Abstract: A subsea hydrocarbon export system includes a riser tower having a riser column extending from a seabed location to a sub-surface buoy that supports the riser column in an upright orientation. A subsea connector is operable underwater to couple the riser column temporarily to a hose suspended from a surface shuttle tanker vessel for an export operation and to release the hose after the export operation.

Abstract: A riser intervention system for use with a subsea test tree includes a lower riser package spool, an intermediate spool, and a riser stress joint. The lower riser package spool may include a bore and a shoulder projecting into the bore such that the subsea test tree is landable on the shoulder within the lower riser package spool. The intermediate spool is connectable to the lower riser package spool to secure the subsea test tree within the bore of the lower riser package spool such that the lower riser package spool is in fluid communication with the intermediate spool. The riser stress joint is releasably connectable to the intermediate spool using such that the intermediate spool is in fluid communication with the riser stress joint.

Abstract: A free-standing riser system connects a subsea source to a surface structure. The system includes a concentric free-standing riser comprising inner and outer risers defining an annulus there between. A lower end of the riser is fluidly coupled to the subsea source through a lower riser assembly (LRA) and one or more subsea flexible conduits. An upper end of the riser is connected to a buoyancy assembly and the surface structure through an upper riser assembly (URA) and one or more upper flexible conduits, the riser also mechanically connected to a buoyancy assembly that applies upward tension to the riser. The riser may be insulated for flow assurance, either by a flow assurance fluid in the annulus, insulation of the outside of the outer riser, or both. The system may include a hydrate inhibition system and/or a subsea dispersant system. The surface structure may be dynamically positioned.

Abstract: The present invention relates to an accessory device which comprises a damping sleeve (100), which is coupled to a bend stiffener (4), capable of acting in the anchoring operation of a riser (3) so as to eliminate the need for fuse cables and safety straps, the need to use a team of divers, and to guarantee the implementation of the operation in all sea conditions.

Abstract: A riser configuration having a rigid riser portion and a flexible riser portion. The riser configuration also includes a subsea buoy across which the riser portions are connected. Buoyancy means are mounted on the flexible riser portion.

Abstract: The disclosure relates to an assembly including a supporting buoy and an anchoring assembly (28) comprising a base (100) attached to the bed (12) of the expanse of water. The assembly comprises a flexible anchoring line (30) connecting the anchoring assembly (28) to the supporting buoy (26). The anchoring line (30) comprises a lower section (84) made of chain links (92). The anchoring assembly (28) comprises a device (110) for guiding the lower section (84). The lower section (84) is movably mounted in the guide device (110) relative to the base (100), between an extended configuration and a contracted configuration, and a locking member (114) which can be released from the anchor line (30) on the anchoring assembly (28).

Abstract: A bottom-to-surface connection installation between a plurality of undersea pipes resting on the sea bottom and a floating support on the surface and anchored to the sea bottom, the floating support including a turret; and a plurality of flexible hoses extending from the turret to respective ones of a plurality of rigid pipes, the rigid pipes providing connections between the flexible hoses and respective ones of the plurality of undersea pipes resting on the sea bottom, wherein the installation includes a guide structure maintained in the subsurface between the turret and the top of the rigid pipes, the guide structure being suitable for guiding the flexible hoses, the guide structure having a plurality of first guide elements with respective ones of the plurality of flexible hoses passing therethrough in such a manner that the flexible hose has at least a bottom flexible hose portion in a dipping catenary configuration, and a second flexible hose portion extending entirely above the point of contact between

Abstract: A buoyancy element, riser assembly including a buoyancy element and a method of supporting a riser are disclosed. The buoyancy element includes a body of at least partly flexible structure having a volume that is adjustable between an expanded and contracted position, and an entry port for fluid to be supplied to and/or removed from the body to thereby adjust the volume of the body.

Abstract: A riser assembly and method for providing buoyancy to a riser assembly are disclosed. The riser assembly which is of the type for transporting fluids from a sub-sea flowline to a floating structure comprises a first segment of flexible pipe, a further segment of flexible pipe and a rigid buoyancy support for providing at least one buoyancy element at the support.

Abstract: An installation of bottom-to-surface connections having a plurality of bottom-to-surface connections arranged in a fan from a common floating support. The installation having a first number k of first bottom-to-surface connections, with each first number of connections having a first riser connected to a first undersea pipe tensioned in substantially vertical manner by a first float, and a diving first flexible connection pipe connecting the floating support and first riser. The installation further having a second number m of second bottom-to-surface connection, with each second number of connections having a second rigid pipe connected to a second undersea pipe and tensioned by a second buoyancy element, and a second flexible connection pipe providing the connection between the floating support and the second rigid pipe.

Abstract: Systems and methods for the prevention or dissolution of hydrates in an undersea well. One example system includes a submersible isolation bell for capturing effluent being exhausted from the well, and an umbilical. A power cable supplies electric power to the submersible isolation bell, for example for heating of the interior of the submersible isolation bell to prevent or discourage the formation of methane hydrates and the precipitation of other byproducts. Diluents may be supplied to the submersible isolation bell to further discourage the formation of hydrates and precipitation of other byproducts. The diluents may be heated locally at the submersible isolation bell, using electric power supplied by the power cable. A conformable seal may substantially seal the submersible isolation bell to a riser or other structure at the wellhead.

Abstract: Apparatus and method for supporting a riser are disclosed. The apparatus includes an anchoring element (420) for anchoring a riser to a fixed structure, and a supporting portion (412) configured to support a section of flexible pipe (406), the supporting portion having a bearing surface for the section of flexible pipe to bear against to thereby restrain the flexible pipe from upward movement.

Abstract: There is disclosed a floating system positioned in a body of water having a water bottom, the system comprising a host member floating on a surface of the water; a flotation module floating under the surface of the water; a flexible hose connecting the host member to the flotation module; and an elongated underwater line structure, comprising a top portion connected to the flotation module; a bottom portion extending to the water bottom and adapted to connect to a flowline lying on the water bottom; and at least one of the top portion and the bottom portion comprising a catenary configuration.

Abstract: A free standing hybrid riser system including: a vertical section including an upper strengthening joint; a buoyant unit; a top riser assembly (TRA) below the buoyant unit and connected at a first connection point on the TRA to the upper strengthening joint; the buoyant unit is connected to the TRA at a second connection point on the TRA; and a flexible jumper is connected to the TRA at a third connection point on the TRA; wherein a first bending moment is applied about the first connection point to the TRA by the buoyant unit, and a second bending moment is applied about the first connection point to the TRA by the flexible jumper, wherein the first and second bending moments oppose each other.

Abstract: A method, system and apparatus for deploying a subsea well intervention system from a surface vessel to a subsea tree, including connecting a spoolable compliant guide (SCG) to a subsea intervention package; testing the connection; lowering overboard the intervention package into a water column using a primary lifting device; gradually paying out the SCG from a reel thereof as the intervention package is lowered to a seabed; transferring the weight of the intervention package to a secondary lifting device, wherein the intervention package functions as a dead weight to overcome a positive buoyancy of the SCG, a distance between the primary and secondary lifting devices creates and controls a shape of the SCG; and once landed onto a subsea tree with heave compensation, disconnecting the secondary lifting device from the intervention package, and hanging the SCG off at the vessel at deck level.

Abstract: A support for a subsea riser decouples the function of the riser into two separate functions: the load transfer function which supports the hung weight of a subsea riser configuration to a supporting floater (such as the buoy of a disconnectable fluid transfer system) and the fluid transfer function which provides a continuous flow path for the fluid coming to or from the riser.

Abstract: A method for manufacturing flexible pipe body and flexible pipe body of a type suitable for transporting production fluids is disclosed. The flexible pipe body includes an armour layer comprising interlocked windings of armour tape comprising at least one armour locating element and a reinforcement layer comprising a layer of reinforcement tape comprising at least one reinforcement locating element over the armour layer. The armour locating element and reinforcement locating element locate windings of the reinforcement tape with respect to respective windings of the armour tape.

Abstract: A method for drilling a borehole in a producing subsea wellbore wherein a flexible conduit is connected at one end to a surface vessel and at the other end via a pressurized subsea wellhead to the producing wellbore such that a remotely operated electrical drilling device (RODD) can be deployed down the flexible conduit, the method comprising: directing a RODD to the location for drilling in the wellbore; and drilling a further wellbore section with the RODD; wherein the drilling comprises drilling in underbalanced conditions with respect to the formation; and using fluids produced from the formation to transport the drill cuttings away from the drilling device.

Abstract: The invention relates to a hydrocarbon exploration system, comprising a first vessel (1) having a turret (3) around which the vessel can weathervane, the turret being moored to the sea bed (4), and a second vessel (7) connected with at least one riser (12) to a subsea well (5), the first vessel (1) being connected to the second vessel via a fluid transfer duct (20) comprising a first end section (23) attached to the turret of the first vessel (1), a substantially horizontal mid section (24), and a second end section (22) attached at or near the second vessel (7), the second vessel (7) weighing between 2,000 and 15,000 ton its base being attached to the sea bed via taut tendons (9), the weight exerted by the fluid transfer duct (20) on the second vessel being below 1,000 ton, a power generator being situated on the first vessel (1), power being transferred from the power generator via an electrical swivel on the first vessel.

Abstract: A free standing riser system includes a riser, a subsea intervention unit, and an umbilical line. The riser includes interconnected joints linked to one another, a lower-end of the riser being coupled to a wellhead and an upper-end of the riser enclosed in a buoy assembly, including a terminal, the riser being maintained in an erect, substantially vertical position. The subsea intervention unit is provided above the riser, and includes three connections: one connection to the terminal of the riser, one connection to a flexible jumper that is connected to a FPU, and one connection that provides a vertical conveyance to an intervention rig.

Abstract: A technique facilitates formation of connections between compliant tubular members and subsea facilities. A compliant tubular member is deployed to a subsea location in a manner that arranges the compliant tubular member in a curvilinear shape. The distal end of the compliant tubular member is drawn down into proximity with the subsea facility and then moved horizontally into alignment with the subsea facility. Subsequently, the distal end is lowered into engagement with the subsea facility without being detrimentally affected by motion of an upper end of the compliant tubular member.

Abstract: A marine riser system for transferring fluid between a well on the seafloor and a vessel floating on the surface of the sea. The riser system has a turret buoy capable of connecting to a floating vessel; two or more hybrid risers, each of the hybrid risers having a vertical riser, a riser buoy attached to the upper portion of the vertical riser and a flexible jumper connecting the riser buoy to the turret buoy, and wherein the hybrid risers are secured to the seafloor. A flowline may connect a lower portion of each of the vertical risers to a subsea manifold, which interconnects the flowline and a subsea well. The subsea manifold is capable of controlling the flow to or from a subsea well. The hybrid risers are positioned about the turret buoy so that the turret buoy is horizontally balanced while disconnected from a vessel. In another embodiment, the marine riser system is capable of directing a fluid from the floating vessel to a subsea export flowline.

Abstract: An improved subsea manifold system that is capable of being used in an early production system for producing hydrocarbons from a plurality of wells from a common riser system. The subsea manifold is able to control the fluid from a multiple of subsea wet-tree wells while at the same time giving the operator the option to isolate production from a single subsea well for production evaluation. The subsea manifold also includes a pigging loop which enables efficient pigging of the flowline(s) of the early production system.

Abstract: An offshore system allows a vessel (12) to sail to a predetermined sea location (14), quickly set up a loading system and start the transfer of hydrocarbons to or from a pipeline (22), and then quickly disconnect and sail away. The vessel is a DP (dynamic positioning) vessel that does not require mooring or anchor lines, so the only apparatus to install is a conduit (30) that can be picked up by the vessel to extend between a stationary pipe end (24) that lies at the sea floor and the vessel. The conduit includes primarily a flexible hose (70) that extends in a sine wave with two loops (80, 82). The conduit includes a rigid reinforced hose section (34) that is pivotally connected to the sea floor. A chain (114) can be provided with a portion of the chain lying on the sea floor, to help the disconnected hose coupling (42D) remain at a stable position above the sea floor.

Abstract: There is disclosed a floating system positioned in a body of water having a water bottom, the system comprising a host member floating on a surface of the water; a flotation module floating under the surface of the water; a flexible hose connecting the host member to the flotation module; and an elongated underwater line structure, comprising a top portion connected to the flotation module; a bottom portion extending to the water bottom and adapted to connect to a flowline lying on the water bottom; and at least one of the top portion and the bottom portion comprising a catenary configuration.

Abstract: A riser support system for use in a body of water comprises a buoyant and ballastable support structure and a plurality of substantially vertical and rigid risers each of which is attached to the inside of the support structure at a location below the center of buoyancy of the support structure and below the surface of the body of water. Usually, each riser passes through the inside of a single tube in the support structure. Typically, the riser support system is used to support a plurality of risers and their surface wellheads inside the hull of an offshore platform, usually in such a manner that the axial movement of the risers and support structure is independent of the axial movement of the hull.

Abstract: A hull-to-caisson interface connection assembly accommodates high tension loads between the hull and a caisson of a Spar-type platform, while facilitating angular flexing motion and constraining lateral and axial movement. The interface connection assembly includes an annular bearing shoulder at the top end of caisson, and a laminated bearing assembly mounted in the bottom of the hull and defining a passage through which the upper portion of the caisson passes, so that the caisson shoulder seats against the upper end of the bearing assembly. The bearing assembly includes a laminated structure of alternating steel and elastomeric flex elements, bonded to each other to flex together as a unit, rather than sliding relative to each other. The laminated structure of the bearing assembly supports the vertical tensile loads applied by the weight of the caisson on the hull, while also accommodating the angular loads applied between the caisson and the hull.

Abstract: An apparatus for supporting a steel catenary riser (SCR) from a floating structure having a keel includes a flexible support tube or keel sleeve through which the SCR passes. The support tube or keel sleeve includes a pivot mechanism that is lockably received in a receptacle fixed to the floating structure. A method of supporting an SCR from a floating structure includes the steps of inserting a first end of the SCR into a support tube or keel sleeve; fixing the support tube or keel sleeve to the SCR; pulling the support tube or keel sleeve into a receptacle fixed to the floating structure; releasing the support tube or keel sleeve from the SCR; pulling the SCR through the support tube or keel sleeve up to an attachment point on the structure; fixing the SCR to the structure; and fixing the support tube or keel sleeve to the SCR.

Abstract: The invention concerns a seafloor-surface connecting installation for a submarine pipeline (10) set on the seafloor, in particular at great depth, of the hybrid-tower type comprising a static base (13-18) set on the seabed. In the inventive installation: 1) said vertical riser includes a terminal pipe portion (51), and a flexible joint (19) which allows angular movements (?) of the upper part (52) relative to said terminal pipe portion (51); and 2) the terminal part (11) of said pipe resting on the seabed has a an elbow-type terminal curvature; 3) said terminal portion (51) of the vertical riser is connected to said terminal curvature (11) by a single connecting element; and 4) said base plate (13-18) rigidly maintains in fixed vertical position and linked to each other via said connecting element (12): said terminal pipe portion (51) and said elbow-type terminal curvature (12) the latter facing upwards.

Abstract: The present invention relates to a bottom-to-surface connection device comprising at least one undersea pipe or riser (1, 1a-1b) capable of including a single float (2, 21-27), said float being connected at its bottom end to a junction device (8) creating a leaktight flexible joint between the bottom end of the float (2) and said riser (1a), the connection device being characterized in that said junction device (8) is interposed between and secured to a bottom portion (1a) of the riser going down to the sea bottom and a top portion of the riser passing through said float and rising to the surface, said junction device (8) comprising at least one first laminated abutment in the form of a body of revolution having a plurality of elastomer layers defining surfaces of revolution that are frustoconical in shape or ellipsoidal in section.

Abstract: A marine riser system for transferring fluid between a well on the seafloor and a vessel floating on the surface of the sea. The riser system has a turret buoy capable of connecting to a floating vessel; two or more hybrid risers, each of the hybrid risers having a vertical riser, a riser buoy attached to the upper portion of the vertical riser and a flexible jumper connecting the riser buoy to the turret buoy, and wherein the hybrid risers are secured to the seafloor. A flowline may connect a lower portion of each of the vertical risers to a subsea manifold, which interconnects the flowline and a subsea well. The subsea manifold is capable of controlling the flow to or from a subsea well. The hybrid risers are positioned about the turret buoy so that the turret buoy is horizontally balanced while disconnected from a vessel. In another embodiment, the marine riser system is capable of directing a fluid from the floating vessel to a subsea export flowline.

Abstract: A vessel for exploration of hydrocarbons includes one or more risers extending from the vessel to the seabed, a hydrocarbon processing unit connected to the one or more risers and to a storage or transport structure for storing the processed hydrocarbons. The vessel is anchored to the seabed, the vessel includes a lifting member for lowering risers vertically towards the sea bed and for connecting a riser with a first end to a subsea hydrocarbon structure, which riser includes a connector on a second end, the vessel having a connector for attaching to the riser connector and for placing the riser in fluid connection with the processing unit.

Abstract: A guide tube for a flexible pipe for transporting hydrocarbons comprising an internal tubular element of a substantially rectilinear section extending along an axis (A) and extended by a free section having a curvature along its length and a wall which is internal with respect to the curvature against which the flexible pipe is accommodated when frictionally carried through guides. The rectilinear section comprises eccentric guides for directing the flexible pipe away from the axis (A) and in a direction opposite to the curvature of the free section such that the pipe is deviated from the internal wall.

Abstract: A technique for guiding a riser in an offshore environment. The technique utilizes a keel guide that permits the passage of connectors or other components therethrough. A bushing is mounted within the keel guide to guide the relative linear motion of the riser assembly through the keel guide.

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: The invention relates to flexible risers for transfer of hydrocarbons between a sea bed installation and a vessel (10) floating at the sea surface. The riser (18) is provided with means (20) for protecting the riser (18) from impacts. The protection means (20) covers at least the upper part of the riser (18) and is retractable to an inactive position. When in operation, the riser protection means (20) is either suspended from the vessel (10) or from a submerged turret buoy, forming part of a mooring system for the vessel (10).

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 conduit structure (44) connects subsea oil wells to a floating structure (12) such as a vessel, in shallow water, the conduit structure providing a low cost and reliable fluid connection during drift of the vessel. The conduit structure includes a seafloor riser support (50) with a lower end (52) fixed to the seafloor and an upper end (54) lying a plurality of meters above the seafloor. A flexible pipe or hose (46) extends in a double catenary curve from the top of the seafloor riser support, at a downward incline away from the seafloor riser support and then at an upward incline to the floating structure. A rigid pipe (70) can extend along a plurality of meters of the height of the riser support to minimize the required length of flexible hose and facilitate installation.

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: Pipe for great water depths allowing transfer of a fluid between a floating support and a point situated below and at a distance from the water surface, characterized in that it comprises: at least one flexible part connected at one of its ends to the point situated below the surface, at least one rigid part connected to the flexible part at one of its ends and to the floating support at the second end, the rigid part being held up onto the floating support by holding means allowing this part to be essentially tensioned under the effect of its own weight.

Abstract: The present invention relates to an installation providing a bottom-to-surface connection for an undersea pipe resting on the sea bottom, in particular at great depth, the installation being of the hybrid tower type having a static base placed on the sea bottom. In the installation of the present invention, said pipe resting on the sea bottom is connected by a flexible pipe element constituting a bend to a vertical riser whose bottom end is held in fixed position relative to said base.

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 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: A steel catenary riser (SCR) system includes a tensioning mechanism on a floating facility that controllably applies a substantially constant tension to an SCR that is fluidly coupled to the facility by a flexible jumper conduit. More specifically, the system includes a tensioning device located on the floating facility; and an SCR having an upper portion, which, in the preferred embodiment, extends above the surface of the body of water. The upper portion of the SCR is connected to the tensioning device by a connection element, such as a cable, chain, rope, or wire, whereby tension is controllably applied from the tensioning device to the SCR. A flexible jumper conduit is fluidly connected between the upper portion of the SCR and the floating facility for conducting fluid from the SCR to the floating facility.

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: A stress joint for a subsea riser has a reduced diameter intermediate section to reduce bending stresses on the connection between the stress joint and the riser as well as the subsea equipment. The stress joint having a riser joint with a threaded upper end for connection to a riser string. Attached to a lower end of the riser joint is an upper transition section that tapers from the diameter of the riser joint to a reduced diameter. An intermediate section below the upper transition section has a reduced outer diameter. A lower transition section connects the lower end of the intermediate section to the subsea equipment. The lower transition section is tapered from a reduced diameter to a larger diameter to ensure a firm connection with the subsea equipment.

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: 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 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: 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.