Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
1999-03-24
2001-05-22
Lillis, Eileen D. (Department: 3673)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S348000, C166S359000, C285S018000, C285S123100, C285S315000
Reexamination Certificate
active
06234252
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to offshore drilling and production equipment and in particular to a tieback system for connecting a subsea well to a platform.
BACKGROUND ART
One type of tie 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 connecter. The tieback connector must withstand various loading conditions it may see during extended 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 various components of this structure also occurs, depending on whether or not the well is producing at a particular time 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 a connector device which contacts grooves or threads formed on the wellhead housing. A running tool or internal hydraulic cylinders actuate the connector device and joins the riser and wellhead housing. The connector is locked in this position by bolts and various other bolts are in the load path. When released, this type of tieback connector does not have a mechanism to actively release the connector device from the wellhead grooves.
While successful, improvements are desired for tieback connectors wherein large bending forces may be exerted, such as with tension leg platforms or spars.
SUMMARY OF THE INVENTION
The present invention is directed to a device for tying back a riser from a platform to a subsea wellhead housing which can resist high separation and bending loads and is resistant to fatigue from cyclic loading. A connector having features of the present invention comprises a connector body adapted to join to the riser for landing on an upper end of the wellhead housing. A connector housing for insertion over the wellhead housing, depends from the connector body. The connector housing carries more than one dog for mating with and locking in the external grooves. A transfer member is carried in the connector housing in engagement with the dogs and the connector housing for transferring axial loads between the connector housing and the wellhead housing. A piston within the connector housing is linked to an annular cam ring adapted to force the dog members inward into engagement with the external grooves. Both the annular cam ring and piston are adapted to reciprocate axially in the cavity.
The connector may further comprise a release ring which forces the dogs out of engagement when the piston is moved from a downward position upward. The transfer member may be comprised of more than one transfer link, each link having an upper end in engagement with a lower end of one dog and a lower end pivotally engaging the connector housing. Further the transfer member may be below the cam ring.
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Lyle Rockford D.
Pallini, Jr. Joseph W.
ABB Vetco Gray Inc.
Bracewell & Patterson
Lee Jong-Suk
Lillis Eileen D.
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