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 tendon which is divided into compartments enclosing therein pressurized gas. A method for transporting a fluid containing tubular body or assembly of bodies above a sea/river bed floor and within a body of water. In addition to the method for transporting the tendon a method of installing and removing an internal pressurized tendon or assembly of tendons in a vertical position in a body of water.

Abstract: A floating platform for use in a body of water comprises an uppermost buoyant and ballastable hull partially submerged in the water without contacting the floor of the body of water and usually without being moored to the floor of the body of water. The bottom of the uppermost hull is attached to the top of a lower buoyant and ballastable hull after the lower hull has been completely submerged in the water and anchored to the floor of the body of water with flexible moorings.

Abstract: A heave suppressed, floating offshore drilling and production platform comprises vertical columns, lateral trusses connecting adjacent columns, a deep-submerged horizontal plate supported from the bottom of the columns by vertical truss legs, and a topside deck supported by the columns. The lateral trusses connect adjacent columns near their lower end to enchance the structural intergrity of the platform. During the launch of the platform and towing in relatively shallow water, the truss legs are stowed in shafts within each column, and the plate is carried just below the lower ends of the columns. After the platform has been floated to the deep water drilling and production site, the truss legs are lowered from the column shafts to lower the plate to a deep draft for reducing the effect of wave forces and to provide heave and vertical motion resistance to the platform.

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 the seabed. The playload 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 accomodating changing platform pay load requirements.

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: A method of constrcuting a precast, modular marine structure for offshore use, including but not limited to drilling, oil and gas production, and oil storage in a variety of water depths. The marine structure includes an equalized pressure system and concrete modular components cast with at least one cell and a central longitudinal passageway. The equalized pressure system fluidly connects the cell(s) to the adjacent body of water by at least one substantially vertical segmented water column to equalize the hydrostatic pressure differential experienced at a wall of the marine structure. A truss section may be attached to the concrete portion of the marine structure to form a truss spar. A mooring and tether system may be included to maintain the marine structure's station and attitude.

Abstract: A buoyancy system to buoy a riser of an offshore oil platform includes buoyancy compartments coupled around an elongated internal beam. The internal beam can withstand loads between the oil platform and the buoyancy system, while the buoyancy compartments provide buoyancy. The internal beam includes an elongated stem, a plurality of webs extending radially outwardly from the stem, and a plurality of transverse flanges attached to the outer edges of the webs.

Abstract: A method of lowering a floating body of a floating foundation and carrying a structure projecting above the water surface to an end position located beneath the water level, includes threading, through each of the upwardly projecting tubes, which are secured to the floating body above-through-openings formed in the floating body, a cable or a rod and connecting the cable or rod to a set-in-ground anchor, lowering the floating body, with the uptake devices provided at the free ends of the tubes, to the end position of the floating body beneath the water surface against buoyancy of the floating body, and fixidly securing the cables or rods, in the end position of the floating body, to the floating body and cutting off sections of the cables and rods above fixation points of the cables and rods with the floating body and removing the tubes.

Abstract: A modified tension leg platform (referred to as “Soft TLP”)for the exploration of, drilling of, and production from offshore subterranean reservoirs. The buoyant section has been positioned below 100 feet of water depth, to provide this Soft TLP with a reduced surface area in the first 100 feet of water depth to reduce the effect of wave forces on the structure.

Abstract: The present invention provides a tendon divided into compartment enclosing therein pressurized gas. The invention also relates to a method for transporting a fluid containing tubular body or assembly of bodies above a sea/river bed floor and within a body of water. In addition the invention comprises a method of installing and removing an internal pressurized tendon or assembly of tendons in a vertical position in a body of water.

Abstract: A tensioning riser system for supporting marine elements such as risers which extend form a fixed lower end at a subsea base or foundation to a moving, floating superstructure. The tensioning system has a lever arm pivotally connected to both the superstructure and the upper end of the marine element and a tension controlling strut member pivotally connected to both the superstructure and the lever arm.

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 precast, modular marine structure and method of constructing the same for offshore use, including but not limited to drilling, oil and gas production, and oil storage in a variety of water depths. The marine structure includes an equalized pressure system and concrete modular components cast with at least one cell and a central longitudinal passageway. The equalized pressure system fluidly connects the cell(s) to the adjacent body of water by at least one substantially vertical segmented water column to equalize the hydrostatic pressure differential experienced at a wall of the marine structure. A truss section may be attached to the concrete portion of the marine structure to form a truss spar. A mooring and tether system may be included to maintain the marine structure's station and attitude.

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

Abstract: A connector in particular intended for use with a tension leg platform is disclosed. The connector comprises a male part (1) and a female part (2), which male part (1) is designed to engage in the female part (2) and the parts are able to engage with one another without any of the parts having to rotate in respect of the other. The female part (2) comprises an abutment ring having an internal continuous downward facing abutment shoulder (4) and the male part (1) has a discontinuous segmented ring (5). Each individual ring segment (8) is limitary independantly movable, both axially and radially, which segmented ring (5) lies slidably against a mandrel abutment (9).

Abstract: A foundation system for tension leg platforms without use of foundation templates, wherein each tendon (5) is directly connected to a socket (9) inside a pile (8), the piles (8) being positioned for driving purpose by a pile-driving template (10) which is employed as a spacing device. The pile-driving template (10) is positioned with the aid of pins (11) that slot into guides (7) built into the well template (6). After the groups of piles (8) needed to anchor a corner of the platform (1) have been driven in, the pile-driving template (10) is withdrawn and repositioned so as to enable the piles for the other group of legs to be driven; this process continues until all of the pile-driving is finished. Alternatively one single pile-driving template (16) may be employed to guide the driving of all the piles (8) thus doing away with the need to reposition the template every time.

Abstract: A riser system for use in transporting fluid cargo to a floating vessel from a submerged pipe employs a tensioning mechanism that prevents excess slack in a flexible riser that could potentially damage the riser. The tensioning mechanism includes a tensioning arm or element that is pivotally attached at a first end to a submerged base and at its second end to the flexible riser. The arm is free to rotate about the pivot point in a pendulum manner, but is urged toward an equilibrium position by one or more tension-applying elements disposed on the arm, such as a buoyancy element, a weight or both.

Abstract: A connection device for connecting a submerged tubular structure to a floating support structure. The connection device includes first and second tubular connection elements that connect the submerged tubular structure to the floating support structure. The first tubular connection element cooperates with the second tubular connection element to form a first axial abutment in a pulling direction in which the submerged tubular structure is pulled, and a second axial abutment in a direction opposite from the pulling direction. The device further includes a locking and tensioning device that includes at least one actuator secured to the floating support structure and is mounted to pivot on the second tubular connection element about a hinge axis and against the effect of a return spring surrounding the pin so as to enable the first tubular connection element to snap-fasten onto the second tubular connection element.

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

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 marine buoy for the offshore support of subsea production and drilling activities that has a closed-bottomed base section with a solid ballast and variable ballast chambers, a chamber in the base section for storing equipment and supplies, and an upper section with a smaller cross-sectional area than the base section having an elevator shaft leading from the top of the upper section to the chamber in the base section. The upper section supports a deck for housing process equipment for operations that the marine buoy is supporting.

Abstract: A buoyancy system for a deep water floating platform includes at least one composite buoyancy module coupled to the a riser having a length greater than 1000 feet and an associated weight. The composite buoyancy module is sized to have a volume to produce a buoyancy force at least as great as the weight of the riser. The composite buoyancy module may include a vessel with a composite vessel wall. The buoyancy module or vessel may have a non-circular cross-section defining an area which is greater than approximately 79 percent of an area defined by a square with sides tangent to the vessel wall to maximize buoyancy. A second buoyancy module may be directly coupled to the first buoyancy module to achieve a desired buoyancy.

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 floating system for very deep water includes a floating structure (1) subject to the external loadings (7, 8, 9) inducing stresses, the floating structure (1) being held in position on the sea bed by one or several tensioned lines (2) made of a material having given mechanical properties. The tensioned line or lines (2) are made of a material that is not very sensitive to fatigue stresses and the tensioned line or lines are sized in a manner independent of the fatigue phenomena associated with the dynamic behavior of the floating system under the effect of external loadings.

Abstract: An extended-base tension leg substructure, an offshore platform supported on the substructure and a method for supporting an offshore platform on the substructure are disclosed, where the substructure includes a plurality of support columns disposed about a central axis of the substructure and interconnected by at least one pontoon. Each column comprises an above water and submerged portion. The substructure also includes a plurality of wings or arms radiating from the columns and/or the pontoons, each wing fixedly or removably securing at least one tendon extending from a wing to an anchor on the seabed. The substructure includes an open, wave transparent central zone for improved access to well-related equipment, conduits or the like and the wings minimize translational movement and rotational flex in the substructure reducing fatigue in the tendons and their connections.

Abstract: A buoyancy system for a deep water floating platform includes at least one buoyancy module coupled to the a riser. The module may be coupled to a ring structure of an end cap coupled to the riser, or two modules may be coupled to a ring structure to couple them together. The modules have an interior flange extending into the interior cavity and abutting the ring structure. Fasteners couple the interior flange of the module to the ring structure to form an interior attachment. A seal may be formed between the flange of the buoyancy module and the ring structure, and may include a seal member disposed in a groove. A test port extends to the groove to allow testing of the seal. The module may include a material and may have a thickness that together allow a wall of the buoyancy module to expand outwardly under an internal pressure and force the flange against the ring structure to enhance sealing between the flange and ring structure.

Abstract: An installation for producing oil from an off-shore deposit has a semi-submersible platform, at least one riser connecting the platform to the sea bed, and devices for tensioning the riser. The tensioning devices include, for each riser, at least one submerged float connected to a point on the main run of the riser for hauling it towards the surface, and a mechanism for hauling the riser. The mechanism is installed on the platform and applied to the top end of the riser.

Abstract: A tension leg subsea platform (TLSP) (1) comprises a buoyant, submersible hull anchored to the seabed by tendons (3). A jack-up platform (6), either for drilling operations, production operations or any combination of these, is located such that its legs (8), when lowered, rest on the TLSP. In an alternative arrangement (FIG. 3), legs or columns are pre-installed on the TLSP, and the working platform lifted or floated onto them. In either case, the two components can be fabricated and travel separately to the field location. The effective depth of the TLSP may be 30 m to 100 m, while the sea itself is substantially deeper than 100 m. The working platform may be re-used at other locations. A drilling platform may be exchanged for a production platform while the TLSP remains moored on location, and the production platform may in turn be exchanged for a decommissioning platform.

Abstract: A system for use in petroleum production at sea includes a guide frame for one or more riser pipes, on a semisubmersible production vessel. One or more main buoyancy member are arranged separately on at least one riser to carry the main part of the riser's weight. Each riser separately carries a Christmas tree on its top, near a main deck of the vessel. The guide frame comprises vertical main elements extending vertically downwards from the deck, through the splash zone and through the upper, more wave- and current-influenced zone of the sea. The guide frame also includes horizontal guide plates comprising vertically open cells formed of a horizontally arranged framework of beams. Lateral stabilization devices guide the risers' and the main buoyancy members' vertical movement relative to the vessel and restrict horizontal movement of the risers with respect to the guide frame. The guide plates are arranged in at least two levels on the guide frame.

Abstract: An exemplary floatable vessel is described having an upper tower section with a reduced diameter or width and an affixed lower base section having an enlarged diameter or width. The lower section contains weighted ballast distributed upon its lower floor. The lower section also includes flotation tanks which can be filled with air to raise the vessel in the water such that portions of the lower section are raised above the water line. Alternatively, the flotation tanks can be flooded to dispose the lower section and a portion of the upper section below the water level. The upper tower section of the vessel supports a deck structure upon which rig components can be constructed or secured. The tower section includes flotation tanks as well. In preferred embodiments, these tanks are variable tanks that can be partially filled with air and partially flooded with water.

Abstract: A foundation system for tension leg platforms without use of foundation templates, wherein each tendon (5) is directly connected to a socket (9) inside the pile (8), said piles (8) being positioned for driving purpose by means of a pile-driving template (10) which is employed as a spacing device is described. The pile-driving template (10) is positioned with the aid of pins (11) that slot into guides (7) built into the well template (6). After the groups of piles (8) needed to anchor a corner of the platform (1) have been driven in, the pile-driving template (10) is withdrawn and repositioned so as to enable the piles for the other group of legs to be driven; this process continues until all of the pile-driving is finished. Alternatively one single pile-driving template (16) may be employed to guide the driving of all the piles (8) thus doing away with the need to reposition the template every time.

Abstract: A riser tube tower for stabilizing riser tubes extending from respective wellheads associated with a seabed frame on the seabed to a platform, preferably a tension leg platform, at the sea surface. The riser tube tower includes vertical wires connecting the platform with the seabed frame. Horizontally disposed guide plates are fixed in position at one or more levels of the tower. Vertically movable shuttle plates are located in the vertical spaces over, between, and under the guide plates. The vertical wires and riser tubes pass through spaced apertures in the guide plates and the shuttle plates. The apertures in the shuttle plates are aligned with respective apertures in the guide plates. Bushings are disposed in the apertures of the guide plates and the shuttle plates for protecting the guide plates and shuttle plates from the riser tubes and wires, and for reducing friction therebetween. Elevator devices move the shuttle plates vertically above, below, or between the guide plates.

Abstract: An installation for producing oil from an off-shore deposit has a semi-submersible platform, at least one riser connecting the platform to the sea bed, and devices for tensioning the riser. The tensioning devices include, for each riser, at least one submerged float connected to a point on the main run of the riser for hauling it towards the surface, and a mechanism for hauling the riser. The mechanism is installed on the platform and applied to the top end of the riser.

Abstract: A foundation system for tension leg platforms without use of foundation templates, wherein each tendon (5) is directly connected to a socket (9) inside the pile (8), said piles (8) being positioned for driving purpose by means of a pile-driving template (10) which is employed as a spacing device is described. The pile-driving template (10) is positioned with the aid of pins (11) that slot into guides (7) built into the well template (6). After the groups of piles (8) needed to anchor a corner of the platform (1) have been driven in, the pile-driving template (10) is withdrawn and repositioned so as to enable the piles for the other group of legs to be driven; this process continues until all of the pile-driving is finished. Alternatively one single pile-driving template (16) may be employed to guide the driving of all the piles (8) thus doing away with the need to reposition the template every time.

Abstract: A method of installing a foundation for a tension leg platform is described that eliminates the foundation template as a permanent, load bearing part of the foundation. As an embodiment of the invention, piles are installed by, for example, being driven into the ocean floor so that each pile is secured to the ocean floor, but is unsecured to any other structure that is on the ocean floor. A tension leg platform is coupled via tendon structures to the piles so that anchoring load paths are defined from the tension leg platform to the ocean floor in a plurality of generally vertical paths extending in axial alignment through the tendon structures to the pile and the ocean floor. Each of the tendon structure to pile anchoring systems is substantially independent of one another.

Abstract: A precast, modular marine structure and method of constructing the same for offshore use, including but not limited to drilling, oil and gas production, and oil storage in a variety of water depths. The marine structure includes an equalized pressure system and concrete modular components cast with at least one cell and a central longitudinal passageway. The equalized pressure system fluidly connects the cell(s) to the adjacent body of water by at least one substantially vertical segmented water column to equalize the hydrostatic pressure differential experienced at a wall of the marine structure. A truss section may be attached to the concrete portion of the marine structure to form a truss spar. A mooring and tether system may be included to maintain the marine structure's station and attitude.

Abstract: A precast, modular spar system (10) having a cylindrical open-ended spar of relatively uniform cross section. The spar has a freeboard section (50), a buoyancy section (70), and a ballast section (90). The sections are formed by joining arcuate segments and stacking the sections. A pressurizing system allows for the injection of air into the segments to vary the buoyancy of the modular spar system.

Abstract: A pressurized slip joint for a marine intervention riser decouples the flowhead assembly in the moon pool of a vessel from the riser string, enabling safe changeover of equipment during workover operations. One part of the slip joint assembly is coupled to the flowhead assembly through a flexible joint assembly. A second part of the slip joint assembly supports the riser string and is coupled to the tensioning mechanism. The first part may be inserted into the second part and locked in place during workover operations except when equipment changeover is taking place. When changeover is being carried out, the first and second parts are unlocked, so that the flowhead assembly does not move relative to the vessel. In the locked position, a metal-to-metal high pressure seal, with a secondary and tertiary seal controls the pressure in the riser. In the unlocked position, a hydraulically operated dynamic low pressure seal is used.