U.S. patent application number 13/062773 was filed with the patent office on 2011-06-30 for offshore seabed to surface conduit transfer system.
This patent application is currently assigned to MISC BERHAD. Invention is credited to Adam Timothy Brumley, Poul Erik Christiansen, Zanussi Mohd Zain, Khodijah Yaacub.
Application Number | 20110155383 13/062773 |
Document ID | / |
Family ID | 42005308 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155383 |
Kind Code |
A1 |
Christiansen; Poul Erik ; et
al. |
June 30, 2011 |
OFFSHORE SEABED TO SURFACE CONDUIT TRANSFER SYSTEM
Abstract
The present invention relates to a transfer system for
transferring hydrocarbons, power or electrical/optical signals as
the case may be from the seabed to the vessel or other buoyant
structure in the shallow water when exposed to the environmental
loadings from wind, wave and current. The conduit transfer system
comprising a flexible pipe or umbilical extends from the buoyant
unit at one end and to the seabed at the other end; and a riser
support fixed to the seabed for supporting the flexible pipe
characterized in that the flexible pipe a plurality of buoyancy
beads for creating one or more inverse catenary curves of the
flexible pipe to provide an excursion envelope.
Inventors: |
Christiansen; Poul Erik;
(Malaysia, MY) ; Brumley; Adam Timothy; (Malaysia,
MY) ; Yaacub; Khodijah; (Malaysia, MY) ; Mohd
Zain; Zanussi; (Malaysia, MY) |
Assignee: |
MISC BERHAD
|
Family ID: |
42005308 |
Appl. No.: |
13/062773 |
Filed: |
August 28, 2009 |
PCT Filed: |
August 28, 2009 |
PCT NO: |
PCT/MY2009/000130 |
371 Date: |
March 8, 2011 |
Current U.S.
Class: |
166/345 |
Current CPC
Class: |
E21B 17/015 20130101;
H02G 9/12 20130101; F16L 1/24 20130101 |
Class at
Publication: |
166/345 |
International
Class: |
E21B 17/01 20060101
E21B017/01 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2008 |
MY |
PI 20083484 |
Claims
1. A conduit system for transferring hydrocarbons from a seabed to
a floating vessel or structure comprising: a flexible pipe extends
from the floating vessel or structure at one end and to the seabed
at the other end; and a riser support fixed to the seabed for
supporting the flexible pipe characterized in that the flexible
pipe is fitted with a plurality of buoyancy beads for creating one
or more inverse catenary curves of the flexible pipe to provide an
excursion envelope.
2. The conduit system as claimed in claim 1, wherein the flexible
pipe is fitted with a plurality of weight modules to regulate a
catenary shape of the dynamic response of the flexible pipe.
3. The conduit system as claimed in claim 1, wherein the flexible
pipe is attached to a fixed point elevated substantially above the
seabed.
4. conduit system as claimed in claim 1, wherein the riser support
is a rigid structure fixed to the seabed.
5. The conduit system as claimed in claim 1, wherein the flexible
pipe is fitted with external wear protection for allowing the
flexible pipe to touch the seabed without damaging the flexible
pipe.
6. The conduit system as claimed in claim 1, wherein the flexible
pipe is provided with a bend stiffener for allowing the flexible
pipe to bend gradually.
7. The conduit system as claimed in claim 1, wherein the flexible
pipe is provided with a tether for anchoring and preventing the
flexible pipe from being over floated.
8. The conduit system as claimed in claim 1, further comprises, a
communication system for carrying communication signals from a
seabed to a floating vessel or structure.
9. The conduit system as claimed in claim 1, further comprises a
power system for power transmission from a seabed to a floating
vessel or structure.
10-16. (canceled)
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a conduit system for
transferring hydrocarbons, power or electrical/optical signals from
the seabed to a floating structure in the shallow water when
exposed to the environmental loadings from wind, wave and
current.
BACKGROUND OF THE INVENTION
[0002] In offshore oil and gas production a variety of buoyant
structures are used to support oil and gas processing equipment,
storage facilities or other facilities that condition fluids which
are being transferred between the seabed and the buoyant structure.
Such buoyant structures includes monohull vessels type structures
known as FSO (Floating Storage Offloading) or FPSO's (Floating
Production Storage Offloading) , semi submersibles, tension leg
platforms, caisson structures including spar types, CALM (Crude and
a loading buoy) buoys etc. Common for all these structures is that
when exposed to a combination of wind, wave and current the
structures will displace in the horizontal and vertical plane.
Conduits between such structures and the seabed will therefore need
to incorporate some means of accommodating this relative
movement.
[0003] Flexible pipes constructed from a combination of rubber,
plastics and metallic elements are frequently used in applications
to overcome the above aforementioned relative displacements. Such
pipe structures are commonly known as "Flexible Pipe" and when
applied for the purpose of transferring flowing media between the
seabed and the sea surface the pipe structure is referred to as a
"Flexible Riser".
[0004] Umbilicals constructed from small bore pipes and/or
electrical cables and/or optical cables together with possible
armor wiring and external thermoplastic sheeting are frequently
used to transfer electrical or hydraulic power and/or electrical or
optical control signals between the seabed and the sea surface. The
umbilical used in such a dynamic application is commonly referred
to as a "Dynamic Umbilical". In the description of the invention
the focus will be on its applicability to Flexible Riser, however,
the invention equally apply to Dynamic Umbilicals.
[0005] A number of configurations are used when suspending the
flexible pipe between the seabed and the buoyant unit. The main
riser configurations are those known by names of "Free Hanging
Catenary", "Chinese Lantern", "Steep S", "Steep Wave", "Lazy S",
"Lazy Wave" and "Pliant Wave". The shape of the various riser
configurations is attained by use of concentrated or distributed
buoyancy elements fixed to the riser and sometimes tethered back to
the seabed as well as weight elements and tether lines to seabed
anchors.
[0006] In all these configurations the flexible pipe is continues
from the unit to the seabed except for any joints at some mid water
depth required to join flexible pipes of different construction is
so required or joining made via shot length of hard pipe over
support structures such as mid water arches employed in for
instance the "Steep S" and "Lazy S" configurations.
[0007] In particular shallow water and harsh environment a large
proportion of the total riser length is exposed to hydrodynamic
loads from the wave action and any buoy structures used in
producing the riser configuration is equally exposed to said wave
loading. This in combination with the excursions of the surface
unit can lead to extreme dynamic movements of the flexible pipe
with over stressing, over bending of the pipe or unacceptable
compressive loads in the flexible pipe. Also buoyant support
structures may become unstable and exhibit unacceptable dynamic
motions rendering the system unfeasible.
[0008] A further complication may arise in shallow water
applications when the riser system is used in combination with a
surface unit that may at times be over the riser system, such as
for instance with a turret moored monohull vessel that will weather
vane in response to the prevailing environmental loadings. In this
instance the available height from the seabed that can be used to
generate a riser configuration is limited by the requirement to
provide clearance to the bottom of the vessel above, which will
experience vertical motions up and down in addition to the water
currents.
SUMMARY OF THE INVENTION
[0009] The object of the present invention is to improve the
response of the flexible pipe such that a flexible pipe based
system can be used in harsher and shallower water applications.
[0010] Unlike the known riser configurations where the riser is
terminated at the seabed in close proximity to the mudline in the
current invention the riser is suspended from a rigid structure
extend up from the seabed to somewhere at mid water depth. The
connection at this point is fixed and will not be subject to any
significant movement even when exposed to extreme environmental
loadings. The flexible pipe in its simplest configuration is
suspended in a catenary configuration between the mid water
connection point and the surface unit. This arrangement was
proposed by Kelm et al refer U.S. Pat. No. 7,040,841 B1. However,
in the current invention the further buoyancy beads are added to
the flexible pipe to provide one or more inverse catenary shapes
along the length of the riser, which will further greatly enhance
the relative movements that can be accommodated between the surface
unit and the mid water fixity points. Buoyancy beads may also be
attached to the flexible pipe to add weight locally to change the
shape of the configuration and the riser's dynamic response if
required. Subject to the seabed conditions the riser may be allowed
to touch the seabed and external wear modules may be attached to
the flexible pipe in the touch down area should this feature be
required.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Other features and advantages of the present invention will
be clear from reading the description hereafter, given by way of
non-limitative example, with reference to the accompanying drawing
wherein:
[0012] FIG. 1 illustrates a conduit system of the present
invention.
BRIEF DESCRIPTION OF THE INVENTION
[0013] Other features and advantages will become more apparent form
the description of one preferred embodiment of the invention and
from the appended drawing depicting the invention.
[0014] The present invention relates to a conduit system to carry
liquid or gas or a combination of such media i.e. hydrocarbons and
or power and or electrical/optical signals to or from a buoyant
unit 1 at or near the sea surface and the seabed 2. In case of
hydrocarbons the flow is carried via a flexible pipe 3 attached to
the buoyant unit 1 via a flanged or similar type pipe connection.
The flexible pipe is attached to a fixed point 4 elevated
substantially above the seabed mudline 5. The conduit for the media
from the fix point 4 to the seabed connection point 6 is via fixed
or flexible pipe 7 as the case may be.
[0015] The fixed or flexible pipe 7 is supported of a riser support
8 preferably a rigid structure that can be constructed from steel,
concrete or other rigid construction material. The riser support 8
is fixed to seabed and the structures foundation can be drilled or
driven piles 9 connected to the structure such suction cans 10 or
gravity type foundation or a combination of such foundations.
[0016] The fixed or flexible pipe 7 may include valve arrangement
11 for isolation and manifolding if more than one riser is used,
pig launcher or pig receiver. Since such devices can be installed
at mid water depth it may allow diver intervention using air diving
technique rather than saturation diving required at greater
depth.
[0017] The flexible pipe 3 may be fitted with weight modules 12 to
change the catenary shape and/or improve the dynamic response of
the flexible pipe when subject to environmental loadings and
movements of the surface unit 1. The flexible pipe 3 may be allowed
to touch the seabed and can if required be fitted with external
wear protection 13.
[0018] To accommodate even larger excursions of the buoyant unit 1
the flexible pipe will be fitted with buoyancy beads 14 to create
one or more inverse catenary shapes along the length of the
flexible pipe. These inverse catenary shapes greatly enhance the
excursion envelope of the surface unit the system can accommodate
as compared to a riser hanging in a simple catenary shape as
proposed in prior art.
[0019] The flexible pipe 3 may require bend stiffener 15 to provide
a gradual increase in bend stiffness and so as to not over bend or
kink the pipe at or close to its attachment points. The pipe may
also be supported by an arch or a gutter structure 16 to avoid the
flexible pipe being over bend in the in and out of plane
directions. The tether 17 may be required to anchor and prevent the
flexible pipe 3 from over float.
[0020] One advantage of the present invention is that it increases
the excursions and movements that the flexible pipe can accommodate
with out exceeding its allowable mechanical properties for stress
and bending. This reduces the requirement to the mooring
arrangement required for the surface unit and also allows the
system to be deployed in more shallow and harsh environment.
[0021] Another advantage with the current invention is that it
reduces the length of flexible pipe to be used and since flexible
pipe is more expensive than normal rigid pipe the invention offers
savings on flexible pipe material, which can be significant
particular when a large number of risers are configured as
proposed.
[0022] The proposed invention is also less sensitive to changes in
the density of the fluid being conveyed inside the flexible pipe
and so can for instance readily accommodate slug flow where the
flow regime consist of gas flow separated by liquid slugs flowing
through the system
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