Abstract: A tendon or riser connector has a separate lock-down device that overrides the connector's ability to unlock if the riser or tendon goes slack. The connector has a lock ring that engages a groove profile on a receptacle and is prevented from accidentally unlocking with a cam ring and set of blocks. The blocks are movably positioned between engaged and disengaged positions that correspond to the locked and unlocked positions of the lock ring.

Abstract: A pipe comprising a flexible membrane that is disposed over a plurality of spaced-apart tendons is disclosed.

Abstract: A riser is connected to subsea well equipment and extends to a vessel. A tubular conductor is mounted stationarily to and around the riser, the conductor passing through an opening in the vessel. A set of rollers is mounted to the vessel around the opening for engagement with the conductor as the vessel moves relative to the riser. Hydro-pneumatic cylinder units are connected between the riser and the vessel for applying tension to the riser. An external flange is located on a lower portion of the conductor. A shock absorber is positioned around the conductor and mounted to the vessel for movement relative to the conductor. The shock absorber absorbs shock when the cylinder units are in an extreme stroke position.

Abstract: A tensioner assembly for moveably carrying a conductor that communicates from a wellhead to a piece of well access equipment on a rig. The tensioner assembly includes a support frame, at least one hydraulic cylinder connected to the support frame, and at least one primary accumulator in fluid communication with the hydraulic cylinder.

Abstract: A tendon bottom connector assembly has a receptacle with a bore having an annular locking profile divided into segments by axially extending slots. The connector has a housing that inserts into and locks in the receptacle. The housing and receptacle have mating an anti-rotation elements. The lock ring has an outer surface with an annular locking profile divided into segments by axially extending slots. The lock ring is carried by the housing initially in the installation position with its segments aligned with the slots of the receptacle. This position allows the housing to be fully inserted into the receptacle. An ROV then rotates the ring from the installation position to a locked position, with the segments of the lock ring engaging the segments of the receptacle. Alternately, a split ring with one end fixed rotates the lock ring.

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 method for supporting top tension drilling and production risers on a floating vessel using a tensioner assembly above the water line of the vessel. The method can include attaching at least one hydraulic cylinder on a first end to a first position on a floating vessel and on a second end to a tension frame below the first position. The next step of the method can be forming a fluid connection between the at least one hydraulic cylinder and at least one primary accumulator.

Abstract: The floating platform of the invention is intended for supporting industrial, commercial, cultural, and dwelling structures and is suitable for deployment in shallow as well as in deep waters, The platform is assembled from prefabricated hollow structural elements in such a way that the unified center of masses of the loads that consist of a plurality of arbitrarily distributed loads of different masses supported by the platform is always maintained in the same position whereby the platform is always maintained in a horizontally counterbalanced position. This is achieved by locally adjusting the buoyancy of the structural elements. Furthermore, the loads are positioned on the platform so that moments created by these loads relative to the aforementioned unified center of masses are equal. This allows maintaining the loads on the platform in equilibrium.

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 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: A tendon or riser connector has a separate lock-down device that overrides the connector's ability to unlock if the riser or tendon goes slack. The locking device has blocks that are radially actuated through a hole in a receptacle to engage a profile in the connector. When the blocks are pushed in, they prevent the connector from moving downward, and thus prevent any unlocking of the connector. The blocks are secured with pivotable gates that engage and retain the blocks in both positions.

Abstract: A wave attenuation system having a floating member, at least one anchor member, and a plurality of interconnected wave attenuation members. The floating member has a generally flat top surface and a bottom surface. The top surface is configured to be disposed above a waterline and the bottom surface is configured to be disposed below the waterline. The anchor member is disposed below the water line and is interconnected with the floating member through at least one elastic member. The wave attenuation members are connected to the floating member and disposed below the bottom surface of the floating member.

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 method and system for attaching a TLP to its tendons using pull-down lines to rapidly submerge the hull to installation draft while compensating for inherent hull instability during submergence and to provide motion arrest and aid in station keeping. The system includes tensioning devices mounted on the TLP, usually one for each tendon. Each tensioning device is equipped with a pull-down line which is connected to the corresponding tendon. The TLP hull is submerged to lock-off draft by applying tensions to the pull-down lines connected to the top of the tensions, or by a combination of applying tensions to the pull-down lines and ballasting the hull. As the tensioners take in pull-down line, the hull submerges, i.e. the draft increases.

Abstract: An arrangement for anchoring a floating structure comprising a mooring boom 120a, b; 650a, b pivotally arranged at either end, wherein each mooring boom at its free end has a bushing 124a, b: 654a, b through which anchor chains or wires can run. The anchor chain that runs through one of the bushings is fastened to the opposite end of the structure. In addition, for reasons of stability there may be tensioned lines which connect the free ends of both mooring booms to the structure.

Abstract: A deepwater windpower plant (DWP) has a tension leg-type floating platform with an evacuable base for adjusting its buoyancy for installation at ocean depths ranging from 40 meters up to 1.5 kilometers and more. The DWP has a typical offshore wind turbine assembled close to shore which is then towed to a desired installation site on the ocean, and held in place by a gravity anchoring base (GAB), to which an evacuable portion or space of the DWP platform is anchored. The GAB has upwardly extending mooring tethers and a power cable which are brought to the ocean surface by attached buoys. The GAB is sunk to the ocean floor at the installation site under controlled conditions so that the GAB lands flat on the ocean floor. As the GAB sinks to the ocean floor, the mooring tethers and power cable are pulled to the surface by their respective buoys. The GAB is loaded with heavy ballast material that can be dropped from barges on the ocean surface into the upwardly open GAB below the barges.

Abstract: A tendon for mooring a tension leg platform having an uppermost pipe segment with a reduced diameter compared to at least one of the lower pipe segments. The tendon is watertight and sealed from the ocean environment, preferably filled with air at one atmosphere of pressure. One or more interior bulkheads may be included to divide the tendon into multiple compartments. The reduced outer diameter of the uppermost pipe segment provides reduced drag due to waves and currents and accommodates smaller tendon support buoys and vortex fairings, while the greater diameter of the lower pipe segment provides for increased tendon buoyancy.

Abstract: A deep draft semi submersible structure wherein the semi-submersible has a center of gravity below its center of buoyancy and the structure is a floating vessel with at least three vertically oriented buoyant columns. Each of the vertically oriented buoyant columns have at least one ballasted compartment and the columns are spaced apart at a sufficient distance to reduce vortex induced vibration amplitude. There are at least two connecting structural sealed trusses connected to the columns below sea level, they are positioned to minimize hydrodynamic wave action on the trusses and to transfer shear loads between the columns while remaining transparent to wave and ocean current motion.

Abstract: A tendon or riser connector has a separate lock-down device that overrides the connector's ability to unlock if the riser or tendon goes slack. The connector has a lock ring that engages a groove profile on a receptacle and is prevented from accidentally unlocking with a cam ring and set of blocks. The blocks are movably positioned between engaged and disengaged positions that correspond to the locked and unlocked positions of the lock ring.

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: An offshore system for petroleum production has a buoyant platform. A tendon assembly secures to the platform and extends down to a counterweight located near the lower end. A piling is embedded in the sea floor. A socket at the counterweight telescopingly slides over the upper end of the piling to prevent lateral movement of the platform. A dampening chamber is located between the socket and the piling. Ports for the chamber are arranged to allow a faster downward movement of the piling than upward movement.

Abstract: A method for deploying a floating platform at an offshore wellsite uses pull-down lines to provide stability to the platform while ballasting. The platform is equipped with a number of tension devices and towed to a staging site while at a first draft, At the staging site, the operator connects lines from the sea floor to the tension devices on the platform. The operator gradually adds ballast to the platform and simultaneously applies tension to the lines with the tension devices. When at a desired second draft, the operator detaches the lines and tows the platform to a well site. The platform is moored with a catenary mooring system at the well site.

Abstract: A composite tendon comprises a main body of rope type construction. The ends of the tendon body terminate in eye splices for connection to termination connectors. Component strands of the composite tendon may form separate eye splices for connection to the termination connectors. Multiple composite tendons of rope type construction may be joined to a single termination connector. The termination connectors secure one end of the tendon to the seabed and the opposite end thereof to a floating platform.

Abstract: The present invention discloses a process for installing a floating platform to the ocean floor using a spoolable (preferably composite) tether, comprising installing the spooled tether onto the floating platform; towing the floating platform to a site for installation; unspooling the tether; connecting a bottom end connector of the tether to a foundation on the ocean floor; and connecting a top end connector of the tether to the floating platform. A preferred floating platform is a tension leg platform, and the invention includes a novel tension leg platform (TLP) comprising a spooled tether installed thereon. In a preferred embodiment the foundation is a suction anchor, and the suction anchor is connected to the bottom end connector prior to unspooling the tether and attached to the ocean floor after unspooling the tether. The floating platform may be uninstalled, moved and re-installed according to the invention.

Abstract: A tension leg platform is secured to the sea floor with a plurality of tendons, each of the tendons being in tension due to buoyancy of the platform. The tendons are made up of joints of pipe secured together to define a hollow interior sealed from entry of sea water. A lower section of the joints of pipe of each of the tendons has smaller inner and outer diameters and greater wall thicknesses than an upper section of the joints of pipe. Bulkheads are sealed within the interior of the upper and lower sections of the joints of pipe of each of the tendons. The bulkheads are spaced apart from each other along the lengths of the upper and lower sections of the joints of pipe to define separate compartments sealed from each other.

Abstract: A floating foundation for wind turbines is disclosed, where the foundation essentially comprises at least three submerged buoyancy bodies connected to the lower end of the tower of the wind turbine at a common node member situated well above the surface of the sea. The buoyancy bodies are connected to the node member by means of relatively thin leg sections, whereby wave load on the foundation is reduced. By applying the foundation according to the present invention, stress concentrations and torques in the node member are reduced, whereby it becomes possible to apply a relatively lightweight and hence cheap node member. The overall weight of the construction is thereby reduced and hence the volume of the buoyancy bodies necessary to counteract the overall weight of the construction.

Abstract: A tendon for an offshore floating platform has a tubular section formed of joints of steel pipe secured together. The tubular section has an interior sealed from sea water to provide buoyancy. A composite fiber section is secured to a lower end of the tubular section. The composite fiber section is formed of non metallic fibers and has a solid interior.

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: Minimized Wave-zone Buoyancy is a new approach to oil and gas platform design with superior construction and performance characteristics compared to state-of-art off-shore drilling and production platforms. Minimized Wave-zone Buoyancy platforms capitalize on low cross sectional area of the portion of the platform exposed to waves. The low cross sectional area reduces buoyancy forces that result from vertical platform movement, enabling the platform to oscillate at a low natural frequency. The low cross sectional area also minimizes the cyclical vertical forces induced by waves. Compare to current designs, application of the Minimized Wave-zone Buoyancy concept will result in a lower natural frequency of oscillation, lower overall weight of platform, or both. Minimized Wave-zone Buoyancy offers an attractive alternative with improved platform stability, fatigue considerations, lower construction and installation costs, and shorter implementation schedule.

Abstract: The present invention relates to a floating structure to receive maritime production or drilling installations that is provided with means to reduce movement caused by the action of environmental forces on it. These means confer a more stable behavior on the structure's movements.

Abstract: A method and system for attaching a TLP to its tendons using pull-down lines to rapidly submerge the hull to installation draft while compensating for inherent hull instability during submergence and to provide motion arrest and aid in station keeping. The system includes tensioning devices mounted on the TLP, usually one for each tendon. Each tensioning device is equipped with a pull-down line which is connected to the corresponding tendon. The TLP hull is submerged to lock-off draft by applying tensions to the pull-down lines connected to the top of the tensions, or by a combination of applying tensions to the pull-down lines and ballasting the hull. As the tensioners take in pull-down line, the hull submerges, i.e. the draft increases.

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 temporary stability module and method for marine structures during construction, transportation and installation is taught. The device and method permit the structure, including platforms, deck and equipment to be constructed in an upright position, towed to an ocean installation site, and installed by ballasting the structure or temporary stability module and subsequent removal of the module.

Abstract: Expandable and contractible buoyancy modules are assembled to the risers of a deepwater exploration spar or other offshore structure to provide an upwardly directed buoyancy force to offset at least a portion of the weight of the riser. The buoyancy modules have a fabricated pressure tight expandable and contractible envelope composed of rubber or rubber-like material which is mounted onto a tubular member having a central passage for receiving the riser to be supported. The tubular member projects beyond the respective upper and lower ends of the envelope and defines upper and lower riser joint connectors and buoyancy module travel stops which secure the buoyancy module to the riser and provide for force transmission from the buoyancy module to selected locations along the length of the riser or to the upper end of the riser.

Abstract: An elongated, annular hull of a floating offshore platform includes one or more segmented, helical strakes disposed on an outer peripheral surface of the hull to reduce vortex-induced vibrations resulting from water currents. The hull may comprise a single annular hull or a plurality of parallel, adjacent hulls. Each strake includes a plurality of generally rectangular segments extending substantially radially outward from the hull. Each of the segments includes a pair of spaced-apart radial stanchions supporting a generally rectangular frame to which a corresponding panel is attached. The panels have a radial width that is about 13 percent of the effective diameter of the hull. The segments are arranged in a spaced-apart, end-to-end relationship that defines a discontinuous, but generally helical band extending around the circumference of the hull from about 35 feet (11.7 m) below the mean water line of the hull to its lowermost end.

Abstract: A lateral mooring system for tendon-based platforms is disclosed, which provides reduced installation and/or operational cost associated with the installation and operation of an extended-base tension leg platform. The lateral mooring system includes a plurality of mooring lines that provide lateral support to the platform in mild metocean conditions, but may have application in more severe oceanic condition. A method for installing the system on the platform and a method for drilling wells on a offshore site.

Abstract: A semi-submersible floating platform for offshore drilling and/or production of petroleum product from the seabed includes a base having a first moon pool; a plurality of vertical outer buoyancy columns extending upwardly from the base; a deck structure supported by the buoyancy columns and having a second moon pool; a central columnar buoyancy apparatus having a lower portion guided within the first moon pool and an upper portion guided within the second moon pool; and at least one vertical riser passing through the buoyancy apparatus. Each riser has a lower portion that is horizontally restrained within the buoyancy apparatus below the center of gravity thereof. In a preferred embodiment, the platform includes at least two vertical risers attached to a single buoyancy apparatus.

Abstract: In one example embodiment, a floating deep draft caisson vessel for drilling and production is provided. The vessel comprises an outer hull, wherein the outer hull has a hollow centerwell. The vessel further comprises a centerwell buoy guided within the centerwell. At least one tendon assembly secures the centerwell buoy to the sea floor and the tendon assembly is attached along essentially the centerline of the centerwell buoy.

Abstract: A tether system include tethers each having an upper section (1) attached to a tension leg platform (TLP) (4), and each upper section has a large diameter so that the upper section (1) is positively bouyant. This buoyancy can be designed to compensate for the weight of the lower section (2) of each tether, so as to make the total buoyancy of each tether closer to neutral. The selection process for each section is driven by requirements for buoyancy, stiffness and external pressure resistance.

Abstract: A temporary stability module and method for marine structures during construction, transportation and installation is taught. The device and method permit the structure, including platforms, deck and equipment to be constructed in an upright position, towed to an ocean installation site, and installed by ballasting the structure or temporary stability module and subsequent removal of the module.

Abstract: A receptacle 20 is removably secured to hull 12 of an offshore structure 10, and supports an elongate member 14, which may be a riser string, extending downward to the sea bed or to another structure. The elongate member 14 includes a tapered supporting surface 18, which may be provided on a tapered stress joint or flex joint 16. The receptacle 20 includes a mounting bracket 22 secured to the structure 10, and a basket housing 30 which has a tapered interior surface 34 for mating engagement with the exterior surface 18. According to the method, the mounting bracket is fixed to the structure, and the receptacle basket positioned about the elongate member and the assembly then positioned for being supported on the bracket. The supporting surface on the basket may be arranged for positioning the elongate member at a selected azimuth and declination relative to the offshore structure.

Abstract: A vessel includes a riser and/or tendon tensioning construction. A connector, such as an arm or deck structure, is suspended from cables movable relative to cable guides. The connector carries two or more risers and/or tendons extending from a subsea structure to above water level. The free ends of the cables are attached to weights for exerting a tensioning force on the risers, which are substantially decoupled from pitch, roll and heave motions of the vessel.

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: 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 tendon system for anchoring a floating platform to the seabed comprises composite tendon groups including one or more steel tendons in combination with tendons fabricated of synthetic materials. The synthetic composite tendons may be coaxially located within the steel tendons. Tendon resonance is inhibited by exerting damping forces through supplementary tendons/cables connecting a passive or active damping force system to the seabed. In another aspect of the invention, a passive tuned oscillator or an active driven mass oscillator provides damping of platform resonance motions.

Abstract: A method of connecting two or more elongate connection members (105) between the seabed and a floating vessel (106) carrying a connector (102) which is suspended from the vessel by at least two spaced apart suspension members for relative displacement of the connector with respect to the vessel, at least one suspension member being connected to tensioning elements (109, 109′) for exerting an upward force on the connector. The method comprises the steps of: a) attaching one or more connection members to the connector, b) increasing the tensioning force of the tensioning elements, or vice versa, and c) repeating steps a and b until the connection members are installed between the vessel and the seabed.

Abstract: A bottom-to-surface link with at least one underwater pipe having a portion with a substantially constant diameter and one or more floats in a string, the floats constituting cans surrounding the pipe and being located in a float zone around the top underwater portion of the pipe. The pipe is held at the surface by a guide device, preferably on a floating float support. The link includes at least one stabilizer situated in the top portion of the pipe. The link is arranged so that the bottom portion of the float zone, is preferably on or level with the lowest float and a transition zone is between the floats and the substantially constant diameter portion of the pipe.

Abstract: A floating offshore platform configuration is provided, which decouples pitch, roll, and heave motions from acting on tensioned risers and accommodates the angular displacement induced by floating offshore platform surge and/or sway excursion without inducing bending in the riser at its entrance to the floating offshore platform. The risers are guided by an inner structure that is tethered from the sea floor and centered inside an outer hull structure. Outer hull structure heave, pitch and roll motions are substantially isolated from acting on the inner structure through a connection mechanism, and each riser is allowed to individually expand or contract.

Abstract: An offshore floating platform for the drilling and/or production of petroleum products from the seabed includes a production deck and a buoyancy apparatus vertically guided and restrained within the platform. The buoyancy apparatus includes a well deck on its upper surface on which are mounted at least two surface trees. At least two vertical risers are supported by the buoyancy apparatus and are attached to the well deck. Each of the risers is connected to one of the surface trees and extends down through the buoyancy apparatus for connection to a seabed wellhead. At last one tendon assembly secures the buoyancy apparatus to the seabed. The tendon assembly is constructed with at least two concentric tubular tendon elements, and it is attached to the well deck and extends along the vertical centerline of the buoyancy apparatus.

Abstract: A bottom connector for the tendon of a tension leg platform uses a latch ring with an outer profile to engage a mating profile in a receptacle on the sea floor. The latch ring moves radially within a housing, relative to the receptacle, between an engaged position and a retracted position. The latch ring engages the receptacle by lowering the connector into the receptacle below the mating profile and then lifting it until the latch ring locks into the receptacle. The latch ring disengages the receptacle by lowering the connector beyond a recess located below the mating profile and then lifting the connector out of the receptacle. As the connector is lifted above the recess, a retaining ring is actuated by the recess to retain the latch ring in its retracted position.