Hydraulic and earth engineering – Marine structure or fabrication thereof – With anchoring of structure to marine floor
Patent
1991-08-06
1992-07-07
Corbin, David H.
Hydraulic and earth engineering
Marine structure or fabrication thereof
With anchoring of structure to marine floor
405228, E02B 1702
Patent
active
051277670
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method of mounting the piles associated with the installation of a pile-founded off-shore platform, e.g. a production platform, wherein these are driven down into the sea bed through pile guide attached to the foundation of the platform.
Platforms of this type have previously been installed by means of very large floating cranes which serve to submerge the platform which has been transported to the drilling location on a barge, to position the foundation piles in the guides of the platform and to lift the drive means, e.g. a hammer or a vibrator for driving the piles into the sea bed. Only few of these special cranes are available in the world, and to this should be added that they are extremely expensive to rent and use, and this entails that there may be undesirably long waits when a platform is to be installed, and that the installation costs will be excessively high in particular for smaller platforms.
The object of the invention is to provide a method of the type stated in the opening paragraph, by which in particular smaller platforms may be installed at much lower costs than in the past and without having to await the arrival of a special floating crane.
This is obtained in that the method of the invention is characterized in that the piles are hoisted one by one with the pile head uppermost by means of a winch which is arranged in or in connection with the derrick on a drilling rig, positioned at the drilling location, to a suitable location above the platform, where the pile preferably hangs freely in the wire of the winch with a smaller distance to the central axis of the platform than the upper end of the associated pile guide, and that the pile is then lowered, with its tip being initially guided obliquely outwardly and downwardly away from the central axis of the foundation towards the upper end of the pile guide during said movement until it extends into said end, following which the pile continues down through the pile guide to the sea bed and is finally driven down to the desired depth in said bed by a drive means which is suspended from the wire of the winch, and whose preferably lower end is initially guided obliquely inwardly and upwardly towards the central axis of the foundation during the subsequent hoisting of the drive means until the drive means hangs freely downwardly in the vertical of the wire. Thus, it is possible to install in particular smaller platforms by means of a conventional drilling rig for drilling wells. Usually, such a drilling rig is present at the drilling location or not far from it, and since this drilling rig is much cheaper to operate than the above mentioned very big floating cranes, both waiting time and large crane renting costs are saved.
In a particular simple and expedient embodiment of the method of the invention the pile tip is initially guided obliquely outwardly and downwardly towards the upper end of the pile guide during lowering of the pile until it extends into said end, the tip being slidably guided along a chute which is preferably C- or U-shaped in cross section and extends with a suitable inclination upwardly from the upper end of the pile guide to a location at any rate substantially below the position which the pile tip assumes in said freely hanging position of the pile.
Further, in the method of the invention, a drive means for driving the pile down in the sea bed e.g. by repeated blows or vibrations is hoisted by means of the winch of the derrick to a suitable position which is substantially vertical above the pile head of the pile to be driven down, and the drive means is then lowered to engage the pile head and drive down the pile to the desired depth in the sea bed, following which the drive means is hoisted again and preferably its lower end is initially guided slidingly up the chute during said movement until the drive means hangs freely downwardly in the vertical of the wire. The drilling rig may thus also be used for driving down the piles, without this entailing that the drive means, which may e.g. be a h
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patent: 4069683 (1978-01-01), Jansz
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Corbin David H.
Maersk Olie Og Gas A/S
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