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: An offshore platform includes a buoyant hull comprising three or more interconnected pontoons and a plurality of support columns. The support columns support a deck or structure that supports equipment and/or payloads above a water surface. The support columns extend upwardly from respective ends of the pontoons to the deck or structure supported above the water surface. Anchoring members anchor the platform to the seabed.

Abstract: A submerged or partially submerged structure includes one or more non-cylindrical support columns interconnected at the lower ends thereof by horizontally disposed pontoons. The support columns include one or more strakes mounted thereon. The columns and strakes contribute to the stability of the structure during free floating operations and installation by reducing vortex induced motion.

Abstract: A tension leg platform includes a deck supported on the upper ends of three or more columns interconnected at the lower ends thereof by horizontally disposed connecting members. The columns are battered inwardly and upwardly from the platform base to the deck. Tendons connected at the columns anchor the platform to the seabed. The footprints of the base of the battered columns and the tendons are larger than the footprint of the deck supported on the upper ends of the columns.

Abstract: A tendon top connector for a moored, floating structure such as a tension leg platform, a tension leg buoy or the like has a bowl-shaped extension on the member which transfers the tension of the tendon to the flex connector. A dome-shaped structure at least partially surrounds the bowl-shaped extension but is spaced apart from it to permit at least some rotational movement of the connector. The dome-shaped structure may be attached by clamps or other mounting means to a flange member affixed to the tendon porch. This arrangement provides a load path when the tendon top connector is reverse loaded that extends from the tendon length adjustment joint, through slips, through the bowl-shaped extension, through the dome-shaped structure, through the segmented clamps, and finally into a flange attached to the tendon porch. In this way, detachment of the tendon top connector is prevented if a reverse load is applied such as may occur during extreme metocean conditions.

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 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 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 fairing for the reduction of vortex-induced vibration and the minimization of drag about a substantially cylindrical element immersed in a fluid medium. The fairing also eliminates the galloping phenomenon typically associated with a teardrop-shaped fairing. The fairing having a U-shaped cylindrical shell with opposing edges defining a longitudinal gap and parallel fins extending outwardly from the opposing edges of the shell, the parallel fins being positioned so as to reduce vortex-induced vibration, minimize drag and to eliminate the galloping phenomenon on the cylindrical element.

Abstract: A tension leg platform includes a deck supported on the upper ends of three or more columns interconnected at the lower ends thereof by horizontally disposed pontoons. The columns are battered inwardly and upwardly from the pontoons to the deck. Tendons connected at the columns anchor the platform to the seabed. The footprints of the base of the battered columns and the tendons are larger than the footprint of the deck supported on the upper ends of the columns.

Abstract: A fairing for the reduction of vortex-induced vibration and the minimization of drag about a substantially cylindrical element immersed in a fluid medium. The fairing also eliminates the galloping phenomenon typically associated with a teardrop-shaped fairing. The fairing having a U-shaped cylindrical shell with opposing edges defining a longitudinal gap and parallel fins extending outwardly from the opposing edges of the shell, the parallel fins being positioned so as to reduce vortex-induced vibration, minimize drag and to eliminate the galloping phenomenon on the cylindrical element. Preferably, the length to diameter ratio of the fins is 1.5 to 2.50.

Abstract: A floating platform for recovery of oil and gas from offshore oil and gas fields includes a hull having a portion located substantially below the water surface, and including a portion thereof which extends above the water surface. The platform is anchored to the seabed by one or more tendons secured to the base of the hull and to the seabed. The payload capacity of the floating platform is increased without redesigning the structural design of the hull by attaching a column extension or mounting a detachable buoyancy module to the lower end of the hull for accommodating changing platform payload requirements.

Abstract: A floating platform includes a hull and a deck mounted on the uppermost end of the hull. The platform is anchored to the seabed by a plurality of tendons connected to the hull at the upper ends thereof and secured to the seabed at the lower ends thereof. The platform includes detachable buoyancy means providing supplemental buoyancy for hydrostatically stabilizing the platform without utilizing a derrick barge while ballasting the platform during installation.

Abstract: A top tensioned riser extends substantially vertically from a platform hull to the seabottom. The riser includes length adjustment at its upper end and is detachably connected to an anchor pile at its lower end. Riser tension is monitored via load cells incorporated in the riser porch. The riser is connected to one or more import/export flowlines or pipelines.

Abstract: A riser centralizer for transferring lateral loads from the riser to a platform hull includes a keel centralizer mounted on a keel joint. The keel centralizer is received within a keel guide sleeve secured in a support mounted at the lower end of the platform hull. The keel centralizer includes a nonmetallic composite bearing ring having a radiused peripheral profile for minimizing contact stresses between the keel centralizer and the keel guide sleeve in extremes of riser and platform motion. The internal surface of the keel guide sleeve is clad with a corrosion resistant alloy and coated with a wear resistant ceramic rich coating.

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: A floating platform for recovery of oil and gas from offshore oil and gas fields supports one or more decks above the water surface to accommodate equipment for drilling and processing oil, gas and water recovered from the oil and gas field. The platform includes a central column having a portion substantially below the water surface, and including a portion which extends above the water surface. The central column includes a base node and a plurality of pontoons extending outwardly therefrom and is anchored to the seabed by one or more tendons secured to the pontoons and to the seabed. Ballast modules fixedly or removably secured to the base node and/or the pontoons accept solid or liquid ballast for lowering the vertical center of gravity of the platform.

Abstract: A floating platform system supports one or more decks (14) above the water surface for accommodating equipment to process oil, gas and water recovered from a subsea hydrocarbon formation. The platform is secured to the seabed by one or more tendoms (17). A central column (12) of the platform includes a moonpool (19) extending axially through the central column (12). The moonpool (19) is open at the lower and upper ends thereof. Riser lateral restraint members (32) are supported within the moonpool (19) for laterally restraining risers (16) disposed in the moonpool (19) and minimizing riser spacing and riser deflection.

Abstract: In a tension-leg mooring system a production platform supporting one or more decks above the water surface for accommodating equipment to process oil, gas, and water recovered from a subsea hydrocarbon formation is mounted on a single water surface piercing column formed by one or more buoyancy tanks located below the water surface. The surface piercing column includes a base structure comprising three or more pontoons extending radially outwardly from the bottom of the surface piercing column. The production platform is secured to the seabed by one or more tendons per pontoon which are secured to the pontoons at one end and anchored to foundation piles embedded in the seabed at the other end.

Abstract: An offshore production platform includes one or more decks supported above the water surface for accommodating equipment to process oil, gas, and water recovered from subsea hydrocarbon formations. The decks are supported on surface piercing columns which are mounted on a support platform substructure, secured to the seabed by tubular piles driven below the mudline through skirt pile sleeves located at the respective corners of the substructure and connected to the substructure by grouting or mechanical means. The base of the platform includes an open framework permitting the platform to be placed over a well template, through which one or more wells may be drilled.