Removal of platforms at sea

Abstract

The present invention relates tot a method of removing an upper part of a platform which rests on a seabed and which extends above the waterline, the platform comprising legs which extend upwards from the seabed, the method comprising the subsequent steps of:providing a vessel comprising a single hull, the hull defining a contour of the vessel when viewed from above;providing a support structure which is configured to rest on the vessel, the support structure comprising one or more beams, the one or more beams having connection ends that are constructed to extend outside the contour of the hull on opposite sides of the vessel, the connection ends configured to be connected to the legs of the platform;positioning the vessel between the legs of the platform;connecting the connection ends to the legs of the platform;disconnecting the upper part of the platform from the lower part;lifting the upper part of the platform from the lower part by the vessel via the support structure;moving the vessel and the upper part of the platform away from the lower part of the platform.The present invention further relates to a system for carrying out the method.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 102,570, filed Dec. 10, 2007, the contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a method and system for removing a part of a platform at sea, the platform resting on a seabed.[0003]Methods for removing such platforms are known in the field of the art.[0004]It is widely known that platforms at sea, for instance in the oil and gas industry, have a certain life span, after which they are to be decommissioned and removed. This removal process often is a costly, complicated and sometimes dangerous operation. There is a general need in the field of the art for cost-effective, simple, and safe methods for removing such platforms.PRIOR ART[0005]US2003 / 0108392 discloses a system for removing decks from offshore structures. A drawback of this system is that it requires two barges, which is expensive and cu...

AI Technical Summary

Benefits of technology

[0012]It is an object of the invention to provide a simple, cost-effective and reliable method and device for removing an upper part of a platform which rests on a seabed.

[0059]ballasting the vessel such that the vessel moves downward and the support beams engage the support members, thereby shifting the weight of the upper part of the platform from the vessel to the docking station via the one or more support beams;

Problems solved by technology

A drawback of this system is that it requires two barges, which is expensive and cumbersome during transport.

A disadvantage of the system of GB2165188 is that it comprises a support frame 20 (comprising of girders 51) which is integral with the deck module itself, see FIG. 2 and page 1, lines 78-80 of GB2165188.

A disadvantage of the system of GB2165188 is further that it requires barges which extend to a substantial height above the water surface, in order to remove the deck module from the leg assembly.

One drawback of this system is that it requires two vessels, which is expensive and cumbersome during transport.

Another drawback of this system is that it is difficult to unload the sea-going structure from the vessels once it is lifted with the vessels.

Images