Undersea drilling template release mechanism and method

Details Undersea drilling template release mechanism and method Undersea drilling template release mechanism and method

1999-05-18

2001-12-04

Bagnell, David (Department: 3673)

Boring or penetrating the earth

Boring a submerged formation

Boring with submersible vertically movable guide

C166S358000, C166S365000, C175S007000

Reexamination Certificate

active

06325160

ABSTRACT:

FIELD OF THE INVENTION
The field of this invention relates to an undersea drilling template.
BACKGROUND OF THE INVENTION
Undersea drilling templates are placed adjacent the seabed to provide a stable hole through which drillbits, drillpipes and other undersea drilling equipment are passed into holes drilled into the seabed by drilling platforms seeking oil and gas deposits. The template's main purpose is to stabilize the seabed adjacent the top of the drill hole to avoid collapsing of the wet sand adjacent the hole. The templates are generally a metal annulus having an outer diameter of about 3048 mm (12 ft) and an inner diameter of about 974 mm (38.38″).
Templates are lowered to the seabed over distances ranging from 100 meters to 2500 meters by a running tool attached to the drillpipe by a box-pin thread.
When the template has been lowered to the seabed, the tension in the drillpipe is released to allow the running tool to be rotated out of engagement with the template and then pulled to the surface. A drillbit is then attached to the drillpipe and lowered to the seabed where it must be maneuvered into passing through the central hole in the template for drilling to commence.
This can be a very time-consuming process, taking from between 3 hours in shallow depths to up to 24 hours in deep depths. Further, it can be extremely difficult to maneuver the drillbit into alignment with the template hole as it must first pass through various depths of sea. Remote control submarines fitted with video cameras are often used to assist in maneuvering the drillbit into the template hole.
It is an object of the present invention to substantially overcome or at least ameliorate one or more of the prior art deficiencies.
SUMMARY OF THE INVENTION
In a first aspect, the present invention provides an undersea drilling template adapted to be lowered onto a seabed by a drillpipe. The template comprises a template base and at least one arm having a releasable clamping assembly for releasably connecting the template to the drillpipe, wherein the clamping assembly is adapted to be clamped to the drillpipe during lowering of the template and to release from the drillpipe when the lowering is completed.
Preferably, the arm(s) have a first end mounted to the template base and a second end including all or a portion of the clamping assembly.
Preferably, the template includes a pair of V- or U-shaped arms having their free ends pivotally mounted to the template base and a portion of the clamping assembly at their apex or base.
The clamping assembly is desirably adapted to slide along the drillpipe into abutting relationship with a first shoulder provided on the drillpipe for suspending the template base below the first shoulder.
The clamping assembly is preferably adapted to release from the drillpipe when the continued downward travel of the drillpipe, after the template has been lowered onto the seabed at the completion of the template lowering, causes the clamping assembly to contact a second shoulder provided on the drillpipe above the first shoulder.
The clamping assembly preferably includes a pair of part cylindrical portions with external flanges that may be clamped together around the drillpipe by bolts, shear pins or the like. The second upper shoulder preferably includes a downwardly facing frusto-conical portion adapted to fracture the bolts, shear pins or the like after being driven into the cylindrical portions.
In another embodiment, the clamping assembly includes a latching member pivotally mounted to one of the arms and releasably engageable with the other, the latching member being adapted to be pivoted out of engagement from the other arm after the latching member is contacted by the second shoulder. In one form, the latching member includes a striking plate adapted to release the latching member when contacted by a downwardly facing frusto-conical portion comprising the second shoulder.
The template base preferably includes an inner substantially central hole and the arms are adapted to pivot away from the hole when released so as to provide the drillbit at the end of the drillpipe with access to the inner hole.
The template base also includes a number of compartments adapted to hold ballast material.


REFERENCES:
patent: 4625804 (1986-12-01), Allen, Jr.
patent: 5379844 (1995-01-01), Glasscock et al.
patent: 805896-A (1980-09-01), None
Derwent-Acc-No: 1982-13793E; abstract of South Africa patent document 1980-ZA-0005896; 1982.

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