U.S. patent application number 12/053769 was filed with the patent office on 2008-10-02 for process, vessel and system for transferring fluids between floating vessels using flexible conduit and releasable mooring system.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Jimmie Dean Adkins, John S. Hartono, David T. McDonald.
Application Number | 20080242165 12/053769 |
Document ID | / |
Family ID | 39792222 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080242165 |
Kind Code |
A1 |
Adkins; Jimmie Dean ; et
al. |
October 2, 2008 |
PROCESS, VESSEL AND SYSTEM FOR TRANSFERRING FLUIDS BETWEEN FLOATING
VESSELS USING FLEXIBLE CONDUIT AND RELEASABLE MOORING SYSTEM
Abstract
A system is provided for transferring fluids such as liquefied
natural gas between a floating transport vessel and a floating
storage vessel utilizing a transfer vessel to deploy, operate and
return a fluid conduit to the storage vessel. The fluid is
transferred through at least one submerged-subsea catenary flexible
conduit, at least one floating flexible conduit, or any combination
thereof. A transfer vessel, including a releasable mooring system,
is provided for deploying the conduit from the storage vessel to
the transport vessel, mooring with a transport vessel, maintaining
a unified connection during fluid transfer, releasing the mooring
once fluid transfer is completed, returning to and parking on the
storage vessel, and storing the conduit between fluid transfers.
The transfer vessel and releasable mooring system allows safe,
controlled operation and fluid transfer in open sea conditions.
Inventors: |
Adkins; Jimmie Dean; (San
Ramon, CA) ; Hartono; John S.; (Oakland, CA) ;
McDonald; David T.; (Walnut Creek, CA) |
Correspondence
Address: |
CHEVRON CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron U.S.A. Inc.
San Ramon
CA
|
Family ID: |
39792222 |
Appl. No.: |
12/053769 |
Filed: |
March 24, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60908723 |
Mar 29, 2007 |
|
|
|
Current U.S.
Class: |
441/4 |
Current CPC
Class: |
B63B 22/021 20130101;
Y10T 137/87973 20150401; B63B 27/24 20130101 |
Class at
Publication: |
441/4 |
International
Class: |
B63B 22/02 20060101
B63B022/02 |
Claims
1. A process for transferring a product between a first vessel and
a second vessel, the process comprising: mooring a transfer vessel
to a surface of a second vessel with a mooring device capable of
dampening the relative motions between the transfer vessel and the
second vessel; connecting a fluid conduit on the transfer vessel to
the second vessel; and flowing product between a first vessel and
the second vessel through the fluid conduit.
2. The process of claim 1, wherein the fluid conduit is in fluid
communication with the first vessel.
3. The process of claim 1, wherein the fluid conduit is in fluid
communication with a second transfer vessel moored to the first
vessel.
4. The process of claim 1, further comprising the step of
disengaging the mooring device from the surface of the second
vessel without adding ballast to the transfer vessel.
5. The process of claim 1, further comprising the step of
disconnecting the fluid conduit from the second vessel without
adding ballast to the transfer vessel.
6. The process of claim 1, further comprising the steps of
disengaging the mooring device from the surface of the second
vessel and mooring the transfer vessel with the first vessel.
7. The process of claim 1, wherein the transfer vessel is moored to
the second vessel such that the transfer vessel does not contact a
bottom surface of the second vessel or pass under a bottom surface
of the second vessel.
8. The process of claim 1, wherein the first vessel comprises an
FPSO vessel, an FSO vessel, an FLNG vessel, an FSRU vessel, an LNG
carrier, or an LNG ice-breaking carrier.
9. The process of claim 1, wherein the second vessel comprises an
FPSO vessel, an FSO vessel, an FLNG vessel, an FSRU vessel, an LNG
carrier, an LNG ice-breaking carrier, a crude carrier, or a refined
product carrier.
10. The process of claim 1, wherein the step of mooring the
transfer vessel to the second vessel comprises attaching at least
one of air vacuum pad mooring, water vacuum pad mooring and
electromagnetic pad mooring to a side of the second vessel.
11. The process of claim 1, wherein the product is selected from
the group consisting of liquefied natural gas, liquefied heavy gas,
liquefied petroleum gas, crude oil, diesel, syncrude, petroleum
condensate, synthetic lube oil, naphtha, and methanol and mixtures
of the same.
12. The process of claim 1, wherein the step of flowing the product
further comprises pumping the product through at least one of
subsea catenary conduit, a surface floating conduit, a pipe
supported by a floating jetty or arm and a pipe supported by a
vessel or submerged jetty or arm.
13. A transfer vessel comprising: a floating vessel having a
vertical portion; a fluid conduit disposed on the floating vessel;
and a mooring device connected to the vertical portion for
releasably mooring the transfer vessel to a surface of a second
vessel, wherein the mooring device is capable of dampening the
relative motions between the floating vessel and the second
vessel.
14. The transfer vessel according to claim 13, further comprising a
plurality of fluid conduits.
15. The transfer vessel according to claim 14, further comprising a
valve manifold connected to the plurality fluid conduits.
16. The transfer vessel of claim 14, wherein the plurality of fluid
conduits is connected to a product source on a first vessel and
wherein the valve manifold is capable of directing a flow of
product back to the first vessel.
17. The transfer vessel according to claim 13, wherein the mooring
device comprises at least one of an air vacuum pad mooring system,
a water vacuum pad mooring system and an electromagnetic pad
mooring system.
18. The transfer vessel according to claim 13, wherein the mooring
device further comprises dampening means for dampening the relative
motions between the floating vessel and the second vessel.
19. The transfer vessel according to claim 13, further comprising
at least one of a hard pipe loading arm, an aerial hose, and a
flexible aerial pipe, connected to an upper portion of the floating
vessel for connecting to the second vessel.
20. The transfer vessel of claim 13, further comprising
ballast.
21. The transfer vessel according to claim 13, further comprising
an emergency release system for disconnecting the fluid conduit
from a second vessel.
22. The transfer vessel according to claim 13, wherein the fluid
conduit comprises at least one of a subsea catenary conduit, a
surface floating conduit, a pipe supported by a floating jetty or
arm, and a pipe supported by a subsea submerged jetty or arm.
23. The transfer vessel according to claim 13, wherein the mooring
device is positioned on the vertical portion so that when the
transfer vessel is moored to a second vessel the transfer vessel
does not contact a bottom surface of the second vessel.
24. The transfer vessel according to claim 13, further comprising a
booster pump connected to the fluid conduit.
25. The transfer vessel according to claim 13, further comprising a
dynamic positioning propulsion system.
26. A transfer vessel comprising: a floating vessel having a
vertical portion; a fluid conduit disposed on the floating vessel;
and a mooring device connected to the vertical portion for
releasably mooring the transfer vessel to a surface of a second
vessel, wherein when the transfer vessel is moored to a second
vessel the transfer vessel does not contact a bottom surface of the
second vessel or pass under a bottom surface of the second
vessel.
27. A product transfer system comprising: a first vessel; a
transfer vessel comprising: a floating vessel having a vertical
portion; a fluid conduit disposed on the floating vessel and in
fluid communication with the first vessel; and a mooring device
connected to the vertical portion for releasably mooring the
transfer vessel to a surface of a second vessel, wherein the
mooring device is capable of dampening the relative motions between
the floating vessel and the second vessel.
28. The product transfer system of claim 27, further comprising a
second transfer vessel, comprising: a floating vessel having a
vertical portion; a fluid conduit disposed on the floating vessel
and in fluid communication with the first vessel; and a mooring
device connected to the vertical portion for releasably mooring the
transfer vessel to a surface of a third vessel, wherein the mooring
device is capable of dampening the relative motions between the
floating vessel and the third vessel.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a transport vessel with a
fluid transfer conduit and a releasable mooring system that enables
fluid transfer between floating vessels in open sea conditions.
More particularly, the present invention relates to a system for
mooring a transfer vessel to another vessel for the purpose of
transferring fluids between vessels.
BACKGROUND OF THE INVENTION
[0002] Transferring fluids on the open ocean in unprotected
locations offers particular hazards in terms of personnel safety
and damage to the vessels or facilities involved. The fluids which
are transported in a transport vessel from a remote location may be
delivered to either a tank located at the offshore facility, or by
pipeline to a land-based receiving terminal. Offshore tank storage
facilities may either be floating or settled on the seafloor.
[0003] No commercially proven technology exists that allows fluid
transfer in harsh open ocean conditions between standard
(non-dedicated) transport vessel and a floating storage vessel. As
an example, a floating storage vessel is a fixed asset near a
market site that could be used for storing fluid for eventual
delivery to on-shore facilities. For such floating storage vessels
to become technically and commercially viable in many locations, a
reliable fluid transfer system is needed that can transfer fluids
between the storage vessel and standard transport carriers (and
other vessels having diverse features and configurations) under a
variety of conditions but with a relatively high berth availability
rating.
[0004] Commercially proven technologies exist for oil transfer in
harsh open ocean conditions, but require dedicated transport
carriers with extensive bow modifications. Conversely, commercially
proven technologies exist for oil transfer between a standard oil
carrier and a floating storage vessel or SPM buoy, but not in harsh
open ocean conditions; these systems cannot operate in harsh open
ocean conditions due to marine operations issues and safety
concerns with support vessels, i.e. tug boats and offshore service
vessels. No commercially proven system exists that can transfer
fluids between a standard oil carrier and a floating storage vessel
in harsh open ocean conditions.
[0005] Conventionally, fluid transfer to/from floating transport
vessels is most often accomplished thru articulated hard-pipe
loading arms, such as an FMC "Chicksan" arm. Fluid transfer
operations using such loading arms generally require relatively
benign conditions, such as are found in sheltered locations in
harbors or behind breakwaters. As a result, many operational fluid
transfer terminals are located onshore, in harbors, bays, rivers or
waters that are sheltered from open ocean conditions. Requiring
protected fluid transfer sites limits the number of potential sites
for new terminals, and in many regions a suitable site simply is
not available. Additionally, where the fluid to be transferred is
hydrocarbon or petroleum based, public pressure is forcing the
proposed fluid transfer facilities increasingly further offshore
and to remote locations both onshore and offshore. For example on
the US West Coast, few shallow water sites are available and the
Pacific Ocean Meteorological and Oceanographic (metocean)
conditions (sea states, currents and winds) complicate the problem
and further limit the number of potential solutions.
[0006] Applying articulated loading arm technology in an open ocean
location has been contemplated by many fluid transfer terminal
projects. In shallow water locations with milder metocean
conditions, a gravity based structure (GBS) is a technically
feasible solution. It basically serves as a breakwater, thus
allowing loading arms to be used in a side-by-side berthing
layout.
[0007] In deeper water applications, a floating storage vessel that
is single point moored (SPM) allows the vessel to weathervane into
the dominant metocean conditions, thus minimizing floating storage
vessel motions. Loading arms have been proposed for fluid transfer
between two vessels in a side-by-side berthing (mooring)
arrangement, but have not been employed to date for a variety of
reasons. Unlike a GBS, a floating storage vessel does not serve as
a breakwater, and thus the side-by-side moorings must take the full
force of the metocean conditions. Being able to predict the
relative motions between the vessels with the necessary high degree
of certainty has proven to be difficult. The mooring line
arrangement in a side-by-side mooring is difficult at best in that
the vessels are often very close in overall length, and thus proper
bow and stern mooring line geometries can not be achieved. Also,
tug boat operational problems are further compounded by the
approach layout in a side-by-side berthing. Additional concerns
include damage to the vessels due to high relative motions between
the vessels, and increased potential for breakout due to high loads
on the mooring lines. All these issues combine to produce
significant concerns for conventional fluid transfer systems in
side-by-side offshore terminal concepts, and thus, exacerbate
concerns with being able to meet fluid delivery commitments.
[0008] Thus, development work to date on new offshore fluid
transfer systems has concentrated on vessels that are moored in a
tandem arrangement. This is particularly true for cryogenic fluids,
where the development work has centered on aerial (in-air) systems
and more recently on floating hose systems. It has been found that
these systems can require the use of specially designed (dedicated)
transport carriers, can be overly complicated and expensive,
difficult to operate in other than benign weather conditions, and
in some cases can require the use of technology that is not widely
endorsed by the maritime industry. More specifically, none of these
systems have solved the problem of how to safely deliver and
connect the fluid transfer hose, pipe or conduit between vessels in
harsh open ocean conditions. Other `in-water` bottom founded
systems have been conceptualized, as well as a variety of platform
based concepts, all of which utilize either loading arms or aerial
hoses, but have the same problems or concerns as stated above.
[0009] More recently, the industry has renewed interest in floating
hose based transfer systems, particularly for cryogenic fluids, and
has started development work. The appeal of a floating hose based
system is that it mimics tandem ship-to-ship oil transfer systems,
which are well understood and have a long, well proven history of
safe, successful operation in relatively benign environments.
Several significant concerns exist for any floating hose system for
cryogenic fluid transfer. Hose manufactures have only recently
begun work to explore ways to retrieve/deploy the hose between
liftings, but difficulties remain with all of these concepts. In
particular, the means of lifting the hoses out of the water and
connecting them to the floating transport vessel manifold and
supporting them during the transfer operation is problematic and
has yet to be defined. Moreover, how to manage the hoses during an
emergency disconnect is likewise unresolved.
[0010] For floating hose based oil transfer systems, a
deployment/retrieval system capable of operating in harsher open
ocean environments and capable of connecting to a standard
carrier's midship manifold would significantly improve operability
and safety while also elevating terminal berth availability.
[0011] What is required is a fluid transfer system that provides
safe operation, high berth availability, universal applicability,
regardless of ship design and features, and convenient conduit
handling methods for offshore fluid transfer between floating
vessels.
SUMMARY OF THE INVENTION
[0012] The present invention achieves the advantage of a system
that enables fluid transfer between floating vessels in open sea
conditions.
[0013] In an aspect of the invention, a transfer vessel includes: a
floating vessel having a vertical portion; a fluid conduit disposed
on the floating vessel; and a mooring device connected to the
vertical portion for releasably mooring the transfer vessel to a
surface of a second vessel, wherein the mooring device is capable
of dampening the relative motions between the floating vessel and
the second vessel.
[0014] In another aspect of the invention, a product transfer
system includes: a first vessel; a transfer vessel comprising: a
floating vessel having a vertical portion; a fluid conduit disposed
on the floating vessel and in fluid communication with the first
vessel; and a mooring device connected to the vertical portion for
releasably mooring the transfer vessel to a surface of a second
vessel, wherein the mooring device is capable of dampening the
relative motions between the floating vessel and the second
vessel.
[0015] In another aspect of the invention, a process for
transferring a product between a first vessel and a second vessel
includes: mooring a transfer vessel to a surface of a second vessel
with a mooring device capable of dampening the relative motions
between the transfer vessel and the second vessel; connecting a
fluid conduit on the transfer vessel to the second vessel; and
flowing product between the first vessel and the second vessel
through the fluid conduit.
[0016] In another aspect of the invention, a transfer vessel
includes: a floating vessel having a vertical portion; a fluid
conduit disposed on the floating vessel; and a mooring device
connected to the vertical portion for releasably mooring the
transfer vessel to a surface of a second vessel such that when the
transfer vessel is moored to a second vessel a portion of the
transfer vessel does not contact a bottom surface of the second
vessel.
[0017] In another aspect of the invention, a process for
recirculating a fluid product includes: mooring a transfer vessel
to a surface of a product vessel with a mooring device capable of
dampening the relative motions between the transfer vessel and the
product vessel; connecting a fluid conduit on the transfer vessel
to the product vessel; and recirculating the fluid product through
the fluid conduit and the product vessel.
DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 illustrates an embodiment of the invention, showing a
fluid floating storage vessel with attached conduits, and with an
associated transfer vessel parked (releasably moored) on the stern
of the fluid floating storage vessel for supporting the conduits
between fluid transfers.
[0019] FIG. 2 illustrates a fluid floating storage vessel and a
fluid floating transport vessel in a tandem ship-to-ship mooring
arrangement, with conduits and the transfer vessel in place for
transferring a fluid from the transport vessel thru the transfer
vessel and onto the storage vessel, or from a storage vessel thru
the transfer vessel and onto the transport vessel.
[0020] FIG. 3 illustrates a transfer vessel releasably moored to a
fluid floating transport vessel and an articulated hard pipe
loading arm connected to the transport vessel mid-ship
manifold.
[0021] FIG. 4 illustrates a transfer vessel releasably moored to a
fluid floating transport vessel and an aerial pipe based transfer
system connected to the transport vessel mid-ship manifold.
[0022] FIG. 5 illustrates two transfer vessels releasably moored
with a fluid floating transport vessel.
[0023] FIG. 6 illustrates one transfer vessel releasably moored
with one transport vessel and another transfer vessel releasably
moored to another transport vessel.
DETAILED DESCRIPTION OF THE INVENTION
[0024] In this disclosure, the term fluid refers to liquefied
natural gas, liquefied heavy gas, liquefied petroleum gas, crude
oil, diesel, syncrude, petroleum condensate, synthetic lube oil,
naphtha, methanol and mixtures of the same.
[0025] Liquefied natural gas (LNG) is a cryogenic fluid comprising
predominately methane (C1) with decreasing amounts of C2+
hydrocarbons, and is sufficiently cold to remain liquid at near
atmospheric pressures. Liquefied heavy gas (LHG) is a cryogenic
fluid comprising predominately C1 hydrocarbons, with lesser amounts
of C2's thru C4's, and with decreasing amounts of C5's+
hydrocarbons, but requires pressurization (often between 500 and
750 psig) to remain liquid at temperatures well above that of LNG.
Liquefied petroleum gas (LPG) is a near-cryogenic fluid comprising
predominately C3 and C4 hydrocarbons, which can either be
refrigerated to remain liquid at near atmospheric pressures or
pressurized to remain liquid at atmospheric temperature. All of the
above mentioned fluids can be transferred in the process and in the
system of this invention.
[0026] In the following embodiments of the invention, a fluid is
transferred between floating vessels designed for handling,
processing, storing and/or transporting the fluid.
[0027] In an embodiment, one of the vessels is a transportation
vessel for transporting the fluid from one location, such as a
location where the fluid is prepared, to a second location, such as
near to or connected with a market site for the fluid. A second
floating vessel may be a floating storage vessel for the fluid,
located at or near the site where the fluid is prepared, or at or
near the site where the fluid is delivered to a market. Further,
the second floating vessel may have on-board facilities for
processing the fluid, adding heat to regassify the fluid, and
optionally for preparing the fluid for passage into a delivery
system such as a pipeline for transport to a market location.
[0028] In another embodiment, the fluid is transferred between a
floating transportation vessel and a fixed deepwater assembly, for
delivering the fluid to a land-based facility. The fixed assembly
for delivering the fluid is anchored to the bottom of the seafloor
to make it sufficiently stationary and robust for locating in the
sea.
[0029] In another embodiment, the fluid is transferred between a
transportation vessel, a storage vessel, and another transportation
vessel. The one transportation vessel is specifically designed for
transporting the fluid from one location to the storage vessel
under peculiar circumstances, for example thru sheet ice, and the
other transportation vessel is for transporting the fluid from the
storage vessel to a second location under different circumstances,
for example such as high speed trans-Atlantic service, near to or
connected with a market site for the fluid.
[0030] More specifically, at least one transfer vessel is utilized
in the above embodiments to allow fluid transfer between the
floating vessels designed for handling, processing, storing and/or
transporting the fluid. In one embodiment, the transfer vessel is
"parked" at the stern of a floating storage vessel and supports the
first end of a conduit. Prior to arrival of the floating transport
vessel, the transfer vessel moves away from the floating storage
vessel with the conduit, which allows the floating transport vessel
to tandem moor to the floating storage vessel by a conventional
hawser system. The transfer vessel moves to the floating transport
vessel and moors along side at the midship manifold utilizing a
releasable mooring system. The releasable mooring system comprises
at least one of an air vacuum pad mooring system, a water vacuum
pad mooring system and an electromagnetic pad mooring system. With
the transfer vessel securely moored to the floating transport
vessel, the relative motions between the vessels can be dampened
and controlled by hydraulics in the releasable mooring system.
Conventional articulated loading arms could be utilized to attach
to the midship manifold. Alternatively, a crane could be provided
on the transfer vessel to deploy aerial flexible pipes (hoses) and
connect them to the midship manifold, then control and retrieve
them.
[0031] Once fluid transfer operations are completed, the
articulated arms or aerial pipes (hoses) are disconnected from the
midship manifold and retrieved, and the releasable mooring system
is released without the need for ballasting the transfer vessel.
The transfer vessel then backs away from the floating transport
vessel, which un-berths and departs, at which point the transfer
vessel moves back into the "parked" position on the stern of the
floating storage vessel. In the "parked" position, the transfer
vessel moors at the stern of the floating storage vessel utilizing
the releasable mooring system. The fluid transfer system can be
connected to the storage vessel and maintained in a "ready to
operate" state at normal pressures and/or temperatures as
appropriate. Alternately, the fluid transfer system can be cross
connected on the transfer vessel and fluids recirculated back to
the storage vessel via a conduit and thus maintained in a "ready to
operate" state at normal pressures and/or temperatures as
appropriate. In the case of cryogenic fluids, either arrangement
can be utilized to recirculate the fluid to maintain cryogenic
temperatures and preclude boil off gas generation, or the system
can remain static (no flow) and boil off gas collected and vented
or routed to a safety system.
[0032] Reference is now made to an embodiment of the invention
illustrated in FIG. 1. In FIG. 1, a fluid storage vessel (5) is
moored by a single point mooring turret (10). The turret is
anchored to the sea floor via anchor lines (15). A transfer vessel
(20), which is positioned on the stern of the storage vessel (5),
supports one end of a multiplicity of conduits (25). The other end
of the conduit (25) is supported on the storage vessel (5).
According to the invention, the conduits (25) are for use in
delivering a fluid to (or from) the storage vessel (5).
Conduit
[0033] FIG. 1 illustrates a conduit assembly comprising a
multiplicity of flexible catenary conduits (25), each supported at
one end by a support connection means (30) on a storage vessel (5)
and further supported at the other end by a support connection
means (35) on a transfer vessel (20). In this way, each flexible
conduit, having a catenary configuration, is substantially
submerged in the body of water below mean water level (50), with
one end of the conduit being supported out of the water by the
storage vessel (5) and the other end of the conduit being supported
in the water below the wave zone by the transfer vessel (20).
Alternately, the other end of the conduit could be supported out of
the water by the transfer vessel (20). Any number of conduits,
including a single conduit, is encompassed within the broad
specification of this invention. In the example of LNG transfer, it
is desirable to have at least one cryogenic liquid delivery conduit
and at least one vapor return conduit.
[0034] Although a subsea catenary conduit is illustrated in FIG. 1,
it is also possible to use a multiplicity of flexible surface
floating conduits to accomplish fluid transfer from the transport
vessel, thru the transfer vessel and onto the storage vessel, or
visa-versa. The floating conduits would be stored on reels on the
storage vessel, and permanently connected to the storage vessel
fluid system by piping and swivels. The conduit would be further
supported at the other end by a support connection means on the
transfer vessel.
[0035] Another embodiment of the conduit includes a multiplicity of
conduits (for example pipes) supported by a floating (or submerged)
jetty or arm that connects the storage vessel to the transfer
vessel. The jetty or arm would be articulated at the stern of the
storage vessel, and would simply trail behind the storage vessel
when not in use. The jetty or arm would propel itself to the side
of the storage vessel and out of the way to allow a transport
vessel to hawser moor to the storage vessel, after which it would
move into position at the mid-ship manifold and moor to the
transport vessel with the releasable mooring system.
Floating Storage Vessel
[0036] In FIG. 1, each conduit is supported by attachment to a
connection means (30) on the fluid floating storage vessel (5).
Storage vessels of this type are identified by one of a number of
terms, such as a Floating Storage & Regas Unit (FSRU) vessel, a
Floating Liquefied Natural Gas (FLNG) vessel, or a Floating
Production, Storage and Offloading (FPSO) vessel, or a Floating
Storage and Offloading (FSO) vessel. In one embodiment, each
conduit is supported on the storage vessel, and passes thru a hawse
pipe thru a double wall ballast tank. The hawse pipe arrangement
mitigates concerns with wave loadings on the conduit as it exits
the storage vessel well below the high energy wave zone. Use of the
hawse pipe configuration also provides an opportunity to install
articulated loading arms on the storage vessel. This allows
side-by-side fluid transfers should periods of mild metocean
conditions exist, and also provides a back-up system should the
fluid transfer system of this invention be unavailable.
[0037] The connection means for attaching the conduit to the
storage vessel may be located on the midship manifold, which is
intended for delivering the fluid to various tanks in the storage
vessel. Any connection means with which the storage vessel is
supplied is suitable for use in the present invention. Example
connection means which are useful include a flanged connector or a
quick connect/disconnect coupling. An in-line swivel is desirably
provided on each hose to allow the hose to rotate, thus eliminating
any torsional concerns imparted in the hose during connection,
during use, or during transfer from one vessel to another.
Floating Transfer Vessel
[0038] In one embodiment, one end of the conduit remains connected
to the floating storage vessel and the other end of the conduit
remains connected to the connection means of the transfer vessel
during a sequence of fluid transfer operations. In this case, one
step in the process of the invention involves mooring the transfer
vessel with the floating transport vessel for transfer of the fluid
from one vessel to another. As shown in FIGS. 1-4, the conduit is
supported at its first end by the storage vessel (5). A transfer
vessel (20) is further positioned near the storage vessel (5) for
supporting the conduit with its connection means (35) at its second
end. The transfer vessel is also provided with releasable mooring
means (36), a booster pump (37), and a dynamic positioning thruster
(38)
[0039] The connection means of the transfer vessel may be a hard
pipe with its first end at the top of the transfer vessel and its
second end protruding well below the wave zone. The conduit is
connected to the second end of the connection means and a flexible
aerial hose/pipe (41) or an articulated hard pipe loading arm (42)
is connected to the first end of the connection means. Although a
catenary conduit is illustrated as being connected to the second
end of the connection means in this embodiment, it is also possible
to use a floating hose.
[0040] The releasable mooring means may be one or any combination
of an air vacuum pad mooring system, a water vacuum pad mooring
system and an electromagnetic pad mooring system. The mooring means
is connected to a vertical portion of the transfer vessel and is
utilized for releasably mooring the transfer vessel to a surface of
transport or storage vessel. In the moored position, the transfer
vessel does not contact or pass under a bottom surface of a vessel
to which it is moored. The mooring device is capable of dampening
the relative motions between the transfer vessel and the vessel to
which it is moored. An exemplary releasable mooring means can be
provided by the MoorMastert system, which is commercially available
from Cavotec MoorMaster Ltd., Christchurch, New Zealand.
[0041] Once the transfer vessel is along side the transport
vessel's midship manifold, the releasable mooring means is
activated and the transfer vessel becomes securely attached
(moored) to the side of the transport vessel. Once securely moored,
the relative motions between the vessels can be dampened and
reduced in magnitude, but can be monitored, controlled, adjusted
and optimized via the hydraulic control system. Thus, articulated
loading arms may be conveniently attached to the midship manifold
without the need for modifications to the standard transport
vessel. Alternatively, a crane (40) may be provided to deploy
flexible aerial pipes (hoses) and attach them to the midship
manifold. Thus, flexile aerial pipes (hoses) may be conveniently
attached to the midship manifold without the need for modifications
to the standard transport vessel.
[0042] Two types of emergency systems are utilized in this
invention. First, an Emergency Release System (ERS) is part of the
loading arms, and is utilized to release the bulk of the arm from
the ship in an emergency situation. One block valve and the QC/DC
stays on the ship manifold flange and must be retrieved later.
Second, the transfer vessel mooring system includes an emergency
release system to disengage the moorings so that the transfer
vessel can disengage and depart from the transport vessel. It would
be timed such that the transfer vessel disengages after the fluid
transfer ERS has released the loading arm (or flexible hose) and it
has retracted out of the way. This allows the floating transport
vessel to depart under the emergency conditions while minimizing
the potential for damage to the transport vessel, the transfer
vessel or the fluid conduits.
[0043] The transfer vessel provides a platform to install a valve
manifold being connected to the plurality of conduits. An exemplary
use of the valve manifold is that liquid product and vapor return
can be directed to the correct fluid path and manifold flange on
the product transport vessel. Another exemplary use of the valve
manifold is that it is capable of directing a flow back to the
storage vessel between loadings or should there be idle periods
during fluid transfer operations.
[0044] Also, the liquid booster pump could be installed on the
transfer vessel to assist in overcoming frictional losses in the
system, to mitigate boil off gas generation, or to increase product
transfer flowrates and reduce overall product transfer durations;
thus negating the need to upgrade each product transport vessel
with higher capacity pumps, or to operate at reduced flowrates.
[0045] The dynamic propulsion thruster system is provided to propel
the transfer vessel between the storage vessel and the transport
vessel, and to assist in mooring the transfer vessel to the
transport vessel. It could also be utilized to reduce the
longitudinal loading on the releasable mooring system by
counteracting the longitudinal environmental loads on the transfer
vessel. The thruster may be powered via an auxiliary power line
from one of the other vessels.
[0046] The transfer vessel may be a vertical semi-submersible
vessel, having ballast, particularly designed for the purpose
described. Otherwise, the transfer vessel may be any other form of
service boat, offshore supply vessel or other type of vessel with
sufficient stability and capacity to meet the service duty.
Floating Transport Vessel
[0047] FIG. 2 illustrates a fluid floating transport vessel (105)
in tandem ship-to-ship mooring arrangement with a storage vessel
(5). The fluid storage vessel (5) is moored by a single point
mooring turret (10), which is anchored to the sea floor via anchor
lines (15). Transport vessels of this type are identified by one of
a number of terms, such as a crude oil carrier, a refined product
carrier, an LNG carrier (LNGC), an LNG ice-breaking carrier and an
LPG carrier. The floating transport vessel may be any sea-going
vessel equipped to transport a fluid, such as a liquefied natural
gas or liquefied petroleum gas, from a production or storage site
to the storage vessel. The transport vessel is generally equipped
with a midship manifold. In the practice of the invention,
according to the embodiment illustrated in FIG. 2, the transport
vessel is attached to the storage vessel (5) by a hawser (110).
Such an arrangement permits the storage vessel and the transport
vessel to move independently to some degree in response to wave
action and the wind, while maintaining the general tandem
configuration.
[0048] After the transport vessel is positioned and secured to the
storage vessel, the transfer vessel moves into place and moors to
the transport vessel with the releasable mooring system. Then
articulated loading arms or flexible aerial pipes (hoses) from the
transfer vessel are connected to the midship manifold to allow
fluid transfer to commence. During the fluid transfer, the transfer
vessel remains unified with the transport vessel.
OTHER EMBODIMENTS
[0049] FIG. 5 illustrates a mooring barge (7) and with two
associated transfer vessels (20) (one and two) parked (releasably
moored) on the mooring barge (7) for supporting conduits (25)
between fluid transfers. Also, as shown, an auxiliary power line
(111) may be connected between the mooring barge (7) and at least
one of the transfer vessels (20). The auxiliary power line (111)
may supply additional power to the transfer vessel (20), i.e. for
the liquid booster pump (37), the dynamic propulsion thruster
system (38), etc.
[0050] FIG. 6 illustrates a mooring barge (7) and a second and a
third fluid floating transport vessel (105) in tandem ship-to-ship
mooring arrangement, with conduits (25) and a first and a second
transfer vessel (20) in place for transferring a fluid from the
second transport vessel (105) thru the first transfer vessel (20)
to the second transfer vessel (20) and onto the third transport
vessel (105), and possibly onto the mooring barge (7). Alternately,
the fluid could be transferred from the third transport vessel
(105) thru the second transfer vessel (20) to the first transfer
vessel (20) and onto the second transport vessel (105), and
possibly onto the mooring barge (7). Also, as shown, an auxiliary
power line (111) may be connected between the mooring barge (7) and
at least one of the transfer vessels (20). The auxiliary power line
(111) may supply additional power to the transfer vessels (20),
i.e. for the liquid booster pump (37), the dynamic propulsion
thruster system (38), etc.
* * * * *