CN107249978B

CN107249978B - Method of using floatable offshore storage

Info

Publication number: CN107249978B
Application number: CN201680011965.8A
Authority: CN
Inventors: 尼古拉斯·约翰内斯·万登沃姆
Original assignee: Jurong Shipyard Pte Ltd
Current assignee: Jurong Shipyard Pte Ltd
Priority date: 2015-02-24
Filing date: 2016-01-27
Publication date: 2020-03-13
Anticipated expiration: 2036-01-27
Also published as: WO2016137644A3; PH12017500847A1; IL251983A0; CA2966036C; CA2966036A1; WO2016137644A2; MX2017006313A; MY192128A; RU2017133090A; EP3261918A2; CN107249978A; KR20170121183A; AU2016223269A1; BR112017017982B8; BR112017017982A2; RU2683920C2; BR112017017982B1; KR102365572B1; SG11201706647RA; EP3261918A4

Abstract

A method of using a floatable offshore depot to provide a sheltered area for safe and easy ground water or docking of ships and safe and easy boarding or disembarking of personnel using tunnels. The method may be used for transporting equipment between a vessel and a floatable offshore depot using the inner dock side of the tunnel. The floatable offshore depot may have a buoy, a keel, a main deck and at least two connection sections between the keel and the main deck. The connector section may extend downwardly from the main deck towards the keel and may have an upper cylindrical side section, a transition section, and a lower cylindrical section. The method uses a tunnel at the operating depth, wherein the tunnel opening is open to the exterior of the float to receive the vessel.

Description

Method of using floatable offshore storage

Cross Reference to Related Applications

This application claims priority and benefit of a co-pending U.S. patent application serial No. 14/630,576 entitled "METHOD USING FLOATING OFFSHORE warehouse" filed 24/2015, published as U.S. patent No.9,180,941/2015 11/10 and filed 27/2014 10/14/524,992, part of a co-pending U.S. patent application entitled "BUOYANT structrue" filed 12/13/2013, part of a co-pending U.S. patent application serial No. 14/524,992 filed 13/2013, serial No. 14/105,321 entitled "float marine" (published as U.S. patent No.8,869,727/2012/28/2014) filed 13/369,600/2/2015, and No.8,869,727 filed 359/2/9/2014, A partial continuation of co-pending U.S. patent application entitled "STABLE offshore floatable DEPOT", now published as U.S. patent No.8,662,000 on 3-4.2014, No.8,662,000 being a partial continuation of U.S. patent application No. 12/914,709 on 28.10.2010 (published as U.S. patent No.8,251,003 on 28.8.2012), which claims the benefit of U.S. provisional patent application serial No. 61/521,701 filed on 9.8.2011, U.S. provisional patent application serial No. 61/259,201 filed on 8.8.2009, and U.S. provisional patent application serial No. 61/262,533 filed on 18.11.18.11.2009. These references are incorporated herein in their entirety.

Technical Field

Embodiments of the present invention generally relate to methods of using floatable offshore buoyant vessels, platforms, caissons, pontoons, masts, or other structures for supporting offshore oil and gas operations.

Background

Stable offshore warehouses for supporting offshore oil and gas operations are known in the art. Offshore production structures, which may be, for example, ships, platforms, caissons, pontoons or masts, typically include a buoyant body that supports an superstructure. The float includes internal area divisions for ballasting and storage, and the superstructure provides drilling and production facilities, helicopter airports, crew quarters, and the like.

In offshore operations, such as on drilling and production platforms, the main operating costs result from the transportation of the support and supply of onshore equipment. Almost everything must be transported by ship or by air. These supply lines are susceptible to inclement weather and sea conditions, the more distance the supply requires, the greater its impact.

Thus, stable floatable structures designed to be towed out of the ocean and moored close to several production platforms within a specified area are known in the art. These structures can be used to provide shelter for transport vessels and support equipment, including storage, maintenance, fire, medical, and mooring equipment. Offshore base stations, warehouses, or hub stations may allow for reduced platform operating costs because they allow for safer and more cost-effective transportation of personnel and supplies from land that may be temporarily staged and distributed to local platforms. The prior art includes floating offshore support structures that include a protected interior for receiving a vessel.

Floating structures are susceptible to environmental forces from wind, waves, ice, tides and water currents. These environmental forces result in acceleration, displacement, and oscillatory motion of the structure. The response of the floating structure to these environmental forces is affected not only by its hull design and superstructure, but also by its mooring system and any accessories. Thus, floating structures have several design requirements: suitable reserve buoyancy to safely support the weight of the superstructure and payload, stability under all conditions, and good sea endurance. The ability to reduce vertical heave is highly desirable with respect to good sea endurance requirements. Heave motions can cause tension variations in the mooring system which can cause fatigue and failure. The large heave motions increase the risk of starting and retrieving boats and helicopters and loading and unloading supplies and personnel.

The sea endurance of floatable offshore warehouses is affected by several factors, including the waterplane area, the hull contour, and the natural period of movement of the floating structure. It is highly desirable that the natural period of the floating structure is either significantly larger or significantly smaller than the wave period of the sea in which the structure is located, in order to significantly decouple the motion of the structure from the wave motion.

Vessel design includes balancing the competing factors in a given set of factors to achieve an optimal solution. Cost, constructability, durability, practicality, and installation issues are included in many considerations in ship design. Design parameters for a floating structure include draft, waterplane area, draft rate of change, location of center of gravity ("CG"), location of center of buoyancy ("CB"), height of center of gravity ("GM"), sail area, and total mass.

The total mass comprises the additional mass, i.e. the mass of the water around the floating body of the floating structure that is forced to move when the floating structure moves. The attachment to the structure of the float for additional mass augmentation is a cost effective way to fine tune the structural response and performance characteristics when subjected to environmental forces.

Several general shipbuilding rules apply to the design of marine vessels. The waterplane area is proportional to the resulting heave force. A structure symmetrical about a vertical axis is less affected by yaw forces as a whole. As the size of the vertical hull profile increases in the wave band, the lateral wave forces caused by the waves also increase. The floating structure can be modeled with the natural period of motion in the heave and wave directions as a spring. 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 the additional mass) of the structure increases, the natural period of motion of the structure becomes longer.

One method for providing stability is to moor the structure under tension, such as in a tension legged platform, with vertical tendons. Such a platform is advantageous because it has the added benefit that heave is significantly limited. However, tension leg platforms are expensive structures and are therefore not suitable for all applications.

Self-stability (i.e., stability independent of the mooring system) can be achieved by creating a larger waterplane area. When 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 higher than the center of buoyancy, the structure may remain stable at relatively large roll angles. However, heave endurance for larger waterplane areas in the wave band is generally undesirable.

Providing inherent self-stability when the center of gravity is below the center of buoyancy. The combined weight of the superstructure, floats, payload, ballast and other elements may be arranged to lower the centre of gravity, but such an arrangement may be difficult to achieve. One method of lowering the center of gravity is to add a fixed ballast below the center of buoyancy to balance the weight of the superstructure with the payload. Structured fixed ballast such as pig iron, iron ore and concrete is arranged within or attached to the floating structure. The benefit of this ballast arrangement is that stability can be achieved without adversely affecting sea endurance due to the large waterplane area.

The self-stabilising structure has the benefit that stability is independent of the function of the mooring system. Although the heave endurance of a self-stabilizing floating structure is generally inferior to that of a tendon-based platform, the self-stabilizing structure is preferred in many situations due to the higher cost of the tendon-based structure.

Prior art floating structures have been developed with various designs for buoyancy, stability and sea endurance. Appropriate discussion of floating structure design considerations and description of several exemplary floating structures are known in the industry.

Various spar buoy designs are known as examples of inherently stable floating structures, in which the center of gravity ("CG") is set below the center of buoyancy ("CB"). Spar buoy hulls are elongated and typically extend more than six hundred feet below the water surface when installed. The longitudinal dimension of the float must be large enough to provide a mass that lengthens the heave natural period, thereby reducing the wave induced heave. However, due to the large size of the cylindrical hull, manufacturing, transportation and installation costs are increased. It is desirable to provide the following structure with an integrated superstructure: the structure can be manufactured close to the quay at reduced cost, yet is inherently stable due to the centre of gravity being lower than the centre of buoyancy.

The prior art discloses offshore platforms employing a retractable center column. The central column is raised above keel level to allow the platform to be pulled over the airways from shallow water to deep water installations. At the installation site, the center column is lowered to extend below keel level to improve vessel stability by lowering the center of gravity. The center post also provides pitch damping for the structure. However, the central column adds complexity and cost to the configuration of the platform.

Other marine system hull designs are known in the art. For arctic operations of ships, octagonal hull structures with sharp corners and steep sides are used to cut and break ice. Unlike most conventional offshore structures designed to reduce rolling, the structure of Srinivasan is designed to induce heave, roll, pitch and surge motions to accomplish ice cutting.

Drilling and production platforms with cylindrical hulls, where the center of gravity of the structure is above the center of buoyancy, rely on a large waterplane area for stability, while heave durability is reduced. Although there is a circumferential recess formed around the float near the keel for pitch and roll damping, the location and contour of such recess has little effect on dampening heave.

It is believed that the offshore structures of the prior art, and in particular the offshore warehouses or terminal stations arranged to provide shelter for ships used to transport supplies and personnel to offshore platforms, are not characterized by all of the following beneficial characteristics: a float body symmetrical about a vertical axis; the center of gravity is located below the center of buoyancy to achieve inherent stability without the need for complex retractable columns and the like, exceptional heave damping characteristics without the need for mooring with vertical tendons, and the ability for quayside integration and "erection" transport of the superstructure to the installation site, including transport through shallow waters. It is desirable for an offshore depot or terminal to have all of these features.

There is a need for an offshore warehouse: the offshore depot provides the ability to absorb kinetic energy from the vessel by providing a plurality of dynamically movable tilt-prone mechanisms within a tunnel formed in the offshore depot.

There is also a need for offshore warehouses: the offshore warehouse provides wave damping and wave breaking within a tunnel formed in the offshore warehouse.

There is a need for an offshore warehouse: the offshore depot provides friction to the floats of the vessels in the tunnel.

Embodiments of the present invention meet these needs.

Drawings

The detailed description will be better understood in conjunction with the following drawings:

fig. 1 depicts a perspective view of a floatable offshore depot moored to a seabed, according to one or more embodiments.

Fig. 2 depicts an axial cross-sectional view of a float profile of a floatable offshore depot, according to one or more embodiments.

Fig. 3 depicts an enlarged perspective view of the floatable offshore warehouse showing details of the tunnel, tunnel doors, and small personnel transfer vessels.

Fig. 4A depicts a top view of a plurality of dynamically movable tilt-prone mechanisms located in a tunnel before a vessel contacts the dynamically movable tilt-prone mechanisms.

Fig. 4B depicts a top view of a plurality of dynamic movable tilt mechanisms located in a tunnel when a vessel contacts the dynamic movable tilt mechanism.

Fig. 4C depicts a top view of a plurality of dynamically movable lean mechanisms in a tunnel connected to a vessel, with doors closed.

Fig. 5A depicts a front perspective view of one of the dynamic movable tilt mechanisms.

Fig. 5B depicts a top view of the folding of one of the dynamic movable tilt mechanisms.

Fig. 5C depicts a side view of an embodiment of one of the dynamic movable tilt mechanisms.

Fig. 5D depicts a side view of another embodiment of a dynamically movable recliner mechanism.

Fig. 6 depicts a perspective view of a boatlift assembly of a floatable offshore warehouse disposed within a tunnel.

Figure 7 depicts a side view, partly in section, of a floating body of a floatable offshore depot showing baffles for reducing waves in the tunnel.

Fig. 8 depicts a side view, partially in section, of a buoyant body of a floatable offshore warehouse, in accordance with one or more embodiments.

Fig. 9 depicts a horizontal section taken through a float of the floatable offshore depot, showing a straight tunnel formed completely through the float.

Fig. 10 depicts a horizontal section taken through a float of a floatable offshore depot according to one or more embodiments.

Fig. 11 depicts a top view of a Y-tunnel in a float of a floatable offshore depot.

Embodiments of the present invention are described in detail below with reference to the listed figures.

Detailed Description

Before the present method is explained in detail, it is to be understood that the method is not limited to particular embodiments and that the method can be practiced or carried out in various ways.

Embodiments of the present invention relate to methods of using floatable offshore warehouses for supporting offshore oil and gas operations.

Current methods involve stably moored floatable offshore warehouses such as would be used for safety handling, staging, and transportation of personnel, supplies, ships, and helicopters.

Embodiments of the method enable a vessel to safely enter a floatable offshore warehouse in both a harsh offshore environment with 4-400 feet of ocean waves and a good offshore environment.

Embodiments of the method prevent personnel injury from equipment falling from the floatable offshore warehouse by providing the following tunnels within the floatable offshore warehouse: the tunnel is used for accommodating and protecting a ship for receiving personnel.

Embodiments of the method provide a floatable offshore depot located in the offshore field that enables many people to leave the offshore structure quickly at the same time in case a hurricane, tsunami or any other natural disaster is imminent.

Embodiments of the method provide means to safely transfer a number of people, such as 200 to 500 people, from an adjacent fire platform to a floatable offshore warehouse quickly in less than 1 hour.

Embodiments of the method enable a floatable offshore structure to be towed to a marine disaster relief and operated as a command center to facilitate disaster control and may be used as a hospital or triage center.

Embodiments relate to a method of using a floatable offshore depot providing a shelter area using a tunnel to safely and easily groundwater/dock and safely and easily embark/disembark personnel using an inner docking side of the tunnel.

A further use of the floatable offshore storage is to provide a sheltered area for transferring equipment between the vessel and the floatable offshore storage by using a tunnel.

The floatable offshore depot may have an inner dock side of the tunnel.

The floatable offshore depot may have floats that may be circular, oval, elliptical or polygonal.

The floatable offshore depot may have: keel, main deck and be located keel and main deck between at least two connecting portion sections. The at least two connecting sections may be joined in series and symmetrical about a vertical axis.

At least two connection sections may extend downwardly from the main deck towards the keel. The connecting section may have at least two of an upper cylindrical side section, a transition section, and a lower cylindrical section. The tunnel may have a tunnel opening to the exterior of the float when the floatable offshore depot is at the operating depth. The tunnel may be sized to receive a vessel.

The vessel may be a ferry, construction vessel, ship, such as a barge, with or without a propeller, up to 600 feet in length. The vessel may also be a submarine. Ship can toolThere are different shapes of the float, such as catamaran, trimaran, monohull, hovercraft or even hydrofoil. The tunnel may receive what is also known as zepparin^TM(ZEPPLIN^TM) The airship of (1).

Turning now to the drawings, FIG. 1 illustrates a floatable offshore warehouse 10 for operably supporting offshore exploration, drilling, production, and storage equipment in accordance with one or more embodiments.

The floatable offshore warehouse 10 is shown as floatingly moored to the seabed 312. The floatable offshore depot comprises a floating body 12 on which the floating body 12 can carry an superstructure 13. The superstructure 13 may include equipment and structures such as residences for personnel, equipment storage, helicopter airports, and many other structures, systems, and various collections of equipment depending on the type of offshore operation to be supported. The superstructure 13 may be fitted with at least one crane 53. The buoyant body 12 may be moored to the sea floor by a plurality of catenary mooring lines 16 a-16 o.

The superstructure 13 is shown supporting at least one takeoff and

landing surface

54a and 54 b. The at least one takeoff and

landing surface

54a and 54b is shown as a helicopter airport. The superstructure 13 may include an aircraft hangar 50. In an embodiment, the aircraft hangar may house at least one takeoff and

landing aircraft

400a, 400b, and 400 c. A control tower 51 may be built on the superstructure 13. The control tower may have a dynamic positioning system 57.

In this embodiment of the method, the floatable offshore warehouse 10 may have a tunnel opening 31 for a tunnel formed in the floating body 12.

The tunnel opening 31 is capable of receiving water when the floatable offshore warehouse 10 may be at the working depth 71.

The floatable offshore warehouse 10 may have at least one closable door 34 b.

In an embodiment of the method, the tunnel may be configured to provide selective isolation of the tunnel from the exterior; thus, the tunnel can be operated in a wet state or a dry state when the floatable offshore warehouse 10 can float in the water body.

Floatable offshore warehouse 10 may have a unique shape.

The buoyant hull 12 of the floatable offshore warehouse 10 may have a main deck 12a and a height H, wherein the main deck 12a may be circular. An upper frustoconical portion (which is shown as a combination of components) may extend downwardly from the main deck 12 a.

In an embodiment of the method, the upper frustoconical portion may have an upper cylindrical side section 12 b. In other embodiments, the upper cylindrical side section 12b may extend downward from the main deck 12 a.

Floatable offshore warehouse 10 may also have a lower frustoconical side section 12d extending downwardly from an upper conical section 12c that may flare outwardly. Both the upper tapered section 12c and the lower frustoconical side section 12d may be below the working depth 71.

The upper cylindrical side section 12b may be connected to the transition section 12 g.

A lower cylindrical section 12e may extend downwardly from the lower frustoconical side section 12d, and the lower cylindrical section 12e may have a mating keel 12 f.

Floatable offshore warehouse 10 may have at least one fin-shaped

appendage

84a and 84 b.

In embodiments of the method, floatable offshore warehouse 10 may be configured to transition from a floating orientation having a floating operational depth 71 or a floating transport depth.

In an embodiment of the method, the floatable offshore depot may be a marine vessel.

Fig. 2 illustrates that the vertical height H1 of the upper conical section 12c may be significantly greater than the vertical height, shown as H2, of the lower frustoconical section 12 d. The vertical height H3 of upper cylindrical side section 12b may be slightly greater than the vertical height of lower cylindrical section 12e, shown as H4.

The upper cylindrical side section 12b may be connected to the transition section 12g to provide a main deck with a radius larger than the radius of the buoyant body and a main deck that may be spherical, square or other shape. The transition section 12g may be located above the working depth 71.

The tunnel 30 may have at least one

closable door

34a and 34b, which at least one

closable door

34a and 34b may alternatively or in combination provide weather and water protection to the tunnel 30.

A fin attachment 84 may be attached to the lower exterior of the outer side of the float.

Tunnel 30 may have a plurality of dynamically movable tilt-

prone mechanisms

24d and 24h disposed within and connected to the tunnel sides.

The tunnel may have a tunnel floor 35, the tunnel floor 35 may receive water when the floatable offshore warehouse may be at a working depth 71.

The tunnel floor 35 allows a dry dock environment to be created within the float 12 when the tunnel 30 is drained.

The plurality of dynamically movable tilt-

prone mechanisms

24d and 24h may be oriented above tunnel floor 35 and may have a portion positioned above working depth 71 and a portion extending below working depth 71 within tunnel 30.

In an embodiment of the method, at least one

closable door

34a and 34b can close on the tunnel opening 31.

The main deck 12a, upper cylindrical side section 12b, transition section 12g, upper conical section 12c, lower frustoconical side section 12d, lower cylindrical section 12e, and mating keel 12f may all be coaxial with the common vertical axis 100. In an embodiment, the float 12 may be characterized as having an ellipsoidal cross-section when taken perpendicular to the vertical axis 100 at any height.

Due to the ellipsoidal planar form of the floating body 12, its dynamic response can be independent of the wave direction (ignoring any asymmetries in the mooring system, the elevators and the underwater appendages), thereby minimizing wave-induced yaw forces.

In addition, the conical form of the floats 12 is structurally efficient when compared to conventional ship-shaped offshore structures, providing higher payload and storage capacity per ton of steel. The float 12 may have ellipsoidal walls that are ellipsoidal in radial cross-section, but this shape may also be approximated by a larger number of flat metal plates rather than bending the plates into the desired curvature. Although an ellipsoidal float planar form is preferred, a polygonal float planar form may be used according to alternative embodiments.

In an embodiment of the method, the float 12 may be circular, oval or elliptical, forming an ellipsoidal planar form.

The oval shape is advantageous when the floatable offshore warehouse is moored next to another offshore platform to allow for a gangway passage between the two structures. The elliptical floating body may minimize or eliminate wave interference.

The particular design of the upper conical section 12c and the lower frustoconical side section 12d produces a large amount of radial damping, resulting in little heave expansion for any wave period, as described below.

The upper conical section 12c may be located in a zone. At the working depth 71, the water line may be located on the upper tapered section 12c and slightly below the intersection of the upper tapered section 12c and the upper cylindrical side section 12 b. The upper tapered section 12c may be inclined at an angle of 10 to 15 degrees relative to the vertical axis 100. The inward tilt can significantly dampen the sag before reaching the water line due to the increased water line surface area caused by the downward motion of the float 12. In other words, the float area of the water-breaching surface normal to the vertical axis 100 will increase with downward float motion, and this increased area experiences opposing resistance from the air and/or water interface. It has been found that a 10 to 15 degree expansion provides the desired amount of damping for a sink without sacrificing too much storage capacity of the vessel.

Similarly, the lower frustoconical side segment 12d dampens the rise. The lower frustoconically shaped side section 12d may be located below the wave band (about 30 meters below the water line). Since the entire lower frustoconical side section 12d may be located below the water surface, a larger area (the area orthogonal to the vertical axis 100) is required to achieve upward damping. Thus, the first diameter D of the lower float section₁May be larger than the second diameter D of the upper tapered section 12c₂。

The lower frustoconical side section 12d may be inclined at an angle (g) of 55 to 65 degrees relative to the vertical line 100. The lower section may 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 helps to make the natural period of heave roll and pitch greater than the expected wave energy.

The upper limit of 65 degrees may be based on avoiding abrupt changes in stability during initial ballasting at installation. In other words, the lower frustoconical side section 12d may be perpendicular to the vertical axis 100 and achieve a desired amount of rising damping, but such a float profile would result in an undesirable step change in stability during initial ballasting when installed. The location of the connection between the upper frustoconical portion 14 and the lower frustoconical side section 12D may have a diameter greater than the first diameter D₁And a second diameter D₂Small third diameter D₃。

The floating transport depth 70 represents the water line of the float 12 as it transitions to the offshore operation location. Floating transport depths are known in the art to reduce the energy required to transport a buoyant vessel a distance above water by reducing the profile of the floatable offshore warehouse that is in contact with the water. This floating transport depth is approximately the intersection of the lower frusto-conical side section 12d and the lower cylindrical section 12 e. However, weather and wind conditions may provide the need for different floating transport depths to meet safety guidelines or to enable rapid deployment from one location to another on the water surface.

Ballast added to the float 12 may be used to lower the center of gravity. In an embodiment, the floatable offshore depot may have a float with a lower center of gravity 87 that provides inherent stability to the structure.

In an embodiment of the method, the floating body may feature a positive metacentric center.

Floatable offshore warehouses are active against roll and pitch and may be referred to as "stable". Harshness vessels are often characterized by sudden jerky accelerations when a large righting moment resists pitch and roll. In particular, the orientation of the fixed and fluid ballast increases the natural period of the floatable offshore warehouse to be greater than the period of the most common waves, thereby limiting acceleration in all degrees of freedom caused by waves.

In an embodiment of the method, the floatable offshore depot may have a plurality of

thrusters

99a, 99b, 99c and 99d for use with dynamic positioning.

In an embodiment, the vertical cross-section of the fin-shaped appendage 84a may have the shape of a right triangle, wherein the right angle may be positioned adjacent to the lowermost exterior sidewall of the lower cylindrical section 12e of the float 12 such that the base 184 of the triangular shape may be coplanar with the mating keel 12 f.

In an embodiment, the hypotenuse of the triangular shape may extend upward and inward from the distal end of the base 184 of the triangular shape to attach to the outer sidewall of the lower cylindrical section 12 e.

The number, size and orientation of the at least one fin-shaped appendage may be varied to optimize the heave suppression effect. For example, the bottom edge 184 may extend radially outward a distance that may be about half the vertical height of the lower cylindrical section 12e, with the hypotenuse attached to the lower cylindrical section 12e up to about one quarter of the vertical height of the lower cylindrical section 12e from the keel level.

Alternatively, the radius (r) at the lower cylindrical section 12e is defined as the first diameter D₁In this case, the bottom edge 184 of the at least one fin-shaped appendage 84a may extend radially outward. Although at least one fin-shaped appendage 84a defining a given radius range is shown, multiple fin-shaped appendages defining a larger radius range or a smaller radius range may be used to vary the amount of added mass required. Additional mass may be desirable depending on the requirements of a particular floating structure. However, to affect the natural period of motion, the additional mass may generally be the least costly way to increase the mass of the floating structure.

Fig. 3 shows a floatable offshore warehouse 10 with a main deck 12a and an superstructure 13 located thereon.

At least one crane 53 is shown mounted to the superstructure 13. The floatable offshore warehouse 10 may include at least one takeoff and

landing surface

54b and 54c, such as a helicopter airport, which enables at least one takeoff and

landing aircraft

400b and 400c, such as a plurality of helicopters or similar takeoff and landing aircraft, to takeoff and land on the plurality of takeoff and landing surfaces simultaneously rather than sequentially.

The term "aircraft" as used herein may be helicopters, short take-off and landing aircraft, airships, drones, airships, and the like. In an embodiment, the aircraft may be remotely controlled.

In an embodiment of the method, the at least one takeoff and

landing surface

54b and 54c, respectively, may be mounted on a pedestal extending from a float of the floatable offshore depot. In other embodiments, the at least one takeoff and

landing surface

54b and 54c may be supported by a pedestal.

In method embodiments, the at least one takeoff and

landing surface

54b and 54c may be mounted to the main deck 12a or partially or completely transition through the superstructure 13, such as an overhang or a supported overhang supported on the main deck 12 a.

In this view, the vessel 200 has entered the tunnel through the tunnel opening 31 into the tunnel and is located in the tunnel with the vessel 200 positioned between the tunnel sides, wherein the first tunnel side 202 is marked. Also shown in the tunnel is a boatlift 41, which boatlift 41 can raise the vessel in the tunnel above the working depth.

The tunnel opening 31 is shown with two doors, each door having at least one door shield 38a and 38b, the door shields 38a and 38b serving to mitigate damage to a vessel attempting to enter the tunnel without impacting the doors.

In an embodiment of the method, the floatable offshore warehouse 10 may have at least one door shield 38a and 48b positioned at: (i) inside the tunnel to reduce wave action and provide clearance guidance for the vessel, or (ii) outside the tunnel opening 31 so that the vessel 200 is self-guided into the tunnel, or positioned at both position (i) and position (ii) while reducing wave action.

In the event that the pilot cannot directly enter the tunnel from a location external to the floating body 12 due to at least one of a large wave or a high water flow motion, the at least one door shield 38a and 38b may allow the vessel 200 to strike the at least one door shield 38a and 38b in a safe manner.

The floatable offshore warehouse 10 may have at least one self-steering dock flap 79.

A plurality of catenary mooring lines 16 a-16 o are shown originating from the main deck 12 a.

A mooring facility 60 is shown in part of the transition section 12g of the floating body 12.

The transition section 12g is shown connected to the upper conical section 12c and the upper cylindrical side section 12 b.

Also shown is a chamber 55 located on the superstructure.

Fig. 4A shows the vessel 200 entering the tunnel 30 and located between a first tunnel side 202 and a second tunnel side 204, the first tunnel side 202 and the second tunnel side 204 being connected to a plurality of dynamically movable tilt-prone mechanisms 24A-24 h. Adjacent the tunnel opening are

closable doors

34a and 34b, which

doors

34a and 34b may be sliding doors to provide weather protection or water barrier protection of the tunnel from the outside environment. Also shown are the starboard 206 hull of the vessel and the port 208 hull of the vessel.

Fig. 4A shows a tunnel 30 for safe and easy launching/docking of a vessel 200 and safe and easy boarding/disembarking of personnel, the tunnel 30 having an inner docking side 29 that allows personnel to walk down or storage facilities similar to a dock.

The tunnel 30 is also depicted as having a lower tapered surface 81 that can create a "beach-like" action to rise out of the water. Also depicted is a vessel 200 located within a portion of the tunnel and between a first tunnel side 202 and a second tunnel side 204, the first tunnel side 202 and the second tunnel side 204 being connected to a plurality of dynamically movable tilt-prone mechanisms 24 a-24 h.

Also shown are at least one

closable door

34a and 34b and a vessel having a port side 208 and a starboard side 206.

Fig. 4B shows the vessel 200 within a portion of the tunnel between a first tunnel side 202 and a second tunnel side 204, the first tunnel side 202 and the second tunnel side 204 being connected to a plurality of dynamically movable tilt-prone mechanisms 24 a-24 h.

A plurality of dynamically movable

lean mechanisms

24g and 24h are shown contacting the port 208 hull of the vessel 200. It is observed that the dynamically movable

lean mechanisms

24c and 24d contact the starboard 206 hull of the vessel 200. At least one

closable door

34a and 34b is also shown.

Fig. 4C shows the vessel 200 positioned within the tunnel between the first tunnel side 202 and the second tunnel side 204 and also connected to the ramp 77, the first tunnel side 202 and the second tunnel side 204 being connected to the plurality of dynamically movable lean mechanisms 24 a-24 h. Adjacent to the tunnel opening may be at least one

closable door

34a and 34b, which at least one

closable door

34a and 34b may be a sliding door oriented in a closed position to provide weather protection or water barrier protection of the tunnel from the outside environment. A plurality of dynamically movable lean mechanisms 24 a-24 h are shown in contact with the floats of the vessel on both the starboard side 206 and the port side 208 of the vessel. A lower tapered surface 81 is also shown.

Fig. 5A shows one of the plurality of dynamically movable tilt mechanisms 24 a. Each of the plurality of dynamically movable tilt-prone mechanisms may have a pair of

parallel arm portions

39a and 39b mounted to the first tunnel side or the second tunnel side.

At least one tunnel shield 45 is connected to the pair of

parallel arms

39a and 39b on the opposite side of the parallel arms to the first or second tunnel side.

The plate 43 may be mounted to the pair of

parallel arm portions

39a and 39b and located between the at least one tunnel shield 45 and the first tunnel side 202.

The plate 43 may be mounted above the tunnel floor 35 and positioned to extend within the tunnel above the working depth 71 and simultaneously extend within the tunnel below the working depth 71.

The plates 43 may be configured to dampen the movement of the vessel as it moves from side to side in the tunnel. The plate 43 and all of the plurality of dynamically movable lean mechanisms may prevent damage to the hull and push the vessel away from the hull toward the center of the tunnel without breaking the vessel. This embodiment makes it possible to retract the vessel in the tunnel without damage.

A plurality of pivot anchors 44a and 44b may connect one of the

parallel arms

39a and 39b to either of the tunnel sides 202 and 204.

Each of the plurality of pivot anchors 44a and 44b enables the plate 43 to swing from a folded orientation against the tunnel side to a deployed orientation at an angle 62 of up to 90 degrees relative to the plane 61 of the wall, thereby enabling the plate 43 and at least one tunnel shield 45 on one of the pair of

parallel arm portions

39a and 39b to simultaneously (i) protect the tunnel from wave and water shock, (ii) absorb the kinetic energy of the vessel as it moves in the tunnel, and (iii) apply a force to push the vessel away from the tunnel side.

A plurality of shield pivots 47a and 47b are shown, wherein each of the plurality of shield pivots 47a and 47b may form a connection between each of the

parallel arm portions

39a and 39b and at least one tunnel shield 45.

Each shield pivot may allow the shield to pivot at least 90 degrees from one side of the parallel arm to the opposite side of the parallel arm when the vessel contacts the at least one tunnel shield 45.

The plurality of openings 52a through 52ae in the plate 43 may reduce wave action. Each of the plurality of openings 52 a-52 ae may have a diameter of from 0.1 to 2 meters. In an embodiment, the openings 52 a-52 ae may be oval-shaped.

Each parallel arm may be connected to at least one

hydraulic cylinder

28a and 28b to provide resistance to vessel pressure on the shield and to deploy and retract the panels from the sides of the tunnel.

Fig. 5B shows one of the pair of parallel arm portions 39a in the folded position mounted to the first tunnel side 202.

One of the pairs of parallel arms 39a may be connected to one of the plurality of pivot anchors 44a that engage the first tunnel side 202.

At least one of the plurality of shield pivots 47a may be mounted on one of the pair of parallel arms opposite one of the plurality of pivot anchors 44 a.

The at least one tunnel shield 45 may be mounted to at least one shield pivot of the plurality of shield pivots 47 a.

The plate 43 may be attached to one arm of the pair of parallel arms 39 a.

At least one hydraulic cylinder 28a may be attached to the parallel arm sections and the tunnel wall.

Fig. 5C shows a plate 43 having a plurality of openings 52a to 52ag in the shape of ellipsoids. The plate 43 is shown mounted above the tunnel floor 35.

Plate 43 may extend both above work depth 71 and below work depth 71.

Also shown is the first tunnel side 202, the plurality of pivot anchors 44a and 44b, the

parallel arm sections

39a and 39b, the plurality of

shield pivot members

47a and 47b, the tunnel 30, and the at least one shield 45.

Fig. 5D illustrates an embodiment of a dynamically movable tilt mechanism formed by frame 74 rather than a plate. The frame 74 may have a pair of intersecting

tubular members

75a and 75b, the pair of intersecting

tubular members

75a and

75b forming openings

76a and 76b to allow water to pass when the water in the tunnel is at the working depth 71.

The first tunnel side 202, tunnel floor 35, plurality of pivot anchors 44a and 44b, pair of

parallel arm sections

39a and 39b, plurality of

shield pivot members

47a and 47b, and at least one tunnel shield 45 are shown.

In one or more embodiments of the method, a boatlift assembly 40 may be disposed within the tunnel.

The boatlift assembly 40 can include a boatlift assembly frame 42 that carries the stator 144 and can be positioned and arranged to support the vessel 200. In an embodiment, the boatlift assembly frame 42 may be formed from a rectangular shaped I-beam, and the boatlift assembly frame 42 may be about 15 meters wide by about 40 meters long with a safe working load of from 200 tons to 300 tons.

The boat elevator assembly frame 42 may be adapted to lift a fast transfer unit ("FTU"), such as an aluminum water jet propelled trimaran capable of transporting up to 200 people at transport speeds of up to 40 knots. For example, a drive assembly 46, a piston-cylinder arrangement, or a mobile padlock system raises and lowers the boatlift assembly frame 42 under its payload, wherein the drive assembly 46 may include a rack and pinion gear arrangement. The boatlift assembly is capable of lifting the vessel 200 from 1 meter to 2 meters or more to eliminate any heaving and rolling of the vessel 200 relative to the floatable offshore depot, thereby establishing a safe environment for passengers to board and disembark.

In an embodiment of the method, high pressure air nozzles and/or high pressure water nozzles may be arranged at various points in the tunnel under the water to let air invade the water column to influence the wave and local swell effects inside the tunnel.

In an alternative embodiment of the method, the vessel 200 is lifted using an active boatlift assembly, and the floatable offshore depot may be ballasted to lower its position in the water, allowing the vessel 200 to enter the tunnel. Once the vessel 200 can be positioned above the appropriate fixed tray, the floatable offshore warehouse may be de-ballasted, lifting the floatable offshore warehouse further out of the water, and draining the water from the tunnel and seating the vessel 200 in its fixed tray in a dry dock environment.

Fig. 7 depicts a side view, partly in section, of a floating body of the floatable offshore warehouse 10, showing a plurality of baffles 37a to 37h for reducing waves in the tunnel 30.

The floatable offshore warehouse 10 may be configured to be floatable to transition from a floating orientation having a floating operating depth 71 or a floating transport depth 70 to a ballasting orientation resting on the seabed 312.

Pedestals 88a, 88b and 88c are described as supporting at least one take-off and landing surface that may be mounted to the main deck or partially or completely transition through an superstructure, such as an overhang or a supported overhang supported on the main deck. A plurality of takeoff and

landing aircraft

400a, 400b, and 400c are shown.

An inlet portion 33 is depicted as being disposed at or near the entrance to the tunnel 30, the inlet portion 33 may reduce the wave energy entering the tunnel 30. At least one of the plurality of baffles 37a to 37h may be included on the tunnel floor 35 to further reduce the sloshing tendency within the tunnel 30.

The tunnel 30 may be formed within the floating body 12 at the water line or through the floating body 12. The tunnel 30 may provide a sheltered area within the float 12 for safe and easy ground water/docking of the ship and safe and easy boarding/disembarking of personnel. The tunnel 30 may have a lower tapered surface 81, the lower tapered surface 81 providing a "beach action" that absorbs most of the surface wave energy at the tunnel entrance, thereby reducing the shock and harmonic action on the vessel as it passes or moors within the tunnel 30. The tunnel 30 is optionally part of or includes a moonpool that opens through the mating keel 12 f. If a moonpool is provided, it may be open to the ocean below, for example, with a grating to prevent objects from falling through it, or it may be closed by watertight hatches, as desired. An open moon pool may provide a slightly better overall motion response.

In an embodiment of the method, the tunnel 30 may have at least one closable door at each entrance. In embodiments, the at least one closable door may be watertight or weathertight and may be opened and closed as desired. The at least one

closable door

34a and 34b may also serve as a guidance and righting system, as the at least one

closable door

34a and 34b may be fitted with a durable rubber shield to reduce potential damage to the float 12 and vessel in the event of an impact. The interior of the tunnel 30 may include a shield to facilitate docking. When the at least one

closable door

34a and 34b is closed, the tunnel 30 with tunnel floor 35 may be drained using, for example, a high capacity pump or a gravity based drainage system located in a pump room of a floatable offshore warehouse to create a dry dock environment within the floating body 12. Weathertight doors, which may include openings below the water line, may be used in place of watertight doors to allow water to circulate between the tunnel 30 and the exterior in a controlled manner. The at least one

closable door

34a and 34b may be hinged or may slide vertically or horizontally as is known in the art.

The tunnel 30 may comprise a single branch or multiple branches with multiple penetrations through the float 12. The tunnel 30 may include straight, curved, tapered sections and intersections in a variety of frontal views and configurations.

Figure 8 depicts a side view in partial cross-section of a floating body of the floatable offshore depot showing a plurality of baffles 37a to 37h for reducing waves within the tunnel 30.

Floatable offshore warehouse 10 may be configured to be floatable to transition from a floating orientation having a floating operational depth 71.

In embodiments, the tunnel 30 may be formed within the floating body 12 at the water line or through the floating body 12. The tunnel 30 may provide a sheltered area within the float 12 for safe and easy ground water/docking of the ship and safe and easy boarding/disembarking of personnel. The tunnel 30 may have a lower tapered surface 81, the lower tapered surface 81 providing a "beach action" that absorbs most of the surface wave energy at the tunnel entrance, thereby reducing the impact or harmonic effects on the vessel as it passes or moors within the tunnel 30. The tunnel 30 is optionally part of or includes a moonpool that opens through the mating keel 12 f. In embodiments, if a moonpool is provided, the moonpool may be open to the ocean below, for example, with a grating 152 to prevent objects from falling through it, or may be closed by watertight hatches as desired. An open moon pool may provide a slightly better overall motion response.

closable door

In an embodiment, the tunnel 30 may be a straight tunnel of a diameter that passes completely through the float 12.

At least one of the fin shaped appendages 84 a-84 d may be used to create additional mass and to reduce heave and otherwise stabilize the floatable offshore warehouse 10. A plurality of fin shaped appendages 84 a-84 d may be attached to the outer lower portion of the lower cylindrical side section of float 12.

In one or more embodiments as shown, the plurality of fin-shaped appendages 84 a-84 d may have at least four fin-shaped appendages that are spaced apart from each other by a gap. The gap 86 is shown receiving one of the plurality of catenary mooring lines 16a on the exterior of the buoy 12 and not in contact with the plurality of fin appendages 84 a-84 d. A plurality of catenary mooring lines 16 a-16 p are also shown.

Fig. 10 depicts a horizontal section taken through a float 12 of a floatable offshore depot according to one or more embodiments.

In an embodiment, the tunnel 30 may be a cross-shaped tunnel having inlets formed at ninety degree intervals through the float 12.

In this embodiment, the cruciform shape 89 forms a plurality of tunnel openings 31a to 31d in the buoyant hull 12 of the floatable offshore depot.

The tunnel 30 provides four entrances spaced ninety degree intervals around the float 12. Ideally, the floatable offshore depot may be moored such that at least one of the plurality of tunnel openings 31a to 31d may be on a leeward side from prevailing winds, waves and currents.

Each of the plurality of tunnel openings 31a to 31d may be formed in the floating body and open to the outside of the tunnel 30. Each of the plurality of tunnel openings 31a to 31d may have at least one tunnel shield 45a to 45 l.

At least one fin-shaped appendage 84 a-84 d and a plurality of catenary mooring lines 16 a-16 p are depicted. The gap 86 is shown to accommodate one of the plurality of catenary mooring lines 16a that is located outside of the hull 12 and not in contact with the at least one fin appendage 84 a-84 d.

In an embodiment, the tunnel 30 may be Y-shaped in the floating body 12 and have a tunnel opening 31a communicating with a first branch 36a and a second branch 36b leading to

further tunnel openings

31b and 31c, respectively.

In operation, a fast transfer unit FTU or similar vessel may arrive in the vicinity of a moored and stable floatable offshore warehouse. Ideally, the vessel may be close to the tunnel entrance, which may be the tunnel entrance most immune to wind, waves and water currents. If not already in a flooded state, the tunnel may be flooded. At least one closable door may be opened and the vessel may then enter the tunnel under its own power. The at least one door shield and the at least one self-guiding righting dock of the tunnel may provide a safe and reliable clearance guide. More than one self-guiding righting dock may be used.

The at least one tunnel shield may eliminate or significantly reduce vessel drift and impact against the inner dock side of the tunnel. After the vessel passes the entrance, the at least one closable door may be closed to reduce wave, wind and surge effects from external environmental conditions. The vessel may then be positioned on the boatlift assembly, optionally assisted with a controlled and monitored underwater camera and transporter system. The vessel may then be lifted as required by the boatlift assembly. The reverse procedure can be used to launch the vessel.

The floatable offshore warehouse may be designed and sized to meet the requirements of any particular application. The dimensions can be measured using the well-known Froude measurement technique. The tunnel may be approximately 17 meters wide and 21 meters high, and the size may be suitably adjusted. This size is suitable for the above-described triple hull FTU.

In an embodiment of the method, the floatable offshore depot may have a floating transport depth and a working depth, wherein the working depth may be achieved by means of ballast pumps and filling of ballast tanks in the floating body with water after moving the structure at the floating transport depth to the working position.

In an embodiment of the method, the floating transport depth may be from about 7 meters to about 15 meters, and the working depth may be from about 45 meters to about 65 meters. The tunnel may be free of water during transport.

In an embodiment of the method, the straight, curved or tapered sections in the floating body form a tunnel.

In an embodiment of the method, the method provides a casino comprising gaming and/or recreation on a floatable offshore warehouse.

In an embodiment of the method, the method provides a military staging area on a floatable offshore depot.

In an embodiment of the method, the plate, the at least one closable door and the float may be made of steel.

In an embodiment of the method, the floatable offshore depot may have a lower frustoconically shaped side section extending downward from the upper cylindrical side section.

In an embodiment of the method, the floatable offshore depot comprises a frustoconical side section between the transition section and the lower frustoconical side section.

In an embodiment of the method, the method may utilize a floatable offshore depot for providing a sheltered area within the buoy using the tunnel for safe and easy groundwater/docking of the vessel and safe and easy boarding/disembarking of personnel using the inner docking side of the tunnel, and for transferring equipment between the vessel and the floatable offshore depot using the inner docking side of the tunnel.

The method may use a floatable offshore depot with the following floats: the float has a float plane form in the shape of a circle, oval, ellipse or polygon.

In an embodiment of the method, the buoyant body may have a mating keel and a main deck.

In an embodiment of the method, there may be at least two connection sections between the buoy and the main deck that are joined in series and are symmetrical about a vertical axis.

In an embodiment of the method, the connecting section may extend downwardly from the main deck towards the mating keel and may have at least two of: an upper cylindrical side section, a transition section, and a lower cylindrical section.

In other embodiments of the method, the floating body may have a tunnel at the working depth. The tunnel may have a tunnel opening in the float that opens to an exterior of the float and is sized to receive the vessel.

In an embodiment of the method, the floatable offshore depot may have an upper conical section located between the transition section and the lower frustro-conical side section.

In an embodiment of the method, a floatable offshore depot provides selective isolation of the tunnel from the exterior; thus, the tunnel may be operated in a wet state or a dry state while the floatable offshore depot is floating in the body of water.

In an embodiment of the method, the floatable offshore depot may be configured to maintain the tunnel in a wet state or a dry state while the floatable offshore depot floats in the body of water.

In an embodiment of the method, the floatable offshore depot may have a second tunnel opening for a tunnel in the buoy leading to the outside of the buoy.

In an embodiment of the method, the floatable offshore depot may have a first branch and a second branch for the tunnel, wherein each branch may penetrate the float.

In an embodiment of the method, the floatable offshore depot may have a cross-shaped tunnel, thereby forming a plurality of tunnel openings in the floating body.

In an embodiment of the method, the floatable offshore depot may have a main deck configured to carry the superstructure thereon; and the superstructure may comprise at least one member selected from the group consisting of: a mooring facility, a cabin, at least one helicopter, at least one crane, a control tower, and at least one aircraft garage.

In an embodiment of the method, the floatable offshore depot may have an optional baffle to reduce waves within the tunnel.

In an embodiment of the method, the floatable offshore depot may have a moonpool configured to engage the tunnel, wherein the moonpool is configured to be opened by a mating keel.

In an embodiment of the method, the floatable offshore depot may have at least one tunnel shield disposed within the tunnel to reduce wave action and provide clearance guidance for the vessel; and outside the tunnel opening so that the vessel can be self-guided into the tunnel.

In an embodiment of the method, the tunnel of the floatable offshore depot may have a self-guiding righting dock.

In an embodiment of the method, the floatable offshore depot may have a gangway to allow for movement to and from the structure to an adjacent structure.

In an embodiment of the method, the floatable offshore depot may have a buoyancy body with a low center of gravity, thereby providing inherent stability to the structure.

In an embodiment of the method, the floatable offshore depot may have at least one fin-shaped appendage attached to an outer lower portion of the buoyant body.

In an embodiment of the method, the floatable offshore depot may have a lower tapered surface at the entrance of the tunnel, providing a "beach action" that absorbs most of the surface wave energy.

In an embodiment of the method, the floatable offshore depot may have a tunnel floor, such that the floatable offshore depot is adapted to drain the tunnel to form a dry dock environment within the floating body.

In an embodiment of the method, the floatable offshore depot forms a tunnel in a straight, curved or tapered section in the float.

In an embodiment of the method, the floatable offshore warehouse may have a plurality of thrusters and a plurality of catenary mooring lines to dynamically moor the floatable offshore warehouse to the seabed or to provide dynamic positioning when communicating with the global positioning system.

In an embodiment of the method, the floatable offshore depot may be configured to float on a body of water and to be ballasted down and seated on the seabed. In essence, this particular floatable offshore depot may be adapted to float at two different heights and to sit on the seabed for different operational and transport purposes.

While the embodiments have been described with emphasis on the various embodiments, it should be understood that within the scope of the appended claims, the embodiments may be practiced other than as specifically described herein.

Claims

1. A method of using a floatable offshore depot, the method comprising:

a. providing a sheltered area configured as a tunnel within the buoyant body for safe and easy groundwater or docking of a vessel, wherein the tunnel comprises a first tunnel side and a second tunnel side between which the vessel is received, and at least one of the first tunnel side and the second tunnel side comprises a recess;

b. providing an inner dock side within the tunnel for personnel to board or disembark;

c. providing the sheltered area within the float configured as the tunnel with the inner dock sides for transporting equipment between the vessel and the floatable offshore warehouse;

wherein the inner dock side is located in the recess and allows a person to walk down like a dock or allows a storage device;

wherein the floatable offshore depot comprises:

(i) the float having a hull plan form that is circular, oval, elliptical, or polygonal;

(ii) a mating keel and a main deck, wherein the main deck and the mating keel are configured to facilitate offshore stability;

(iii) a tunnel floor that enables a dry dock environment to be formed within the float when the tunnel is drained of water;

(iv) a plurality of dynamic movable tilt-prone mechanisms disposed within and connected to the first tunnel side and the second tunnel side, wherein the plurality of dynamic movable tilt-prone mechanisms are disposed between the recess and the tunnel floor;

(v) at least two connection sections joined between the mating keel and the main deck, the at least two connection sections joined in series and symmetrical about a vertical axis, wherein the at least two connection sections extend downward from the main deck toward the mating keel, the at least two connection sections comprising at least two of:

1. an upper cylindrical side section;

2. a transition section; and

3. a lower cylindrical section; and

wherein the tunnel of the float is formed within the float for receiving the vessel when the float is at a floating operational depth, the tunnel comprising a tunnel opening in the float that is open to an exterior of the float and sized to receive the vessel; and

wherein the floatable offshore warehouse is configured to be floatable to transition from the floating operation depth or floating transport depth to resting on a sea floor.

2. The method of claim 1, wherein the floatable offshore depot comprises a lower frustoconical side section extending downwardly from the upper cylindrical side section.

3. The method of claim 1, wherein the floatable offshore depot comprises an upper conical section between the transition section and a lower frustoconical side section.

4. The method of claim 1, wherein the floatable offshore depot provides selective isolation of the tunnel from an exterior of the float, wherein the tunnel is operable in a wet state or a dry state while the floatable offshore depot is floating or resting on a sea bed.

5. The method of claim 1, wherein the floatable offshore depot comprises an additional tunnel opening in the buoyant body leading to an exterior of the buoyant body.

6. The method of claim 1, wherein the tunnel of the floatable offshore depot comprises at least one branch, wherein each branch has an additional tunnel opening.

7. The method of claim 1, wherein the floatable offshore depot comprises a cross-shaped tunnel forming a plurality of tunnel openings in the buoyant body.

8. The method of claim 1, wherein the floatable offshore warehouse comprises the main deck configured to carry an superstructure, wherein the superstructure comprises at least one member selected from the group consisting of: mooring facilities, cabins, take-off and landing surfaces, cranes, control towers, aircraft garages, casinos including games and/or recreation, and military staging sites.

9. The method of claim 1, wherein the floatable offshore depot comprises a plurality of baffles to reduce waves within the tunnel.

10. The method of claim 1, wherein the floatable offshore depot comprises a moon pool configured to fluidly engage the tunnel and configured to be opened by the mating keel.

11. The method of claim 1, wherein the floatable offshore depot comprises a plurality of shields, wherein the plurality of shields are at least one door shield and at least one tunnel shield, wherein the at least one tunnel shield is positioned at a location within the tunnel to reduce wave action and provide clearance guidance for the vessel and is positioned outside the tunnel opening to enable self guidance of the vessel into the tunnel.

12. The method of claim 1, wherein the floatable offshore depot comprises the tunnel with a self-guiding righting dock.

13. The method of claim 1, wherein the floatable offshore warehouse comprises a gangway to and from the floatable offshore warehouse and an adjacent structure.

14. The method of claim 1, wherein the floatable offshore depot comprises the floating body having a lower center of gravity, thereby providing inherent stability to the floatable offshore depot.

15. The method of claim 1, wherein the floatable offshore warehouse comprises at least one fin-shaped appendage attached to an outer lower portion of an outer side of the floating body.

16. The method of claim 1, wherein the floatable offshore depot comprises a lower tapered surface at the entrance of the tunnel, thereby providing a "beach action" that absorbs surface wave energy.

17. The method of claim 1, wherein the buoyant hull of the floatable offshore depot comprises at least one of straight, curved, or tapered sections forming at least one of the first tunnel side and the second tunnel side.

18. The method of claim 1, wherein the floatable offshore warehouse comprises a plurality of thrusters and a plurality of catenary mooring lines that dynamically position the floatable offshore warehouse or dynamically moor the floatable offshore warehouse to a sea floor when in communication with a dynamic positioning system.

19. The method of claim 1, wherein the floatable offshore warehouse comprises a plurality of takeoff and landing surfaces, wherein each of the takeoff and landing surfaces is configured to allow a plurality of takeoff and landing aircraft to simultaneously takeoff and land from one of the plurality of takeoff and landing surfaces.

20. The method of claim 2, wherein the floating transport depth is approximately at the intersection of the lower frustoconical side section and the lower cylindrical section.

21. The method of claim 3, wherein the floating operating depth is on the upper tapered section and slightly below the intersection of the upper tapered section and the upper cylindrical side section.