Note: Descriptions are shown in the official language in which they were submitted.
CA 02544222 2006-04-20
SEA VESSEL DOCKING STATION
Background of the Invention
The present invention relates generally to offshore oil and gas exploration
and
production systems, and in a specific, non-limiting embodiment, to a system
and
method of capturing, lifting and coupling a plurality of sea vessels using a
centralized
wet docking station, so that relative deck sizes are effectively increased,
and
equipment packages and other facilities are exchanged between the decks of
captured
vessels in a stable and efficient manner.
Background of the Invention
Innumerable systems and methods have been employed in efforts to find and
recover hydrocarbon reserves around the world. At first, such efforts were
limited to
land operations involving simple but effective drilling methods that
satisfactorily
recovered reserves from large, productive fields. As the number of known
producing
fields dwindled, however, it became necessary to search in ever more remote
locales,
and to move far offshore, in the search for new resources. Eventually,
sophisticated
drilling systems and advanced signal processing techniques enabled energy
companies to search virtually anywhere in the world for recoverable
hydrocarbons.
Initially, deepwater exploration and production efforts consisted of
expensive,
large scale drilling operations supported by tanker storage and transportation
systems,
due primarily to the fact that most offshore drilling sites are associated
with difficult
and hazardous sea conditions, and thus large scale operations provided the
most stable
and cost-effective manner in which to search for and recover hydrocarbon
reserves. A
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major drawback to the large-scale paradigm, however, is that explorers and
producers
have little financial incentive to work smaller reserves, since potential
financial
recovery is generally offset by the lengthy delay between exploration and
production
(approximately 3 to 10 years), and by the large capital investment required
for
conventional platforms and related drilling, production and transportation
equipment.
Moreover, complex regulatory controls and industry-wide risk aversion have led
to
standardization, leaving operators with few opportunities to significantly
alter the
prevailing paradigm. As a result, offshore drilling operations have
traditionally been
burdened with long delays between investment and profit, excessive cost
overruns,
and slow, inflexible recovery strategies dictated by the operational
environment.
More recently, deepwater sites have been found in which much of the danger
and instability usually present in such operations can be avoided. For
example, off
the coast of West Africa, Indonesia and Brazil, potential drilling sites have
been
identified where surrounding seas and weather conditions are relatively mild
and calm
in comparison to other, more volatile sites such as the Gulf of Mexico and the
North
Sea. These recently discovered sites tend to have favorable producing
characteristics,
yield positive exploration success rates, and admit to production using simple
extraction and transportation techniques similar to those employed in dry land
or near-
shore operations.
However, since lognormal distributions of recoverable reserves tend to be
spread over a large number of small fields, each of which yield less than
would
normally be required in order to justify the expense of a conventional large-
scale
operation, most such regions have to date been underexplored and underproduced
relative to their potential. Consequently, many potentially productive smaller
fields
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have already been discovered, but remain undeveloped due to economic
considerations.
Currently, most deep water exploration and production operations are
facilitated by means of a large, expensive floating production and storage
offtake
(FPSO) vessel, which is used to arrange and store essentially all of the
facilities and
equipment packages likely to be required aboard a single ship, with lesser
vessels
being employed only in support roles for purposes such as transporting crews
back
and forth from shore, delivery of new or replacement equipment packages, etc.
As seen in prior art Figure 1, for example, an FPSO system 100 similar to
those presently being employed in the field is depicted, wherein the FPSO
comprises
a large deck surface (e.g., in excess of about 20,000 square feet) capable of
accommodating useful operational structures such as a helicopter pad 101;
officer,
crew and control rooms 102; a water treatment facility 103; one or more fluid
injection pumps 104; one or more oil, gas, sand and water separators 105; a
gas
treatment injection facility 106; a power generator 107; and a gas flare 108.
The FPSO has deck space for uploading additional equipment packages from
other vessels on an as-needed basis, and serves as a central station for the
entire
exploration and production operation. In one common application, the FPSO is
held
in place during operations by a mooring system using a plurality of mooring
lines (not
shown) that are tied off to other vessels, mooring buoys, etc. In alternative
embodiments, the FPSO is moored to a turret, so that it essentially revolves
around a
fixed point; and in a further embodiment, the FPSO is dynamically positioned,
so that
it is allowed to move in response to wave and swell actions, while still being
held in
position relative to the support vessels and drilling sites in the surrounding
area.
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A modern FPSO used to service subsea production wells 110 and/or injection
wells 111 will typically have a keel length of between about 900 and 1,500
feet, with
a storage section 109 having a storage capacity of between about 500,000
barrels and
about four million barrels disposed beneath the ship's deck surface. In
vessels where
the storage volume is essentially zero but all of the other facilities and
equipment
packages necessary for injection and production operations are present, the
vessel is
instead called a floating production unit (FPU).
While relatively effective in deepwater environments, those of ordinary skill
in the art will appreciate that FPSO systems also have several major
drawbacks. For
example, a modern FPSO can take as long as eight to ten years from start-up to
completion before it can be used at sea, and the total cost associated with
manufacturing the vessel can run in excess of one billion dollars.
Moreover, since an FPSO is so large and expensive to manufacture, only very
large field operations (e.g., those producing about 50,000 barrels a day or
more) will
economically justify an operator's investment in such a vessel. Consequently,
a great
many lesser fields (for example, fields have the capacity to yield only about
10,000
barrels a day) are known by explorers to contain reserves, but are not being
worked by
producers because the cost of production using an FPSO would exceed the
profits that
could be obtained from recoverable reserves.
Past efforts to provide simpler, less expensive vessel docking systems include
U.S. Letters Patent No. 853,328 to Wiking, which discloses a pontoon-type
floating
dock, which captures and lifts one or more vessels so as to serve as an
extension of an
attendant dry dock. The Wiking system is deficient, however, in that it is
useful "only
for small vessels," lacks the buoyant capacity to capture and lift vessels of
any
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significant size and weight (which is, of course, a critical aspect of any
modern
exploration and production system), and utterly fails to contemplate the
coupling of
multiple deck surfaces in order to form a larger, unified deck from which
exploration
and production operations can be carried out.
Similarly, U.S. Letters Patent No. 6,336,419 to Breivik discloses a barge
having one or more docking stations formed at either end in which captive
ships can
be docked, but fails to appreciate the advantages of lifting and coupling two
or more
vessels so that their respective deck surfaces are combined into a larger,
unitary
surface from which exploration and production operations can be carried out
with
maximum efficiency and safety.
There is, therefore, a need for a system and method of exploring and
producing offshore wells in such a manner that the functions of two or more
vessels
can be combined to work the wells without interruption, and where a number of
closely disposed sites can be worked simultaneously by a limited number of
such
vessels.
There is also a need for a system and method by which a centralized, floating
docking station provides access to a number of associated deck surfaces
flexibly
capable of meeting the changing needs of operators during exploration and
production, so that the delay between operator investment and profit is
minimized.
There is also a need to provide a substitute for existing floating production
and
storage offtake vessels that admits to safe and reliable transfer of equipment
packages
(e.g., drilling packages, testing packages, production packages, workover
packages,
etc.) between and amongst associated deck surfaces, and for secure vessel
connections
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so that associated deck surfaces can be safely and easily connected and/or
disconnected during operations.
There is also a need to provide a surface vessel arrangement wherein a
plurality of associated deck surfaces are complementary in function, so that
unnecessary delays and undesirable safety conditions are avoided throughout
the
entirety of exploration and production.
Finally, there is a need for vessel capturing, lifting and coupling systems
that
permit older, less expensive and more widely available exploration and
production
vessels to participate in offshore operations by serving as a platform from
which
equipment packages and extracted hydrocarbon reserves are loaded, stored and
transported in a safe, efficient and well-organized manner.
Summary of the Invention
A wet docking station for exploring and producing offshore energy sites is
provided, in which the wet docking station includes at least: a buoyant
central docking
station; an adjustable buoyancy chamber for adjusting the buoyancy of the
buoyant
central docking station; and at least one subordinate docking station for
capturing and
lifting at least one sea vessel.
A method of exploring and producing offshore energy sites using a wet
docking station is also provided, in which the method includes at least:
disposing a
buoyant central docking station in communication with an adjustable buoyancy
chamber, wherein said adjustable buoyancy chamber is used to adjust the
buoyancy of
said buoyant central docking station; and disposing the buoyant central
docking
station in communication with at least one subordinate docking station,
wherein the
subordinate docking station is used to capture and lift at least one sea
vessel.
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Brief Description of the Drawings
Figure 1 is a side view of a floating production and storage offtake vessel
presently known in the prior art.
Figure 2 is a side view of an example wet docking station according to the
invention.
Figure 3 is a rear view of a combined central stabilizer and bumper guard
structure useful with the wet docking station depicted in Figure 2.
Figure 4 is the wet docking station depicted in Figure 3, shown after two
vessels have been captured within the docking station.
Figure S is a rear view of a portion of the docking station depicted in Figure
4,
shown with two ships that have already been captured being lifted and pinched
between a central divider and a plurality of side stabilizers.
Figure 6 is an elevated depiction of a wet docking station according to the
invention.
Figure 7 is an elevated view of a wet docking station having additional
storage
capacity according to the invention.
Figure 8 is a rear view of a wet docking station used to load and offload
equipment, material, supplies, etc., between the decks of captured vessels.
Figure 9 is a front view of a wet docking station having additional storage
capacity and additional deck surface for accommodating and storing equipment
packages, technical facilities, etc.
Figure 10 is a top view of an alternative wet docking system according to the
invention, in which a plurality of individual wet docks are coupled together.
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Figure 11 is a front view of the wet docking station depicted in Figure 10,
wherein vessels of different sizes are shown captured, lifted and coupled
together, so
that associated deck surfaces are combined into a single, unitary whole.
Detailed Description
The present invention is directed to an offshore docking system in which a
number of multifunctional sea vessels are captured, lifted and coupled in a
central
"wet" dock using one or more adjustable buoyancy chambers. For the purposes of
this application, a wet docking station is defined as a docking station
capable of rising
up from beneath sea level to capture and couple one or more vessels, so that
greater
deck and storage space, and a more flexible combination of facilities and
equipment
packages, is achieved.
The buoyancy chambers are generally disposed beneath the hulls of either the
wet docking station or the vessels captured within the dock (or both), so that
the
buoyancy chambers are capable of transmitting a significant lifting force
toward the
bottom of the hulls; however, in some embodiments the adjustable buoyancy
chambers are disposed within the hull of the docking station itself, with
external
buoyancy chambers being added to the system on an as-needed basis.
Once the captured vessels are lifted and secured within the central docking
station, their deck surfaces are then coupled to one another, so that
equipment
packages, technical facilities, etc., can be quickly transferred between the
vessels in a
safe and controlled manner, thereby reducing the risk of accidents and
collisions, as
well as establishing a large combined deck surface from which operations can
be
carried out. Consequently, project time horizons are reduced, and a flexible,
modularized exploration and production system is achieved on a cost effective
basis.
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In the specific, non-limiting embodiment of the invention depicted in Figure
2,
for example, a sea vessel docking station according to the invention comprises
a rib
shaped support hull or other central docking station 200; one or more
adjustable
buoyancy chambers 201, which are held or connected to the bottom of the
docking
station 200 by adjustment control means 202; and one or more vessel capturing
stations 203 used to capture incoming vessels prior to lifting and coupling
them
together.
In practice, adjustable buoyancy chamber 201 and the vessel capturing stations
203 rise up from beneath the hull of a vessel and apply a significant lifting
force,
thereby lifting, supporting and pinching the vessel together in the arms of
the docking
station 200, so that a mutual deck surface can be established between the
newly
captured vessel and other, previously captured vessels in a safe and reliable
manner.
In the depicted embodiment, the depth at which adjustable buoyancy chamber
201 is disposed beneath the wave surface is controlled by an adjustable
control means
202, though in other embodiments adjustable buoyancy chamber 201 is disposed
in
direct communication with support hull 200. In still other embodiments, either
(or
both) of adjustable buoyancy chamber 201 and adjustment control means 202 are
withheld from the system, and support hull 200 is instead equipped with one or
more
buoyancy chambers (such as an internal ballast system), so that the depth of
the
docking station is controlled by either flooding or evacuating the buoyancy
chambers
disposed in support hull 200 with a fluid, such as sea water, pneumatic
pressure
supplied from an outside source, etc.
During this process, the central docking station can be dynamically positioned
with respect to surrounding vessels and buoys (not shown), fixed to a turret
so that the
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station revolves around a mooring, or simply tied off to suction anchors 204
or the
like using one or more sets of mooring lines 205.
As seen in the example embodiment depicted in Figure 3, portions of the
central docking station 300 comprise a divider 301 disposed between the
capturing
stations, so that captured vessels cannot collide or transmit wave forces
toward other
vessels captured in the docking station 300. In other embodiments, outer
portions of
divider 301 and the inner portions 302 of the capturing stations are fitted
with ship
bumpers 303 or the like, so that captured vessels can be lifted and pinched
against the
bumpers 303 by, for example, tying off the vessel against the bumpers using
ropes or
chains, or by inwardly pivoting an arm of the station about a pivoting member
305.
In a further embodiment, captured vessels are lifted and held in place against
the ship bumpers 303 by means of an adjustable buoyancy chamber 304. In cases
where the captured vessels are of significantly different sizes, an adjustable
buoyancy
chamber 304 disposed in the capturing station can be used to lift the decks of
the
vessels to a similar elevation, so that a mutual deck surface can be
established
between them, and equipment packages and the like can be transferred from ship
to
ship.
As seen in the example embodiments depicted in Figures 4 and 5, however,
vessels of similar size and dimensions 401, 402 and 501, 502, respectively,
can be
captured and controlled in such a manner that adjoining deck surfaces are
disposed in
a relatively even and level plane without requiring a secondary buoyancy
chamber to
lift either vessel. In such embodiments, portions 400, 500 of the docking
station will
still comprise primary buoyancy chambers used for raising the station up from
beneath the vessels and initiating the capturing process, and for sinking the
station
CA 02544222 2006-04-20
back into the sea so that captured vessels can be maneuvered away to make room
for
other, newly acquired vessels.
Turning now to the detailed, non-limiting embodiment depicted in Figure 6, a
wet docking station 600 according to the invention is shown which illustrates
how
two or more vessels can be captured, lifted and coupled in the station so that
a unitary,
multifunctional, sea-worthy vessel is created for furthering an exploration
and
production operation.
A principle advantage of the system is that the total deck surface area of a
smaller vessel 601 can effectively be increased by adding the deck surface
area of a
second, adjoining vessel 602 that has been captured, lifted and coupled to the
first
vessel 601. For example, if first captured vessel 601 has a working deck space
of
about 150 in length and about 50 feet wide, then the total available workspace
on that
vessel is about 7,500 square feet. Likewise, if second captured vessel 602 has
a
working deck space of about 200 feet in length and 70 feet wide, then the
total
available workspace is about 14,000 square feet. By lifting and coupling the
two
vessels together, however, a total available working deck space of about
21,500
square feet (7,500 plus 14,000) is achieved.
In this particular example embodiment, first captured vessel 601 is equipped
with one or more of a power generator 603; a water treatment facility 604; a
water
injection package 605 with attendant water injection lines 617; and a crew
housing
and control unit 606. Those of ordinary skill in the art will appreciate,
however, that
virtually any number of other packages, production and storage units, stacks
of riser
or drilling equipment, etc., can instead be disposed on the first vessel.
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While such a vessel would be helpful for supporting an existing exploration
and production project, it lacks many of the structures and technical packages
necessary to initiate and complete an ongoing operation. For example, first
captured
vessel 601 lacks an oil and gas separator, gas compression and injection
units, an oil
treatment unit, and many other facilities and packages customarily found on
floating
storage and offtake vessels that might prove useful during operations.
According to
the invention, therefore, a second vessel 602 is captured, raised to an
essentially equal
deck height as the first vessel, and then coupled to either the first vessel
or the
docking station so that personnel can safely and reliably enjoy the advantages
of both
vessels simultaneously, even as the two coupled vessels and the docking
station
proceed as a single, unitary whole.
In the depicted embodiment, for example, captured second vessel 602 further
comprises a helicopter pad 607; a gas compressor 608 having attendant gas
injection
lines 616; oil, gas and/or water separators 609; a gas treatment unit 618; an
oil
treatment unit 610; a gas flare boom 611; and a plurality of oil production
lines 615.
In one embodiment, the vessel is controlled by ballasting at least part of the
docking
station down into the sea, and then floating the vessel over the docking
station 600 so
that it can be captured and raised to the deck height of the first vessel.
Alternatively,
at least part of the docking station 600 is ballasted down into the sea, moved
beneath
the hull of the vessel intended for capture, and then raised, so that the
vessel is now
securely held in the dock, and the facilities and packages disposed thereupon
can be
used by operators in conjunction with the facilities and packages disposed on
the first
captured vessel 601.
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In this particular embodiment, since all of the technical facilities and
equipment packages necessary to carry out operations in a typical exploration
and
production project are provided, it might not be necessary for any other
vessels to be
brought in with additional equipment in order to complete the operation.
However,
should it turn out that additional facilities or packages are in fact
required, one (or
both) of the vessels presently captured in the station can be released, and a
third ship,
a fourth ship, and so on, can be captured and employed to achieve the
advantages of
their technical configurations.
In this embodiment, the station releases a captured vessel by employing a
protocol that is essentially the reverse of the capturing process. For
example, if it is
desirable to release second captured vessel 602 from the station for some
reason, at
least part of the station beneath the vessel is ballasted down until the
vessel is free of
the frictional forces holding the vessel between central stabilizer 613 and
side docking
ribs 614; the vessel is then moved out of the station under its own power,
towed out of
the station using a support vessel, or simply held in place using either a
tethering
system or dynamic positioning techniques while the station is moved out from
under
the vessel.
In the example embodiment of Figure 7, a barge-like storage tank 700 is
equipped with a ribbed hull docking station comprising a central stabilizer
701 and a
plurality of side stabilizers 702, which define a first vessel docking port
703 and a
second vessel docking port 704, as described above with respect to various
other
embodiments. In this embodiment, however, a large fluid storage facility 705
is also
provided, wherein about 500,000 barrels of fluid can be stored during
production, and
then discharged into a tanker when its storage capacity has been reached or is
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otherwise convenient for operators. The entire docking station, or,
alternatively, part
of the docking station can be submerged beneath sea level 705 at any given
time, so
long as the station remains sufficiently stable to accommodate the lifting and
coupling
of captured vessels.
As mentioned, it may at times be desirable to replace or remove equipment
packages disposed on one or more of the vessels captured in the station. Thus,
Figure
8 depicts another embodiment of a sea vessel docking station according to the
invention, wherein the system's improved loading and offloading capabilities
are
emphasized.
As in previous embodiments, an offshore wet dock 800, within which a
plurality of vessels 801, 802 are captured, is provided, comprising two or
more
docking stations formed by a plurality of docking station inner surfaces 807,
808 and
a plurality of lockable, pivoting side stabilizers 805, 806. The buoyancy of
wet dock
800 is controlled by either an external buoyancy chamber, or by one or more
internal
ballast chambers used to either improve or retard the dock's buoyancy
characteristics,
depending on whether water or another fluid is being pumped into or evacuated
from
the ballast chambers. Those of ordinary skill in the art will appreciate that
such
ballast chambers satisfy the definition of the term "adjustable buoyancy
chamber"
within the context of claimed design.
In such embodiments, the functionality of secondary buoyancy chambers 809,
810 can be replaced by a more conventional, mechanical lifting system (not
shown)
without departing from the scope of the invention. Other presently
contemplated
methods of leveling captured vessels' decks include holding the height of one
of the
deck surfaces in a static position while raising the deck surface of a second
vessel,
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and/or holding one of the deck surfaces at a static height and then lowering
the deck
surface of the other vessel. Since many ships already include ballast systems
that
admit to the raising and lowering of a deck surface by raising or lowering the
profile
of the entire vessel, it is also possible to utilize that functionality and
avoid the need
for a secondary lifting system contained within the docking station in order
to level
the deck surfaces of captured vessels.
In this particular embodiment, wet dock 800 is further equipped with a
docking station connecting member 811, comprised of one or more vertical
support
members 812, a conveyer belt and roller assembly 813, and, in the depicted
embodiment, a spool for winding and unwinding cable or chain, etc., in
response to
winch system 814, 817, which feeds its line over pulley 816 so that cargo or
equipment package 815 can be transferred from the deck of captured vessel 802
down
onto the surface of conveyer belt and roller assembly 813. The cargo or
equipment
package can then be moved closer to the deck surface 818 of captured vessel
801, or
else moved on board the deck surface 818 of captured vessel 801, so that
operators
can begin to use the equipment package 815 while captured vessel 802 is
allowed to
leave the docking station.
In a detailed example of this embodiment, captured vessel 802 has a testing
package aboard that is useful in conjunction with an exploration package
stored on
vessel 801. By coupling the raised deck surface of vessel 802 with the lower
deck
surface of the docking station 800, the testing package is transferred down
onto the
deck surface of the docking station by means of an elevated winch and pulley
system,
a hoist, or a small crane or the like. Continuing the process, vessel 802 is
then
CA 02544222 2006-04-20
removed from the docking station, and a third ship is captured and raised in
its place,
so that additional equipment can be transferred onto the deck of docking
station 800.
As seen in the example embodiment of Figure 9, a larger intermediate deck
surface 907 disposed above the entirety (or part) of the docking station hull
900 will
result in the creation of a large, stable platform surface having a total area
greater than
even the combined deck surfaces 908, 909 of the captured vessels 901, 902 from
which additional operations can be carned out. In some embodiments, a portion
of
wet dock 900 is large enough to serve as a fluid storage container, which can
be fully
or partially submerged beneath sea level until such time as a transfer of
stored fluids
becomes either desirable or necessary (e.g., in the case where the storage
container
becomes full of stored fluid during the course of operations).
In the example embodiment depicted in Figure 10, the general-purpose hull of
the prior embodiments is replaced with a floating frame 1000, within which an
individual vessel can be captured. Additional floating frames 1001, 1002, each
of
which house other captured vessels 1003, 1004, are then connected to the first
floating
frame 1000 using a known connecting means 1006 (e.g., ship bumpers, connecting
rods, etc.), so that the resultant structure becomes coupled into a single,
modularized
whole.
In some embodiments, the entire structure is supported by an external
adjustable buoyancy chamber (not shown); in other embodiments, however, the
structure is not supported by a separate buoyancy chamber, and instead relies
on its
own ballast and weighting systems to raise and lower the frames beneath
desired
vessels' hulls prior to capture.
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In still other embodiments (see, for example, Figure 11), after the deck
surfaces of the captured vessels 1103, 1104 are raised to a desired height, a
mutual
deck surface 1111 or other, similar structure is fitted over the topmost
surfaces of
each ship. In this manner, the two vessels 1103, 1104 are coupled, so that
necessary
operations can be carned out while the system continues to safely perform at
sea as a
single unitary structure. For example, once the vessels 1103, 1104 have been
coupled
together, operators can thereafter use all of the various equipment packages
(e.g.,
drilling packages, testing packages, production packages, workover packages,
etc.)
originally stored on the individual ships as if the packages were originally
all present
on a single FPSO.
In practicing the invention, a number of older, less expensive vessels can be
used to duplicate the effectiveness of a far more costly, fully equipped,
modern FPSO
vessel, which in practice is often unavailable on short notice, or infeasible
due to
financial considerations. A principal advantage of the invention in this
respect is that
ships of any size, age and hull design can be captured and coupled in the
docking
station, while the docking station itself proceeds at sea, essentially
performing as an
integrated, unitary housing within which various ships are serviced. Since the
captured ships collectively contain all of the equipment and design packages
required
to satisfy the many different needs of an exploration and production vessel,
piecemeal
assembly of the technical packages required for any particular operation is
achieved,
without the need for a large, expensive, exploration and production vessel
that
contains all of the equipment that might ever be useful in an operation
irrespective of
whether it is actually needed in the application at hand.
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In short, the invention disclosed herein provides a unique system and method
by which a central docking station can capture, lift and couple a plurality of
sea
vessels, so that a flexible, modularized production system is achieved on a
cost
effective basis. The capabilities of a number of older, less expensive vessels
can be
combined to achieve an effective FPSO substitute that allows lower producing
fields
to be explored and produced in a profitable manner. Time horizons between
initiation
and consummation of field operations are reduced, and older vessels that might
otherwise be scrapped or retired are again made useful and seaworthy.
The foregoing specification is provided for illustrative purposes only, and is
not intended to describe all possible aspects of the present invention.
Moreover,
while the invention has been shown and described in detail with respect to
several
exemplary embodiments, those of ordinary skill in the pertinent arts will
appreciate
that minor changes to the description, and various other modifications,
omissions and
additions may also be made without departing from either the spirit or scope
thereof.
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