Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
1999-08-06
2001-10-16
Bagnell, David (Department: 3673)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S075140, C166S338000, C166S382000
Reexamination Certificate
active
06302211
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates in general to subsea wellheads and in particular to a load shoulder for a casing hanger that is remotely installable in a subsea wellhead housing.
When drilling a well for oil or gas, typically a wellhead housing will be mounted at the upper end of the well to a large diameter string of conductor pipe. The well is then drilled deeper and a string of casing will be run. Subsequently, the well will be drilled to a greater depth and at least one more strings of casing will be installed.
A casing hanger is located at the upper end of each string of casing, the casing hanger landing on a load shoulder in the wellhead housing. In one type of wellhead housing, the lowest shoulder is machined into the bore of the wellhead housing. Upper casing hangers are supported on lower casing hangers. In another type, the load shoulder is a separate high strength ring that is installed into a groove in the wellhead housing while the wellhead housing is being manufactured. In both cases, the inner diameter of the wellhead housing bore will decrease in a downward direction, with the smaller inner diameter located below the load shoulder.
The stepped diameter bore has a disadvantage. Drilling tools can be no larger than the minimum inner diameter located below the load shoulder. Sometimes, it is desired to utilize a drill bit or tool that is larger than minimum inner diameter.
For example, in a wellhead system that is used in containment of offshore shallow flow zones, it is desired to run a casing, which is typically 18″ in diameter, through a subsea high pressure housing having a minimum bore that is typically 18.63″. The nominal seat of the high pressure housing, i.e., the insert load shoulder, must be removed or left off of the assembly prior to running a high pressure housing and then reinstalled subsequent to the installation of the casing. Therefore, it is desirable to provide a means to install a nominal seat in a high pressure housing, run in an appropriate wear bushing and test the blowout preventer in a single trip, thereby saving two additional trips and the costs associated therewith.
SUMMARY OF THE INVENTION
In this invention a running tool is employed to run a split lock ring. The running tool has a cylindrical wear bushing that lands on a locator shoulder provided in the bore above a grooved lower profile in a wellhead housing. The running tool carries a load shoulder ring and a split lock ring. The installation process consists of preparing the tool and running the tool subsea. On a rig floor, a load shoulder ring, a lock ring and a wear bushing are installed on a running tool. Flowby ports are provided in the running tool, which remain open during installation to speed the trip-in operation. Previously, the high pressure housing will have been landed. The high pressure housing should have a locator shoulder located below a grooved upper profile. A riser will extend from the high pressure housing to the drilling platform. The running tool is lowered on the drill pipe through the riser and landed in the high pressure housing. The flowby ports are then closed. The flowby ports may be closed by rotating the drill string, thereby disengaging a pin from a J-housing on the running tool. The operator then lowers the drilling platform, causing a central mandrel in the tool to drop.
The blowout preventer is then closed on the drill string. Pressure is applied to a choke-and-kill line below the blowout preventer. An internal piston within the running tool transfers the pressure to an intermediate portion of the wear bushing. The wear bushing is ratcheted downward, which drives the load shoulder ring downward, expanding the lock ring into engagement with the grooved lower profile on the inside of the wellhead housing. The downward motion of the load shoulder ring compresses annular springs and maintains the annular springs in a compressed configuration.
The blowout preventer may then be tested. Finally, the tool is removed by pulling upwards on the drill pipe. By pulling up on the drill pipe, upper ports on the flowby passages are exposed, thereby opening the flowby ports to speed up the trip-out operation.
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SPE/IADC 37615 “Wellbore Design W/Reduced Clearance Between Casing Strings” /Barker/1997.
Brammer Norman
Milberger Lionel J.
Nelson John E.
Radi Amin
ABB Vetco Gray Inc.
Bagnell David
Bracewell & Patterson LLP
Lee Jong-Suk
LandOfFree
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