Abstract: A system for drilling a subsea well from a rig through a subsea wellhead below the rig includes a wellhead stack which is mounted on the subsea wellhead. The wellhead stack includes at least a subsea blowout preventer stack and a subsea diverter. A drill string extends from the rig through the wellhead stack into the well to conduct drilling fluid from the rig to a drill bit in the well. A riser which has one end coupled to the wellhead stack and another end coupled to the rig internally receives the drill string such that a riser annulus is defined between the drill string and the riser. A well annulus extends from the bottom of the well to the subsea diverter to conduct fluid away from the drill bit. A pump has a suction side in communication with the well annulus and a discharge side in communication with the rig and is operable to maintain a selected pressure gradient in the well annulus.

Abstract: A method for transporting petroleum products in deep water from the seabed up to a floating or semi-submersible surface structure wherein at least one rigid and straight hybrid riser extends vertically. The hybrid riser has a rigid central hollow tubular structure surrounded by a cylindrical block of syntactic material which provides buoyancy and thermal insulation for the riser. A plurality of rigid pipelines are embedded in the syntactic material and surround the central tubular structure for receiving petroleum products from wells on the sea bed. The bottom of the riser is connected to a suction or gravity anchor at the sea bed. A submerged float is attached to the top of the riser and exerts an upward vertical force thereon. Flexible pipelines connect the rigid pipelines in the riser to the floating or semi-submersible structure.

Abstract: A spar platform is disclosed having a deck supported by a buoyant tank assembly having a first buoyant section connected to the deck and defining a central moonpool and a second buoyant section disposed beneath and axially vertically aligned with the first buoyant section. A buoyant section spacing structure connects the first and second buoyant sections in a manner providing a horizontally extending vertical gap therebetween and a counterweight spacing structure connects the counterweight to the buoyant tank assembly. A flexjoint receptacle connected to the exterior base of the second buoyant section receives a receptacle connection on the exterior of the riser to support a catenary section of the riser between the receptacle connection and the seafloor. An exterior section of the riser mounts to the exterior of the second buoyant section and an ingress section passes through the horizontally extending vertical gap to the moonpool.

Abstract: A connector for tying back a riser from a subsea wellhead to a platform, wherein the wellhead has an internal wellhead housing with external grooves thereon. The connector having a plurality of dog members carried within a cavity which engage the external grooves. The dog members are actuated by axial movement of a piston linked to a cam ring. The connector has a plurality of transfer members located within the cavity to support the dog members and transfer upward loading to the wellhead housing during tension on one side due to bending. Further, the connector has a release ring which forces the dog members out of engagement with the external grooves when the connector is released.

Abstract: A riser system connecting a oil or gas well head and a surface vessel comprises a first riser section maintained substantially vertically under tension, attached for example by a tension cable to a constant load tensioner means mounted on the vessel, and a flexible second riser section arranged above the first riser, the second riser being able to flex to accommodate movements in the surface vessel. The second riser section includes a curvature limiter, achieved for example by making the riser from a material of variable stiffness along the riser's length. An emergency disconnect valve is provided between the lower riser section and the upper flexible section. An alternative curvature limiter comprises a plurality of discrete collars which are connected together and surround the outer diameter of the second riser.

Abstract: A dynamically positioned, concentric riser, drilling system comprising a dynamically positioned drilling unit operable to float at least partially above the surface of a body of water, a first, outer, low-pressure, marine riser extending from the drilling unit into the body of water, a tensioning system to support the first marine riser, a second, inner, high-pressure, marine riser concentrically extending within the first, outer, low-pressure, marine riser, a surface blowout preventor, a lower marine riser package, a subsea blowout preventor, and a connector at the base of the lower marine riser package to release the risers from the wellhead in the event of a loss of station of the drilling unit.

Abstract: A connector for tying back a riser from a subsea wellhead to a platform, wherein the wellhead has an internal wellhead housing with external grooves thereon. The connector having a plurality of dog members carried within a cavity which engage the external grooves. The dog members are actuated by axial movement of a piston linked to a cam ring. The connector has a plurality of transfer members located within the cavity to support the dog members and transfer upward loading to the wellhead housing during tension on one side due to bending. Further, the connector has a release ring which forces the dog members out of engagement with the external grooves when the connector is released.

Abstract: A latching assembly includes a first mating portion and a second mating portion disposed adjacent and rotationally restrained relative to the first mating portion. A first cam member having a first cam profile is mounted on the first mating portion. A second cam member having a second cam profile is mounted on the second mating portion. The second cam profile is adapted to inter-fit with the first cam profile. Torque induced by the cam members when the cam profiles are engaging rotates the first cam member until the first cam profile is inter-fitted with the second cam profile.

Abstract: A rotating diverter for isolating fluid in a well from other fluid above the well is provided. The rotating diverter includes a housing body which has a bore running through it. A retrievable spindle assembly which includes a spindle and a bearing assembly is disposed in the bore. The bearing assembly supports the spindle for rotation. The spindle is adapted to receive and seal around a tubular member, and rotation of the tubular member rotates the spindle within the bore. A lock member is disposed in the housing body to secure the retrievable spindle assembly to the housing body.

Abstract: A ship type floating oil production system for access to subsea wells through installation of surface wellheads on a ship type surface vessel on the sea comprises a cylindrical turret moored to a seabed is located within a moon pool formed in the ship type surface vessel such that the ship type surface vessel is freely rotatable about the cylindrical turret. A plurality of riser pipes have a rigid structure and extend downward to subsea wells through the cylindrical turret, and each riser pipe is provided at its top portion with a surface wellhead including valves of the riser pipe. Accordingly, workover operations can be facilitated as needed by running workover tools through the surface wellhead of the corresponding riser pipe through use of a work-over-rig installed on the ship type surface vessel.

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.

Abstract: A bore selection apparatus (38) is described for facilitating access from a single bore riser to a production bore (34,34a) or annulus bore (36, 36a) without using a wireline-run whipstock. The bore selector apparatus disposed within the bore of a BOP stack (12) and which can be coupled between casing or tubing and a sub-sea test tree. The bore selector apparatus (38) can be actuated from the surface or from an ROV to provide a coupling between the tubing bore (44) and the production bore (34, 34a) or between the tubing bore (44) and the smaller annulus bore (36, 36a).

Abstract: A deepwater riser assembly is disclosed for a riser connecting subsea equipment to a surface wellhead. A buoyancy can assembly provides an open ended buoyancy can tube which surrounds the upper end of the riser and an upper seal which effectively closes the annulus between the riser and the buoyancy can tube. A load transfer connection in the buoyancy can assembly then connects the riser to buoyancy can tube. A pressure charging system communicates with the annulus between the riser and the buoyancy can tube below the upper seal. Injecting gas into this annulus then provides support to the riser.

Abstract: A dual phase riser flotation system contains a number of passive phase buoyancy modules of syntactic foam contained within an outer skin, and a number of active phase buoyancy modules which are similar to air canisters in that they may be inflated or deflated as required to provide levels of buoyancy. The passive phase buoyancy modules may contain tubes filled with air, a compressed gas such as nitrogen, or evacuated to provide additional buoyancy. Charge and discharge valves connect gas flow lines to a manifold system serving the active phase buoyancy modules.

Abstract: A subsea wellhead assembly located at the sea floor that includes a subsea wellhead and a stationary blowout preventer mounted to the subsea wellhead for controlling a well during drilling. A drill pipe defines an annulus within the stationary blowout preventer. The drill pipe extends to a rotational drive mechanism on a drilling rig at the surface. A drilling head forms a seal against a drill pipe with a rotatable inner portion. The rotatable inner portion rotates with the drill pipe and prevents drilling fluid returns from flowing up the annulus around the drill pipe and prevents drilling fluid returns from discharging onto the seabed. The drilling head is mounted on top of the stationary blowout preventer. A riser extends upward from the drilling head and extends to a floating drilling rig. The riser has a lower end that connects into the drilling head below the drill pipe seal for receiving mud-returns flowing up around the annulus of the drill pipe.

Abstract: Apparatus and method are provided for applying a force to a movable subsea member to move it into a preferred location for joining to a fixed member while the location of the movable member is monitored. Nozzles in the device are placed in the direction such that fluid exiting the nozzles creates a force so as to move the movable member into the preferred location. Fluid is pumped through the device and out through one or more nozzles. An environmental conductor may be tied back from a subsea wellhead using the apparatus and method by observing the location of the conductor over the subsea wellhead using a remotely operated vehicle (ROV) while fluid is pumped at the pressure and rate so as to move the conductor into position over the wellhead and lowering the conductor into the wellhead.

Abstract: A subsea wellhead connector has an upper body that abuts the rim of a wellhead member. A hydraulic wellhead connector is carried by the upper body and extends over the wellhead member. The hydraulic wellhead connector carries dogs for moving into an engaged position with a profile on the exterior of the wellhead member. The mating or complementary stepped profile at the top or rim of the wellhead housing is designed to engage at three surfaces. The first surface is the flat surface at the inner diameter. The second surface is the tapered surface at the step. The third surface is the flat surface on the rim from the tapered surface to the outer diameter of the rim. The profiles are dimensioned with bias toward initial contact at the outer diameter flat on the rim of the well housing, second contact is at the inner diameter flat on the rim of the well housing, and the third contact is at the tapered step.

Abstract: Apparatus for use in the completion and workover of a subsea well adapted for coil tubing intervention comprises a surface tree having an upper end on which a coil tubing injection unit may be mounted, a tension joint adapted to be connected to the upper end of a lower riser section extending to a subsea tree and to be suspended from a tensioning system at the surface to enable the lower riser section to be maintained in tension, an upper riser section for connection at its upper end to the surface tree and at its lower end to the tension joint, and a surface joint mounted on and surrounding the riser section in position to extend through the spider at the floor of an offshore rig.

Abstract: An apparatus for performing workover operations on a subsea well that has a subsea production tree with a production passage and an annulus access passageway. The subsea production tree is secured to a lower riser portion. The lower riser portion connects to the tree and has a production passage which registers with a production passage of the tree. The apparatus also has an annulus access passage which registers with the annulus access passage of the tree. The apparatus further includes a monobore riser which extends downward from the surface. A string of tubing, preferably coiled tubing, extends through the monobore riser and defines an inner riser passage and an annular riser passage. A circulation plug is secured proximate a lower end of the coiled tubing and is landed in the lower riser portion of the subsea well. The circulation plug communicates the inner riser passage with the annulus access passage.

Abstract: A spanner joint assembly for connecting between an upper riser and a conventional dual bore tubing hanger in a subsea well. The spanner joint assembly includes upper and lower spanner joint portions connected to each other through an emergency disconnect portion. The upper spanner joint portion has a longitudinal production bore and a longitudinal annulus. The lower spanner joint portion has a longitudinal production bore with a production bore valve and a longitudinal nonconcentric annulus access bore. The emergency disconnect portion includes an upper mandrel connected to the upper spanner joint portion and a lower mandrel connected to the lower spanner joint portion. A releasable mechanical connector includes a retaining groove in the lower mandrel and a collet connected to the upper mandrel. The collet has a latching portion extending beyond the upper mandrel which is adapted to be received in the retaining groove.

Abstract: A tensioning device is provided for applying tension to a riser from a surface deck of an offshore oil or gas well. The tensioning device is used with a riser of the type having threads formed on an exterior surface thereof. A tension ring of the tensioning device is formed from first and second ring halves that are clamped together about the riser. The first and second halves have inner threads for engaging the threads of the riser. A clearance exists between the first and second ring halves when the ring halves are clamped together about the riser to allow the first and second ring halves to be tightened against the exterior surface of the riser so that the tension ring is securely fastened to the riser. Fastening means are used for clamping the first and second ring halves together about the riser. Tensioning members that couple at one end to the tension ring and at the other end to the surface deck are used to apply tension to the riser from the surface deck.

Abstract: An offshore oil or gas well riser system which forms a connection between the well head and a surface vessel. The system has a first riser section which extends vertically and is essentially rigid and a second riser section which is made of a flexible material to accommodate movements of the surface vessel. The first riser section has buoyancy means attached to its upper end to support at least partly the weight of the first riser section, and the first and second riser sections have corresponding first and second bores which provide a continuous path between the surface vessel and the well head. The profile of the flexible second riser section is variable to provide a smooth continuous path through its corresponding second bore and such that the path does not extend below the upper end of the first riser section.

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: An undersea telescopic joint for a riser system is connected to a drilling vessel with a plurality of tensioners. The joint has a bearing with inner and outer annular mating members. A cap seals the outer member to the joint. The outer member closely receives and is axially movable relative to the inner member. A flat thrust bearing is located in a chamber between the two members. The members are sealed to one another with upper and lower swivel seals. A passage communicates hydraulic fluid to the chamber. The bearing has a pressure gage which registers with a passage that extends between the swivel seals. The chamber is filled with hydraulic fluid so that the two members are separated and the drilling vessel may rotate easily. The gage is used to detect whether the primary swivel seal is leaking.

Abstract: A fairing system is disclosed for protecting multiple, parallel, bundled but separate cylindrical elements deployed in offshore applications. The fairing system deploys a plurality of elongated fairing surface elements foldable about an axis with a connection system joining the elongated edges of the fairing surface elements in a folded manner about the axis. A plurality of thrust bearings are orthogonally connected across the fairing surface elements at each axial end and an axially extending circular rotational surface is defined by the interior of each of the folded fairing surface elements and a transverse edge of the thrust bearings connected thereto. This rotational surface has a diameter which circumscribes the multiple bundled cylindrical elements. A plurality of clamps interconnect the bundled, cylindrical elements and a bearing collar on the axial ends of the clamps is provided to receive the thrust bearings of the axial ends of the fairing elements.

Abstract: In a device for oil production at great depths at sea, production/drilling equipment is provided on a floating structure (2) at the surface of the sea, such as a platform structure or a vessel structure, for instance a ship, which is connected to a flotation unit (5) under water, which is anchored with a tension mooring (4) to the sea floor and with a riser system (6) which extends upwardly to the deck (9) of the structure. The structure (2) is equipped with an open vertical frame construction (8), such as a trusswork projecting downwardly in the water, the lower part of which forms a guide (17) and protection for the flotation unit (5). The rigid risers (4) from the sea bed continue up with the system (6) through the flotation unit (5) and further, enclosed by the frame (8) up to the level of the deck (9) above the water surface, where they are terminated in a Christmas tree device (7), or a manifold. A flexible riser system (11) extends from the valve arrangement (7), e.g.

Abstract: A device for connection or suspension between a detachable flexible or semi-flexible riser pipe (4) and a pipe system (14) on a fixed or floating platform or ship (15) has a rotary connection which is designed in such a way that the connection between the riser pipe (4) and the pipe system (14) is moment-free or mainly moment-free. The rotary connection may appropriately have a swivel housing (3) which, on one side, is fitted with a first tubular shaft (1) which is connected to the pipe system (14) on the platform or ship and, on the other side, is fitted with a second tubular shaft (2) which is arranged in a swivel housing at an angle of 90.degree. to the first tubular shaft (1) and which is connected to the riser pipe (4). The two shafts (1, 2) communicate with each other via a cavity in the swivel housing (3), but are closed to the surroundings at their ends.

Abstract: A stand-off assembly to attach to a cylindrical support member. The stand-off assembly includes a first component having a first arcuate portion adapted to conform to an outer surface of the cylindrical support member. The first component has a first attachment upright. A second component has a second arcuate portion adapted to conform to the outer surface of the cylindrical support member and also includes a second attachment upright. The second component is connected to the first component with a hinge connection. The first and second arcuate portions in combination extend substantially around the cylindrical support member and the first and second attachment uprights are parallel but separated from each other when the first and second arcuate portions are extended substantially around the cylindrical support member.

Abstract: A drilling, production, test, and oil storage caisson for use in deep water offshore well operations. Separate low pressure and high pressure drilling risers are independently supported on buoyancy modules. Multiple drilling and production risers are left in the water and connected to the drilling rig and well(s) as needed to prevent the need for the raising and lowering of different risers during the various steps involved in beginning and completing wells. Surface and lower BOP stacks are utilized. Means for controlling the accelerations and velocity of the drilling riser buoyancy modules in the event of riser failure is provided. A subsea tree with dual master valves allows for production directly through a vertical production riser, flowline, to the production manifold on the caisson. A twisted tubing production riser is formed from three strings of tubing that are used for the flowline, annulus, and conduit for control lines.

Abstract: Vertical movement of a floating marine platform is reduced by tendons extending from the platform to anchors on the seabed. A final tension adjustment to equalize the load on all of the tendons is made by a respective tension adjustment mechanism incorporated into the top connector of each tendon. The tension adjustment mechanism includes a split load ring assembly having an upper ring and a lower ring. The upper ring and the lower ring abut each other at respective complementary surfaces. Each surface has a series of serrated ramps. A rotation of one ring with respect to the other causes the upper ring to climb over the lower ring to thereby increase the tension in the tendon. Rotation of the upper ring with respect to the lower ring, for example, is achieved by a motor driven gear ring.

Abstract: The connection between a surface terminus for subsea production risers and a surface collection vessel is facilitated by a connection which utilizes slack loop flexible jumper hoses between the surface terminus of the subsea risers and a swivel coupling located on the surface vessel.

Abstract: A controlled-pressure multi-cylinder riser tensioner has a plurality of preferably six control-cylinder units (1) with proximal ends (2) attached pivotally to a bottom surface of an operational floor (3) and distal ends (5) attached pivotally to a riser-tensioner ring (6). Pressure lines (20, 38) in communication with opposite ends of the control cylinders lead to sources of pressure (46, 47, 48, 52, 53, 62, 63) that are separately controlled. Stroke length of the control-cylinder units is typically 50 feet. Projection of the control-cylinder units downwardly into a moon pool (9) avoids their obstruction of work space on an operational floor (3) of a vessel (4). Positioning pneumatic and hydraulic machinery (10) below deck with tubing leading to the control cylinders lowers center of gravity for marine stability. An over-capacity for tensioning the marine riser with a portion of the control cylinders inactive or incapacitated increases reliability.

Abstract: A single tubular member, or monobore riser, is provided for tubing hanging operations via a drilling riser and BOP, where wireline and/or coiled tubing deployed tools may be directed into production and annulus bores via a dual bore safety package and a dual bore selector and where various circulation modes may be established in cooperation with the choke and kill conduits in the BOP stack or with a length of tubing through the monobore riser in cooperation with selectively operable valves in the production and annulus bores of the safety package, a retainer valve in a single bore at the top of the dual bore selector, and by means of BOP rams capable of closing about a spool of the safety package and with a side outlet in the safety package. For Xmas Tree (XT) operations, the identical monobore riser is provided for surface communication to a dual bore selector and dual bore Riser Safety Package (RSP) secured to the top of the XT.

Abstract: An offshore fluid transfer system (10) is provided, of the type that includes a riser (32) having an upper end (34) connected through a universal joint (36) to a turret (22) on a vessel and having a lower end (36) anchored by catenary chains (40), and that also includes hoses (70, 71) extending from a base (50, 58) on the seafloor to the turret on the vessel, which avoids the need for a complicated hose structure to pass fluid across the universal joint. A fluid coupling (73) near the bottom of the turret, which is widely spaced from the universal joint, connects to a hose that extends from the fluid coupling in a sinuous path down to the seafloor base. The long length of hose, enables it to bend when the vessel drifts, to avoid excessive hose tension or riser contact during such vessel drift. A riser connector (102) can be operated to disconnect the riser from the turret so the riser can sink. The fluid coupling can include a fluid connector (100) which can separately disconnect the hose from the turret.

Abstract: A passive riser tensioner apparatus for tensioning riser pipes on floating platforms and tension leg platforms utilizes one or more elongate elastic tensioning elements connected at top and bottom ends to the upper end of a riser pipe that are capable of being axially stretched. Each tensioning element has a threaded length adjustment rod and tension preload nut at its top end which adjusts the axial length to produce a predetermined preload tension force in the tensioning element between its connection to the riser pipe. A riser support collar slidably received on the length adjustment rod and riser pipe upper end is configured to be supported on the deck of the platform and allow axial movement of the riser pipe. A tension locking nut on the length adjustment rod releasably engages the length adjustment rod with the riser support collar when it is supported on the deck.

Abstract: A subsea wellhead tieback connector operatively used to connect to a marine riser pipe or a well conductor in a manner that that will not unthread or unloosen the joints of the riser pipe being unlocked. The tieback connector operates with a novel internal latching mechanism having a hydraulic piston, an inner body that stretches and deflects in a unique manner resulting in compression spring forces at two locations, an expanding lock ring, a threaded adjustment ring, and a reaction ring. During operation the tieback connector creates an enhanced mechanical advantage to originate a required pre-load force without the necessity of having to generate a large hydraulic force that would otherwise be needed.

Abstract: The present invention relates to a system which makes use of a multiple reel on which groups of flexible lines supported by articulated structures (8, 9) are wound. The groups of flexible lines are interconnected at one end to flexible production and utility lines (4) emerging from the seabed and, at the other end, to connection blocks (10, 11) which may be connected to connection plates (15, 16, 17, 18) on at least one connection tower (13, 14) fixed to the vessel. As the connections are redundant, it is always possible to reposition one group of flexible lines while another group is connected, which gives the transfer system (2) total freedom of movement.

Abstract: A protective sleeve protects a riser that extends between a subsea wellhead and a floating vessel. The protective sleeve has less resistance to bending than the riser so as to allow the riser to bend normally due to normal movement of the vessel. The stiffness of the protective sleeve augments the stiffness of the riser only if the acceptable level of bending is exceeded. The protective sleeve is made up of at least three segments that are articulated together to facilitate bending.

Abstract: A drilling, production, test, and oil storage caisson for use in deep water offshore well operations. Separate low pressure and high pressure drilling risers are independently supported on buoyancy modules. Multiple drilling and production risers are left in the water and connected to the drilling rig and well(s) as needed to prevent the need for the raising and lowering of different risers during the various steps involved in beginning and completing wells. Surface and lower BOP stacks are utilized. Means for controlling the accelerations and velocity of the drilling riser buoyancy modules in the event of riser failure is provided. A subsea tree with dual master valves allows for production directly through a vertical production riser, flowline, to the production manifold on the caisson. A twisted tubing production riser is formed from three strings of tubing that are used for the flowline, annulus, and conduit for control lines.

Abstract: Apparatus is disclosed for use in lowering an object such as a well pipe through a guide tube suspended from the water surface and onto an upstanding subsea conduit beneath the lower end of the guide tube.

Abstract: A deep water riser assembly includes a lower BOP stack positioned adjacent and anchored to the bottom of the ocean and an upper BOP stack attached to the riser at a water level just far enough below the surface to be unaffected by surface currents. The upper BOP stack has shear rams above the pipe rams to sever the section of the drill pipe above the shear rams to allow the upper section of the drill pipe between the shear rams and the drill ship to be retrieved followed by the section of riser above the upper BOP stack to free the drill ship to move as required to better weather a surface storm. A floatation module is attached to the riser below the upper BOP stack and exerts an upward force that holds the riser below the upper BOP stack free-standing and in tension. Means are provided to reconnect the upper section of the riser to the upper BOP stack after the storm has passed.

Abstract: A parasite mooring system is disclosed for restraining a compliant platform with respect to an auxiliary vessel. The parasite mooring system includes a parasite mooring line, a platform termination securing the parasite mooring line to the compliant platform; and a grip securing the parasite mooring line to a mooring line of the auxiliary vessel passing beyond the compliant platform. Another aspect of the present invention is a method for conducting offshore well operations in which a semisubmersible vessel is brought adjacent a compliant platform such that at least one mooring line of the semisubmersible vessel extends past the compliant platform and a parasite mooring line from the compliant platform is connected to the mooring line of the semisubmersible vessel.

Abstract: In a method and device for drilling for oil or gas in an underwater bed by means of a drilling rig with a drilling derrick disposed on a floating drilling platform or on an underwater bed, prior to the placing of a casing string, the placing of a riser string or the drilling of a hole, one or more parts of the casing string, the riser string or the drill string are pre-assembled on the drilling rig at one or more pre-assembly points which are in a position which is different from the position of the drilling derrick.

Abstract: A system for transporting hydrocarbon fluid produced from an offshore well using an offshore production platform and a hydrocarbon fluid storage space in fluid communication with the offshore well via a conduit is provided. The system comprises at least one hydrocarbon fluid export system including a shuttle tanker provided with positioning apparatus capable of limiting movement of the tanker away from a location at a selected distance from the production platform, a flowline for transferring the hydrocarbon fluid to the tanker, at least pan of the flowline being a continuous flexible flowline at one end provided with a connector for releasably connecting the flowline to the tanker so as to allow fluid transfer from the flowline to the tanker, and with a valve for opening or closing the flowline, the flexible flowline extending along the seabed and from the seabed in the form of a riser to the tanker when the flowline is connected to the tanker.

Abstract: A release assembly for operating a remote mechanism such as a subsea well connector includes a funnel-shaped body adapted to engage the well connector and a movable arm adapted to engage and disengage a locking cap of the well connector and provide lifting force in order to actuate the locking cap.

Abstract: An ocean riser assembly for conveying fluids between the seabed and the surface of the sea includes a fluid conveying pipe formed into a helical configuration or into a planar cyclically undulating configuration, such as a sinusoid, that extends longitudinally from the bottom of the sea to the surface. One or more flexible and preferably elastic tension members extend in the longitudinal direction of the riser assembly and are secured to the pipe at spaced intervals, so that they absorb tension forces applied between the ends of the riser assembly. The helical or undulating configuration of the riser pipe decouples axial stresses in the pipe caused by internal fluid pressure from stresses caused by external tension forces acting on the riser assembly, the external tension forces being converted to torque and bending moments acting on the pipe itself. This arrangement permits substitution of carbon steel pipe for flexible pipe, at substantial cost savings.

Abstract: A system and method is provided for storing a continuous length of an assembled jointed tubular conduit on an offshore vessel and for conveying the tubular conduit between the deck of the vessel and a subsurface wellhead on the floor of the body of water. The system includes a carousel positioned around the perimeter of the vessel defining a continuous close-curved carousel pathway in parallel or coplanar alignment with the horizontal deck. The assembled tubular conduit is maintained in coiled storage along the carousel pathway until it is desired to convey the tubular conduit into or out of the carousel. Horizontal and vertical directing means are provided that, in cooperation with rotation of the carousel, enable uncoiling of the tubular conduit from the carousel into the water or recoiling of the tubular conduit into the carousel from the water.

Abstract: A dual string high pressure riser system is disclosed for use in drilling a deepwater well through a subsea wellhead. An outer riser extends from the surface and sealingly engages the wellhead and an inner riser extends from the surface downwardly, concentrically through the outer riser to communicate with the well. A surface BOP provides well control at the top of the dual high pressure riser. In another aspect of the present invention, a method is disclosed for conducting deepwater drilling operations in which a surface BOP and a lightweight outer riser are installed in communication with a subsea wellhead and a first interval is drilled through the outer riser. Casing is run through the outer riser into the first interval, cemented within the borehole and sealed at wellhead.

Abstract: A connector employs a segmented nut and a seal. The connector includes a housing with a bore having a bowl in it. A shaft extends through the bore, the shaft having exterior threads. Segments are carried on the bowl and move between a upper retracted position to an engaged position. A drive system slides the segments down and rotates them until threads from the segments align with the shaft threads. Each segment has a resilient seal which also has a portion of a thread for sealing against the threads of the shaft. An actuator will move the seals from an outboard position which occurs during rotation to a sealing position after rotation.

Abstract: The interruptive mobile production (IMP) system comprises a floating semisubmersible structure with equipment and facilities for hydrocarbon production in association with a small tension leg wellhead platform (TLWP) having direct vertical access. The small TLWP has an upper deck positioned above the surface of the water with wellhead equipment thereon and has risers generally vertically connecting subsea wells to the upper deck.Lateral bending restraints of the risers and tendons are preferably located at about the same horizontal level as the lower pontoon section. The semisubmersible structure can be conveniently disconnected from its moorings and from the wellhead platform for demobilizing to another location while the TLWP remains tethered in place.