 supported at its top end by a floating tank 12. The
floating tank 12 is often called a buoyancy can or air can. The
floating tank 12 is at a depth of at least 50 meters so that the
effects of surface currents and waves upon the floating tank 12 are
significantly attenuated. The floating tank 12 is filled with air
so that it supports the weight of the vertical steel pipe 11 and
also maintains the vertical steel pipe 11 in tension for stability.
A length of pipe or flexible riser 13 in a catenary connects the
top of the vertical steel pipe 11 to a production platform 14 on
the surface. A mooring connection 15 such as a length of chain
provides a link between the floating tank 12 and the top of the
vertical steel pipe 11.
[0037] In FIG. 1, the bottom configuration of the riser system 10
on the seabed 16 is shown at a larger scale than the floating tank
12 and the production platform 14 near the surface. The base for
the riser 10 is a suction pile 17 in the seabed 16. A bottom
connector receptacle 18 is mounted on the top of the suction pile
17 to receive a bull nose 19 on an extension 20 welded to the
bottom end of the vertical steel pipe 11.
[0038] When guided into the receptacle 18 by an alignment cone 21,
the bull nose 19 latches into the receptacle 18 forming a bottom
connector assembly. The bull nose 19 has a flexible joint 22
permitting riser motion 23 with some stiffness as the inclination
of riser 11 deviates from a desired vertical orientation. The bull
nose 19 is also mounted to the extension 20 for free rotation about
the vertical axis of the steel pipe 11. Further details of the
bottom connector assembly are described in Peppel U.S. Pat. No.
4,943,188 issued Jul. 24, 1990.
[0039] The bottom of the vertical steel pipe 11 has a branch pipe
24 to a bottom riser connector 25. The bottom riser connector 25
connects a jumper 26 to a stationary pipeline end termination
(PLET) connector 27 mounted on a sled 28 resting on the seabed 16
and providing a connection to an export pipeline 29.
[0040] In the example of FIG. 1, the vertical steel pipe 11 conveys
fluid such as oil or gas downward from the floating production
facility 14 to the subsea pipeline 29. The subsea pipeline 30 may
then convey the fluid to an on-shore facility. In an alternative
configuration, the vertical steel pipe 11 conveys fluid from one or
more wells on the seabed 16 upward to the floating platform 14 for
transfer of the fluid to vessels for shipment.
[0041] The conventional freestanding hybrid riser system (FHRS) 10
in FIG. 1 has a problem of loading upon the branch pipe 24 and the
jumper 26 from the vertical steel pipe 11 to the stationary
pipeline end termination (PLET) connector 27. To reduce stress from
pivoting of the vertical steel pipe 11, the jumper 26 may include a
number of bends or loops between the vertical steel pipe 11 and the
stationary pipeline end termination (PLET) connector 27. However,
the required size of the jumper 26 and the required number of bends
increase significantly with the pipe diameter. This is due to the
need to maintain 3D bends for pigging, and the increase in
stiffness of the pipe section increasing to the 4.sup.th power of
the pipe diameter.
[0042] The present invention relates to an improved freestanding
hybrid riser system (FHRS) and a method for installing it, in which
the bottom connection at the base of the riser has a diverless pipe
connector allowing the riser to connect to a mating foundation
structure so that riser fluid may flow through the foundation
structure such as a suction pile to a static jumper connection
point. The base of the riser or the mating foundation structure has
at least one flexible pipe joint that permits pivoting of the riser
with respect to the foundation. This is a functional improvement
for the bottom connection configuration of the FHRS system. This
reduces the bending and deflection in the rigid jumper, and removes
riser motion from the jumper, thus reducing the size of the jumper
and simplifying the design of the jumper. This also eliminates the
need for a bottom connector assembly of the kind shown in FIG.
1.
[0043] FIG. 2 shows a first example of a freestanding hybrid riser
system 40 in accordance with the present invention. The
freestanding hybrid riser system 40 includes a vertical steel pipe
41 supported at its top end by a floating tank 42. The floating
tank 42 supports the weight of the vertical steel pipe 41 and also
maintains the vertical steel pipe 41 in tension for stability. A
length of pipe or flexible riser 43 in a double catenary connects
the top end of the vertical steel pipe 41 to a production platform
44 on the surface. A mooring connection 45 such as a length of
chain provides a link between the floating tank 42 and the top end
of the vertical steel pipe 41.
[0044] The anchor or base for the riser 40 is a suction pile 47 in
the seabed 46. A bottom connector receptacle 48 is rigidly mounted
to the top of the suction pile 47 by ribs 49, 50 or other
reinforcements welded to the bottom connector receptacle 48 and
welded to the top of the suction pile 47. The bottom of the
vertical steel pipe 41 is fixed to a hub 52 having a built-in
flexible pipe joint 53. The flexible pipe joint 53 has an upper
extension 39, which is welded to the bottom of the vertical steel
pipe 41. The flexible pipe joint 53 includes alternate elastomer
layers and metal layers reinforcing the elastomer layers. Further
details regarding the construction of such a flexible pipe joint 53
are found in Moses et al., U.S. Pat. No. 7,341,283 issued Mar. 11,
2008, entitled High Temperature Flexible Pipe Joint, incorporated
herein by reference.
[0045] The hub 52 and the bottom connector receptacle 48 together
form a diverless pipe connector 54. The bottom connector receptacle
48 has an alignment cone 55 for guiding the hub 52 into the bottom
connector receptacle 48. The hub 52 mates with a hub 56 on an upper
end of a J-tube 57. The upper end of the J-tube 57 is attached to
the diverless pipe connector receptacle 48, and the J-tube has a
lower end for providing a static connection to a subsea pipeline 59
on the seabed 46 so that fluid may flow between the vertical steel
pipe 41 and the subsea pipeline 59 and through the flexible pipe
joint 53, through the diverless pipe connector hub 52, and through
the J-tube 57. The J-tube 57 provides a smooth bend of at least
three pipe diameters and more preferably five or more pipe
diameters transitioning from vertical at the bottom connector
receptacle 48 to a horizontal pipeline end connector 58 connecting
the J-tube to the subsea pipeline 59. The pipeline end connector 58
is stationary, and the pipeline end connector 58 can be a flanged
connector or a diverless pipe connector.
[0046] In the example of FIG. 2, the bend of the J-tube 57 is
contained within the suction pile 47. A horizontal section of the
J-tube 57 passes through a hole 60 in the outer circumference of
the suction pile 47. Any gap between this hole 60 and the outer
circumference of the J-tube 57 is closed by a fillet weld around
the outer circumference of the J-tube 57 in the vicinity of the
hole 60. In a similar fashion, a vertical section of the J-tube 57
passes through a hole 61 in the top of the suction pile 47, and any
gap between this hole 61 and the outer circumference of the J-tube
57 is closed by a fillet weld around the outer circumference of the
J-tube 57 in the vicinity of the hole 61. Therefore the interior of
the suction pile 47 remains sealed from the external sea water, so
that suction may be applied to the interior of the suction pile in
order to drive the suction pile into the seabed 46 in the usual
fashion.
[0047] The diverless pipe connector 54 may use a non-articulated
connector or an articulated connector depending on whether the
suction pile 47 has or has not been driven vertically into the
seabed 46. If the suction pile 47 has been driven vertically into
the seabed 46, then a non-articulated connector can be used. If the
suction pile 47 has not been driven vertically into the seabed,
then an articulated connector can be used to make up for the
deviation from the desired vertical orientation of the suction pile
47. In any event, it is desired for the hub 52 on the bottom of the
vertical steel pipe 41 to have a vertical orientation regardless of
whether the suction pile 47 and the receptacle 48 are tilted.
[0048] An articulated connector, for example, has the hub 52
terminating in a quasi-spherical ball that engages a matching
socket in the hub 56. When an engagement mechanism 63 is actuated,
the ball is locked into a fixed position with respect to the
socket, forming a metal-to-metal seal. The ball remains locked into
the fixed position with respect to the socket while the flexible
pipe joint 53 permits some pivoting 62 of the vertical steel pipe
41 about a true vertical orientation.
[0049] An annular sealing element may be interposed between the hub
52 on the bottom of the vertical steel pipe and the hub 56 on the
top of the J-tube 57. For example, the hubs 52, 56 have relatively
hard polished metal surfaces, and the sealing element is made of a
relatively softer metal that may deform slightly under pressure to
complete a fluid-tight metal-to-metal seal with the relatively hard
polished metal surfaces of the hubs. Further details of such an
annular sealing element are described in Tarlton U.S. Pat. No.
7,467,799 issued Dec. 23, 2008, incorporated herein by
reference.
[0050] The diverless pipe connector 54 may use various kinds of
engagement mechanisms to engage the hub 52 on the bottom of the
vertical steel pipe 41 with the hub 56 on the top of the J-tube 57.
For example, the engagement mechanism is a clamp-style mechanism,
or the engagement mechanism is a collet-style mechanism. A
collet-style mechanism is described in Wittman et al., U.S. Pat.
No. 4,477,105 issued Oct. 16, 1984, incorporated herein by
reference. The use of such a collet-style mechanism for a subsea
termination pipeline connection is described in Tarlton et al.,
U.S. Pat. No. 6,142,708 issued Nov. 7, 2000, incorporated herein by
reference. A clamp-style mechanism for an articulated connector is
described in Spiering et al. U.S. Pat. No. 6,305,720 issued Oct.
23, 2001, incorporated herein by reference, and Spiering et al.
U.S. Pat. No. 6,698,800, issued Mar. 2, 2004, incorporated herein
by reference.
[0051] The engagement mechanism 63 is sized to provide a sufficient
level of force upon the hubs 52, 56 to contain the fluid pressure
within the vertical steel pipe 41 and the J-tube 57 and also to
react to the tension from the vertical steel pipe 41. For example,
the fluid pressure is up to 15,000 psi (103 MPa). In general, the
tension upon the suction pile 47 from the vertical steel pipe 41
will be a fraction of the weight of the vertical steel pipe 41. For
example, the length of the vertical steel pipe 41 is 1,300 meters
for a seabed depth of 1350 meters, and for a 22 inch (55.9 cm) pipe
diameter, the maximum tension upon the suction pile 47 is 450 Te
(4410 kN). In this case, the suction pile 47 has a weight of at
least 190 Te (1862 kN), a length of 32 meters, and a diameter of
eight meters, in order to sustain the maximum tension.
[0052] Fabrication of the assemblies for the freestanding hybrid
riser 40 is performed on-shore or on the deck of a surface vessel.
The two basic assemblies are: (1) the assembly of the steel pipe 41
and the flexible pipe joint 53 and diverless pipe connector hub 52;
and (2) the subsea foundation structure including the suction pile
47 and the components welded or otherwise mounted to the suction
pile 47.
[0053] The foundation structure is assembled by welding the upper
end of the J-tube to the hub 56 in the diverless pipe connector
receptacle 48. Then the J-tube 57 is inserted through the holes 61,
60 in the suction pile in order to mount the receptacle 48 to the
top of the suction pile 47, and then the receptacle 48 is welded to
the top of the suction pile 47 via the ribs 49, 50. Then the J-tube
57 is welded to the suction pile 47 to close the gaps between holes
61, 60 and the J-tube. Then a hub of the connector 58 is welded to
the lower end of the J-tube 57.
[0054] The suction pile 47 is then shipped and sunk so that it is
delivered to a desired position on the seabed 46, and then driven
into the seabed, so that the lower end of the J-tube is aligned
with the end of the subsea pipeline 59. Then the J-tube 57 is
connected via the connector 58 to the subsea pipeline 59. At this
point, the subsea foundation structure has been installed, and the
steel pipe 41 of the riser is ready to be oriented over the subsea
foundation structure and landed into the receptacle 48. The steel
pipe 41 is oriented over the subsea structure and the diverless
pipe connector hub 52 is landed into the receptacle 48 by control
of the buoyancy of the floating tank 42, and control of the
position of the floating tank 42 by surface vessels, while a
remotely operated vehicle (ROV) on the seabed guides the hub 52
into the receptacle 48. The engagement mechanism 63 of the
diverless pipe connector 54 is actuated once the floating tank 42
has been positioned so that the steel pipe 41 is oriented in a
vertical position.
[0055] The foundation structure installation procedure just
mentioned above may be modified to suit the required size of the
foundation, the depth of foundation, and availability of materials
and any pre-existing foundation on the seabed. For example, for a
large foundation, it may be convenient to install the foundation on
the seabed separate from the other foundation structure, and then
mount the other foundation structure to the foundation. In this
case, the foundation could include a number of suction piles or
cemented casing structures, which could be installed separately and
then joined together by the mounting of the other foundation
structure. One or more of the suction piles or cemented casing
structures could be a pre-existing foundation.
[0056] FIG. 3 shows a second example of a freestanding hybrid riser
system 80 in accordance with the present invention. The
freestanding hybrid riser system 80 includes a vertical steel pipe
81 supported at its top end by a floating tank 82. The floating
tank 82 supports the weight of the vertical steel pipe 81 and also
maintains the vertical steel pipe 81 in tension for stability. A
length of pipe or flexible riser 83 in a double catenary connects
the top end of the vertical steel pipe 81 to a production platform
84 on the surface. A mooring connection 85 such as a length of
chain provides a link between the floating tank 82 and the top end
of the vertical steel pipe 81.
[0057] The anchor or base for the riser 80 is a drilled and grouted
pile 87 in the seabed 86. In other words, the pile 87 is a length
of pipe or well casing that has been placed is a well bore 107 in
the seabed 86, and then the annulus between the pipe and the well
bore is filled with grout 88 that sets over time. If a subsea field
already has a dry wellbore at a convenient location for use as a
riser base, then a drilled and grouted pile 87 may be the most
convenient base for a riser.
[0058] The foundation structure includes a flanged or diverless
pipe connector 89 on the top of the pile 87, a forged branch
fitting 90 such as a Y-fitting coupled by the connector 89 to the
pile 87, and a receptacle 91 of a diverless pipe connector 92. The
branch fitting 90 has a first arm 105 mounted to the upper end of
the pile 87 via the pipe connector 89. The branch fitting 90 has a
second arm 106 that provides an upper portion of a J-tube, which
further includes a lower portion 93 coupling the branch fitting to
a stationary pipeline end termination connector 94. The pipeline
end termination connector 94 couples the lower portion 93 of the
J-tube to a subsea pipeline 95. The pipeline end termination
connector 94 can be a flanged connector or a diverless pipe
connector.
[0059] The branch fitting 90 provides a fluid path from a hub 96
within the connector receptacle 91 to the lower portion 93 of the
J-tube, but the branch fitting does not provide a fluid path to the
pipe connector 89. For example, the branch fitting 90 is a forged
or cast body Y-fitting with a curved bore machined to match a
typical 5D bend and a pipe wall thickness. The hub 96 is welded to
a short piece of straight pipe 97, which is inserted into the top
of the Y-fitting 90, and then the short piece of pipe 97 and the
connector receptacle 91 are welded to the body of the Y-fitting 90.
Then the curved pipe 93 is inserted into the Y-fitting 90 and
welded to the Y-fitting. Then a hub of the connector 94 is welded
to the curved pipe 93. Then a short piece of straight pipe 98 is
inserted into the bottom of the Y-fitting 90 and welded to the
Y-fitting. Then a hub of the connector 89 is welded to the pipe 98.
The connector 89 need not contain fluid pressure, but the connector
89 is subject to the tension from the vertical steel pipe 81 and
bending moment from pivoting 102 of the vertical steel pipe 81.
[0060] The diverless pipe connector receptacle 91 receives a hub 99
having an integral flexible pipe joint 100. The flexible pipe joint
100 has an upper extension 101, which is welded to the bottom of
the vertical steel pipe 81. The flexible pipe joint 100 permits a
limited range of riser motion 102 when the hub 99 is locked in a
vertical orientation in the receptacle 91.
[0061] The hub 99 is guided into the receptacle 91 by an alignment
cone 103. Once the steel pipe 81 of the riser is aligned in a
vertical orientation, an engagement mechanism 104 in the receptacle
91 is actuated to lock the hub 99 into engagement with the hub 96.
The engagement mechanism is sized to provide a sufficient level of
force upon the hubs 96, 99 to contain the fluid pressure within the
vertical steel pipe 81 and the J-tube 90, 93 and also to react to
the tension from the vertical steel pipe 81. For example, the fluid
pressure is up to 15,000 psi (103 MPa).
[0062] The three basic assemblies of components for the riser
system 80 in FIG. 3 are: (1) the pile 87 capped with a hub for the
connector 89; (2) the steel pipe 81 having is lower end attached to
the flexible pipe joint 100 and diverless pipe connector hub 99;
and (3) the subsea structure including the connector receptacle 91,
the branch fitting 90, and the other components welded or otherwise
mounted to the branch fitting 90 including the curved pipe section
93 attached to a hub for the subsea pipeline end termination
connector 94, and the straight pipe section 98 attached to a hub
for the pile connector 89. The second and third of these three
assemblies are assembled on-shore or on the deck of a surface
vessel.
[0063] If a pile capped with a connector hub is not already found
at the desired location of the riser base, then a pipe string
capped with a connector hub is inserted into a wellbore at the
desired location of the riser base, and the annulus between the
wellbore and the pipe string is filled with grout.
[0064] The hub 99 is secured to the bottom of the steel pipe 81 by
welding the extension 101 to the bottom of the vertical steel pipe
81.
[0065] The assembly of the diverless pipe connector receptacle 91,
the branch fitting 90, and the other components attached to the
branch fitting is fabricated or delivered to a surface location
above the pile 87, and then this assembly is sunk and aligned over
the pile 87. Then the connector 89 is engaged to mount this
assembly to the top of the pile 87. Then the connector 94 is
engaged to connect the lower portion 93 of the J-tube to the subsea
pipeline 95.
[0066] At this point, the subsea foundation structure for the riser
80 has been installed, and the steel pipe 81 is ready to be
oriented over the foundation structure and landed into the
receptacle 91. The vertical steel pipe 81 is oriented over the
subsea structure and the diverless pipe connector hub 99 is landed
into the receptacle 91 by control of the buoyancy of the floating
tank 82, and control of the position of the floating tank by
surface vessels, while a ROV on the seabed guides the hub 99 into
the receptacle 91. Then the engagement mechanism 104 of the
diverless pipe connector 92 is actuated once the floating tank 82
has been positioned so that the steel pipe 81 is oriented in a
vertical position. Then the buoyancy of the floating tank 82 is
increased to put the vertical steel pipe 81 in a state of tension
for stability.
[0067] FIG. 4 shows a freestanding hybrid riser installation method
for the installation of the riser 40 in FIG. 2. This installation
method is also applicable to the installation of the riser 80 in
FIG. 3.
[0068] In a first step 110 of FIG. 4, a foundation structure is
installed upon the seabed. The foundation structure includes a
receptacle for a diverless pipe connector, and a J-tube from the
receptacle to a stationary subsea pipeline end termination. The
J-tube provides a vertical-to-horizontal transition from the
receptacle to the subsea end termination. Next, in step 111, a
first end of a flexible pipe joint is attached to a bottom end of
the steel pipe of the riser. The flexible pipe joint has a second
end terminated by a diverless pipe connector hub.
[0069] Then, in step 112, the steel pipe of the riser is oriented
over the foundation structure, and the diverless pipe connector hub
is landed into the receptacle. Once the diverless pipe connector
hub has been landed and the steel pipe of the riser has been
oriented in a vertical position, the engagement mechanism of the
diverless pipe connector is actuated, in order to make a connection
between the diverless pipe connector and the receptacle for the
flow of fluid between the vertical steel pipe and the subsea
pipeline end termination and through the flexible pipe joint,
through the diverless pipe connector hub, and through the J-tube.
The engagement mechanism also locks the diverless pipe connector
hub into a fixed engagement position with respect to the receptacle
for the diverless pipe connector. Finally, in step 113, the
buoyance of the floating tank is increased to place the vertical
steel pipe of the riser in a state of tension for stability.
[0070] FIG. 5 shows an open configuration of the collet connector
engagement mechanism 63 introduced in FIG. 2. The engagement
mechanism 63 includes a cylindrical housing 121 mounted via a cover
122 to the hub 52. The housing 121 serves as a hydraulic cylinder
for a cylindrical and tubular piston 123 that reciprocates in an
axial direction to open and close the engagement mechanism 63 by
rocking fingers 124, 125, 126, etc., in a circular array of the
fingers.
[0071] FIG. 6 shows the engagement mechanism 63 in a closed
configuration. A reversible pump 127 removes hydraulic fluid such
as oil or water from an annular region 128 between the housing 121
and the piston 123 in order to switch the engagement mechanism 63
from the open configuration in FIG. 5 to the closed configuration
show in FIG. 6. The pump 127 supplies hydraulic fluid to the
annular region 128 in order to switch the engagement mechanism back
to the open configuration.
[0072] FIGS. 7 and 8 show the upper portion 131 of a clamp style
diverless pipe connector. The upper portion 131 includes an upper
hub 132 having a lower flange 133 and a pair of split ring clamps
134, 135 mounted to the upper hub around the lower flange.
[0073] As shown in FIG. 8, The split ring clamps 134, 135 are held
together by a pair of screws 136, 137. Each screw 136, 137 includes
a respective hexagonal head 138, 139 configured for engagement with
a wrench tool of a remotely operated submersible vehicle (ROV) (not
shown). Each screw 136, 137 also includes a respective left-hand
thread 141, 142 engaging a respective pin 143, 144 in the clamp
134, and a respective right-hand thread 145, 146 engaging a
respective pin 147, 148 in the clamp 135. Consequently, when the
ROV wrench tool turns any one of the screws 136, 137 in a clockwise
direction, the clamps 134, 135 are drawn together towards the
flange 133, and when the ROV wrench tool turns any one of the
screws 136, 137 in a counter-clockwise direction, the clamps 134,
135 are pulled apart away from the flange 133.
[0074] In order to mount the clamps 134, 135 to the hub 132, each
clamp is slotted for receiving a respective C-shaped guide 151,
152. Each guide 151, 152 is secured to a respective half 153, 154
of a split ring that is received in an annular groove 155 cut in
the periphery of the hub 132. The split ring is clamped to the hub
132 by bolts 156, 157. A respective helical compression spring 158,
159 is disposed between each of the clamps 134, 135 and its
respective guide 151, 152 in order to center the clamps 134, 135
about the flange 133.
[0075] FIG. 10 shows a diverless collet-style pipe connector 170
having an elastomeric flexible pipe joint 175 integrated with the
collet mechanism, shown in an open configuration. The collet-style
pipe connector includes a top flange 171 for connection to the
bottom end of a riser, and a bottom flange 172 for connection to
foundation structure such as a suction pile or branch fitting. The
top flange 171 is attached to an extension pipe 173 having a
semispherical lower flange 174. An annular elastomeric flex element
175 is bonded to the semispherical lower flange 174. The flex
element 175 includes alternate elastomer layers 176, 177 and
annular metal layers 178, 179 reinforcing the elastomer layers. The
elastomer layers 176, 177 are formed by imbedding the metal layers
178, 179 in elastomer during a molding process. The elastomer, for
example, is made of natural rubber or nitrile butadiene rubber
(NBR).
[0076] The flex element 175 is also bonded to an inner cylindrical
housing 180 that is attached to an outer cylindrical housing 181. A
cylindrical and tubular piston 182 for the collet mechanism is
disposed within the outer cylindrical housing 181 and between the
inner housing 180 and the outer housing 181. The outer housing 181
serves as a hydraulic cylinder in cooperation with the piston 182
for actuating the collet mechanism. The inner housing 180 is
attached to an internal pipe 183 terminated with an upper pipe
connector hub 184. The internal pipe 180 and the extension pipe 183
together provide a lumen for the flow of riser fluid between the
upper flange 171 and the upper pipe connector hub 184. The upper
pipe connector hub 184 has been landed on a lower pipe connector
hub 185 of an extension pipe 186 terminated by the lower flange
172.
[0077] FIG. 11 shows the closed configuration of the diverless
collet-style pipe connector 170. The piston 182 has been extended
downward to rock the fingers 187, 188 to forcibly engage the upper
pipe connector hub 184 with the lower pipe connector hub 185.
[0078] Although the FIGS. 10 and 11 show the flange 171 as the
upper flange and flange 172 as the lower flange, the diverless
collet-style pipe connector 170 is just as operable for anchoring
the bottom end of the riser to foundation structure when the
diverless collet-style pipe connector 171 is turned upside down. In
this case, the flange 171 would be connected to the foundation
structure such as a suction pile or branch fitting, and the flange
172 would be attached to the bottom end of the riser pipe. When a
single flexible pipe joint is used between the bottom end of the
riser and the foundation, the choice between these two alternatives
is a matter of which one is more convenient for installation and
possible removal of the flexible pipe joint. In other cases, it is
desirable to use more than one flexible pipe joint between the
bottom of the riser and the foundation in order to accommodate an
increased deflection angle of the riser from a vertical
orientation. In these other cases, depending on the availability of
diverless pipe connectors and flexible pipe joints, it may be most
convenient to use at least one flexible pipe joint attached to the
foundation below the diverless pipe connection.
[0079] FIG. 12 shows such an alternative arrangement, in which two
diverless collet-style pipe connectors 191, 192 having respective
integral flexible pipe joints 193, 194 joined together by an
extension pipe 195 having an upper hub 196 and a lower hub 197. In
this case, the flexible pipe joint 193 of the upper diverless
collet-style pipe connector 191 would be attached to the bottom end
of the riser pipe and would be above the diverless pipe
connections, and the flexible joint 194 of the lower diverless
collet-style pipe connector 192 would be attached to the foundation
and would be below the diverless pipe connections.
[0080] FIG. 13 shows an open configuration of a diverless
clamp-style pipe connector 201 with a flexible pipe joint 202
located on the riser side of the connection. FIG. 14 shows the same
assembly in a closed configuration. In this example, a bottom
flange 203 of the flexible pipe joint 202 is configured to serve as
an upper hub 203 of the clamp-style pipe connector 201. The upper
hub 203 mates with a lower hub 204 of an extension pipe 205. When
two split-ring clamps 206, 207 are drawn together, for example by a
screw mechanism as described above with reference to FIGS. 7, 8,
and 9, the upper hub 203 becomes clamped to the lower hub 204 as
shown in FIG. 14.
[0081] For connecting the bottom end of a riser to a foundation,
the bottom end of the riser is secured to an upper flange 208 of
the flexible pipe joint 202, and a lower flange 209 of the
extension pipe 204 is mounted to the foundation. In an alternative
configuration, the assembly shown in FIGS. 13 and 14 is turned
upside down so that the bottom end of the riser is connected to the
flange 209 of the extension pipe 205, and the flange 208 of the
flexible pipe joint 202 is mounted to the foundation.
[0082] FIG. 15 shows a closed configuration of a diverless
clamp-style pipe connector 211 joining two flexible pipe joints 212
and 213. The flexible pipe joint 212 is on the riser side of the
connection, and the flexible pipe joint 213 is on the foundation
side of the connection. A lower flange 214 of the flexible pipe
joint 212 is configured as an upper hub for the pipe connector 211,
and an upper flange 215 of the flexible pipe joint 213 is
configured as a lower hub for the pipe connector. Two split ring
clamps 216, 217 have been drawn together in order to clamp the
flanges 214, 215 together.
[0083] FIG. 16 shows a closed configuration of a diverless
collet-style pipe connector 221 joining two flexible pipe joints
222 and 223. The flexible pipe joint 222 is on the riser side of
the connection, and the flexible pipe joint 223 is on the
foundation side of the connection. A lower flange 224 of the upper
flexible pipe joint 222 is configured as an upper hub for the pipe
connector 221, and an upper flange 225 of the lower flexible pipe
joint 223 is configured as a lower hub for the pipe connector. The
collet actuation mechanism of the connector 221 is built around the
upper flexible pipe joint 222.
[0084] For connecting the bottom end of a riser to a foundation,
the bottom end of the riser is secured to an upper flange 226 of
the upper flexible pipe joint 222, and a lower flange 227 of the
lower flexible pipe joint 223 is mounted to the foundation. In an
alternative configuration, the assembly shown in FIG. 16 is turned
upside-down so that the bottom end of the riser is connected to the
flange 227 of the flexible pipe joint 223, and the flange 226 of
the flexible pipe joint 222 is mounted to the foundation.
[0085] FIGS. 2 and 3 have shown static connections of the
foundation structures to horizontal rigid subsea pipelines. There
are various other ways that a foundation structure may provide a
static connection to a subsea pipeline.
[0086] FIG. 17 shows a flange type connector 241 connecting a
foundation structure 242 to a horizontal rigid subsea pipeline 243.
The foundation structure 243 includes a hub 244 and an alignment
cone 245 for the riser connection. The foundation structure 242
also includes a J-tube 246 providing a connection between the hub
244 and the flange connector 241 for the flow of riser fluid.
[0087] FIG. 18 shows a horizontal diverless collet-style pipe
connector 251 connecting a foundation structure 252 to a horizontal
rigid subsea pipeline 253.
[0088] FIG. 19 shows a first vertical diverless collet-style pipe
connector 261 connecting a foundation structure 262 to a first end
of a vertical rigid jumper 263. A second vertical diverless
collet-style pipe connector 264 connects a second end of the
vertical rigid jumper 263 to a pipeline end termination (PLET) 265
of a horizontal rigid subsea pipeline 266. This particular
configuration provides a way of accommodating considerable
misalignment between the foundation structure 262 and the rigid
subsea pipeline 266.
[0089] FIG. 20 shows a horizontal diverless collet-style pipe
connector 271 connecting a foundation structure 272 to a horizontal
flexible subsea pipeline 273. This is a way of accommodating more
misalignment between a foundation structure and a subsea
pipeline.
[0090] FIG. 21 shows a vertical diverless collet-style pipe
connector 281 and a diverless vertical connector jumper 282
connecting a foundation structure 283 to a flexible pipeline 284.
This is a way of accommodating still more misalignment between a
foundation structure and a subsea pipeline.
[0091] In view of the above, there has been described an improved
freestanding hybrid riser system and a method for installing it, in
which the bottom connection at the base of the riser has a
diverless pipe connector with a flexible pipe joint allowing the
riser to connect to a mating tube and foundation structure, and
allowing the riser fluid to flow through the foundation structure
such as a suction pile to a static jumper connection point. This
reduces the bending and deflection in the foundation structure, and
eliminates the need for a jumper with multiple bends or loops
between the lower end of the vertical steel pipe of the riser and
the stationary pipeline end termination. Therefore there is a
significant cost savings in the riser foundation structure,
especially in deep and ultradeep water.
* * * * *