Abstract: A vertically installed Spar-type floater for offshore wind turbine and related construction method are provided. The floating system is a gravity stabilized deep-draft floater including a plurality of vertically extending columns, each column containing a ballast material; a ballast tank coupled to the lower end of each of the columns; a top deck having a plurality of through-bores approximate its periphery coupled to the upper end of each of the columns; a wind turbine assembly supported by the top deck at the center; a plurality of mooring lines linking the floating system to the sea floor. The floating system has a temporary vertically towing configuration which: allows the entire, floating wind turbine system to be assembled at a quayside and towed vertically to an offshore site, and self-installed into operating configuration.

Abstract: A method is disclosed herein for lifting thrusters on vessels enabling for on vessel maintenance at sea. The method can include engaging a thruster mounting flange with a thruster well bottom flange; installing alignment guide plates to provide a rough alignment; positioning a seal to provide a connection; installing fasteners to secure the flanges; actuating clamps to secure the flanges while compressing the seal; raising the thruster out of the thruster well; transporting the thruster to a deck of the floating vessel; actuating clamps to hold the flanges; removing the fasteners; flowing water into the thruster well; disengaging the clamps; and lifting the thruster with the lifting means.

Abstract: A removable retractable externally mountable dynamic positioning self contained diesel hydraulic thruster system for a floating semi-submersible vessel having a hull with a ballasted waterline, a first pontoon integral with the hull and a second pontoon integral with the hull. The hull supports a deck, wherein the system comprises: at least a pair of azimuthing thrusters, wherein at least one azimuthing thruster is removably mounted to a pontoon of a semi-submersible vessel.

Abstract: A large deck area floating platform with wave attenuating outriggers provides equivalent payload and deck operating area to a fixed, piled, and jacketed platform alternative for coastwise and offshore applications. The floating platform integrates large deck areas for industrial applications with a main ship-shaped hull and a submersible system of outriggers and column risers to form a stable, transportable, and structurally sound industrial facility that may be tuned hydro-dynamically to attenuate wave forces on the moored structure. The platform provides from 2 to 10 acres of weather deck and associated superstructure space, a ship-like hull, and direct subsea access via enclosed areas between the main hull and outriggers. Through the medium of differential ballasting, the displacement and freeboard of the facility may be adjusted to maintain hydro-dynamic tuning for changing wave conditions or to provide additional freeboard for storm survival.

Abstract: A floating platform system includes a hull design configuration (40, 50) for limiting maximum tendon loads and aiding in inhibiting resonant responses in the platform system leading to better motions for personnel, equipment and riser support, and to lighter and lower cost tendon systems.

Abstract: A floating vessel is equipped with perforated plates which exhibit both an added-mass effect and a damping effect. The addition of porosity to an added mass plate phase-shifts the added mass force so that it becomes at least partially a damping force which does not depend on large velocities to develop a large damping force. Preferred porosity is in the range of about 5% to about 15% of total plate area. A semi-submersible vessel may have damper plates fitted between its surface-piercing columns, within a support grid in the area between the pontoons and/or extending from the sides of its pontoons. A truss spar offshore platform may have damper plates installed within its truss structure intermediate its hull and ballast tank. Drill ships and similar vessels may be equipped with damper plates extending from the sides of their hulls to reduce both heave and roll.

Abstract: A semisubmersible platform includes a deck supported on the upper ends of support columns extending upwardly from a horizontally disposed pontoon-ring. The columns are battered inwardly and upwardly from the pontoon-ring to the deck. Mooring lines passing through fair leads on the outer faces of the base nodes anchor the platform to the seabed. The footprint of the battered columns is greater than the footprint of the deck supported on the upper ends of the columns.

Abstract: A floating vessel is equipped with perforated plates which exhibit both an added-mass effect and a damping effect. The addition of porosity to an added mass plate phase-shifts the added mass force so that it becomes at least partially a damping force which does not depend on large velocities to develop a large damping force. Preferred porosity is in the range of about 5% to about 15% of total plate area. A semi-submersible drilling rig may have damper plates fitted between its surface-piercing columns and/or extending from the sides of its pontoons. A truss spar offshore platform may have damper plates installed within its truss structure intermediate its hull and ballast tank. Drill ships and similar vessels may be equipped with damper plates extending from the sides of their hulls to reduce both heave and roll. In certain embodiments, the damper plates are retractable so as not to interfere with docking and to reduce drag while the vessel is underway.

Abstract: The present invention is a lubrication system for movable pins connecting pivotable structural members of a deepwater floating oilfield production platform. The lubrication provides adequate lubrication for easing movement of the pins and also for maintaining the long-term functionality of the pins by reducing the corrosion of the pin assemblies. The lubrication of each of the pins is provided by a closed loop circulation system that provides sufficient flow and pressure to establish hydrostatic bearings around the bearing surfaces of the pin-connected members that are being axially assembled and between pin-connected members that are being rotated relative to each other. The lubrication system provides for continuously lubricating a static pinned connection for the purpose of preventing water intrusion and subsequent corrosion. Furthermore, the lubrication system provides a means for ensuring the lubrication of the most highly loaded zones of a laterally loaded pin connection.

Abstract: A floatable vessel is associated with an excavated area or foundation such that the floatable vessel rises and falls with changes in the water level of the surrounding environment. The foundation comprises a plurality of stabilizing posts that include telescopic sections where an upper telescopic section is connected to the floatable vessel. As the water level in the foundation rises or falls, the telescopic sections extend or retract as the buoyant floatable vessel moves with the water level. This action maintains the floatable vessel's connection with the foundation at various water levels. When there is no water within the foundation, or when the water level is sufficiently low, the floatable vessel rests on a plurality of pillars within the foundation. A tether cable is provided within the stabilizing posts as a back-up securing structure. Pivoting grates bridge the gap between the floatable vessel and the surrounding land.

Abstract: A semi-submersible structure. The hull includes four columns that are supported by two pontoons. The columns support the topsides and the topsides structural framing serves as horizontal framing between the columns. A truss frame is attached to the columns. The truss frame preferably includes heave plates. The truss frame extends downward below the pontoons a sufficient distance in the water such that it minimizes motions caused by environmental forces. The hull section and the truss space frame are constructed separately and assembled together at the offshore site where the structure is used for drilling and/or production.

Abstract: A pontoonless tension leg platform (TLP) has a plurality of buoyant columns connected by an above-water deck support structure. The design eliminates the need for subsea pontoons extending between the surface-piercing columns. In certain embodiments, the buoyancy of the columns is increased by the addition of subsea sections of increased diameter (and/or cross-sectional area) to provide the buoyancy furnished by the pontoons of the TLPs of the prior art. A pontoonless TLP has a smaller subsea projected area in both the horizontal and vertical planes than a conventional multi-column TLP of equivalent load-bearing capacity having pontoons between the columns. This reduction in surface area produces a corresponding reduction in the platform's response to ocean currents and wave action and consequently allows the use of smaller and/or less costly mooring systems.

Abstract: A jackup rig having a built-in capability of driving and extracting piles without need for dedicated pile drivers or extractors. The jackup rig provides an ice breaking functional capability, supplied by a jacking system, for operating in icy waters.

Abstract: A semi-submersible floating platform for use in offshore applications having a semi-submersible hull structure including motion damping support columns, a pontoon structure adjoined to the motion damping support columns at a lower end thereof, and a deck structure supported at an upper end of thereof for supporting equipment mounted thereon above the water surface. Each motion damping support column has an inner water trapping damper chamber of closed base or open base construction that allows natural flooding of said inner water trapping damper chamber during installation and before reaching an operating draft of the platform, and which when flooded provides hydrodynamic mass, damping, and in-water weight to said platform during operation. A plurality of smaller columns are disposed on the perimeter of the upper portion of each support column and surround the upper portion of the inner water trapping damper chamber.

Abstract: By efficiently lowering a water temperature of a sea surface to thereby suppress an evaporation of a water vapor from the sea surface by lowering the water temperature of the sea surface, a generation of an atmospheric depression is prevented or its strength is weakened. Further, by suppressing a rise of the sea surface temperature, a generation of a red tide or a blue tide is prevented or reduced.

Abstract: A method for providing a sustainable offshore community that includes a floatable, low cost platform structure which covers a large amount of real estate and is supported above the surface of the ocean from columns which pass through the structure such that the extremities of the structure are supported with stays that run from the top of the columns to the extremities of the platform. This type of staying structure permits the formation of the large floatable platform for supporting self sustaining communities by providing sizeable living and recreational areas, thus to permit an offshore community to exist at sea for a number of years.

Abstract: A mounting system is disclosed for mounting structures and equipment, such as wind-electric generators on water. The structure is attached to a carrier, which is attached to a foundation through connecting elements. Buoyancy tanks or the inherent buoyancy of the carrier or the connecting elements are used to maintain a stable position of the carrier in the water. Utilizing connecting elements that transfer pushing and pulling forces, undesirable movements of the carrier are suppressed while requiring only moderate forces on the foundation.

Abstract: A floating vessel is equipped with perforated plates which exhibit both an added-mass effect and a damping effect. The addition of porosity to an added mass plate phase-shifts the added mass force so that it becomes at least partially a damping force which does not depend on large velocities to develop a large damping force. Preferred porosity is in the range of about 5% to about 15% of total plate area. A semi-submersible drilling rig may have damper plates fitted between its surface-piercing columns and/or extending from the sides of its pontoons. A truss spar offshore platform may have damper plates installed within its truss structure intermediate its hull and ballast tank. Drill ships and similar vessels may be equipped with damper plates extending from the sides of their hulls to reduce both heave and roll. In certain embodiments, the damper plates are retractable so as not to interfere with docking and to reduce drag while the vessel is underway.

Abstract: A semi-submersible floating platform (10, 10A) for use in offshore applications has a semi-submersible hull structure (11) including support columns (12), a pontoon structure (13) adjoined to the lower ends thereof, and a deck structure (14) supported at an upper end of the columns for supporting the deck and equipment mounted thereon above the water surface. One or more passive damper weight members (15) are suspended below the hull by flexible connection members (16) at variable distances to provide hydrodynamic mass, damping, and in-water weight to the platform during operation, and the flexible connection members are maintained in tension by the damper weight(s) during operation.

Abstract: A semisubmersible platform includes a deck supported on the upper ends of support columns extending upwardly from a horizontally disposed pontoon-ring. The columns are battered inwardly and upwardly from the pontoon-ring to the deck. Mooring lines passing through fair leads on the outer faces of the base nodes anchor the platform to the seabed. The footprint of the battered columns is greater than the footprint of the deck supported on the upper ends of the columns.

Abstract: The invention relates to the fixed platform which enables to locate on the water any fixed structure such as the house, garden, road, airport, car park, children's park and holiday village in the seas, lakes and rivers.

Abstract: A method for making a deep draft semi-submersible drilling/production vessel having a center of gravity below its center of buoyancy by constructing a plurality of buoyant individual columns. The method connects a pair of columns with at least a first top truss and a first bottom truss. The method additionally floats a connected first and second columns horizontally in water. The method floats the semi-submersible structure to a location for installation. The method concludes by deballasting the semi-submersible structure with connected deck forming a semi submersible drilling/production vessel having a center of gravity below its center of buoyancy with a draft between 300 and 500 feet.

Abstract: The present invention relates to pins that may be selectably operated to engage and disengage socket bores in the assembly and disassembly of large structures, such as floating offshore platforms for deepwater applications. The pin connections can be engaged or disengaged robotically or under direct operator control. The construction and installation of structures utilizing the pin connections will typically use multiple sets of selectably operable pins to connect, support and stabilize the structural components of the structure.

Abstract: The support (1) includes a working deck (2) and floatation members (3) supporting this deck (2). According to the invention, the spacing between the vertical axes (Z) passing through the centre of the floatation members (3) is such that the sum of the moments, taken in relation to the horizontal axis passing through the centre of the support (1) is perpendicular to the swell direction, of the vertical excitation forces of the swell on the floatation members (3) situated on one side of the vertical plane (P) passing through this horizontal axis is equal to the corresponding sum associated with the floatation members (3) situated on the other side of this plane, when the swell period is equal to the period of a swell having this direction and of which the yearly probability of being encountered on the site or the support where it is installed is 1/100.

Abstract: The invention concerns a building (1-6) provided with vertical displacement means (4-5), for moving the building (1-5) between an extended position interacting with the surroundings and a sheltered position for protection, and inversely. The vertical displacement means (4-5) comprise means forming hydraulic ballast (4), for moving the building (1-5) between said extended position corresponding to a discharge of the hydraulic ballast and said sheltered position corresponding to a filling of the hydraulic ballast (4). The building (1-6) comprises service rooms (6) implanted in the natural environment and independent of the vertical displacement means (4-5).

Abstract: A floating terminal for offloading an LNG carrier vessel in the sea. The floating terminal of open frame construction is moored toward its front end with a rotatable mooring arrangement so that the terminal may weathervane in response to environmental forces. Marine thrusters are provided at the aft end of the terminal for swinging the terminal away from and back toward a line defined by the path toward the terminal of an approaching LNG carrier. Offloading equipment and heat exchangers are provided on a deck of the floating structure. When an LNG carrier vessel approaches the terminal, the thrusters swing the floating terminal away from the carrier vessel approach line while a hawser at the front end of the terminal pulls the vessel close to the terminal. The floating terminal swings back toward the carrier vessel in response to operating the marine thrusters in an opposite direction until the carrier vessel and floating terminal are side-by-side.

Abstract: A floating moored oilfield production structure for deepwater application. An apparatus and a method for the construction and installation of floating oilfield production structures, wherein the deck structure is supported by multiple pairs of inclined buoyant legs which in turn support a subsurface damping plate structure for reducing the motions of the platform. The structure initially is initially constructed in a first configuration in relatively shallow water and then towed to a deepwater location where it is reconfigured to its operational configuration. The major structural components are joined by selectably operable pin connections.

Abstract: The present invention is a deep draft partially submersible and buoyant floating vessel comprised of at least three independent vertical columns. The columns have an upper column with an upper column diameter and a lower column integrally connected to the upper column with a lower column diameter smaller than the upper column diameters. The lower column contains a variable ballast, a free flooding ballast, and a lower column fixed ballast. The lower pontoon is connected to each lower column opposite the upper column. The lower pontoon has lower pontoon fixed ballast means. A deck is located on the columns for supporting a tensioner assembly.

Abstract: A semi-submersible vessel has a pair of vertically spaced pontoons with varied buoyancy. The lower pontoon is retained in a close vertical proximity to the upper pontoon when the vessel is in transit. The lower pontoon is ballasted at the deployment site, dropping the pontoon to a depth of about 32 meters below the first pontoon baseline. As a result, stability and motion characteristics of the vessel are significantly improved.

Abstract: An improved lift boat includes a hull, a plurality of legs (preferably three), a plurality of pads, one pad attached to each leg, and a jacking mechanism for moving each upward and downward. Recesses in the hull receive the pads when the lift boat is underway. Preferably, the total bottom surface area of the pads is at least 30% of the surface area of the deck of the lift boat Preferably, the total bottom surface area of the pads is large enough such that, when the boat is loaded to capacity and is jacked up, the pads exert pressure of less than 7 p.s.i. on the sea floor. Preferably, the pads are partially recessed into the hull and extend laterally outward from the hull when the boat is underway to provide increased stability to the lift boat when it is underway.

Abstract: The invention relates to a floating platform (1) for offshore drilling or production of hydrocarbons, comprising a topsides (2) and a substructure (3) having a lower pontoon (4) and columns (5) connecting the pontoon (4) to the topsides (2). Heave motion (s1, s2) of the platform (1) causes a change in the metacentric height (GM) of the platform. To counteract this change in metacentric height, the columns (5) are so adapted that the moment of area inertia of the waterline area of the columns (5) decreases on downward heave motion (s1) and increases on upward heave motion (s2).

Abstract: An efficient double-ended watercraft is disclosed that comprises four low-Froude number hulls: two forward, two aft, two on the port side, and two on the starboard. Each hull comprises an independent engine that drives a propeller shaft and propeller that is located amidships. The propeller shafts on the starboard are collinear, as are the propeller shafts on the port. The propellers on the starboard are near each other and counter rotate, as do the propellers on the port. The propellers are variable-pitch propellers. When the ferry is changes from moving forward to moving in reverse and from reverse to forward, the propellers on the starboard exchange pitch. This enables the ferry to move as efficiently in reverse as it does when forward. The propellers on the port also exchange pitch when changing from moving forward to moving in reverse and from reverse to forward.

Abstract: An extendable draft platform, having a deck and buoyancy columns installed in leg wells in the deck for vertical movement from a raised position to a submerged position, includes a connection arrangement for securing the columns to the deck when the columns are in the submerged position. In the connection arrangement, a plurality of first guide elements near the top of each column is engageable by a plurality of complementary second guide elements secured to the deck around each leg well when the column is lowered to its submerged position. A locking mechanism is operable between the columns and the deck when the first guide elements are engaged with the second guide elements. The first and second guide elements may be configured so that the connection between the deck and the columns may be enhanced by over-ballasting the columns and/or by welding the columns to the deck.

Abstract: A semi-submersible offshore vessel including a rectangular ring-pontoon having a first transverse pontoon section at a first end of the vessel and a parallel second transverse pontoon section at a second end of the vessel, and two parallel pontoon sections extending between the first and the second end of the vessel. Four support columns extend upwardly from respective edge-portions of the ring-pontoon to support an upper deck structure. The first pontoon section has a vertical mean cross-section area (A) which exceeds the corresponding vertical mean cross-section area (B) of the second pontoon section, and the support columns in the second column pair each has a water-plane area (F) which exceeds the water-plane area (D) of each of the support columns in the first column pair.

Abstract: A deep water support platform, suitable for use as a hydrocarbon exploration or production facility in very deep waters of 10,000 ft or more is presented. The platform is attached to the floor of the ocean with a buoyant pile that includes buoyant members attached about the periphery of the pile. The buoyant pile and buoyant members include tubular members that can be filled with water, oil, air or other materials to produce a structure that has improved buoyancy and stability over prior platforms. Embodiments include configurations of buoyant members that have constant and equal diameter and spacing, and other configurations where the diameter and/or spacing of the buoyant members changes along the pile. In addition, the buoyant members are arranged about the pile to reduce vortex induced vibrations on the platform by interfering with current flow about the support structure.

Abstract: A bottom-supported jack-up rig has a hollow ring mat with a central opening for accommodating a lower portion of a hull nested therein when the rig is in transit. The ring mat has a predetermined surface footprint sufficient to provide stability to the rig when embedded in the sea bottom. The mat buoyancy helps support the hull and the legs in a floating position when the rig is in transit, while allowing lowering of the mat to the sea bottom without assistance of a ballasting/de-ballasting means.

Abstract: A semi-submersible offshore vessel has a substantially ring-shaped lower pontoon, starboard and port forward columns extending upwards from the lower pontoon, and starboard and port aft columns extending upwards from the lower pontoon. An upper deck structure connects upper portions of the columns with each other. The upper deck structure has a substantially rectangular module recess for receiving one or more operation modules, for example, carrying hydrocarbon-processing equipment. The upper deck structure is generally C-shaped, having a forward torsion box extending transversally between the starboard and the port forward columns of the semi-submersible offshore vessel, and two mutually parallel longitudinal side beams extending aft from the starboard and port forward columns to the starboard and port aft columns, respectively, in such a way that the module recess exhibits an open aft end, the width of which substantially corresponds to the width of an operation module.

Abstract: A semi-submersible, multicolumn, deep draft, floating offshore oil and gas drilling and production platform comprises a floating hull having an adjustably buoyant base, a plurality of columns vertically upstanding from the base, and an equipment deck that is supported atop the columns when the platform is operationally deployed. Each of the columns comprises a cellular structure that includes a plurality of elongated tubes having a variety of cross-sectional shapes extending from the base to the top of the column. Each of the tubes defines one or more closed compartments. At least one of the compartments has a buoyancy that is fixed, and at least another one of the compartments has a buoyancy that is adjustable. The buoyancy of the compartments and the base can be controllably adjusted with pressurized air to provide a safer and less costly method for deploying the platform for offshore operations.

Abstract: In accordance with the present invention, an oscillation suppression system is provided to inhibit vertical and rotational resonance of a floating platform. The oscillation suppression system includes energy absorption chambers mounted in or about the hull of the floating platform. The chambers may be separately attached or integrated as part of the structure. The chambers are comprised of gas in an upper portion, and water mass in a lower portion. The chambers are closed or partially vented at the upper ends and open at their bottom ends. The enclosed gas in the upper portion of the chamber acts as a gas spring reacting against the floating platform and the water mass. The suppression of resonant oscillations of the floating platform system is accomplished through the gas-spring pressure changes acting on the floating platform system in phase opposition to external forces.

Abstract: Jacket frame floating structures comprise one or more elongate vertical support columns formed of an open cross-braced jacket formwork of tubular members interconnected together and at least one cylindrical buoyancy capsule disposed in the open framework near an upper end and at least one cylindrical second buoyancy capsule near a lower end in vertically spaced relation. The buoyancy capsule(s) may be a single, or a plurality of upper and lower capsules bundled in circumferentially spaced relation with a central opening therethrough. Alternatively, a keel tank may replace the lower capsule.

Abstract: A semi-submersible offshore platform (1) comprising: a substantially ring-shaped lower pontoon (2); at least three columns (4) extending upwardly from said lower pontoon (2), and an upper beam structure (5) connecting upper portions (6) of the columns (4) with each other. According to the invention, said upper beam structure (5) forms a system of lateral beams (7), arranged in such a way as to allow one or more operation modules (8) to be placed upon or adjacent to the columns (4) next to the lateral beams (7), either directly on the columns (4), on brackets (10) connected to the columns (4) or on a deck (9) arranged between upper ends (6) of the columns (4) and said operation modules (8), the lateral beams (7) protruding vertically upwards above a bottom plane (11) of the operation modules, said operation modules (8) containing, for example, hydrocarbon processing equipment and/or accommodation quarters.

Abstract: An apparatus and method for ballasting and de-ballasting a vessel having a hull with a plurality of watertight ballast compartments wherein each ballast compartment has an individual pump caisson extending vertically to the top of the hull, but the ballast/de-ballast system contains no valves within the hull. An external caisson is used to provide a source of seawater. Several submersible pumps are available for rigging into and out of the internal and external caissons and provide the ballast and de-ballast operations via an installed manifold system at the top of the columns. Venting of the ballast tanks may be accomplished through a connection to atmosphere near the top of the pump caissons.

Abstract: An improved lift boat includes a hull, a plurality of legs (preferably three), a plurality of pads, one pad attached to each leg, and a jacking mechanism for moving each upward and downward. Recesses in the hull receive the pads when the lift boat is underway. Preferably, the total bottom surface area of the pads is at least 30% of the surface area of the deck of the lift boat Preferably, the total bottom surface area of the pads is large enough such that, when the boat is loaded to capacity and is jacked up, the pads exert pressure of less than 7 p.s.i. on the sea floor. Preferably, the pads are partially recessed into the hull and extend laterally outward from the hull when the boat is underway to provide increased stability to the lift boat when it is underway.

Abstract: A floating hull for a spar-type offshore oil and gas drilling and production platform comprises a plurality of parallel tubular cells that are subdivided into compartments having a buoyancy controlled by one or both of fixed and variable ballast. The cells may be fabricated in a variety of ways and shapes and include side wall openings for admitting and discharging seawater and petroleum ballast with pumps. Fixed and/or variable ballast may be disposed on or in the cells to adjust buoyancy, trim, and stability. Lower and upper portions of the cells may extend above or below the others for trim or stability. Longitudinal recesses may be formed in an exterior peripheral surface for routing of mooring lines and piping. Stepped helical strakes can be disposed on an outer peripheral surface of the platform or some of the cells to reduce vortex-induced vibrations of the platform. Methods are described for efficient construction of the floating hull in water.

Abstract: In accordance with the present invention, an oscillation suppression system is provided to inhibit vertical and rotational resonance of a floating platform. The oscillation suppression system includes energy absorption chambers mounted in or about the hull of the floating platform. The chambers may be separately attached or integrated as part of the structure. The chambers are comprised of gas in an upper portion, and water mass in a lower portion. The chambers are closed or partially vented at the upper ends and open at their bottom ends. The enclosed gas in the upper portion of the chamber acts as a gas spring reacting against the floating platform and the water mass. The suppression of resonant oscillations of the floating platform system is accomplished through the gas-spring pressure changes acting on the floating platform system in phase opposition to external forces.

Abstract: An apparatus for guiding the legs of a lift boat. Roller assemblies are used to guide the legs. The rollers may be placed at any location or in any number either vertically or around the leg to adequately center the leg. The roller can either have a metal surface that rolls along the leg or be coated with a resilient material. The base of the roller can either be rigidly mounted to the vessel or incorporate resilient material between the roller and the vessel. A means of adjusting the clearance between the leg and roller may be incorporated in the roller assembly.

Abstract: There is disclosed improved mooring apparatus and method suitable for use with large offshore vessels. To avoid deploying an anchor with a full weight of mooring chain, they are deployed separately. An anchor, such as a suction anchor (1), is fitted with a short chain (C1) with one end permanently connected (6) thereto and its free end temporarily placed in a chain locator (8), which is positioned so as to be accessible after deployment of the anchor to the seabed, minimising the potential for seabed material to cause disruption. The anchor with its short chain is deployed to the seabed and at some stage the free end of a mooring chain (C2) is lowered to and accurately guided (100) into the chain locator, such that both free ends align. A pin (101) is inserted by an ROV to interconnect the two chains, after which the combined mooring chain (C) is tensioned, withdrawing it from the chain locator.

Abstract: Column-stabilized floating structures having a deck and a plurality of vertical buoyant caissons bridged together in distantly spaced relation by a plurality of open frame horizontal truss pontoon members and vertical truss columns at a lower end. The buoyancy of the caissons is selectively adjusted by means of ballast control. Water is selectively pumped into or out of keel tanks at the bottom of the truss structure such that the water mass and weight is adjustably tuned to raise or lower the center of gravity of the entire mass of the floating structure relative to its center of buoyancy. By tuning and positioning the center of gravity relative to the center of buoyancy, the floating structures can be tuned according to ballast and other variable or fixed loads including the deck payloads and to compensate for different operational, environmental, and survival conditions and towing and installation stages.

Abstract: An improved lift boat includes a hull, a plurality of legs (preferably three), a plurality of pads, one pad attached to each leg, and a jacking mechanism for moving each upward and downward. Recesses in the hull receive the pads when the lift boat is underway. Preferably, the total bottom surface area of the pads is at least 30% of the surface area of the deck of the lift boat. Preferably, the total bottom surface area of the pads is large enough such that, when the boat is loaded to capacity and is jacked up, the pads exert pressure of less than 7 p.s.i. on the sea floor. Preferably, the pads are partially recessed into the hull and extend laterally outward from the hull when the boat is underway to provide increased stability to the lift boat when it is underway.

Abstract: Deploying an offshore oil and gas production platform comprises placing a buoyant equipment deck on a buoyant pontoon so that elongated legs on the pontoon, each comprising a buoyant float, extend movably through respective openings in the deck. Chains extending from winches on the deck are reeved through fairleads on the pontoon and connected back to the deck. The chains are tightened to secure the deck to the pontoon for conjoint movement to an offshore location. The chains are loosened and the pontoon and leg floats ballasted so that the pontoon and leg floats sink below the floating deck. The chains are then re-tightened until pawls on the leg floats engage the deck. The buoyancy of at least one of the pontoon and leg floats is increased so that the deck is thereby raised above the surface of the water. The chains are connected to mooring lines around an offshore well site, and the raised deck and submerged pontoon are maintained in a selected position over the site with the winches.