AU2004100459A4 - Structure upending sub - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT STRUCTURE UPENDING SUB The following statement is a full description of this invention, including the best method of performing it known to me: ICON Engineering Pty Ltd ACN 009 171 528 16 th June 2004 1 STRUCTURE UPENDING SUB The present invention relates to a structure upending sub and the method of lifting and rotating a structure under the cantilever of a Self Elevating Mobile Offshore Drilling Unit (Jackup Rig).

Some steel offshore structures are installed using jackup drilling rigs. The structure to be installed is typically positioned below the Jackup Rig Cantilever, either free floating, on a barge or resting horizontal on the seabed, and then lifted by the rig and set into final correct orientation. Often, structures require upending from a near horizontal position to a vertical position due to the ease of towing structures to site horizontally. If an upending sub is not used, the upending operation can involve complex rigging, expensive modifications to the rig and is time consuming and costly.

In accordance with the present invention there is provided a structure upending sub which is a lifting device which simplifies the upending operation. The structure upending sub is an integral part of the lift rigging which can be temporarily supported at the drill floor part way through the lifting and upending operation. At the appropriate stage of the lifting operation the structure upending sub is supported at the drill floor and this allows one side of the structure lifting arrangement to be lowered by the rig hook, while the other side is supported by the rig structure, thereby effecting the upending of the structure.

The invention can be better understood by referring to the following description of a preferred embodiment with reference to the accompanying drawing.

The structure is presented below the drill floor of the jackup rig and a retrieval line sent down to pick up the rigging attached to the structure upending sub (Figure 1).

The lift rigging is connected to top drive, the lifting apparatus of the Jackup Rig, and the structure is lifted clear of the barge. The barge then begins to move away clearing the area for the upending process (Figure 2).

The structure is then lifted further until the structure upending sub has reached the drill floor and is supported at the drill floor (Figure 3).

The upending slings are then lowered through structure upending sub starting the upending process (Figure 4) while the other slings remain fixed to the structure upending sub that is supported at the drill floor.

Full payout of the upending slings shows that the structure has been fully upended and is no longer under any load, hence enabling the removal (Figure Setdown of the structure onto the seabed is completed by lowering the structure upending sub and consequently the structure (Figure Alternatively, the Jackup Rig can jack down while the substructure upending sub remains fixed at the drill floor thereby lowering the structure on the seabed.

The structure upending sub itself consists of a steel tube with a steel collar that allows the structure upending sub to be supported at the drill floor. The base of the structure upending sub has a connection point for the static rigging. The centre of the tube is large enough to allow for the upending running slings and fittings to pass through. The top of the structure upending sub has connection points to allow the whole load to be supported from it and also for supporting the rigging during the intermediate upending steps.

ICON Engineering Pty Ltd ACN 009 171 528 16 th June 2004