Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
1999-07-02
2001-07-17
Bagnell, David (Department: 3672)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S365000
Reexamination Certificate
active
06260624
ABSTRACT:
TECHNICAL FIELD
This invention involves a riser tieback connector. More specifically, this invention is a hydraulically operated connector for tying back a riser from a platform to a subsea wellhead.
BACKGROUND ART
One type of subsea well employs a wellhead housing located at the sea floor and a drilling blowout preventer or production Christmas tree located at the surface on a platform. Large diameter casing will be lowered from the platform and connected to the wellhead housing with a tieback connector. The tieback connector must withstand various loading conditions it may see during extended periods of operation. Particularly with a tensioned leg or spar platform where the upper end of the riser is permitted to move horizontally, a bending moment is produced at the wellhead. This may occur even with a fixed platform where there is significant current force acting on the riser. The connection to the wellhead must also be capable of carrying substantial vertical force either in compression, where insufficient load is carried by the platform, or in tension, where excessive load is carried by the platform. Thermal expansion of the riser and wellhead also occurs dependant on whether the well is producing and the temperature of the fluid being produced. Furthermore, the riser must endure these stresses through many cycles over many years.
One type of connector has a downward facing funnel that slides over the wellhead housing. It has a body with an internal connector device with dogs that engage grooves formed in the wellhead housing. The connector is pre-loaded on the wellhead housing by forcing the dogs into the grooves and requires a high actuation force to achieve a high pre-load. The dogs resist all compressive and tensile loads transmitted from the riser into the wellhead. These connectors provide high load and separation capacity, but have a large outside diameter. In many cases, a reduced diameter is desired, such as for use in a spar platform.
While designs similar to this have gained acceptance, improvements are desirable in increasing static strength and pre-load capacity to increase the connector's resistance to separation loads.
SUMMARY OF THE INVENTION
The present invention is directed toward an internal tieback connector that uses hydraulics to provide a high pre-load while maintaining a near flush outer diameter. The connector is for tying back a riser from a platform to a subsea wellhead housing. The wellhead housing has a bore with an internal groove thereon. The connector has an inner body adapted to be secured to the riser or to be integral with it. There is an external profile on the inner body and a load shoulder spaced below. A housing is moveably carried on the inner body for landing on the wellhead. An upper lock member is carried by the housing. The upper lock member is inwardly, radially moveable to engage the profile on the inner body. The profile is configured to move the inner body upward relative to the housing when engaged by the upper lock member. A cam sleeve is carried on the inner body for axial movement relative to the inner body forcing the upper lock member inward into engagement with the profile on the inner body. A latch member with a load transferring portion is carried on the inner body in sliding engagement with the load shoulder. The load transfer portion of the latch member is adapted to move radially outward and engage the internal groove in the wellhead when the inner body and the load shoulder are moved upward relative to the housing.
Preferably, the connector further comprises a piston member which cooperates with the cam sleeve to define a hydraulic fluid chamber. The chamber is adapted to receive hydraulic fluid pressure to stroke the cam sleeve axially. The external profile is preferably a downward facing inclined shoulder. It is preferred that the lock member be a plurality of dogs. It is also preferred that the housing have substantially the same outer diameter as the wellhead housing and land on a rim of the wellhead housing. Preferably the latch member is a plurality of segmented fingers. Each finger has a finger extending upwardly from the load transfer portion. The finger has an outer protruding portion on an upper end that engages a recess in the housing. The finger has an inner surface that is engaged by the inner body when the inner body has moved upward to an upper position. The lock member has a surface which bears downwardly on the housing as the cam sleeve moves axially to exert a pre-load force on the wellhead by pushing the housing down on top of the wellhead while pulling up on the inner housing.
The invention is also directed toward a method of tying back a riser from a platform to a subsea wellhead where the wellhead has a bore with an internal groove. Provide a connector with an inner body, a housing axially moveably carried on the inner body, and a latch member mounted for axial sliding movement on an inclined load shoulder on the inner body. Connect the inner body to the riser and lower the connector onto the wellhead such that the inner body extends into the bore and the housing lands on the wellhead. Move the inner body upward relative to the housing to an upper position while restraining upward movement of the latch member causing the latch member to slide radially outward on the load shoulder and engage the groove in the wellhead, thus preventing further upward movement of the inner body while applying a downward force on the housing against the wellhead and locking the inner body in the upper position.
Preferably the inner body is moved upward and downward force is applied on the housing with hydraulic pressure in a chamber between the inner body and the housing. It is also preferable that the locking comprises pushing a lock member carried by the housing radially inward into a profile on the inner body. The lock member is pushed radially inward by moving a cam sleeve axially.
A connector for tying back a riser from a platform to a subsea wellhead housing. The housing has a bore with an internal groove thereon. The connector has an inner body adapted to be secured to the riser. A housing is carried on the inner body for landing on the wellhead. The inner body is axially moveable relative to the housing, to an upper position. A latch member is carried by the inner body and wedges between the inner body and the wellhead when the inner body is moved to the upper position. A lock member, for holding the inner body in an upper position, wedges between the inner body and the housing when the inner body moves up. A cam sleeve carried on the inner body is used to wedge the lock member between the inner body and the housing.
A stinger on the lower end of the inner body is adapted to engage a bowl of a casing hanger in the wellhead.
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Pallini, Jr. Joseph William
Rhodes Jerry Keith
ABB Vetco Gray Inc.
Bagnell David
Bracewell & Patterson L.L.P.
Bradley James E.
Dougherty Jennifer R.
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