US3837309A

US3837309A - Stably buoyed floating offshore device

Info

Publication number: US3837309A
Application number: US00228278A
Authority: US
Inventors: F Biewer
Original assignee: OFFSHORE Tech CORP
Current assignee: OFFSHORE Tech CORP
Priority date: 1971-06-17
Filing date: 1972-02-22
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24

Abstract

A floating offshore device including a closed vessel, such as a water tight hull, which is adapted to be ballasted to a submerged stage; and when submerged, it is retained in position by buoying means that can sway relative to the hull. The vessel is provided with a plurality of tanks and compartments, at least, one of the tanks receiving ballast and other compartments receiving some of the materials necessary for carrying out work to be performed. Upright means is fastened to the vessel and extends above the water. This upright means, in the form of structural columns, supports a floatable platform above the water when the device is in operable working position, the platform carrying some of the machinery for carrying out the work to be performed. The platform rests on the vessel when the device is being moved.

Description

United States Patent Biewer STABLY BUOYED FLOATING OFFSHORE DEVICE Inventor: Frank N. Biewer, San Diego, Calif.

Offshore Technology Corporation, Escondido, Calif.

Filed: Feb. 22, 1972 Appl. No.: 228,278

Related US. Application Data Continuation-in-part of Ser. No. 153,959, June 17, 1971, abandoned, which is a continuation-in-part of Ser. No. 839,223, July 7, 1969, abandoned.

Assignee:

US. Cl 114/.5 D Int. Cl B63b 35/44 Field of Search 114/.5 D, 43.5; 61/465 Glosten 114/.5 D Khelstovsky 114/.5 D

9/1971 Yu 114/.5 D

Primary Examiner-Trygve M. Blix Assistant Examiner-Stuart M. Goldstein Attorney, Agent, or Firm-Brown & Martin [5 7 ABSTRACT A floating offshore device including a closed vessel, such as a water tight hull, which is adapted to be ballasted to a submerged stage; and when submerged, it is retained in position by buoying means that can sway relative to the hull. The vessel is provided with a plurality of tanks and compartments, at least, one of the tanks receiving ballast and other compartments receiving some of the materials necessary for carrying out work to be performed. Upright means is fastened to the vessel and extends above the water. This upright means, in the form of structural columns, supports a floatable platform above the waterwhen the device is in operable working position, the platform carrying some of the machinery for carrying out the work to be performed. The platform rests on the vessel when the device is being moved.

5 Claims, 27 Drawing Figures PAIENTE 88241974 sum 10F a INVENTOR.

FRANK N. B/EWER A 7' TORNE Y PAIENIEBsP24|914 3'. 831; 309

mm SN 8 INVENTOR. FRANK N. BIEWER m i a STABLY BUOYEI) FLOATING OFFSHORE DEVICE CROSS REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of the inventors copending application Ser. No. 153,959 filed June 17, 1971, which was a continuation-in-part of the inventors application Ser. No. 839,223 filed July 7, 1969, both applications now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is directed to offshore stably buoyed devices.

2. Description of the Prior Art The art cited by the U.S. Patent Office in the parent application; namely, the patents to Templeton U.S. Pat. Nos. 3,001,370; Khelstonsky, 3,294,051; and OReilly, et al., 3,490,406, appears to be the most pertinent prior art. In addition to that art, the following patents are made of record: U.S. Pat. No. 3,408,821 to Redshaw; British Pat. Specification No. 1,017,944; and British Pat. Specification No. 1,153,652. However, none of the patents disclose a device in which the platform can be supported above the surface of the water by a closed vessel that is buoyed while in a submerged position by buoys that can sway relative to the vessel.

SUMMARY OF THE INVENTION The floating offshore device comprises an air-sealed vessel in the form of a floatable hull adapted to be ballasted to a submerged stage. It is buoyed in the submerged position by buoying means in the form ofa plurality of buoys that are spaced laterally from one another and coupled for swinging or swayable movements relative to the vessel. Upright structural columns are fixed to the vessel, and when the device is in working position, these structural columns extend above the surface of the water. A floatable platform in the form ofa hull is attachable to the upper parts of the columns. A tube is fixed to the lower hull and extends to the upper hull, providing access between the hulls.

The closed vessel contains all equipment, machinery, supplies, etc., necessary for carrying out work offshore. Preferably, all controls for controlling ballasting and deballasting of the tanks in the vessel and the buoys are in or on the platform. Like controls for other equipment are in or on the platform. Too, the platform is compartmented, one or more of which compartments can be used as living quarters.

When it is desired to change the location of the device from a working area to another area, the platform rests on the lower hull. The device is movable under its own power or may be towed.

When it is desirable to render the device operable, as for example for drilling in a deep sea, the vessel is submerged, but is buoyed by the buoying means. The lowering of the vessel will lower the structural columns and the platform is then attached to those columns; thereafter the buoys are sufficiently deballasted so as to raise the device whereby the platform is disposed above the surface of the water, yet the lower hull is maintained submerged.

Other features and the advantages of the present invention will be apparent from the followingdescription, reference being made to the accompanying drawings wherein preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the. floating offshore device showing the same in position for performing work offshore;

FIG. 2 is a side view of the same device, but in a position in which it is propelled from one station to another;

FIG. 3 is a top plan view of the lower hull;

FIGS. 4 and 5 are sectional views taken along lines 4-4 and 5-5, respectively, of FIG. 3;

FIG. 6 is a top plan view of the upper hull;

FIGS. 7, 8 and 9 are sectional views taken along lines 7-7, 8-8, and 9-9, respectively, of FIG. 6;

FIG. 10 is a fragmentary view of the universal coupling and fragments of the attachments on the lower hull and to one of the buoys of the buoying means;

FIG. 11 is a view looking in the direction of arrows 11 of FIG. 10;

FIG. 12 is a view, partly in section, of one of the buoys, part thereof being broken away to show the partitions therein;

FIG. 13 is a top plan view of the buoys shown in FIG. 12;

FIG. 14 is a diagrammatic view of the interior of a buoy showing the valve mechanism for controlling the ingress and egress of water to and from the buoy and the flow of air to and from the buoy;

FIG. 15 is a diagrammatic view of part of the control system;

FIG. 16 is a fragmentary view of one of the structural columns showing the mechanism for lowering the upper hull relative to the structural columns;

FIG. 17 is a sectional view showing a structural column extending through the upper hull and showing the gearing for raising the hull;

FIG. 18 is a fragmentary, top plan view looking in the direction of arrows 18 of FIG. 17;

FIG. 19 is a diagrammatic view of the ballast tanks in the lower hull and showing some of the controls therefor; 1

FIG. 20 is a perspective view of another embodiment of the invention in which the vessel is in the form of a catamaran, the view showing the vessel in a buoyed,

submerged position and the upper hull being in position above the surface of the water, the machinery and other equipment not being shown on the platform;

FIG. 21 is a top plan view of the device shown in FIG. 20;

FIG. 22 is a side view looking in the direction of arrow 22 of FIG. 21;

FIG. 23 is a front view looking in the direction of arrow 23 of FIG. 21;

FIG. 24 is a side view of the device shown in FIG. 20 illustrating the position of the device when it is in transit;

FIG. 25 is a view similar to FIG. 24, but showing the vessel submerged and also showing the upper hull partially elevated, the view also showing the buoys tied in a stationary position;

FIG. 26 is a view similar to FIG. 25, but showing the buoys untied and free to oscillate; and

FIG. 27 is a view similar to FIG. 26, but showing the upper hull in elevated position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring in general to the embodiment shown in FIGS. 1 through 19 of the drawings, the assembled floating offshore device 20 comprises a vessel in the form of a floatable hull 22 which contains tanks 24 for receiving ballast, as for example, water. When the device is in situ and made ready for working, the tanks 24 are ballasted to submerge the lower hull. Buoying means is provided in the form of a plurality of buoys 26, at least three and preferably four of such buoys being provided. In the embodiment shown in FIGS. 1, 2 and 4, these buoys are in the form of hollow columns, the lower ends of which are pivoted to the hull, preferably by universal couplings 28 to provide for swayable movements thereof relative to the lower hull.

A plurality of upright structural columns 30 are fixed at their lower ends to the lower hull 22. These columns, as shown in FIG. 1, extend above the top surface 32 of the water and carry a platform 34 above the surface. If, for example, the device 20 is employed for drilling, then then the working platform 34 carries a derrick 36 and other equipment (not shown). The platform 34 and the hull 22 are provided with aligned vertically extending

holes

38 and 40, respectively, for receiving the drilling equipment (not shown).

The working platform 34 is in the form of a floatable hull, and as hereinafter explained, it can float on the surface 32 of the water; but when the device moves from one station to another, the upper hull rests on and is carried by the lower hull, as is more clearly shown in FIG. 2. Simultaneously, the buoys 26 are partly deballasted so that they float awash in horizontal positions on the water surface 32.

Either of the hulls can accommodate a motor (not shown) for propelling the device when the lower hall 22 is afloat, or the entire device 20 can be towed to a desired position. If desirable, the buoys can be retained attached to the hull 22 as shown in FIG. 2, or they can be detached and be towed fore or aft of the device 20.

Referring now to FIGS. 3, 4 and 5, the lower hull 22 is compartmented to include the elongate and oppositely disposed ballast tanks 24 and several other compartments, such as for a fuel tank 42; a water tank 44; a pump room 46 for housing pumps, compressors for pumping and blowing water, air, ballast, etc., plus the necessary manifolds, control valves, piping, etc.; compressed-air storage compartment 48, and other compartments that may be desirable.

FIGS. 6, 7, 8 and 9 show the upper hull 34 in more detail. It also is compartmented by superimposed floors 50 and vertical walls 52 to provide living quarters, areas for machinery, storage, etc. That hull 34 is also partitioned as at 54 for receiving a tube 56. This tube extends into the pump room 46 of the lower hull 22 and is provided internally with an elevator (not shown). Thus, access is provided between the hulls for transporting persons and equipment, and for conduits for controlling the machinery and valves in the lower hull 22 by controls in the upper hull 34. Only the derrick foundation 58 is shown in FIG. 6.

Referring more in detail to the drawings, the lower hull 22 is provided with four outwardly and fixed extensions 60; the uuper ends of the extensions carry the universal couplings 28. As shown more clearly in FIGS. 10

and 11, the ends of the extensions are bifurcated to provide arms 62 which carry a pin 64 which is pivotally connected to the yoke 66 of a U-shaped link 68, the arms of which link carry a pin 70 which pivotally connects the U-shaped link with the lower extension 72 of the buoy 26. Thus, the buoys can sway relative to the lower hull.

The buoys 26 are shown in more detail in FIGS. 12, 13 and 14. Each buoy comprises an elongate, preferably cylindrical, column 74 which is reinforced internally by transversely disposed partitions or bulkheads 76 to form compartments 78. The top 80 of each column 74 is provided with a manhole which is closed by a removable cover 82. Like manholes and covers therefor are provided for the partitions 76.

Each buoy 26 is provided with a flood drain conduit 84 for water. This conduit extends through the bottom 86 of the column 74 of the buoy and into each compartment 78, the flows therethrough being controlled separately for each compartment by valves 88. A valve 89 shown diagrammatically in FIG. 15 is disposed in conduit 84. This valve 89 can be turned to a position in which water can be delivered to the compartments, and can be turned to a position in which the compartments can be drained of water when air is forced into the compartments.

Each buoy 26 is provided with a flexible pneumatic conduit 90 for conducting air into a compartment 78 for venting the same of water. This conduit 90 extends upwardly through the bottom of the buoy column 74 and into each compartment. The flow of air is controlled separately for each compartment by valves 92. As shown diagrammatically in FIG. 15, valve-control wires 94 extend through the conduit 90 for actuating motors 96 for water-control valves 88; and valve control wires also extend through the conduit for actuating the motors 98 for the air-control valves 92. A valve 99, shown diagrammatically in FIG. 15, is disposed in the air conduit 90. This valve can be turned to a position in which air can be delivered to the compartment, and can be turned to a position in which the compartment can be drained of air when water is delivered to the compartments. Thus, like compartments of all four buoy columns 74 are drained or receive water for governing the positions of the buoys 26 by draining water from or admitting water to the respective compartments.

FIG. 16 shows a fragment ofa rack 100 on one of the structural columns 30. A gear 102 meshes with the rack teeth and is driven by a shaft 104, which shaft is driven by a motor such as a rotary positive displacement hydraulic motor 106, the motor and shaft being shown diagrammatically in FIG. 16. Each structural column 30 is provided with the rack 100, and a partition 112 of upper hull 34 carries a gear 102 and motor 106 (see FIG. 16). It will be understood that the motors are synchronized for like turning of all gears 102 whereby the upper hull 34 is maintained parallel with the hull 22 in all positions of the hulls.

Referring again to FIG. 17 and also to FIG. 18, it will be seen that the upper part of each structural column 30 extends through a hole 110 in the upper hull 34,

partition walls

108 and 112 forming such hole, and each column has a steel plate 114 fixed to the top thereof. A plurality of dogs 115 are pivotally mounted on headed pins 116 which are fixed to the top wall or top floor 117 of the upper hull 34. These dogs are movable from a position in which they do not overlie the plates 114 to a position in which they overlie the plates. When in overlying position, they prevent lowering of the upper hull relative to the structural columns 30. Likewise, the elevated position of the upper hull relative to the columns is limited by the plates. Thus, with the dogs 115 in plate-overlying position, the upper hull 34 cannot move relative to the structural columns. In this manner the gears 102 and motors 106 are not subjected to the strain of retaining the upper hull 34 in its elevated position.

As shown diagrammatically in FIG. 19,a flood and drain conduit 118 is provided for each tank 24, the flow through the conduits being controlled by valves 119. Conduits 120 are connected with a source of air under pressure for forcing air into the tanks to drive the water out of the tanks when the valves 119 are open, and for venting air from the tanks. The air flow to and from the tanks is controlled by valves 122.

Valves

119 and 122, like valves 89 and 99, not shown in FIG. 19, are employed for the same purpose as specified with respect to supplying and removing water and air to and from the compartments. Wires 124 and 126 (see FIG. extend through the conduit 120 and are connected, respectively, with

motors

127 and 128 for controlling, respectively,

valves

119 and 122.

Three-

pole switches

130 and 132 are provided, respectively, for motor 133 and motor 134 for a hydraulic pump 135. Also, the three motors 96 are each controlled independently by a three-pole switch 136, and each of the three motors 98 is controlled independently by a three-pole switch 138. Motors 127 are connected in parallel and are controlled by a three-pole switch 140. Also, motors 128 are connected in parallel and are controlled by a three-pole switch 142.

The wires heretofore specified are connected to the

main wires

144, 146 and 148 which receive current from a three-phase alternating current generator 150 which is driven by an internal combustion engine 152. The engine, the generator, the motor 133, the pump 135, the motors 106 and the three-pole switches are disposed in or on the upper hull 34. It is to be understood that other motors, such as motors for doing work, for example, drilling, are also carried in or on the upper hull.

Referring again to FIG. 15, a motor 154 is connected to the main wires by a three-pole switch 156. Motor 154 drives the water pump 158 for delivering water to the ballast tanks 24. A motor 160 is connected to the main wires by a three-pole switch 162. Motor 160 drives the air pump 164 for delivering air to the ballast tanks 24. Valve 89 is provided with a controller 166, and valve 99 is provided with a controller 168. These

controllers

166 and 168 are like the controller 136 that controls the motor 96. It will be understood that the controllers for controlling the flow of water and air to and from the ballast tanks are controlled from the upper hull 34.

As previously explained, the entire device is moved from station to station as a unit like that shown in FIG. 2. After the unit is at the station where work is to be performed, the preferred manner of raising the upper hull 34 to a position above the surface of the water 32 (as shown in FIG. 1) is to detach the upper hull 34 from the lower hull 22. Then the lower hull 22 is submerged by ballasting the same. The depth to which it is submerged is governed by the degree of ballasting of the buoys 26 and/or the degree of ballasting of the tanks 24 of the lower hull 22. As the hulls separate vertically relative to one another, the racks and the motor driven gears 102 maintain parallelism between the hulls. When the hulls have separated to the desired distance, the upper hull 34 is secured to the structural columns 30. After such securing, the buoys 26 and/or the tanks 24 are deballasted sufficiently to cause the device to move upwardly to the position shown in FIG. 1, wherein the upper hull 34 is above the surface of the water and the lower hull remains submerged.

The sequence of movements to return the device from the position shown in FIG. 1 to the position shown in FIG. 2, i.e., to the towing position, is: first, ballasting the buoys 26 and/or the lower hull 22 until the upper hull 34 is waterborne; then that hull is unlocked from the structural column 30; then the lower hull 22 is deballasted until it not only engages the upper hull, but lifts the same above the surface of the water. The hulls are then suitably locked to one another. The buoys are then deballasted to the desired degree so that they float in horizontal position on the surface of the water.

The following features are recited for this device:

a. Due to the small waterplane area and the large submerged mass, the device has a long natural period of heave with the result that the device is de-tuned from the action of the sea.

b. The device heave amplitude is minimal because the buoys and lower hull 22 are affected by the water particle motion at the deep draft of the device where the motion has been greatly attenuated from that existing at the surface.

c. Lateral motion of the sea which tends to move the device laterally merely causes the buoys to swing back and forth in the waves and very little motion is imparted to the fixed upper hull 34 itself. A vertical column, or spar, tends to oscillate in a seaway about a fulcrum point near the base of the buoys. In this case the lower hull is attached to the buoys where motion is already minimal. A pinned joint will transmit only a force, i.e., it cannot transmit any moment to the structure.

d. The device has a low center of gravity because most of the mass is concentrated in the lower hull 22. The low center of gravity tends to make the upper hull safe.

e. The upper hull is highly damped by the lower hull 22 and the latters trapped mass of water. This damping where water motion is small tends to limit the vertical response of the device, even to a resonant sea.

f. The buoys represent only part of the buoyancy required. Accordingly, the forces at the pinned joints are modest and the joints can be built with large factors of safety.

g. In the event repairs are required, the device may be disassembled while waterborne in the transit mode. Individual components may then be drydocked for repair and maintenance.

h. Large masses are moved by changes in buoyancy, thus large and heavy machinery is not required to raise and lower the hulls.

i. There is a high degree of flexibility in building devices to this design in that a particular hull form is not required and virtually any number of buoys (three or over) may be used. Thus, devices of this type may be large or small with correspondingly large or small payload capability built in.

If desirable, the water tanks 24 in the lower hull 22 can be omitted and ballasting and deballasting can be effected by moving material from the upper hull 34 to the lower hull 22 to ballast the lower hull and vice versa for deballasting the lower hull. For example, the working machinery, normally employed in the lower hull while work is being performed, can be stored in the upper hull when moving from one station to another. Then after reaching the station where work is to be performed, such machinery is lowered into the lower hull. After the work is completed and the upper hull is to be raised, the machinery is lifted from the lower hull and stored in the upper hull.

Referring now to the embodiment 220 shown in FIG. 20 through FIG. 27, the vessel 222 is in the form of a catamaran including two elongate and air-sealed

hulls

222a and 222b and interconnecting

hollow braces

222e, 222d, 222e and 222f. The spaces in those bulls and braces are interconnected so that access can be had between the interiors of those hulls and the braces. Those hulls and braces are welded in position and are compartmented for the purposes as defined for the previous embodiment. Buoying means in the form of four buoys 226 are universally connected adjacent the four corners of the catamaran, i.e., the areas at which the

outer braces

2220 and 222f are joined with the hulls 222a and 22212 by universal couplings 228.

Each of the braces or

hull connectors

222d and 222e support upwardly extending, hollow columns 230. The spaces in the columns and the hollow braces are interconnected so that access can be had between the braces and the columns. The platform 234 is in the form of a hull and is provided with vertical openings therethrough for receiving the hollow columns 230. Each of the columns and the upper hull are provided with cooperating elevating mechanism for raising and lowering the upper hull along the columns. Any desired elevating mechanism can be employed, one form of which is shown in FIG. 16 where there is illustrated a rack 100 that is carried by the upper hull 234 and a pinion 102 carried by the column. There being four columns 230, four synchronized motors I06 drive the pinions 102 whereby the upper and lower hulls are maintained parallel.

The motors and pinions can be within or along the outer sides of the columns. Each of the columns 230 have openings (not shown) in the sides thereof providing access from the exterior to the interior of the column. Instead of employing a tube like tube 56 in the embodiment shown in FIGS. 1 to 5, the hollow columns 230 are provided with elevators to provide access to the interior and the top of the upper hull, and the interior ofthe lower hull for the purposes specified with respect to the embodiment shown in FIGS. 1 through 19. The upper hull 234 is provided with compartments for purposes defined in the embodiment shown in FIG. 1 through FIG. 19.

The sides of the

hulls

222a and 222b carry elongate wings 222g. For example, when the hulls have a length ofapproximately 250 feet, the width of each wing is approximately l2/2 feet. The wings provide a significant increase to the mass of the vessel, thereby lengthening the natural period of oscillation of the vessel. The

damping of oscillatory movements is effective in all modes of oscillation and to the extent that the motion response to resonance is reduced by 50 to I percent. This is particularly advantageous when the lower hull and wings thereon are submerged while the machinery is in operation, for example, during drilling.

The submerging and raising of the catamaran hulls and the raising of the upper hull 234 follow the same procedures as those explained with respect to the lower hull 22 and the upper hull 34.

Unless the buoys 226 are fixed in position, particularly during the initial submerging of the catamaran, they would wobble and could damage themselves and structures about the same. Therefore, the buoys are restrained from wobbling during the initial interval of submerging of the catamaran. When the catamaran is lowered to a position in which the buoys will not wobble to the extent of striking other parts of the catamaran, then the wobble-restraining means is rendered ineffective.

The means for preventing wobbling can be by a winch-actuated cable or the buoys could carry metal which would be welded to stationary parts of the vessel. Another means could be chains, each having a weak link. When the tension on the chains attains a predetermined value, the weak links will break permitting the buoys to oscillate independently of one another. Such chains 235 with the weak links are shown in FIGS. 24 through 27.

The same advantages hereinbefore set out for the embodiment described in FIGS. 1 to 19 are present in the embodiment shown in FIGS. 20 to 27.

Having described my invention, I claim:

1. A floating device comprising in combination,

a watertight floatable vessel having a small water plane area and a large submergable mass,

said vessel having a plurality of ballast tanks in spaced locations across the breath of said vessel,

a plurality of upright, non-water tight and nonbouyant, structural columns fixed at their lower ends to said vessel,

a floatable platform having a plurality of holes therethrough for passing said columns, said platform and vessel being held in vertical and horizontal alignment by said columns,

mechanism means for ballasting said tanks and lowering the vessel to a submerged deep depth draft in the water and for deballasting said tanks to raise the vessel and said platform on said columns, with ones of said tanks being ballasted to provide trim of the vessel and the platform,

a plurality of individually articulating column stabilizer means being fixed by non-moment transferring, universal connections to the vessel in upright positions at spaced locations adjacent the outer edges of the vessel,

and said stabilizer means are elongated water tight vessels that extend from the upper surface of said first vessel at said deep draft, with only the tips of the free ends extending above the water surface, whereby said stabilizers are non-responsive to surface wave action, and platform heave amplitude is minimal as the vessel and column stabilizer vessels are substantially solely affected by the water particle motion at the deep draft which motion is greatly attenuated from that at the surface.

2. A floating device as defined in claim 1 wherein,

each of said stabilizer vessels being vertically compartmented,

trons. 4. A floating device as defined in claim 3, characterized in that the bracing means is hollow.

5. A floating device as defined in claim 3, characterized to include,

horizontally extending and elongate wing means extending longitudinally alongside the vessel sections

Claims

1. A floating device comprising in combination, a watertight floatable vessel having a small water plane area and a large submergable mass, said vessel having a plurality of ballast tanks in spaced locations across the breath of said vessel, a plurality of upright, non-water tight and non-bouyant, structural columns fixed at their lower ends to said vessel, a floatable platform having a plurality of holes therethrough for passing said columns, said platform and vessel being held in vertical and horizontal alignment by said columns, mechanism means for ballasting said tanks and lowering the vessel to a submerged deep depth draft in the water and for deballasting said tanks to raise the vessel and said platform on said columns, with ones of said tanks being ballasted to provide trim of the vessel and the platform, a plurality of individually articulating column stabilizer means being fixed by non-moment transferring, universal connections to the vessel in upright positions at spaced locations adjacent the outer edges of the vessel, and said stabilizer means are elongated water tight vessels that extend from the upper surface of said first vessel at said deep draft, with only the tips of the free ends extending above the water surface, whereby said stabilizers are non-responsive to surface wave action, and platform heave amplitude is minimal as the vessel and column stabilizer vessels are substantially solely affected by the water particle motion at the deep draft which motion is greatly attenuated from that at the surface.

2. A floating device as defined in claim 1 wherein, each of said stabilizer vessels being vertically compartmented, and means for individually ballasting aNd deballasting each of said compartments in each of said stabilizer vessels.

3. A floating device as defined in claim 1, characterized in that the vessel comprises, at least, two elongate hollow sections horizontally spaced from one another, and bracing means interconnecting the vessel sections.

4. A floating device as defined in claim 3, characterized in that the bracing means is hollow.

5. A floating device as defined in claim 3, characterized to include, horizontally extending and elongate wing means extending longitudinally alongside the vessel sections.