Note: Descriptions are shown in the official language in which they were submitted.
METHOD USING A FLOATABLE OFFSHORE DEPOT
M0011 Blank.
FIELD
[0002] The presern embodiments generally relate to a method using floluable
offshore
buoyant vessels. platforms, caissons, buoys, spars, or other structures used
lor
supporting offshore oil and gas operations.
BACKGROUN
[00031 Stable olishore depots for supporting offshore oil and gas
operations are known in
The art, Offshore production structures, which con be vessels, platforms,
caissons,
Date Recue/Date Received 2022-05-10
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buoys, or spars, for example, each typically, include a buoyant hull that
supports a
superstructure. The buoyant hull includes internal compartmentalization for
ballasting and storage, and the superstructure provides drilling and
production
equipment, helipads, crew living quarters, and the like.
[0004] In offshore work, on drilling and production platforms for example,
a major
operating cost arises from the transportation of support and supplies from on-
shore
facilities. Nearly everything must be carried by boat or by air. Such supply
lines are
subject to adverse weather and sea states, which have greater effect the
farther the
supplies must travel.
[0005] Accordingly, stable floating structures designed to be towed out to
sea and moored
close to several production platforms within a given field are known in the
art. These
structures may be used to provide shelter for transportation vessels and to
provide
support facilities, including storage, maintenance, firefighting, medical, and
berthing
facilities. Offshore bases, depots, or terminals may provide a reduction in
platform
operating costs, as they would allow safer and more cost effective transport
of
personnel and be supplied from the shore, which can be temporarily staged and
distributed to local platforms. Prior art includes floating offshore support
structure,
which include a sheltered interior for receiving boats.
[0006] A floating structure is subject to environmental forces of wind,
waves, ice, tides, and
current. These environmental forces result in accelerations, displacements and
oscillatory motions of the structure. The response of a floating structure to
such
environmental forces is affected not only by its hull design and
superstructure, but
also by its mooring system and any appendages. Accordingly, a floating
structure has
several design requirements: Adequate reserve buoyancy to safely support the
weight
of the superstructure and payload, stability under all conditions, and good
seakeeping
characteristics. With respect to the good seakeeping requirement, the ability
to
reduce vertical heave is very desirable. Heave motions can create tension
variations
in mooring systems, which can cause fatigue and failure. Large heave motions
increase danger in launching and recovery of small boats and helicopters and
loading
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and offloading stores and personnel.
[0007] The seakeeping characteristics of a floatable offshore depot are
influenced by a
number of factors, including the waterplane area, the hull profile, and the
natural
period of motion of the floating structure. It is very desirable that the
natural period
of the floating structure be either significantly greater than or
significantly less than
the wave periods of the sea in which the structure is located, so as to
decouple
substantially the motion of the structure from the wave motion.
[0008] Vessel design involves balancing competing factors to arrive at an
optimal solution
for a given set of factors. Cost, constructability, survivability, utility,
and installation
concerns are among many considerations in vessel design. Design parameters of
the
floating structure include the draft, the waterplane area, the draft rate of
change, the
location of the center of gravity ("CG"), the location of the center of
buoyancy
("CB"), the metacentric height ("GM"), the sail area, and the total mass.
[0009] The total mass includes added mass i.e., the mass of the water
around the buoyant
hull of the floating structure that is forced to move as the floating
structure moves.
Appendages connected to the structure of the buoyant hull for increasing added
mass
are a cost effective way to fine tune structure response and performance
characteristics when subjected to the environmental forces.
[00010] Several general naval architecture rules apply to the design of an
offshore vessel.
The waterplane area is directly proportional to induced heave force. A
structure that
is symmetric about a vertical axis is generally less subject to yaw forces. As
the size
of the vertical hull profile in the wave zone increases, wave-induced lateral
surge
forces also increase. A floating structure may be modeled as a spring with a
natural
period of motion in the heave and surge directions. The natural period of
motion in a
particular direction is inversely proportional to the stiffness of the
structure in that
direction. As the total mass (including added mass) of the structure
increases, the
natural periods of motion of the structure become longer.
[00011] One method for providing stability is by mooring the structure with
vertical tendons
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under tension, such as in tension leg platforms. Such platforms are
advantageous,
because they have the added benefit of being substantially heave restrained.
However, tension leg platforms are costly structures and, accordingly, are not
feasible for use in all situations.
[00012] Self-stability (i.e., stability not dependent on the mooring
system) may be achieved
by creating a large waterplane area. As the structure pitches and rolls, the
center of
buoyancy of the submerged hull shifts to provide a righting moment. Although
the
center of gravity may be above the center of buoyancy, the structure can
nevertheless
remain stable under relatively large angles of heel. However, the heave
seakeeping
characteristics of a large waterplane area in the wave zone are generally
undesirable.
[00013] Inherent self-stability is provided when the center of gravity is
located below the
center of buoyancy. The combined weight of the superstructure, buoyant hull,
payload, ballast and other elements may be arranged to lower the center of
gravity,
but such an arrangement may be difficult to achieve. One method to lower the
center
of gravity is the addition of fixed ballast below the center of buoyancy to
counterbalance the weight of superstructure and payload. Structural fixed
ballast
such as pig iron, iron ore, and concrete, are placed within or attached to the
buoyant
hull structure. The advantage of such a ballast arrangement is that stability
may be
achieved without adverse effect on seakeeping performance due to a large
waterplane area.
[00014] Self-stable structures have the advantage of stability independent
of the function of
mooring system. Although the heave seakeeping characteristics of self-
stabilizing
floating structures are generally inferior to those of tendon-based platforms,
self-
stabilizing structures may nonetheless be preferable in many situations due to
higher
costs of tendon-based structures.
[00015] Prior art floating structures have been developed with a variety of
designs for
buoyancy, stability, and seakeeping characteristics. An apt discussion of
floating
structure design considerations and illustrations of several exemplary
floating
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structures are known in the industry.
[00016] Various spar buoy designs as examples of inherently stable floating
structures in
which the center of gravity ("CG") is disposed below the center of buoyancy
("CB").
Spar buoy hulls are elongated, typically extending more than six hundred feet
below
the water surface when installed. The longitudinal dimension of the buoyant
hull
must be great enough to provide mass such that the heave natural period is
long,
thereby reducing wave-induced heave. However, due to the large size of the
spar
hull, fabrication, transportation, and installation costs are increased. It is
desirable to
provide a structure with integrated superstructure that may be fabricated
quayside for
reduced costs, yet which still is inherently stable due to a center of gravity
located
below the center of buoyancy.
[00017] Prior art discloses an offshore platform that employs a retractable
center column.
The center column is raised above the keel level to allow the platform to be
pulled
through shallow waters en-route to a deep water installation site. At the
installation
site, the center column is lowered to extend below the keel level to improve
vessel
stability by lowering the center of gravity. The center column also provides
pitch
damping for the structure. However, the center column adds complexity and cost
to
the construction of the platform.
[00018] Other offshore system hull designs are known in the art. Octagonal
hull structures
with sharp corners and steeply sloped sides to cut and break ice for arctic
operations
of a vessel. Unlike most conventional offshore structures, which are designed
for
reduced motions, Srinivasan's structure is designed to induce heave, roll,
pitch and
surge motions to accomplish ice cutting.
[00019] Drilling and production platforms with a cylindrical hull, wherein
the structure has a
center of gravity located above the center of buoyancy and therefore relies on
a large
waterplane area for stability, with a concomitant diminished heave seakeeping
characteristic. Although, the structure has a circumferential recess formed
about the
buoyant hull near the keel for pitch and roll damping, the location and
profile of
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such a recess has little effect in dampening heave.
[00020] It is believed that none of the offshore structures of prior art,
in particular offshore
depots or terminals that are arranged to provide shelter to the boats that are
used for
transportation of supplies and personnel to offshore platforms, are
characterized by
all of the following advantageous attributes: Symmetry of the buoyant hull
about a
vertical axis; the center of gravity located below the center of buoyancy for
inherent
stability without the requirement for complex retractable columns or the like,
exceptional heave damping characteristics without the requirement for mooring
with
vertical tendons, and the ability for quayside integration of the
superstructure and
"right-side-up" transit to the installation site, including the capability for
transit
through shallow waters. An offshore depot or terminal possessing these entire
characteristics is desirable.
[00021] It is believed that none of the offshore structures of prior art,
in particular offshore
depots or terminals that are arranged to provide shelter to the boats that
used for
transportation of supplies and personnel to offshore platforms, are
characterized by
all of the following advantageous attributes: Symmetry of the buoyant hull
about a
vertical axis, the center of gravity located below the center of buoyancy for
inherent
stability without the requirement for complex retractable columns or the like,
exceptional heave damping characteristics without the requirement for mooring
with
vertical tendons, and the ability for quayside integration of the
superstructure and
"right-side-up" transit to the installation site, including the capability for
transit
through shallow waters. An offshore depot or terminal possessing these entire
characteristics is desirable.
[00022] A need exists for an offshore depot that provides kinetic energy
absorption
capabilities from a watercraft by providing a plurality of dynamic movable
tendering
mechanisms in a tunnel formed in the offshore depot.
[00023] A further need exists for an offshore depot that provides wave
damping and wave
breakup within a tunnel formed in the offshore depot.
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[00024] A need exists for an offshore depot that provides friction forces
to a buoyant hull of
a watercraft in the tunnel.
[00025] The present embodiments meet these needs.
BRIEF DESCRIPTION OF THE DRAWINGS
[00026] The detailed description will be better understood in conjunction
with the
accompanying drawings as follows:
[00027] Figure 1 depicts a perspective view of a floatable offshore depot
moored to the
seabed according to one or more embodiments.
[00028] Figure 2 depicts an axial cross-sectional drawing of the buoyant
hull profile of the
floatable offshore depot according to one or more embodiments.
[00029] Figure 3 depicts an enlarged perspective view of the floatable
offshore depot
showing detail of the tunnel, tunnel doors, and a small personnel transfer
boat.
[00030] Figure 4A depicts a top view of a plurality of dynamic moveable
tendering
mechanisms in a tunnel before a watercraft has contacted the dynamic moveable
tendering mechanisms.
[00031] Figure 4B depicts a top view of a plurality of dynamic moveable
tendering
mechanisms in a tunnel as the watercraft contacts the dynamic moveable
tendering
mechanisms.
[00032] Figure 4C depicts a top view of a plurality of dynamic moveable
tendering
mechanisms in a tunnel connecting to the watercraft with the doors closed.
[00033] Figure 5A depicts an elevated perspective view of one of the
dynamic moveable
tendering mechanisms.
[00034] Figure 5B depicts a collapsed top view of one of the dynamic
moveable tendering
mechanisms.
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[00035] Figure 5C depicts a side view of an embodiment of one of the
dynamic moveable
tendering mechanism.
[00036] Figure 5D depicts a side view of another embodiment of the dynamic
moveable
tendering mechanism.
[00037] Figure 6 depicts a perspective view of a boatlift assembly of the
floatable offshore
depot disposed within the tunnel.
[00038] Figure 7 depicts an elevation side view in partial cross section of
the buoyant hull of
the floatable offshore depot, showing baffles for reducing waves within the
tunnel.
[00039] Figure 8 depicts an elevation side view in partial cross section of
the buoyant hull of
the floatable offshore depot according to one or more embodiments.
[00040] Figure 9 depicts a horizontal cross section taken through the
buoyant hull of the
floatable offshore depot showing a straight tunnel formed completely there
through.
[00041] Figure 10 depicts a horizontal cross section taken through the
buoyant hull of the
floatable offshore depot according to one or more embodiments.
[00042] Figure 11 depicts a top view of a Y-shaped tunnel in the buoyant
hull of the floatable
offshore depot.
[00043] The present embodiments are detailed below with reference to the
listed Figures.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[00044] Before explaining the present method in detail, it is to be
understood that the method
is not limited to the particular embodiments and that it can be practiced or
carried
out in various ways.
[00045] The present embodiments relate to a method using a floatable
offshore depot for
supporting offshore oil and gas operations.
[00046] The current method relates to a stable moored floatable offshore
depot, such as
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would be used for safe handling, staging, and transportation of personnel,
supplies,
boats, and helicopters
[00047] The embodiments of the method enable safe entry of a watercraft
into the floatable
offshore depot in both harsh and benign offshore water environments, with 4
foot to
40 foot seas.
[00048] The embodiments of the method prevent injuries to personnel from
equipment
falling off the floatable offshore depot by providing a tunnel to contain and
protect
watercraft for receiving personnel within the floatable offshore depot.
[00049] The embodiments of the method provide the floatable offshore depot
located in an
offshore field that enables a quick exit from the offshore structure by many
personnel simultaneously, in the case of an approaching hurricane, tsunami, or
any
other natural disaster.
[00050] The embodiments of the method provide a means to quickly transfer
many
personnel, such as from 200 people to 500 people safely from an adjacent
platform
on fire to the floatable offshore depot in less than 1 hour.
[00051] The embodiments of the method enable the floatable offshore
structure to be towed
to an offshore disaster and operate as a command center to facilitate in the
control of
a disaster, and can act as a hospital or triage center.
[00052] The embodiments relate to a method using the floatable offshore
depot to provide a
sheltered area using a tunnel for safe and easy launching/docking of
watercraft and
for safe and easy embarkation/debarkation of personnel using an internal dock
side
of a tunnel.
[00053] The additional uses of the floatable offshore depot provide a
sheltered area using a
tunnel for transferring equipment between a watercraft and the floatable
offshore
depot.
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[00054] The floatable offshore depot can have an internal dock side of
tunnel.
[00055] The floatable offshore depot can have a buoyant hull that can be
circular, oval,
elliptical, or polygonal.
[00056] The floatable offshore depot can have: a keel; a main deck; and at
least two
connected sections between the keel and the main deck. The at least two
connected
sections can be joined in a series and symmetrical about a vertical axis.
[00057] The at least two connected sections can extend downwardly from the
main deck
toward the keel. The connected sections can have at least two of: an upper
cylindrical side section, a transition section, and a lower cylindrical
section. The
tunnel, when the floatable offshore depot can be at an operational depth, can
have a
tunnel opening to an exterior of the buoyant hull. The tunnel can be
dimensioned to
receive a watercraft.
[00058] The watercraft can be a ferry, a workboat, a vessel up to 600 feet
in length with or
without propulsion, such as a barge. The watercraft can also be a submarine.
The
watercraft can have different buoyant hull shapes, such as catamaran,
trimaran,
monohull, hovercraft, or even a hydrofoil. The tunnel can receive a dirigible,
also
known as a ZEPPLINTM.
[00059] Now turning to the Figures, Figure 1 illustrates the floatable
offshore depot 10 for
operationally supporting offshore exploration, drilling, production, and
storage
installations according to one or more embodiments.
[00060] The floatable offshore depot 10 is shown floating moored to a
seabed 312. The
floatable offshore depot includes a buoyant hull 12, which can carry a
superstructure
13 thereon. The superstructure 13 can include a diverse collection of
equipment and
structures, such as living quarters for a crew, equipment storage, a heliport,
and a
myriad of other structures, systems, and equipment, depending on the type of
offshore operations to be supported. At least one crane 53 can be mounted to
the
superstructure 13. The buoyant hull 12 can be moored to the seabed by a
plurality of
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catenary mooring lines 16a-16o.
[00061] The superstructure 13 is shown supporting at least one take-off and
landing surface
54a and 54b. The at least one take-off and landing surface 54a and 54b is
shown as a
heliport. The superstructure 13 can include an aircraft hangar 50. In
embodiments,
the aircraft hangar can hold at least one take-off and landing aircraft 400a,
400b, and
400c. A control tower 51 can be built on the superstructure 13. The control
tower
can have a dynamic positioning system 57.
[00062] In this embodiment of the method, the floatable offshore depot 10
can have a tunnel
opening 31 for a tunnel formed in the buoyant hull 12.
[00063] The tunnel opening 31 can receive water while the floatable
offshore depot 10 can be
at an operational depth 71.
[00064] The floatable offshore depot 10 can have at least one closable door
34b.
[00065] In embodiments of the method, the tunnel can be constructed to
provide for selective
isolation of said tunnel from said exterior; whereby the tunnel can be
operable in
either a wet condition or a dry condition while the floatable offshore depot
10 floats
in a body of water.
[00066] The floatable offshore depot 10 can have a unique shape.
[00067] The buoyant hull 12 of the floatable offshore depot 10 can have a
main deck 12a,
which can be circular; and a height H. Extending downwardly from the main deck
12a can be an upper frustoconical portion (shown as a combination of
components).
[00068] In embodiments of the method, the upper frustoconical portion can
have an upper
cylindrical side section 12b. In further embodiments, the upper cylindrical
side
section 12b can extend downwardly from main deck 12a.
[00069] The floatable offshore depot 10 also can have a lower frustoconical
side section 12d
extending downwardly from the upper conical section 12c which can flare
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outwardly. Both the upper conical section 12c and the lower frustoconical side
section 12d can be below the operational depth 71.
[00070] The upper cylindrical side section 12b can connect to a transition
section 12g.
[00071] A lower cylindrical section 12e can extend downwardly from the
lower frustoconical
side section 12d, which can have a matching keel 12f.
[00072] The floatable offshore depot 10 can have at least one fin-shaped
appendage 84a and
84b.
[00073] In embodiments of the method, the floatable offshore depot 10 can
be configured to
transition from a floating orientation having the floating operational depth
71 or a
floating transit depth.
[00074] In embodiments of the method, the floatable offshore depot can be a
seagoing vessel.
[00075] Figure 2 shows that the upper conical section 12c can have a
substantially greater
vertical height H1 than the lower frustoconical section 12d shown as H2. The
upper
cylindrical side section 12b can have a slightly greater vertical height H3
than the
lower cylindrical section 12e shown as H4.
[00076] The upper cylindrical side section 12b can connect to transition
section 12g so as to
provide for a main deck of greater radius than the hull radius and a main deck
which
can be round, square, or another shape. Transition section 12g can be located
above
the operational depth 71.
[00077] A tunnel 30 can have the at least one closable door 34a and 34b
that alternatively or
in combination, can provide for weather and water protection to the tunnel 30.
[00078] Fin-shaped appendage 84 can be attached to a lower and an outer
portion of the
exterior of the buoyant hull.
[00079] The tunnel 30 can have a plurality of dynamic movable tendering
mechanisms 24d
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and 24h disposed within and connected to tunnel sides.
[00080] The tunnel can have a tunnel floor 35 that can accept water when
the floatable
offshore depot can be at the operational depth 71.
[00081] The tunnel floor 35 enables creation of a dry dock environment
within the buoyant
hull 12 when the tunnel 30 can be drained of water.
[00082] The plurality of dynamic movable tendering mechanisms 24d and 24h
can be
oriented above the tunnel floor 35 and can have portions that can be
positioned both
above the operational depth 71 and extend below the operational depth 71
inside the
tunnel 30.
[00083] In an embodiment of the method, the at least one closable door 34a
and 34b can
close over the tunnel opening 31.
[00084] The main deck 12a, the upper cylindrical side section 12b, the
transition section 12g,
the upper conical section 12c, the lower frustoconical side section 12d, the
lower
cylindrical section 12e, and the matching keel 12f can be all co-axial with a
common
vertical axis 100. In embodiments, the buoyant hull 12 can be characterized by
an
ellipsoidal cross section when taken perpendicular to the vertical axis 100 at
any
elevation.
[00085] Due to its ellipsoidal planform, the dynamic response of the
buoyant hull 12 can be
independent of wave direction (when neglecting any asymmetries in the mooring
system, risers, and underwater appendages), thereby minimizing wave-induced
yaw
forces.
[00086] Additionally, the conical form of the buoyant hull 12 can be
structurally efficient,
offering a high payload and storage volume per ton of steel when compared to
traditional ship-shaped offshore structures. The buoyant hull 12 can have
ellipsoidal
walls which can be ellipsoidal in radial cross-section, but such shape can be
approximated using a large number of flat metal plates rather than bending
plates
into a desired curvature. Although an ellipsoidal hull planform is preferred,
a
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polygonal hull planform can be used according to alternative embodiments.
[00087] In embodiments of the method, the buoyant hull 12 can be circular,
oval, or elliptical
forming the ellipsoidal planform.
[00088] An elliptical shape can be advantageous when the floatable offshore
depot can be
moored closely adjacent to another offshore platform so as to allow gangway
passage between the two structures. An elliptical hull can minimize or
eliminate
wave interference.
[00089] The specific design of the upper conical section 12c and the lower
frustoconical side
section 12d generates a significant amount of radiation damping resulting in
almost
no heave amplification for any wave period, as described below.
[00090] The upper conical section 12c can be located in the wave zone. At
operational depth
71, the waterline can be located on the upper conical section 12c just below
the
intersection with the upper cylindrical side section 12b. The upper conical
section
12c can slope at an angle (a) with respect to the vertical axis 100 from 10
degrees to
15 degrees. The inward flare before reaching the waterline can significantly
dampen
downward heave, because a downward motion of the buoyant hull 12 increases the
waterplane area. In other words, the buoyant hull area normal to the vertical
axis 100
that breaks the water's surface will increase with downward hull motion, and
such
increased area can be subject to the opposing resistance of the air and or
water
interface. It has been found that from 10 degrees to 15 degrees of flare
provides a
desirable amount of damping of downward heave without sacrificing too much
storage volume for the vessel.
[00091] Similarly, the lower frustoconical side section 12d dampens upward
heave. The
lower frustoconical side section 12d can be located below the wave zone (about
30
meters below the waterline). Because the entire lower frustoconical side
section 12d
can be below the water surface, a greater area (normal to the vertical axis
100) can
be desired to achieve upward damping. Accordingly, the first diameter DI of
the
lower hull section can be greater than the second diameter D2 of the upper
conical
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section 12c.
[00092] The lower frustoconical side section 12d can slope at an angle (g)
with respect to the
vertical axis 100 from 55 degrees to 65 degrees. The lower section can flare
outwardly at an angle greater than or equal to 55 degrees to provide greater
inertia
for heave roll and pitch motions. The increased mass contributes to natural
periods
for heave pitch and roll above the expected wave energy.
[00093] The upper bound of 65 degrees can be based on avoiding abrupt
changes in stability
during initial ballasting on installation. That is, the lower frustoconical
side section
12d can be perpendicular to the vertical axis 100 and achieve a desired amount
of
upward heave damping, but such a hull profile would result in an undesirable
step-
change in stability during initial ballasting on installation. The connection
point
between the upper frustoconical portion 14 and the lower frustoconical side
section
12d can have a third diameter D3 smaller than the first diameter D1 and second
diameters Dz.
[00094] The floating transit depth 70 represents the waterline of the
buoyant hull 12 while it
is being transited to an operational offshore position. The floating transit
depth is
known in the art to reduce the amount of energy required to transit a buoyant
vessel
across distances on the water by decreasing the profile of floating offshore
depot
which contacts the water. The floating transit depth can be roughly the
intersection
of lower frustoconical side section 12d and lower cylindrical section 12e.
However,
weather and wind conditions can provide need for a different floating transit
depth to
meet safety guidelines or to achieve a rapid deployment from one position on
the
water to another.
[00095] The addition of a ballast to the buoyant hull 12 can be used to
lower the center of
gravity. In embodiments, the floatable offshore depot can have the buoyant
hull with
a low center of gravity 87, the low center of gravity providing an inherent
stability to
the structure.
[00096] In embodiments of the method, the buoyant hull can be characterized
by a positive
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metacenter.
[00097] The floatable offshore depot aggressively resists roll and pitch
and can be said to be
"stiff." Stiff vessels can be typically characterized by abrupt jerky
accelerations as
the large righting moments counter pitch and roll. In particular, the
orientation of the
fixed ballast or fluid ballast increases the natural period of the floatable
offshore
depot to above the period of the most common waves, thereby limiting wave-
induced acceleration in all degrees of freedom.
[00098] In an embodiment of the method, the floatable offshore depot can
have a plurality of
thrusters 99a, 99b, 99c, and 99d for use with dynamic positioning.
[00099] In embodiments, the fin-shaped appendage 84a can have the shape of
a right triangle
in a vertical cross-section, where the right angle can be located adjacent a
lower
most outer side wall of the lower cylindrical section 12e of the buoyant hull
12, such
that a bottom edge 184 of the triangle shape can be co-planar with the
matching keel
12f.
[000100] In embodiments, a hypotenuse of the triangle shape can extend from a
distal end of
the bottom edge 184 of the triangle shape upwards and inwards to attach to the
outer
side wall of the lower cylindrical section 12e.
[000101] The number, size, and orientation of the at least one fin-shaped
appendage can be
varied for optimum effectiveness in suppressing heave. For example, bottom
edge
184 can extend radially outward a distance that can be about half the vertical
height
of the lower cylindrical section 12e, with the hypotenuse attaching to the
lower
cylindrical section 12e about one quarter up the vertical height of the lower
cylindrical section 12e from keel level.
[000102] Alternatively, with the radius (r) of the lower cylindrical section
12e defined as the
first diameter DI then the bottom edge 184 of the at least one fin-shaped
appendage
84a can extend radially outwardly. Although the at least one fin-shaped
appendage
84a is shown, defining a given radial coverage, a plurality of fin-shaped
appendages
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defining more or less radial coverage can be used to vary the amount of added
mass
as required. Added mass can be desirable depending upon the requirements of a
particular floating structure. Added mass however, can be generally the least
expensive method of increasing the mass of a floating structure for purposes
of
influencing the natural period of motion.
[000103] Figure 3 shows the floatable offshore depot 10 with the main deck 12a
and the
superstructure 13 over the main deck.
[000104] The at least one crane 53 is shown mounted to the superstructure 13.
The floatable
offshore depot 10 can include the at least one take-off and landing surface
54b and
Mc, such as heliports which enable the at least one take-off and landing
aircraft
400b and 400c, such as a plurality of helicopters or similar take-off and
landing
aircraft, to take off and land simultaneously on the plurality of take-off and
landing
surfaces, instead of sequentially.
[000105] The term "aircraft" as used herein can be helicopters, short takeoff
and landing craft,
dirigibles, drones, balloons, and similar craft. In embodiments, the aircraft
can be
remote controlled.
[000106] In embodiments of the method, the at least one take-off and landing
surfaces 54b and
54c can each be mounted on pedestals extending from the buoyant hull of the
floating offshore depot. In further embodiments, a pedestal can support the at
least
one take-off and landing surface 54b and 54c.
[000107] In embodiments of the method, the at least one take-off and landing
surfaces 54b and
54c, can be mounted to the main deck 12a or transitioned through the
superstructure
13 in part or in whole, such as an overhang or a supported overhang supported
on the
main deck 12a.
[000108] In this view, a watercraft 200 is in the tunnel having come into the
tunnel through
the tunnel opening 31 and is positioned between the tunnel sides, of which a
first
tunnel side 202 is labeled. A boat lift 41 is also shown in the tunnel, which
can raise
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the watercraft above the operational depth in the tunnel.
[000109] The tunnel opening 31 is shown with two doors, each door having at
least one door
fender 38a and 38b for mitigating damage to a watercraft attempting to enter
the
tunnel, but not hitting the doors.
[000110] In embodiments of the method, the floatable offshore depot 10 can
have the at least
one door fender 38a and 38b positioned at a location that is either: (i)
within the
tunnel to reduce wave action and provide clearance guidance to the watercraft
or (ii)
outside the tunnel opening 31 enabling self-guiding of the watercraft 200 into
the
tunnel or at both locations (i) and (ii) simultaneously while reducing wave
action.
[000111] The at least one door fender 38a and 38b can allow the watercraft 200
to impact the
at least one door fender 38a and 38b safely if the pilot cannot enter the
tunnel
directly due to at least one of large wave and high current movement from a
location
exterior of the buoyant hull 12.
[000112] The floatable offshore depot 10 can have at least one self-guiding
stabbing dock
shape 79.
[000113] The plurality of catenary mooring lines 16a-16o are shown coming from
the main
deck 12a.
[000114] A berthing facility 60 is shown in the buoyant hull 12 in the portion
of the transition
section 12g.
[000115] The transition section 12g is shown connected to the upper conical
section 12c and
the upper cylindrical side section 12b.
[000116] Accommodations 55 are also shown on the superstructure.
[000117] Figure 4A shows the watercraft 200 entering the tunnel 30 between the
first tunnel
side 202 and a second tunnel side 204 and connecting to the plurality of
dynamic
movable tendering mechanisms 24a-24h. Proximate to the tunnel opening can be
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closable doors 34a and 34b which can be sliding pocket doors to provide either
a
weathertight or watertight protection of the tunnel from the exterior
environment. A
starboard side 206 hull of the watercraft and a port side 208 hull of the
watercraft are
also shown.
[000118] Figure 4A shows the tunnel 30 for safe and easy launching/docking of
watercraft 200
and embarkation/debarkation of personnel having an internal dock side 29 which
allows personnel to step off, like a dock, or equipment to be stored.
[000119] The tunnel 30 is also depicted with a lower tapering surface 81 which
can create a
"beach like" effect rising out of the water. Also depicted is the watercraft
200 inside
a portion of the tunnel between the first tunnel side 202 and the second
tunnel side
204 and connecting to the plurality of dynamic movable tendering mechanisms
24a-
24h.
[000120] The at least one closable door 34a and 34b are also shown along with
the watercraft
having the port side 208 and the starboard side 206.
[000121] Figure 4B shows the watercraft 200 inside a portion of the tunnel
between the first
tunnel side 202 and the second tunnel side 204 and connecting to the plurality
of
dynamic movable tendering mechanisms 24a-24h.
[000122] The plurality of dynamic moveable tendering mechanisms 24g and 24h
are shown
contacting the port side 208 hull of the watercraft 200. Dynamic moveable
tendering
mechanisms 24c and 24d are seen contacting the starboard side 206 hull of the
watercraft 200. The at least one closable door 34a and 34b are also shown.
[000123] Figure 4C shows the watercraft 200 in the tunnel between the first
tunnel side 202
and the second tunnel side 204 and connecting to the plurality of dynamic
movable
tendering mechanisms 24a-24h and also connected to a gangway 77. Proximate to
the tunnel opening can be the at least one closable door 34a and 34b which can
be
sliding pocket doors oriented in a closed position providing either a
weathertight or
watertight protection of the tunnel from the exterior environment. The
plurality of
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the dynamic moveable tendering mechanisms 24a-24h are shown in contact with
the
buoyant hull of the watercraft on both the starboard side 206 and the
watercraft port
side 208. A lower tapering surface 81 is also shown.
[000124] Figure 5A shows one of the plurality of the dynamic movable tendering
mechanisms
24a. Each of the plurality of dynamic movable tendering mechanisms can have a
pair
of parallel arms 39a and 39b mounted to the first tunnel side or the second
tunnel
side.
[000125] At least one tunnel fender 45 can connect to the pair of parallel
arms 39a and 39b on
the sides of the parallel arms opposite the first tunnel side or the second
tunnel side.
[000126] A plate 43 can be mounted to the pair of parallel arms 39a and 39b
and between the
at least one tunnel fender 45 and the first tunnel side 202.
[000127] The plate 43 can be mounted above the tunnel floor 35 and positioned
to extend
above an operational depth 71 in the tunnel and below the operational depth 71
in
the tunnel simultaneously.
[000128] The plate 43 can be configured to dampen movement of the watercraft
as the
watercraft moves from side to side in the tunnel. The plate 43 and the entire
plurality
of the dynamic movable tendering mechanism can prevent damage to the ship
hull,
and push a watercraft away from a ship hull without breaking towards the
tunnel
center. The embodiments can allow a vessel to bounce in the tunnel without
damage.
[000129] A plurality of pivot anchors 44a and 44b can connect one of the
parallel arms 39a
and 39b to either tunnel side 202 and 204.
[000130] Each of the plurality of pivot anchors 44a and 44b can enable the
plate 43 to swing
from a collapsed orientation against the tunnel sides to an extended
orientation at an
angle 62, which can be up to 90 degrees from a plane 61 of the wall enabling
the
plate 43 on the one of the pair of parallel arms 39a and 39b and the at least
one
tunnel fender 45 to simultaneously (i) shield the tunnel from waves and water
sloshing effects, (ii) absorb kinetic energy of the watercraft as the
watercraft moves
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in the tunnel, and (iii) apply a force to push against the watercraft keeping
the
watercraft away from the side of the tunnel.
[000131] A plurality of fender pivots 47a and 47b are shown, wherein each of
the plurality of
fender pivots 47a and 47b can form a connection between each of the parallel
arms
39a and 39b and the at least one tunnel fender 45.
[000132] Each fender pivot can allow the fender to pivot from one side of the
parallel arm to
an opposite side of the parallel arm through at least 90 degrees as the
watercraft
contacts the at least one tunnel fender 45.
[000133] A plurality of openings 52a-52ae in the plate 43 can reduce wave
action. Each of the
plurality of openings 52a-52ae can have a diameter from 0.1 of a meter to 2
meters.
In embodiments, the openings 52a-52ae can be ellipses.
[000134] At least one hydraulic cylinder 28a and 28b can be connected to each
parallel arm
for providing resistance to watercraft pressure on the fender and for
extending and
retracting the plate from the tunnel sides.
[000135] Figure 5B shows one of the pair of parallel arms 39a mounted to a
first tunnel side
202 in a collapsed position.
[000136] One of the pair of parallel arms 39a can be connected to one of a
plurality of pivot
anchors 44a that engages the first tunnel side 202.
[000137] At least one of the plurality of fender pivots 47a can be mounted on
the one of the
pair of parallel arms opposite the one of a plurality of pivot anchors 44a.
[000138] The at least one tunnel fender 45 call be mounted to the at least one
of the plurality
of fender pivots 47a.
[000139] The plate 43 can be attached to the one of the pair of parallel arms
39a.
[000140] The at least one hydraulic cylinder 28a can be attached to the
parallel arm and the
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tunnel wall.
[000141] Figure 5C shows the plate 43 with the plurality of openings 52a-52ag
that can be
ellipsoidal in shape. The plate 43 is shown mounted above the tunnel floor 35.
[000142] The plate 43 can extend both above and below the operational depth
71.
[000143] The first tunnel side 202, the plurality of pivot anchors 44a and
44b, the parallel
arms 39a and 39b, the plurality of fender pivots 47a and 47b, the tunnel 30,
and the
at least one fender 45 is also shown.
[000144] Figure 5D shows an embodiment of a dynamic moveable tendering
mechanism
formed from a frame 74 instead of the plate. The frame 74 can have a pair of
intersecting tubulars 75a and 75b that form openings 76a and 76b for allowing
water
to pass while water in the tunnel is at an operational depth 71.
[000145] The first tunnel side 202, the tunnel floor 35, the plurality of
pivot anchors 44a and
44b, the pair of parallel arms 39a and 39b, the plurality of fender pivots 47a
and 47b,
and the at least one tunnel fender 45 is shown.
[000146] Figure 6 depicts a perspective view of a boatlift assembly of the
floatable offshore
depot disposed within the tunnel.
[000147] In one or more embodiments of the method, a boatlift assembly 40 can
be disposed
within tunnel.
[000148] The boatlift assembly 40 can include a boat lift assembly frame 42
carrying chocks
144 that can be positioned and arranged for supporting the watercraft 200. In
an
embodiment, the boatlift assembly frame 42 can be formed of I-beams in a
rectangular shape, which can be approximately 15 meters by 40 meters with a
safe
working load from 200 tons to 300 tons.
[000149] The boatlift assembly frame 42 can be suitable for hoisting a fast
transport unit
("FTU"), such as an aluminum water-jet-propulsion trimaran crew boat capable
of
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transporting up to 200 persons with a transit speed of up to 40 knots. A drive
assembly 46, which can include rack and pinion gearing, piston-cylinder
arrangements, or a system of running rigging, for example, raises and lowers
the
boatlift assembly frame 42 with its payload. Boatlift assembly can be capable
of
lifting the watercraft 200 from 1 meter to 2 meters or more so as to eliminate
any
heave and roll of the watercraft 200 with respect to the floatable offshore
depot,
thereby establishing a safe condition in which to embark and debark
passengers.
[000150] In embodiments of the method, high pressure air and/or water nozzles
can be
disposed at various points in tunnel below water in order to air raid the
water
column, thereby influencing the wave and the localized swell action within
tunnel.
[000151] In alternative embodiments of the method, using an active boatlift
assembly to raise
the watercraft 200, the floatable offshore depot can be ballasted to lower its
position
in the water to allow the watercraft 200 to enter the tunnel. Once the
watercraft 200
can be positioned above appropriate chocks, the floatable offshore depot can
be
deballasted, thereby raising the floatable offshore depot further out of the
water,
draining water from the tunnel, and causing the watercraft 200 to be seated in
its
chocks in a dry dock condition.
[000152] Figure 7 depicts an elevation side view in partial cross section of
the buoyant hull of
the floatable offshore depot 10, showing a plurality of baffles 37a ¨ 37h for
reducing
waves within the tunnel 30.
[000153] The floatable offshore depot 10, which can be configured to be
floatable to transition
from a floating orientation having the floating operational depth 71 or a
floating
transit depth 70 to be in a ballasted orientation resting on a seabed 312.
[000154] Pedestals 88a, 88b, and 88c are depicted supporting the at least one
take-off and
landing surface, which can be mounted to the main deck or transitioned through
the
superstructure in part or in whole, such as an overhang or a supported
overhang
supported on the main deck. A plurality of take-off and landing aircraft 400a,
400b,
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and 400c are shown.
[000155] Thresholds 33 are depicted disposed at or near the entrances of the
tunnel 30, which
can reduce wave energy entering the tunnel 30. At least one of the plurality
of baffles
37a-37h can be included on the tunnel floor 35 to further reduce the
propensity for
sloshing within the tunnel 30.
[000156] The tunnel 30 can be formed within or through buoyant hull 12 at the
waterline. The
tunnel 30 can provide a sheltered area inside the buoyant hull 12 for safe and
easy
launching/docking of boats and embarkation/debarkation of personnel. The
tunnel
30 can have the lower tapering surface 81 that provides a "beach effect" that
absorbs
most of the surface wave energy at the tunnel entrance(s), thereby reducing
slamming and harmonic effects on boats when traversing or moored within the
tunnel 30. The tunnel 30 can optionally be part of or include a moon pool that
opens
through the matching keel 12f. The moon pool, if provided, can be open to the
sea
below, using grating to prevent objects from falling there through, for
example, or it
can be closeable by a watertight hatch, if desired. An open moon pool can
provide
slightly better overall motion response.
[000157] In embodiments of the method, the tunnel 30 can have, at every
entrance, at least one
closeable door. In embodiments the at least one closeable door can be
watertight or
weathertight, that can be opened and closed as required. The at least one
closeable
door 34a and 34b can also function as a guiding and stabbing system, because
the at
least one closeable door 34a and 34h can be fitted with robust rubber fenders
to
reduce potential damage to the buoyant hull 12 and the watercraft should
impact
occur. The interior of the tunnel 30 can include fenders to facilitate
docking. When
the at least one closeable door 34a and 34b is shut, the tunnel 30 with the
tunnel
floor 35 can be drained using, for example, a gravity based draining system or
high
capacity pumps located in the pump room of the floatable offshore depot, so as
to
create a dry dock environment within the buoyant hull 12. Weathertight doors,
which
can include openings below the waterline, can be used in place of watertight
doors to
allow controlled circulation of water between the tunnel 30 and the exterior.
The at
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least one closeable door 34a and 34b can be hinged, or can slide vertically or
horizontally as is known in the art.
[000158] The tunnel 30 can include a single branch or multiple branches with
multiple
penetrations through the buoyant hull 12. The tunnel 30 can include straight,
curved,
tapering sections and intersections in a variety of elevations and
configurations.
[000159] Figure 8 depicts an elevation side view in partial cross section of
the buoyant hull of
the floatable offshore depot showing a plurality of baffles 37a ¨ 37h for
reducing
waves within the tunnel 30.
[000160] The floatable offshore depot 10, which can be configured to be
floatable to transition
from a floating orientation having the floating operational depth 71.
[000161] The thresholds 33 are depicted disposed at or near the entrances of
the tunnel 30,
which can reduce wave energy entering the tunnel 30. At least one of the
plurality of
baffles 37a-37h can be included on the tunnel floor 35 to further reduce the
propensity for sloshing within the tunnel 30.
[000162] In embodiments, the tunnel 30 can be formed within or through the
buoyant hull 12
at the waterline. The tunnel 30 can provide a sheltered area inside the
buoyant hull
12 for safe and easy launching/docking of boats and embarkation/debarkation of
personnel. The tunnel 30 can have the lower tapering surface 81 that provides
a
"beach effect" that absorbs most of the surface wave energy at the tunnel
entrance(s),
thereby reducing slamming and harmonic effects on boats when traversing or
moored within the tunnel 30. The tunnel 30 can optionally be part of or
include the
moon pool that can open through the matching keel 12f. In embodiments, the
moon
pool, if provided, can be open to the sea below, using grating 152 to prevent
objects
from falling there through, for example, or it can be closeable by a
watertight hatch,
if desired. An open moon pool can provide slightly better overall motion
response.
[000163] In embodiments of the method, the tunnel 30 can have, at every
entrance, at least one
closeable door. In embodiments the at least one closeable door can be
watertight or
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weathertight, that can be opened and closed as required. The at least one
closeable
door 34a and 34b can also function as a guiding and stabbing system, because
the at
least one closeable door 34a and 34b can be fitted with robust rubber fenders
to
reduce potential damage to the buoyant hull 12 and the watercraft should
impact
occur. The interior of the tunnel 30 can include fenders to facilitate
docking. When
the at least one closeable door 34a and 34b is shut, the tunnel 30 with the
tunnel
floor 35 can be drained using, for example, the gravity based draining system
or high
capacity pumps located in the pump room of the floatable offshore depot, so as
to
create a dry dock environment within the buoyant hull 12. Weathertight doors,
which
can include openings below the waterline, can be used in place of watertight
doors to
allow controlled circulation of water between the tunnel 30 and the exterior.
The at
least one closeable door 34a and 34b can be hinged, or can slide vertically or
horizontally as is known in the art.
[000164] Figure 9 depicts a horizontal cross section taken through the buoyant
hull of the
floatable offshore depot showing a straight tunnel formed completely there
through.
[000165] In embodiments, the tunnel 30 can be a straight tunnel that passes
completely
through the buoyant hull 12 on a diameter.
[000166] The at least one of the fin-shaped appendage 84a-84d can be used for
creating added
mass and for reducing heave and otherwise steadying the floatable offshore
depot 10.
A plurality of fin-shaped appendages 84a-84d can be attached to a lower and
outer
portion of lower cylindrical side section of the buoyant hull 12.
[000167] In one or more embodiments as shown, the plurality of fin-shaped
appendages 84a-
84d can have at least four fin-shaped appendages separated from each other by
gaps.
A gap 86 is shown to accommodate one of the plurality of catenary mooring
lines
16a on the exterior of buoyant hull 12 without contact with the plurality of
fin-
shaped appendages 84a-84d. The plurality of catenary mooring lines 16a-16p is
also
shown.
[000168] Figure 10 depicts a horizontal cross section taken through the
buoyant hull 12 of the
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floatable offshore depot according to one or more embodiments.
[000169] In embodiments, the tunnel 30 can be a cruciform shaped tunnel, which
can have
entrances formed through the buoyant hull 12 at ninety degree intervals.
[000170] In this embodiment, the cruciform shape 89 creates a plurality of
tunnel openings
31a-31d in the buoyant hull 12 of the floatable offshore depot.
[000171] The tunnel 30 provides four entrances disposed at ninety-degree
intervals about
buoyant hull 12. The floatable offshore depot can be ideally moored so that at
least
one of the plurality of tunnel openings 31a-31d can be leeward of prevailing
winds,
waves and currents.
[000172] Each of the plurality of tunnel opening 31a-31d can be formed in the
buoyant hull to
the exterior for the tunnel 30. Each of the tunnel openings of the plurality
of tunnel
openings 31a-31d can have at least one tunnel fender 45a-451.
[000173] The at least one fin-shaped appendage 84a-84d is depicted along with
the plurality of
catenary mooring lines 16a-16p. The gap 86 is shown to accommodate the one of
the
plurality of catenary mooring lines 16a on the exterior of the buoyant hull 12
without
contact with the at least one fin-shaped appendages 84a-84d.
[000174] Figure 11 depicts a top view of a Y-shaped tunnel in the buoyant hull
of the floatable
offshore depot.
[000175] In embodiments, the tunnel 30 can be in a Y-shaped in the buoyant
hull 12 with the
tunnel opening 31a, in communication with a first branch 36a and a second
branch
36b going to an additional tunnel opening 31b and 31c respectively.
[000176] In operation, the fast transport unit FTU or similar watercraft can
arrive in the
proximity of the moored and stable floatable offshore depot. The watercraft
ideally
can approach the entrance to the tunnel which can be the tunnel entrance most
sheltered from the effects of wind, waves, and current. If not already in a
flooded
state, the tunnel can be flooded. The at least one closeable door can be
opened, and
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the watercraft can then enter the tunnel under its own power. The at least one
door
fender and the at least one self-guiding stabbing dock shape of tunnel the
tunnel can
provide safe and reliable clearance guidance. More than one self-guiding
stabbing
dock shape can be used.
[000177] The at least one tunnel fender can eliminate or drastically reduce
riding and
bouncing of the watercraft against the internal dock side of the tunnel. After
the
watercraft clears the entrance, the at least one closeable door can be shut to
reduce
wave, wind and swell effects from the outer environmental conditions. The
watercraft can then align over the boatlift assembly, optionally aided by the
use of
controlled and monitored underwater cameras and transporter systems. The
watercraft can then be lifted by the boatlift assembly as desired. The reverse
procedure can be used to launch the watercraft.
[000178] The floatable offshore depot can be designed and sized to meet the
requirements of
any particular application. The dimensions can be scaled using the well-known
Froude scaling technique. The dimensions of the tunnel, which can be scaled as
appropriate, are approximately 17 meters wide by 21 meters high. Such
dimensions
are appropriate for the tri-hull FTUs described above.
[000179] In embodiments of the method, the floatable offshore depot can have a
floating
transit depth and an operational depth, wherein the operational depth can be
achieved using ballast pumps and filling ballast tanks in the buoyant hull
with water
after moving the structure at floating transit depth to an operational
location.
[000180] In embodiments of the method, the floating transit depth can be from
about 7 meters
to about 15 meters, and the operational depth can be from about 45 meters to
about
65 meters. The tunnel can be out of the water during transit.
[000181] In further embodiments of the method, a straight, a curved, or a
tapering section in
the buoyant hull forms the tunnel.
[000182] In embodiments of the method, the method provides a resort including
gaming
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and/or entertainment on the floatable offshore depot.
[000183] In embodiments of the method, the method provides military staging
site on the
floatable offshore depot.
[000184] In embodiments of the method, the plates, the at least one closable
door, and the
buoyant hull can be made from steel.
[000185] In embodiments of the method, the floatable offshore depot can have
the lower
frustoconical side section extending downwardly from the upper cylindrical
side
section.
[000186] In embodiments of the method, the floatable offshore depot comprises
a
frustoconical side section between the transition section and the lower
frustoconical
side section.
[000187] In embodiments of the method, the method can use the floatable
offshore depot to
provide a sheltered area inside the buoyant hull using a tunnel for safe and
easy
launching/docking of watercraft and embarkation/debarkation of personnel using
an
internal dock side of tunnel and to provide a sheltered area inside the
buoyant hull
for transferring equipment between the watercraft and the floatable offshore
depot
using an internal dock side of tunnel.
[000188] The method can use the floatable offshore depot having a buoyant hull
with a hull
planform that is circular, oval, elliptical, or polygonal.
[000189] In embodiments of the method, the buoyant hull can have a matching
keel and a
main deck.
[000190] In embodiments of the method, between the buoyant hull and main deck
can be at
least two connected sections joined in series and symmetric about a vertical
axis.
[000191] In embodiments of the method, the connected sections can extend
downwardly from
the main deck toward the matching keel, and can have at least two of: the
upper
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cylindrical side section, the transition section, and the lower cylindrical
section.
[000192] In further embodiments of the method, the buoyant hull can have a
tunnel at an
operational depth. The tunnel can have a tunnel opening in the buoyant hull
opening
to an exterior of the buoyant hull and dimensioned so as to receive a
watercraft.
[000193] In embodiments of the method, the floatable offshore depot can have a
lower
frustoconical side section to extend downwardly from the upper cylindrical
side
section.
[000194] In embodiments of the method, the floatable offshore depot can have
an upper
conical section between the transition section and the lower frustoconical
side
section.
[000195] In embodiments of the method, the floatable offshore depot provides
for selective
isolation of said tunnel from said exterior; whereby said tunnel can be
operable in
either a wet condition or a dry condition while said floatable offshore depot
floats in
a body of water.
[000196] In embodiments of the method, the floatable offshore depot can be
configured to
keep the tunnel in either a wet condition or a dry condition while the
floatable
offshore depot floats in a body of water.
[000197] In embodiments of the method, the floatable offshore depot can have a
second tunnel
opening in the buoyant hull to an exterior of the buoyant hull for the tunnel.
[000198] In embodiments of the method, the floatable offshore depot can have
the first and the
second branches for the tunnel, wherein each branch can penetrate through the
buoyant hull.
[000199] In embodiments of the method, the floatable offshore depot can have a
cruciform
shape for the tunnel creating a plurality of tunnel openings in the buoyant
hull.
[000200] In embodiments of the method, the floatable offshore depot can have:
the main deck
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configured to carry a superstructure thereon; and said superstructure can
include at
least one member selected from the group consisting of: the berthing facility,
the
accommodations, the at least one heliport, the at least one crane, the control
tower,
and the at least one aircraft hangar.
[000201] In embodiments of the method, the floatable offshore depot can have:
optional
baffles to reduce waves within the tunnel.
[000202] In embodiments of the method, the floatable offshore depot can have:
the moon pool
configured to engage the tunnel with the moon pool configured to open through
the
matching keel.
[000203] In embodiments of the method, the floatable offshore depot can have
the at least one
tunnel fenders disposed within the tunnel to reduce wave action and provide
clearance guidance to the watercraft and outside the tunnel opening enabling
self-
guiding of the watercraft into the tunnel.
[000204] In embodiments of the method, the floatable offshore depot can have a
self-guiding
stabbing dock shape for the tunnel.
[000205] In embodiments of the method, the floatable offshore depot can have
the gangway
for traversing between the structure and an adjacent structure.
[000206] In embodiments of the method, the floatable offshore depot can have a
buoyant hull
with a low center of gravity providing an inherent stability to the structure.
[000207] In embodiments of the method, the floatable offshore depot can have
at least one fin-
shaped appendage attached to a lower portion and an outer portion of the
exterior of
the buoyant hull.
[000208] In embodiments of the method, the floatable offshore depot can have
the lower
tapering surface at an entrance of the tunnel, providing a "beach effect" that
absorbs
most of a surface wave's energy.
CA 02966036 2017-04-26
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[000209] In embodiments of the method, the floatable offshore depot can have a
tunnel floor
with the floatable offshore depot adapted for draining the tunnel so as to
create a dry
dock environment within the buoyant hull.
[000210] In embodiments of the method, the floatable offshore depot a
straight, a curved, or a
tapering section in the buoyant hull forming the tunnel.
[000211] In embodiments of the method, the floatable offshore depot can have
the plurality of
thrusters and the plurality of catenary mooring lines to either dynamic moor
the
floatable offshore depot to the seabed or to provide dynamic positioning while
in
communication with a global positioning system.
[000212] In embodiments of the method, the floatable offshore depot can be
configured to
float on a body of water as well as to ballast down and sit on a seabed. In
essence
this particular floatable offshore depot can be adapted to both float at two
different
levels as well as sit on a seabed for differing operational and transiting
uses.
[000213] While these embodiments have been described with emphasis on the
embodiments,
it should be understood that within the scope of the appended claims, the
embodiments might be practiced other than as specifically described herein.
