Boring or penetrating the earth – Boring a submerged formation
Reexamination Certificate
1999-04-05
2001-06-12
Bagnell, David (Department: 3673)
Boring or penetrating the earth
Boring a submerged formation
C175S065000, C166S358000, C166S363000, C166S368000, C166S086200, C251S001200, C384S097000
Reexamination Certificate
active
06244359
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to rotating drilling heads and in particular to a subsea rotating drilling head that seals against drill pipe during drilling.
BACKGROUND OF THE INVENTION
In a subsea well of the type concerned herein, a wellhead housing locates on the sea floor. Strings of casing extend into the well, with the casings being supported in the wellhead housing. A casing hanger seal is installed between the casing hanger at the upper end of the casing and the wall of the wellhead housing. The operator installs the casing and the seal remotely and sometimes in seas of considerable depths.
There have been a number of types of running tools used and proposed in the patented art. With the advent of metal-to-metal casing hanger seals, the forces required to set these seals are greater than the prior art elastomeric seals. Running tools have to be capable of delivering very large forces. One type utilizes hydraulic pressure, as shown in U.S. Pat. Nos. 4,969,516 and 4,928,769. The hydraulic pressure is generated by axial movement of the drill string, which moves a piston within a sealed hydraulic chamber in the running tool. These hydraulic tools work well. However, they are complex and expensive.
U.S. Pat. No. 5,044,442 shows a type that is hydraulically actuated, but uses annulus pressure. Rams are closed around the drill string, creating a chamber located above the wellhead housing within the riser. A bulk seal seals a portion of the running tool to the wellhead housing above the setting sleeve and casing hanger seal. The bulk seal enables pressure to be applied to a piston of the running tool. Fluid is pumped down a choke and kill line to this chamber, which actuates the piston within the running tool to set the casing hanger seal. The annulus pressure actuated hydraulic tool described in that patent is feasible, however a possibility exists that the bulk seal could seal on the wellhead housing at a point above the desired position. If so, the casing hanger seal might be actuated before it is located fully within the pocket between the casing hanger and the bore of the wellhead housing.
Subsea drilling is a problem in certain areas, such as the Gulf of Mexico. Shallow formations in the Gulf of Mexico present special problems that must be solved with a variety of techniques, which include using extra casing strings, etc. Another solution proposed is drilling with positive pressure. This may require the use of a rotating drilling head, seals and drill pipe. The prior art only used this equipment for horizontal or underbalanced wells at the surface, not subsea.
SUMMARY OF THE INVENTION
An improved system to provide control of mud, aquifer and cement flows experienced during installation of subsea conductor strings is provided. The shallow water flow diverter system of the subsea diverter and rotating drilling head of the invention is for providing a controlled system for mud, cuttings and cement that are produced during the installation of subsea wellhead conductors and isolating the pressure effect created by water depth. The system of the invention has provisions to contain and minimize any shallow water flows that may be encountered and provides the ability to shut off any undesired aquifer flows. Additionally, the system provides the capability of minimizing any flows that are the cause of instability in unconsolidated formations.
The invention includes a diverter housing assembly that consists of an upper housing that is flanged to a lower latch assembly. The upper housing provides a landing shoulder and locking mechanism for a shallow water flow diverter. The locking mechanism consists of a series of dog segments that are stroked radially inward and engage a profile on the diverter insert. The lock and unlock functions for the insert are located on the diverter control panel that is mounted on the diverter housing assembly. An alignment funnel has been incorporated into the top of the diverter housing assembly to guide the shallow water flow diverter insert during installation. In addition, the diverter housing assembly incorporates a choke to channel drilling cuttings and a relief valve that is designed to vent should an overpressure condition occur within the diverter housing assembly. Because the diverter housing assembly is flanged to the lower latch assembly, it can be easily adapted to lower latch assemblies manufactured by other suppliers.
The lower latch assembly consists of a series of locking dogs that mate with a mandrel profile on the 38″ conductor housing. The locking dogs are hydraulically actuated through an ROV hot stab located on the diverter control panel. The lower latch assembly also includes an ROV operated mechanical override to unlatch the locking dogs from the conductor in the event of a hydraulic failure.
The rotating diverter head insert lands and locks into the housing to provide a dynamic seal on the drill pipe during drilling operations. The sealing system incorporates two dynamic seals, the stripper rubber seal and the gripper seal. The stripper rubber seal is a passive elastomer seal that resides on the lower portion of the drilling head insert and forms the primary sealing barrier. The gripper seal is a hydraulically energized element seal that forms the secondary sealing barrier on the drill pipe and grips the drill string. Hydraulic pressure from the diverter control system compresses the gripper seal assembly around the drill pipe. As the drill pipe turns, the gripper seal transmits torque from the drill string to the rotating diverter head insert so it will rotate along with the drill pipe. Heavy-duty bearings are used above and below the gripper seal assembly to facilitate this rotation. The drilling head insert is run along with the drill pipe using a running tool.
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Bridges Charles D.
Cuiper Glen H.
Landriault L. Steven
Monjure Noel A.
ABB Vetco Gray Inc.
Bagnell David
Bracewell & Patteron, L.L.P.
Bradley James E.
Kreck John
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