U.S. patent application number 13/785142 was filed with the patent office on 2013-09-05 for offshore system with subsea riser.
This patent application is currently assigned to CAMERON INTERNATIONAL CORPORATION. The applicant listed for this patent is CAMERON INTERNATIONAL CORPORATION. Invention is credited to David Cain, Shian J. Chou, William F. Puccio.
Application Number | 20130230358 13/785142 |
Document ID | / |
Family ID | 49042922 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130230358 |
Kind Code |
A1 |
Cain; David ; et
al. |
September 5, 2013 |
Offshore System with Subsea Riser
Abstract
An offshore system with a subsea riser, including a floating
platform and a subsea riser made up of sections of pipe. A riser
tension system compensates for movement of the platform while
providing tension to the riser. At least two of the riser sections
are connected with a connector such that a portion of the riser is
able to be placed in compression without buckling.
Inventors: |
Cain; David; (Houston,
TX) ; Puccio; William F.; (Houston, TX) ;
Chou; Shian J.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CAMERON INTERNATIONAL CORPORATION |
Houston |
TX |
US |
|
|
Assignee: |
CAMERON INTERNATIONAL
CORPORATION
Houston
TX
|
Family ID: |
49042922 |
Appl. No.: |
13/785142 |
Filed: |
March 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61606834 |
Mar 5, 2012 |
|
|
|
Current U.S.
Class: |
405/223.1 |
Current CPC
Class: |
E21B 7/12 20130101; E02B
2017/0095 20130101; E21B 17/01 20130101; E21B 19/006 20130101; E21B
15/02 20130101; E02B 17/00 20130101 |
Class at
Publication: |
405/223.1 |
International
Class: |
E21B 19/00 20060101
E21B019/00 |
Claims
1. An offshore system for a subsea well, including: a subsea riser
including sections of pipe; a riser tension system capable of
dynamically compensating for movement while providing tension to
the riser; and at least two of the riser sections being connected
with a connector such that a portion of the riser is able to
withstand a compressive load.
2. The system of claim 1, further including multiple
connectors.
3. The system of claim 1, wherein connectors connect sections of
the subsea riser from the bottom of the riser as high up as the
riser is designed to be in compression when installed.
4. The system of claim 1, wherein each connector includes a pin and
a box.
5. The system of claim 1, wherein each connector includes a body
including a flange and a neck extending from the flange.
6. The system of claim 1, wherein at least some of the supportive
load for the riser is transferred to the connector and the tension
system does provide the full tensioning requirements that the riser
would otherwise need to prevent buckling without the connector.
7. The system of claim 1, wherein the tension system may be
designed only to support a weight less than needed to place the
subsea riser in tension.
8. The system of claim 1, wherein the tension system may support a
riser heavier than the tension system is designed to support.
9. The system of claim 1, wherein the riser is one of a production
riser or a drilling riser.
10. The system of claim 1, wherein the riser tension system
includes a dynamic riser tensioner.
11. An offshore system for a subsea well, including: a floating
platform; a subsea wellhead on the sea floor; a subsea riser
including sections of pipe connecting the subsea wellhead and the
floating platform; a riser tension system capable of dynamically
compensating for movement of the platform while providing tension
to the riser; and at least two of the riser sections being
connected with a connector such that a portion of the riser is able
to withstand a compressive load.
12. The system of claim 11, further including multiple
connectors.
13. The system of claim 11, wherein connectors connect sections of
the subsea riser from the bottom of the riser as high up as the
riser is designed to be in compression when installed.
14. The system of claim 11, wherein each connector includes a pin
and a box.
15. The system of claim 11, wherein each connector includes a body
including a flange and a neck extending from the flange.
16. The system of claim 11, wherein at least some of the supportive
load for the riser is transferred to the connector and the tension
system does provide the full tensioning requirements that the riser
would otherwise need to prevent buckling without the connector.
17. The system of claim 11, wherein the tension system may be
designed only to support a weight less than needed to place the
subsea riser in tension.
18. The system of claim 11, wherein the tension system may support
a riser heavier than the tension system is designed to support.
19. The system of claim 11, wherein the riser is one of a
production riser or a drilling riser.
20. The system of claim 11, wherein the riser tension system
includes a dynamic riser tensioner.
Description
BACKGROUND
[0001] Drilling and producing offshore oil and gas wells includes
the use of offshore platforms for the exploitation of undersea
petroleum and natural gas deposits. In deep water applications,
floating platforms (such as spars, tension leg platforms, extended
draft platforms, and semi-submersible platforms) are typically
used. One type of offshore platform, a tension leg platform
("TLP"), is a vertically moored floating structure used for
offshore oil and gas production. The TLP is permanently moored by
groups of tethers, called a tension legs or tendons, that eliminate
virtually all vertical motion of the TLP due to wind, waves, and
currents. The tendons are maintained in tension at all times by
ensuring net positive TLP buoyancy under all environmental
conditions. The tendons stiffly restrain the TLP against vertical
offset, essentially preventing heave, pitch, and roll, yet they
compliantly restrain the TLP against lateral offset, allowing
limited surge, sway, and yaw. Another type of platform is a spar,
which typically consists of a large-diameter, single vertical
cylinder extending into the water and supporting a deck. Spars are
moored to the seabed like TLPs, but whereas a TLP has vertical
tension tethers, a spar has more conventional mooring lines.
[0002] The offshore platforms typically support risers that extend
from one or more wellheads or structures on the seabed to the
platform on the sea surface. The risers connect the subsea well
with the platform to protect the fluid integrity of the well and to
provide a fluid conduit to and from the wellbore. During drilling
operations, a drilling riser is used to maintain fluid integrity of
the well. After drilling is completed, a production riser is
installed.
[0003] The risers that connect the surface wellhead to the subsea
wellhead can be thousands of feet long and extremely heavy. To keep
the risers as light as possible, they are designed so as to not be
able to withstand their own weight, even when in water. In fact,
the connectors used to connect sections of some risers, e.g.
production risers, are designed to be weaker than the riser
sections themselves. An example of such connectors is a thread and
couple connector where the ends of two adjacent riser sections are
both threaded into the connector. When the riser is placed under
conditions exceeding operating limits, the connectors will actually
be the first components to fail.
[0004] To prevent the risers from buckling under their own weight
or placing too much stress on the subsea wellhead, upward tension
is applied, or the riser is lifted, to relieve a portion of the
weight of the riser. Since offshore platforms are subject to motion
due to wind, waves, and currents, the risers must be tensioned so
as to permit the platform to move relative to the risers.
Accordingly, the tensioning mechanism must exert a substantially
continuous tension force to the riser within a well-defined range
so as to compensate for the movement of the platform.
[0005] Hydro-pneumatic tensioner systems are an example of a riser
tensioning mechanism used to support risers. A plurality of active
hydraulic cylinders with pneumatic accumulators is connected
between the platform and the riser to provide and maintain the
necessary riser tension. Platform responses to environmental
conditions that cause changes in riser length relative to the
platform are compensated by the tensioning cylinders adjusting for
the movement.
[0006] Regardless of the tensioning system used, the system must be
designed to accommodate with weight and movement characteristics of
each riser. However, some risers may require so much tensioning
that the loads transferred to the platform exceed the lower
allowable load requirements of the platform. A way to accommodate
risers when the load requirements exceed the limits of the platform
is needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a detailed description of the preferred embodiments of
the invention, reference will now be made to the accompanying
drawings in which:
[0008] FIG. 1 shows an off-shore drilling or production system in
accordance with various embodiments;
[0009] FIG. 2 shows views of different sections of the riser system
of FIG. 1;
[0010] FIG. 3 shows a first example connector in accordance with
various embodiments; and
[0011] FIG. 4 shows another example connector in accordance with
various embodiments.
DETAILED DESCRIPTION
[0012] The following discussion is directed to various embodiments
of the invention. The drawing figures are not necessarily to scale.
Certain features of the embodiments may be shown exaggerated in
scale or in somewhat schematic form and some details of
conventional elements may not be shown in the interest of clarity
and conciseness. Although one or more of these embodiments may be
preferred, the embodiments disclosed should not be interpreted, or
otherwise used, as limiting the scope of the disclosure, including
the claims. It is to be fully recognized that the different
teachings of the embodiments discussed below may be employed
separately or in any suitable combination to produce desired
results. In addition, one skilled in the art will understand that
the following description has broad application, and the discussion
of any embodiment is meant only to be exemplary of that embodiment,
and not intended to intimate that the scope of the disclosure,
including the claims, is limited to that embodiment.
[0013] Certain terms are used throughout the following description
and claims to refer to particular features or components. As one
skilled in the art will appreciate, different persons may refer to
the same feature or component by different names. This document
does not intend to distinguish between components or features that
differ in name but not function. The drawing figures are not
necessarily to scale. Certain features and components herein may be
shown exaggerated in scale or in somewhat schematic form and some
details of conventional elements may not be shown in interest of
clarity and conciseness.
[0014] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . ." Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection, or through an indirect connection via other devices,
components, and connections. In addition, as used herein, the terms
"axial" and "axially" generally mean along or parallel to a central
axis (e.g., central axis of a body or a port), while the terms
"radial" and "radially" generally mean perpendicular to the central
axis. For instance, an axial distance refers to a distance measured
along or parallel to the central axis, and a radial distance means
a distance measured perpendicular to the central axis.
[0015] Referring now to FIG. 1, a schematic view of an offshore
system 10 is shown. In this example, the system 10 is an offshore
production system and includes a riser 14 between a floating
platform or vessel 16 and a subsea wellhead 12 on the sea floor 13.
Because the example shown is a production system, the riser is
designed as a production riser. However, it should be appreciated
that the offshore system 10 and the riser 14 may also be designed
and configured for drilling operations in accordance with different
embodiments as well. As shown in FIG. 1, mooring lines or tendons
15 may be provided to attach the floating platform 16 to the sea
floor.
[0016] In the example shown in FIG. 1, the riser 14 connects with
the platform 16 (in this example, a SPAR-type platform). Other
types of floating structures 16 that can be used with the invention
include floating production storage and offloading (FPSO) systems,
semi-submersible platforms, tension leg platforms (TLPs), and
others known to those of ordinary skill in the art. The connection
between the subsea wellhead 12 and the platform 16 provided by the
riser 14 allows fluid communication there between.
[0017] As shown in FIG. 2, the riser 14 is shown broken up to be
able to include detail on specific sections but it should be
appreciated that the riser 14 maintains fluid integrity from the
subsea wellhead 12 to the production equipment on the platform
16.
[0018] The platform 16 includes a mezzanine deck 20, the tensioner
deck 22, and a production deck 24 located above the sea level 21.
As shown, the riser 14 includes a tension joint 34 and a transition
joint 36. The riser 14 is attached at its lower end to the subsea
wellhead 12 using an appropriate connection. For example, the riser
14 may include a wellhead connector 40 with an integral stress
joint as shown. As an example, the wellhead connector 40 may be a
tie back connector. Alternatively, the stress joint may be separate
from the wellhead connector 40. The riser 14 may or may not include
other specific riser joints, such as riser joints 42 with strakes
or fairings and splash zone joints 44. The upper end of the riser
14 terminates in a surface wellhead and production tree 50 on the
mezzanine deck 20.
[0019] A riser tension system 60 is attached to the riser 14 at the
tension joint 34 by using a tensioner ring 62 on the riser 14. The
riser tension system 60 is supported on the tensioner deck 22 and
dynamically tensions the riser 14. This allows the tension system
60 to adjust for the movement of the platform 16 while maintaining
at least a portion of the riser 14 under tension. The riser tension
system 60 may be any appropriate system, such as a hydro-pneumatic
tensioner system with tensioning cylinders 64 as shown. The number
of tensioning cylinders used may vary depending on the design of
the system 10.
[0020] Although the tension system 60 is able to compensate for the
motion of the platform 16, the tension system 60 is not designed to
provide all of the required tension to the riser 14 to prevent
buckling. To prevent the riser from otherwise buckling, the riser
14 includes compression connectors 80 that are designed to be
strong enough such that at least a portion of the riser 14 is able
to withstand a compressive load. The amount and location of the
compression connectors will depend on the designed loads and
configuration of the system 10 and the riser 14. It should be
appreciated that the compression connectors 80 need not be used on
the entire length of the riser 14. Instead, the riser 14 need only
include at least one compression connector 80 such that a portion
of the riser 14 may withstand being placed in compression. In this
manner, the tension system 60 does not need to provide the full
tensioning requirements that the riser 14 would otherwise need to
prevent buckling. Thus, the full load needed to support the riser
14 does not need to be transferred to the platform 16 and the
platform 16 may be used to support a riser 14 heavier than it would
otherwise be able to.
[0021] FIG. 3 shows an example of a compression connector. In this
example, the compression connector 80a is a pin and box connector
including a pin 82 and a box 84. The compression connector 80a may
designed to be even stronger than the riser section itself.
[0022] FIG. 4 shows another example of a compression connector. In
this example, the compression connector 80b is a flange connector,
which is typically designed to be stronger than other types of
connectors. The flange connector 80b includes a body with a flange
88 and a neck 86 for each riser section end. The riser section end
connects to the neck 86 either through welding, shrink-fit, or some
other suitable connection method. Once attached, the riser sections
are connected by tightening bolts that run through the adjacent
flanges of the connector 80b.
[0023] Although the present invention has been described with
respect to specific details, it is not intended that such details
should be regarded as limitations on the scope of the invention,
except to the extent that they are included in the accompanying
claims.
* * * * *