Abstract: A tieback connector connects a tieback conduit from an offshore platform to a subsea wellhead assembly. The tieback connector has a mandrel that is connected to a string of tieback conduit and a sleeve and load ring that are carried by the mandrel. The load ring is radially expansible and has a conical portion with internal threads. The load ring has an external grooved profile that engages an internal grooved profile in the subsea assembly. The mandrel is rotatable relative to the sleeve while in its lower position, causing the load ring to further expand outward into engagement with the internal profile. A locking member is carried below the load ring on an exterior cam surface of the mandrel. The cam surface moves the locking member outward when the mandrel moves downward into engagement with an internal profile in the subsea assembly.

Abstract: A riser connector uses a box and upset pin connector threadform design having S-shaped load flanks that provide a variable load angles depending on the radial position along the engaged teeth. This design promotes a load path that changes with position along the axial length of the engaged thread, as well as increasing or decreasing external loads on the connector. The connector also varies radial distention of the pin from the box in a manner that is different from one thread to the next. The threadform uses a combination of thread cuts that vary in shape, pitch, and/or thread cone angle to provide load and stab flanks, as well as a load path, that vary from one axial end of the engaged thread to the other.

Abstract: A riser connector uses a box and upset pin connector threadform design having S-shaped load flanks that provide a variable load angles depending on the radial position along the engaged teeth. This design promotes a load path that changes with position along the axial length of the engaged thread, as well as increasing or decreasing external loads on the connector. The connector also varies radial distention of the pin from the box in a manner that is different from one thread to the next. The threadform uses a combination of thread cuts that vary in shape, pitch, and/or thread cone angle to provide load and stab flanks, as well as a load path, that vary from one axial end of the engaged thread to the other.

Abstract: Keel joint assemblies are described that permit a degree of rotational movement of a riser within the keel of a floating vessel and greatly reduce the amount of stress and strain that is placed upon the riser, as well. Keel joint assemblies described provide a limiting joint between the riser and the keel opening that permits some angular rotation of the riser with respect to the floating vessel. Additionally, the limiting joint permits the riser to move upwardly and downwardly within the keel opening, but centralizes the riser with respect to the keel opening so that the riser cannot move horizontally with respect to the keel opening. In described embodiments, the limiting joint is provided by a single annular joint that allows that riser to move angularly with respect to the can. In some embodiments, the keel joint assembly incorporates a cylindrical stiffening can that radially surrounds a portion of the riser and is disposed within the keel opening.

Abstract: A connection between a riser and a receptacle of a floating platform may be preloaded to reduce fatigue. The platform has a receptacle with upper and lower grooved profiles. A hanger is connected to the upper end of the riser. The hanger has a latch that engages the lower grooved profile in the receptacle to resist downward pull of the riser. A tieback connection inserts from above into the receptacle. The tieback connection has an outer member that lands on the hanger. The outer member has a latch that engages the upper grooved profile. The tieback connection also has an inner member with a set of internal threads. Threads on the inner member engage threads on the latch, rotating the inner member relative to the outer member exerts an outward force on the tieback connection latch. As the latch is pushed into the tieback grooved profile, a downward preload force is created, which passes to the hanger latch.

Abstract: Keel joint assemblies are described that permit a degree of rotational movement of a riser within the keel of a floating vessel and greatly reduce the amount of stress and strain that is placed upon the riser, as well. Keel joint assemblies described provide a limiting joint between the riser and the keel opening that permits some angular rotation of the riser with respect to the floating vessel. Additionally, the limiting joint permits the riser to move upwardly and downwardly within the keel opening, but centralizes the riser with respect to the keel opening so that the riser cannot move horizontally with respect to the keel opening. In described embodiments, the limiting joint is provided by a single annular joint that allows that riser to move angularly with respect to the can. In some embodiments, the keel joint assembly incorporates a cylindrical stiffening can that radially surrounds a portion of the riser and is disposed within the keel opening.

Abstract: An offshore riser includes a plurality of tubular elements, each having a pin member on one end and a box member on the other end for connection with adjacent tubular elements. The pin member has an external thread which engages an internal thread on the box member of the adjacent tubular element. A dual angle torque shoulder locks the box end securely into place against the pin, preventing radial distention of the box end and maintaining bearing pressure between the external sealing surfaces. Also, stress relief grooves are located on the box member and on the pin member, to reduce the incidence of stress fractures, thereby improving the fatigue life of the connection.

Abstract: An attachment extends between an outer sleeve and an inner riser pipe where the pipe penetrates the keel of a platform. In one version, the attachment is a conically-shaped with a small diameter ring that engages the riser pipe and a large diameter ring that engages the outer sleeve. This attachment has elements that are very flexible in bending but relatively stiff and strong in axial load. Other versions include flat rings where lateral load is taken directly into tension and compression in the beams, allowing for relatively high lateral load transfer. Both the conically-shaped attachment and the flat ring have a number of variations that provide low bending stiffness but high axial stiffness of the elements. Depending on whether resistance to axial loads, lateral loads, or resistance to combination of both loads is desired, the attachment and the flat ring may be used alone or in combination.

Abstract: An offshore riser includes a plurality of tubular elements, each having a pin member on one end and a box member on the other end for connection with adjacent tubular elements. The pin member has an external thread which engages an internal thread on the box member of the adjacent tubular element. A dual angle torque shoulder locks the box end securely into place against the pin, preventing radial distention of the box end and maintaining bearing pressure between the external sealing surfaces. Also, stress relief grooves are located on the box member and on the pin member, to reduce the incidence of stress fractures, thereby improving the fatigue life of the connection.

Abstract: A connection between a riser and a receptacle of a floating platform may be preloaded to reduce fatigue. The platform has a receptacle with upper and lower grooved profiles. A hanger is connected to the upper end of the riser. The hanger has a latch that engages the lower grooved profile in the receptacle to resist downward pull of the riser. A tieback connection inserts from above into the receptacle. The tieback connection has an outer member that lands on the hanger. The outer member has a latch that engages the upper grooved profile. The tieback connection also has an inner member with a set of internal threads. Threads on the inner member engage threads on the latch, rotating the inner member relative to the outer member exerts an outward force on the tieback connection latch. As the latch is pushed into the tieback grooved profile, a downward preload force is created, which passes to the hanger latch.

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 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 tieback adapter will connect a tieback string between a subsea wellhead assembly and a platform at the surface. The tieback adapter has a housing in which a sub is carried. The sub has a lower end which contains a seal for sealingly engaging an internal sealing surface of a casing hanger located within the subsea wellhead assembly. The sub is connected on its upper end to the tieback string. The housing has a locking element which locks to an internal locking profile of the subsea wellhead assembly. A retainer carries the sub in an upward position within the housing while the tieback adapter is being lowered into the subsea wellhead assembly. A release device will release the retainer from the sub in response to the landing of the housing in the subsea wellhead assembly. This allows the sub to move downward. A cam surface on the sub simultaneously moves the locking element into engagement with the locking profile and the subsea wellhead assembly housing.

Abstract: A tension leg platform utilizes a top connector for the tendons that has ratcheting segments. Each segment includes a carrier located above and a lower portion containing grooves for engaging the upper end of the tendon. Springs locate between the carrier and the segments. An actuator will move the carriers downward from an upper position to a lower position. The springs allow ratcheting axial movement between the segments and the carriers. The ratcheting movement occurs as the housing moves downward relative to the tendons.