Abstract: The present invention relates to a method and to a system for limiting vortex-induced vibrations on a riser suspended at one end from a support and subjected to substantially transverse fluid flows. The system comprises suspension means (10) for hanging the riser from the support, which include displacement means for moving the end in a transverse direction in relation to the principal axis of the riser.

Abstract: A new marine oil production riser system for use in deepwater applications is disclosed. An efficient means for accommodating movements of the host facility, while maintaining riser top tension within the limits for long-term riser performance. Long riser stroke lengths can be accommodated without requiring complex interfacing with the topsides. The riser assembly comprises: a generally extendable substantially non-vertical section having an upper end adapted to be in flow communication with a generally vertical marine riser carried by a facility floating on the surface of a body of water, and having a lower end adapted to be in flow communication with a fluid source on the seafloor; and tensioning means, mechanically connecting the upper end of the marine riser with the lower end of the marine riser, for biasing said ends towards each other.

Abstract: The present invention relates to an instrumentation assembly intended for an offshore riser (2) operated from a floater (1). It comprises a central processing unit (PC) connected by conducting cables (27) to: a plurality of modules (21–25) fastened to various points of the riser length, the modules comprising measuring means allowing dynamic location of said points in space, another locating module (26) fastened to the lower end (LMRP) of said riser, a series of detectors (W, C, M/W) for measuring the environment: wind, wave, current, an assembly for measuring the position (DGPS, P) of the floater. The measurements are synchronized with one another, managed and recorded by means of the central processing unit.

Abstract: A system for reducing the effects of heave movements of a wellhead in an offshore drilling device is provided that includes a frame; a coiled tubing stack supported by the frame; and a heave compensation system for controlling an amount of load transferred from the coiled tubing stack to the wellhead to reduce relative movements between the coiled tubing stack and the wellhead.

Abstract: An offshore oil well riser system comprises one or more tubular conduits suspended from a floating platform and having bottom ends extending downward substantially vertically toward the sea floor. A bottom end connection and tensioning assembly is disposed at the bottom ends of the conduits and comprises a jumper for connecting the bottom end of each conduit to an associated sub-sea oil well, a weight for applying a vertical tension in the conduits, and an apparatus for constraining the bottom end of the conduits against horizontal movement, while enabling them to move freely in a vertical direction and to pivot freely at their bottom ends in response to motions of the platform on the water surface. The riser system is useful with a wide variety of floating platforms, and can be employed in either dry tree or wet tree completion systems.

Abstract: The invention is directed to a tensioner assembly for providing tensile force from a floating vessel at the surface of the ocean to the blowout preventer stack, or production tree, which is connected to the wellhead at the sea floor. The tensioner assembly compensates for vessel motion induced by wave action and heave and maintains a variable tension to the riser string alleviating the potential for compression and thus buckling or failure of the riser string. The tensioner assembly of the present invention includes a cylinder, a stop tube disposed with the cylinder, and a ram slidably engaged within the stop tube. The tensioner assembly also includes at least one gas, or air, transfer tube to create a pressurized air over hydraulic fluid arrangement to provide tensile force to the tensioner assembly.

Abstract: A system and method to measure positioning with respect to deploying a subsea load, the system comprising a subsea metering head having a position sensor; a controllable winch operatively connected to the winch flexible cable; and a controller operatively in communication with the controllable winch and the position sensor. The controller is capable of controlling the controllable winch in response to a received position feedback sensor signal. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope of meaning of the claims.

Abstract: A vessel (1) comprises a rotatable turret (14) and a supporting structure (3) over or on the turret for supporting a swivel (5). The swivel comprising an inner and an outer ring (21, 21?; 22, 22?) which can rotate with respect to each other and which define at least one fluid distribution path from a geostationary fluid riser (19) connected to one ring (22, 22?) to a product outflow pipe (18) connected to the other ring (21, 21?). A rig (2) is mounted over the turret area above or below the swivel (5), and a substantially rigid pipe extends from the rig, through a moonpool of the turret towards the sea bed, the rigid pipe being in line with the swivel.

Abstract: A closed system drill string compensator having a hydraulic fluid accumulator, at least one air pressure vessel, and a piston and a piston rod slidably engaged within a cylinder. The drill string compensator provides tensioning force for supporting a drill string and permits the drilling vessel to remain connected to the drill string during ocean level changes caused by wave action or ocean heave. In one embodiment, the accumulator surrounds the cylinder and at least one air pressure vessel is radially disposed around the accumulator and the cylinder. In another embodiment, the accumulator surrounds the cylinder and includes two ports, one port for permitting fluid communication between the cylinder and the accumulator and a second port for permitting fluid communication between the accumulator and the air pressure vessel, the first port including a shut-off valve disposed therein. Methods of compensating a drill string are also disclosed.

Abstract: A system for providing motion compensation of a platform attached to an ocean floor. The platform is operatively associated with a riser extending from a subterranean well. The system comprises a frame member positioned on the platform and a deck slidably attached to the frame member, and wherein the deck is attached to the riser. The system further comprises a moving device for moving the frame member relative to the deck. In one of the preferred embodiments, the frame member contains a plurality of guide post and wherein the deck is slidably mounted on the guide post so that the frame member is movable relative to the deck. The moving device may comprise a cylinder member operatively attached to the frame member and a piston operatively attached to the deck and wherein the system further comprises a pressurized recharging vessel configured to direct a pneumatic supply to the cylinder member, and a gas delivery mechanism for keeping the cylinder member within a pressure range.

Abstract: A system and method autonomously clears obstacles and mines from an approach lane. A ship is distantly located from an approach lane spanning a surf zone and beach portion, and the ship has operator control station software in an onboard computer. At least one system delivery vehicle having a storage bay and propulsion system transits from the ship to the approach lane in response to instructions from the operator control station. A line charge is disposed in each bay and has one end coupled to the system delivery vehicle. A line charge delivery vehicle in the bay is connected to another end of the line charge to pull the line charge from the bay and emplace it in a straight path in the approach lane in response to instructions from the operator control station. Explosives in all line charges are detonated to clear the approach lane.

Abstract: A cylinder-stem assembly to floating platform, gap controlling interface guide. A longitudinal wear strip and mating guide are positioned at an angle relative to a tangent to the nominally round exterior cylinder of the cylinder. Cylinder guides may be provided at more than a single elevation. The corners of the contacting surfaces of the wear strips may be rounded to reduce the risk of galling and to avoid any obvious point or line loading. During assembly, the cylinder-stem assembly is rotated after insertion into its slot in the floating platform. The rotation centers the cylinder and also may be used to control the magnitude of the gap or an interference fit.

Abstract: A rotating tower system for transferring hydrocarbons to a ship, comprising a transfer structure extending from the bottom (3) of the ship (1) to the deck (4) thereof, the structure at its lower end being connected to a number of risers (22) and to anchor lines (9) for anchoring of the ship (1), and at its upper end being connected to a rotatable coupling device (20) on the deck of the ship (1). The structure comprises a lower and an upper rotating body (5, 6) which are independently mounted in relation to the ship (1) and are connected to each other via an intermediate connecting unit (7). The lower (5) and possibly also the upper (6) rotating body in its central region is connected to the adjacent end of the connecting unit (7) via an articulated bearing connection (30, 31) allowing occurring angular deviations and possibly absorbing radial and/or axial forces.

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 system for supplying cooling water to a process on board a floating vessel for the production of hydrocarbons, wherein the vessel (1) is anchored by means of a bottom-anchored turning unit (20) mounted in a receiving space (7) in the hull (34) of the vessel and allowing turning of the vessel (1) about the turning unit, and wherein the turning unit (20) supports a swivel unit (24) for the transfer of hydrocarbons from production risers (28) extending between the seabed and the turning unit (20), the system comprising a conduit means (30) depending from the vessel (1) to a depth for taking in cooled sea water, and a pump means (44) for pumping of the sea water from the conduit to a place of use for the process.

Abstract: A device for intervention of a subsea oil and/or gas well by means of a tool (8) suspended by a cable (9), fed from or withdrawn to a vessel (1) and driven by a drive mechanism (12) located on the vessel. The device comprises a lubricator (5) having a tool housing for the insertion of the tool into the well, and a stuffing box (40) sealing around the cable after the tool is inserted into the well. According to the invention an injector which drives the cable in the well is located on the lubricator, and is controllable independently of the drive mechanism for the cable located on the vessel. The drive mechanism and the injector may be synchronized in a manner, among others, providing that the cable is hanging in a predetermined arc during the intervention, whereby the vessel may be moved from the well. Moreover, the invention relates to a method and a cable used together with the device.

Abstract: A riser recoil control system (10) adjusts tension forces (F1, F2) applied to a marine riser (60), which is attached to an anchored, floating vessel (30) and a wellhead (80). The riser (60) is attached to the vessel (30) using tension forces (F1, F2) asserted by riser tensioners (20). Each tensioner (20) has an air shutoff valve (110), and an orifice-controlled fluid valve (120). A disconnection sensing means (200) provides a disconnect signal when the riser (60) is disconnected from the wellhead (80), which closes the valves (110, 120) and adjusts the tension forces (F1, F2) applied by the tensioners (20). The invention includes a method for adjusting the tension forces (F1, F2) applied to the riser (60), including sensing the disconnect signal and adjusting the tension forces (F1, F2) supplied to the riser (60) by closing the air shutoff valves (110) and partially closing the orifice-controlled fluid valves (120).

Abstract: A method for determining heave and heave rate for a vessel is described. The vessel includes an inertial navigation system (INS), and sensors for the INS being located at a point A of the vessel, the vessel having a zero heave reference point B, and the described method provides heave and heave rate at a point C of the vessel. The method includes determining reference coordinates for points A, B, and C of the vessel, generating a velocity signal representative of a velocity at a point on the vessel, generating a heave rate signal based upon the velocity signal, and generating a heave based upon the heave rate signal.

Abstract: A cylinder-stem assembly to floating platform, gap controlling interface guide. A longitudinal wear strip and mating guide are positioned at an angle relative to a tangent to the nominally round exterior cylinder of the cylinder. Cylinder guides may be provided at more than a single elevation. The corners of the contacting surfaces of the wear strips may be rounded to reduce the risk of galling and to avoid any obvious point or line loading. During assembly, the cylinder-stem assembly is rotated after insertion into its slot in the floating platform. The rotation centers the cylinder and also may be used to control the magnitude of the gap or an interference fit.

Abstract: An automated riser recoil control system (10) including a plurality of riser tensioners (20), a vessel heave measurement system (210) and a control processor (70) with each tensioner (20) having a piston travel indicator (27) which signals the processor (70) and a method of operation is disclosed.

Abstract: A floating rig or structure for drilling in the floor of an ocean using a rotatable tubular includes a seal housing having a rotatable seal connected above a portion of a marine riser fixed to the floor of the ocean. The seal rotating with the rotating tubular allows the riser and seal housing to maintain a predetermined pressure in the system that is desirable in underbalanced drilling, gas-liquid mud systems and pressurized mud handling systems. The seal is contemplated to be either an active seal or a passive seal. A flexible conduit or hose is used to compensate for relative movement of the seal housing and the floating structure because the floating structure moves independent of the seal housing. A method for use of the system is also disclosed.

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: The invention describes a cost-effective alternative for deploying and installing subsea equipment using a workboat or other vessel of opportunity. The equipment is not supported directly by the vessel, but is instead supported by one or more buoys below the wave zone. The buoys are controlled by a combination of chain, wire rope, and synthetic line linking it to the workboat. As such, the buoy system described herein decouples vessel motion from the payload by supporting the payload from the buoys below the wave zone. Because the buoys are below the wave action and its associated turbulence, there is little energy and hence little tendency for motion. The result is a stable, inexpensive, maneuverable system capable of servicing large subsea payloads in a wide range of water depths.

Abstract: A floating offshore construction (1) comprising a suspension gear (7) for suspending a riser construction (6). The suspension gear comprises a guide which extends adjacent the water surface during use, with a float (12) disposed therein for axial movement. The float comprises coupling means (13) for coupling to a riser construction. The invention also relates to a float.

Abstract: A closed system drill string compensator having a hydraulic fluid accumulator, at least one air pressure vessel, and a piston and a piston rod slidably engaged within a cylinder. The drill string compensator provides tensioning force for supporting a drill string and permits the drilling vessel to remain connected to the drill string during ocean level changes caused by wave action or ocean heave. In one embodiment, the accumulator surrounds the cylinder and at least one air pressure vessel is radially disposed around the accumulator and the cylinder. In another embodiment, the accumulator surrounds the cylinder and includes two ports, one port for permitting fluid communication between the cylinder and the accumulator and a second port for permitting fluid communication between the accumulator and the air pressure vessel, the first port including a shut-off valve disposed therein. Methods of compensating a drill string are also disclosed.

Abstract: A safety device 30 for compensating for ocean heave motion of a vessel or watercraft connected to a conduit 12 or drill string extending to the subsea. The safety device comprises at least one vertical piston and cylinder assembly 40,41, the piston rod 40a of which connects to an upper beam 35 of the device 30 and the cylinder 40b of which connects to a horizontal beam 42 below the upper beam 35 and supported by vertical tension legs 51,52, each including a gas expansion chamber 51a,52a. A valve controlled conduit system 61,62 connects the chambers 51a,52a and cylinders 40b,41b to a source of pressurized gas whereby a fixed volume of gas and gas pressure positions the pistons at the mid-lengths of the cylinders 40b,41b The safety device 30 is mounted on a frame or rig 11 mounted on the watercraft and the base 33 of the safety device 30 is connected to the bottoms of the tension legs 51,52.

Abstract: A mechanical joint assembly for a steel catenary riser (SCR) is disclosed. The lower section of the mechanical joint assembly is comprised of steel or alternate high strength components, rather than elastomers to absorb the high loads and increase life of the unit. The lower mechanical joint assembly provides for reduction of bending moments and resulting fatigue stresses at the SCR top by removing resistance to movement in all angular directions, providing increased lateral and in-plane angles to provide increased construction tolerances for the pipeline approach corridor. Pipeline approach angle increase is accommodated by providing dual orthogonal trunnions in addition to an axial swivel. The upper mechanical joint assembly, acting without riser tension loads, allows for the use of either flexible high-pressure pipe or swivel arrangements to accommodate angular flexure before the rigid deck piping.

Abstract: The invention is directed to a tensioner/slip-joint module for providing a conduit from a floating vessel at the surface of the ocean to the blowout preventer stack, or production tree, which is connected to the wellhead at the sea floor. The tensioner/slip-joint module compensates for vessel motion induced by wave action and heave and maintains a variable tension to the riser string alleviating the potential for compression and thus buckling or failure of the riser string. The tensioner/slip-joint module of the present invention preferably includes at least one mandrel having at least one hang-off donut; at least one upper flexjoint swivel assembly, at least one radially ported manifold, at least one tensioning cylinder, and at least one slip-joint assembly combined in a single unit.

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: To maintain a riser under tension, the riser can be connected to a gripper (5, 12) which is connected to vertical toothed racks (4) that are in constant engagement with gear wheels (22) which are driven with constant torque, preferably by hydraulic motors (9) at constant pressure. An apparatus is also described for putting the riser under tension. The apparatus includes vertical guides (7) in a derrick, toothed racks (4) in the vertical guides (7), a gripper (5, 12) designed for interaction with a riser connected to the racks (4), and drive units (9) arranged in the derrick for drive-actuation of the racks (4) in the vertical guides (7).

Abstract: A new marine oil production riser system for use in deepwater applications is disclosed. An efficient means for accommodating movements of the host facility, while maintaining riser top tension within the limits for long-term riser performance. Long riser stroke lengths can be accommodated without requiring complex interfacing with the topsides. The riser assembly comprises: a generally extendable substantially non-vertical section having an upper end adapted to be in flow communication with a generally vertical marine riser carried by a facility floating on the surface of a body of water, and having a lower end adapted to be in flow communication with a fluid source on the seafloor; and tensioning means, mechanically connecting the upper end of the marine riser with the lower end of the marine riser, for biasing said ends towards each other.

Abstract: The invention is an apparatus, method and system for supporting risers in a floating platform. The apparatus comprises a table disposed above a hull-top surface, a first riser opening in the table, and a first dedicated riser tensioner attached to the table and disposed about the first riser opening. The apparatus further comprises a second riser opening, and a second dedicated riser tensioner attached to the table and disposed about the second riser opening. The method comprises tensioning a first riser with a first dedicated riser tensioner, and tensioning a second riser with a second dedicated riser tensioner, wherein the first dedicated riser tensioner is responsive to the second dedicated riser tensioner. The system comprises a mechanism for tensioning a first and a second riser, wherein the mechanism for tensioning the first riser is responsive to the second riser.

Abstract: In a substructure (10) for a floating oil or gas production platform, an arrangement to tension a plurality of risers (16) extending from the sea bed up to the substructure, the arrangement comprising: a conventional hydraulic tensioner/heave compensator (17) for each riser, in which there is a soft spring formed by a piston cylinder combination acting against an accumulator, the heave compensators for the risers being disposed to compensate for vertical oscillations of relatively short period (e.g.

Abstract: A system is provided for compensation for motion of a floating platform connected to a riser having at least two segments connected by an elbow. According to various example embodiments, a pre-determined portion of the riser flex in response to heave of the platform. In various example embodiments, the pre-determined portion comprises pre-formed curves that flex in response to the heave of the platform.

Abstract: A substantially rigid riser to offshore platform connector and a process of using the connector allows a riser to be preloaded and adjustably positioned relative to the offshore platform. The connector allows the riser tensile load to be limited by preloading and adjustably positioning the connector. In the preferred embodiment, hydraulic cylinders are used to preload the connector as well as to partially or fully support the riser during maintenance or repair procedures.

Abstract: An apparatus for holding and guiding a floating riser relative to a floating support. The apparatus includes a guidance mechanism secured to the floating support for enabling the riser to rotate about a horizontal axis perpendicular to a longitudinal axis of the riser; and for enabling the riser to slide longitudinally along the longitudinal axis and lateral displacement of the riser to be guided in a horizontal plane perpendicular to the longitudinal axis of the riser. The guidance mechanism includes friction pads mounted on a pad support for enabling the pads to pivot. The pads preferably cooperate with wheels such that the wheels bear against the riser and enable it to slide, and the riser comes to bear against the pads only when the wheels are moved away under the effect of lateral displacements of the riser.

Abstract: For a spar type floating platform having risers passing vertically through the center well of a spar hull, there is provided apparatus for supporting the risers from a gimbaled table supported above the top of the spar hull. The table flexibly is supported by a plurality of non-linear springs attached to the top of the spar hull. The non-linear springs compliantly constrain the table rotationally so that the table is allowed a limited degree of rotational movement with respect to the spar hull in response to wind and current induced environmental loads. Larger capacity non-linear springs are located near the center of the table for supporting the majority of the riser tension, and smaller capacity non-linear springs are located near the perimeter of the table for controlling the rotational stiffness of the table. The riser support table comprises a grid of interconnected beams having openings therebetween through which the risers pass.

Abstract: In one embodiment, the automated riser recoil control system (10) includes a plurality of riser tensioners (20), a vessel heave measurement system (210), and a control processor (70) in electrical communication with the heave measurement system (210) and riser tensioners (20). Each tensioner (20) includes a piston travel indicator (27) which signals the processor (70). In another embodiment, a method for adjusting at least one of the tension forces (F1, F2) applied by the tensioners (20) to the riser (60) includes determining piston travel velocity for each riser tensioner (20), measuring vessel heave velocity, calculating the differences between each of the piston travel velocities and the heave velocity, and adjusting the tension force when some preselected number of the velocity differences exceeds a preselected critical velocity difference. Tension force control is typically effected by throttling at least one fluid flow rate within one or more riser tensioner (20).

Abstract: A semisubmersible multipurpose unit (MPU) having a deck, a multipurpose tower secured to the deck, supports, pontoons connected to the supports with each pontoon adapted for ballast transfer, at least two hawsers connected to the MPU for connecting the MPU to an object at sea having a mooring system, a hawser guidance system to direct each hawser to the object at sea, a crane secured to the deck of a semisubmersible MPU, and at least an 6-point mooring system, wherein the combination of the semisubmersible MPU, hawsers and 6-point mooring system create a global equilibrium between the mooring system of an object at sea and the at least 6-point mooring system and the hawsers have both an elasticity sufficient to accommodate the wave frequency between the object at sea and the MPU and a stiffness adequate to synchronize the average and low frequency movements during a 10-year storm.

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 tensioner for providing a conduit, e.g., drilling and production riser strings, from a floating vessel at the surface of the ocean to the blowout preventer stack, production tree, or other assembly which is connected to the wellhead at the sea floor. The tensioner compensates for vessel motion induced by wave action and heave and maintains a variable tension to the riser string alleviating the potential for compression and thus buckling or failure of the riser string. The tensioner of the present invention preferably includes at least one mandrel having at least one hang-off donut; at least one upper flexjoint swivel assembly, at least one radially ported manifold, and at least one tensioning cylinder co-linearly combined in a single unit. Methods for assembling risers are also disclosed.

Abstract: Initially, a set of locking lugs lock an inner mandrel is locked in position with respect to an outer mandrel. Unlocking the travel joint is accomplished by applying a constant vertical or downward force on the tubing string. That vertical force is transmitted through the tubing string to the outer mandrel, which causes hydraulic pressure with a hydraulic chamber to increase. When the hydraulic pressure exceeds a pressure threshold, a pressure sensitive valve opens, and the hydraulic fluid gradually flows into a reserve hydraulic chamber, allowing the outer mandrel to move with respect to the inner mandrel. A viscosity independent flow restrictor limits the transfer of hydraulic fluid to a preset flow rate. After sufficient hydraulic fluid has been received into the reserve chamber, the outer mandrel aligns with the locking lugs, which then move from the locked position to the unlocked position. The travel joint then releases, allowing the outer mandrel to telescope inward and outward.

Abstract: A tensioner/slip-joint module for providing a conduit from a floating vessel at the surface of the ocean to the blowout preventer stack, or production tree, which is connected to the wellhead at the sea floor. The tensioner/slip-joint module compensates for vessel motion induced by wave action and heave and maintains a variable tension to the riser string alleviating the potential for compression and thus buckling or failure of the riser string. The tensioner/slip-joint module preferably includes at least one mandrel having at least one hang-off donut; at least one upper flexjoint swivel assembly, at least one radially ported manifold, at least one tensioning cylinder, and at least one slip-joint assembly combined in a single unit.

Abstract: A device in connection with a riser (1) for the transport of oil and/or gas, possibly including water, from a transport system, transport pipe (5) or similar structure on the sea bed to a platform or similar arrangement. To permit the use a riser (1) for the transport of oil and/or gas from a small field with low oil/gas production where a transport pipe (5) with a small diameter is used, a flexible pipe (4) with generally the same internal diameter as the transport pipe (5) is arranged inside the riser (1). At its upper and lower ends, the riser (1) is provided with a coupling (6, 7), which forms a seal between the transport pipe (5) and the flexible pipe (4) and also forms a seal at the ends of the riser so that the riser is closed.

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 bottom-to-surface link comprising at least one underwater pipe (1) having at least one float (2), preferably a plurality of floats in a string, said floats constituting cans surrounding said pipe (1) and being located in the top underwater portion of the pipe, said pipe being held at the surface by a guide device, preferably on a floating float support (15).

Abstract: A process and an apparatus for sinking drill holes, in particular exploration and extraction drill holes, with a drill pipe, which at its end facing the floor to be mined is provided with a guide point fixed in the longitudinal direction of the drill pipe and a drill head with at least one cutting element. The drill head can be moved in the longitudinal direction of the drill pipe between a top position, in which the guide point projects beyond the at least one cutting element, and a bottom position in which the at least one cutting element is positioned at the same height as the end of the guide point or projects beyond same in the operating direction. When the drill head is in the top position, the drill pipe is moved in the direction of the drill hole to be produced until the guide point by cooperating with the floor fixes it in position. Then the drill head is moved into its bottom position in order to produce the drill hole.

Abstract: A semisubmersible multipurpose unit (MPU) having a deck, a multipurpose tower secured to the deck, supports, pontoons connected to the supports with each pontoon adapted for ballast transfer, at least two hawsers connected to the MPU for connecting the MPU to an object at sea having a mooring system, a hawser guidance system to direct each hawser to the object at sea, a crane secured to the deck of a semisubmersible MPU, and at least an 6-point mooring system, wherein the combination of the semisubmersible MPU, hawsers and 6-point mooring system create a global equilibrium between the mooring system of an object at sea and the at least 6-point mooring system and the hawsers have both an elasticity sufficient to accommodate the wave frequency between the object at sea and the MPU and a stiffness adequate to synchronize the average and low frequency movements during a 10-year storm.

Abstract: A method of conducting operations to an offshore field from multiple separated drill centers using a floating vessel having a turret-mounted mooring element and a workstation separate from the mooring element in which the vessel is moored at a central mooring element location and operations are sequentially carried out at separate drill centers associated with the mooring element location by allowing the vessel to weathervane to a heading associated with a subsequent drill center once operations have been completed at a first drill center.

Abstract: A surface blow-out prevention support system comprising a support accommodating the blow-out preventor which is adapted to be supported from an associated support structure, the support facilitating connection between the blow-out prevention system and a riser extending from an underwater well, a connector providing a fluid connection between the blow-out preventor and the associated support structure, the support comprising a plurality of suspension members extending between the associated support structure and the support, where the suspension members are mounted to the support at angularly equidistant positions around the central axis of the support, each suspension member comprising a flexible cord member extending between the support and the associated support structure through a sheave arrangement, the sheave arrangement including a resilient tensioning member which is capable of resilient longitudinal extension to cause the spacing between the support and the associated support structure to be varied.