JPS6233993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for replacing mooring cables on offshore platforms, particularly those moored by vertically tensioned cables.

Offshore platforms used for oil extraction from very deep seabeds or as floating islands to support other equipment, e.g. energy production, are constructed as floating assemblies whose moorings to the seabed are , by specifically vertically coupling the cable or cable group to a mooring base previously anchored on the seabed. After these cables are attached, they are tensioned, thereby further sinking the floating assembly, where it creates a hydrostatic thrust;
This provides rigidity to the assembly and allows it to withstand the action of waves.

In such an assembly or installation, it is desirable to eliminate or minimize deep seabed work as much as possible. In particular, the object of the invention relates to a method for replacing a cable with a new one due to partial breakage, damage or other reasons.

According to the invention, such work is carried out using a kind of guiding device. This guiding device releasably engages the cable to be replaced at least at a height between the base of the platform and the mooring base, and during operation, the guiding device It is held in place by a tensioned guide wire. The lifting operation of the cable is carried out by guiding the lower end of the cable along the guide wire by means of this guiding device, and the same guidance is carried out during the lowering operation of a new cable until the cable is connected to the base.

At the same time as the cable is lifted, a device such as a trumpet-like device (hereinafter simply referred to as a tupfer) is temporarily removed from a well provided in the platform for passing the cable. That is, as the cable is released from the guiding device and moved up the well, the end of the cable pulls up the device. The opposite operation is then performed when lowering the new cable.

The guide wires are fed along the outside or inside of the well, for example coupled to a winch located near the wall of the well (for this purpose, a tube is provided in the well for passing these wires).

The lower end of the cable and the mooring base can be connected, for example, by a connecting rod driving device (hereinafter simply referred to as a driving device) controlled from a platform. It may also be done in any other way.

In addition to these configurations, the present invention also includes other configurations that are suitably applied at the same time as these configurations. This will be explained in more detail later.

These objects of the invention will become clearer from the following description with reference to the accompanying drawings. It goes without saying that these drawings merely show one specific embodiment of the present invention and do not limit the present invention in any way.

An example of an application to which the invention is particularly directed is the replacement of cables in platforms moored by tensioned vertical cables, deep under the seabed, as installations for oil drilling or storage.

As shown schematically in FIGS. 1 and 2, in this type of platform the deck 1 is supported by a plurality of columns, for example three columns or piles 2 in the case shown; The piles 2 are connected by retainers 3 and 4. The floating platform assembly thus constructed is moored to the seabed 5 by a cable 6. For example, six of these cables 6 are provided for each pile 2, and are stretched between the pile 2 and a mooring base 7 anchored in advance on the seabed 5 by an appropriate means.

The assembly shown in FIG.
Send it to deck 1 with 6.

The cables 6 cooperate in groups of six for each pile 2 and are connected to the mooring base 7 by a connecting plate 10. The lug 24 of the adapter 11 provided at the lower end of the cable 6 is inserted into the flange 25 of the mooring base 7, and the lug 24 and flange 25 are fixedly connected by a connecting rod driving device 34. The driving device is the jack 33 on the mooring base 7.
It is locked by. This jack is remotely controlled from the platform.

If one cable 6 in such an assembly is to be replaced for some reason, the following device is used.

To lift the replaced cable and lower the new cable, a type of guiding device is used which cooperates with a guiding wire 20 temporarily attached to the cable and stretched between the platform and the mooring base 7. Ru.

This guide device, designated 14 in FIGS. 3 and 4, has a central collar 17 and eyelets 19 on both sides thereof. Color 17 is cable 6
hinge 18 as shown in FIG.
Consisting of two parts pivoted together, eyelet 1
9 receives the guide wire 20. For this reason, these eyelets 19 may also be constructed from two parts, similar to the central collar.

FIG. 3 shows the beginning of a cable replacement operation, where two guide wires 20 have been installed into the platform, for example during construction.

Guide wire 2 paid out from small winch 21
0 is placed, for example, adjacent to the wall of the well 12 through which the cable 6 passes. This may be outside the well wall or, as shown, inside. The guidewire 20 itself may be guided within the platform through a guideway such as a suitable tube 70 (FIG. 8) secured to the wall of the well 12. The tube 70 also serves to guide the vertical movement of members such as the flap 15 cooperating with the cable 6. As shown in FIGS. 7 and 8, the wrapper 15 consists of two parts, each of which is provided on its side with a channel 71 cooperating with a tube 70, thereby providing accurate positioning of the assembly. .

The first operation to be performed here is to attach the guide device 14 to the cable 6 and engage the guide wire 20 with the eyelet 19 of the guide device 14, and then attach the guide wire 20 to the guide device 14 as shown in FIG. The idea is to let them descend together. The guide wire 20 is provided at its lower end with an adapter 22 by which it is secured to a suitable fastener 23 on the coupling plate 10. The adapter 22 and the fastener 23 may be fixed by a diver, or the lug 24 of the cable 6 and the flange 2 may be fixed by a jack 33.
This may be done by remote control in the same way as the fixation in step 5.

After the guide wire 20 and the guide device 14 have been connected, the cable 6 to be replaced is lifted up in the fifth step.
This is done as shown in Figure and Figure 6.

First, the tension on the cable 6 is released by operating the tension jack device 16 (FIG. 5). Then, by actuation of the jack 33 of the coupling plate 10, the lugs 24 are released and the adapter 11 of the cable 6 is freed.

After suitably tensioning the guide wire 20, the cable 6 is lifted by the drum 13, which is connected by a rope 32 to the upper head 31 of the cable 6.

At the same time as this operation, the tension jack device 16, which was locked to the wall of the well 12 by the driving device 48, is removed. This work is done by Gangway 49.
It is carried out from The cable is lifted together with the adapter 11 until this adapter 11 is near the base of the pile 2 of the platform. At this point, the guiding device 14 is freed from the cable 6, after which the cable is lifted further and with it the adapter 11 pulls together the other parts installed in the well 12, such as the gripper 15. Lift up. FIG. 6 now shows the adapter 11 reaching the top of the platform.

Next, drum 13, cable 6, lappa 15
the entire assembly of other parts is removed;
The preparation for installing the new cable is now complete.

A new drum 13 for attaching the new cable is placed in place as shown in FIG. 7, and then the cable is lowered together with its adapter 11.

This adapter is compatible with elements of Ratsupa 15, such as the seventh
Lower the wrapper 15 as shown by the imaginary lines in the figure until the two parts are in the predetermined position as shown in FIG. This descent is guided by channel 71 and pipe 70.
It is carried out in collaboration with.

The tension jack device 16 is also returned to its original position by the gangway 49 and the driving device 48.

Next, the cable may be lowered to the mooring base 7. For this purpose, the guide device 14 is used again under the same conditions as when the cable was previously removed.
Therefore, the guide device 14 is connected to the central collar 17 of this
is engaged with the upper part of the cable adapter 11 until this adapter is in the driving position shown in FIGS. 4 and 5.

Next, the jack 33 is actuated to drive the locking rod into the adapter and apply tension to the cable.

The guide wire 20 can then be removed, or at least wound up again.

With such operational and structural embodiments,
Cable replacement can be done quickly without manual intervention on the seabed, where the invention has particular advantages in conventional systems.

It goes without saying that the invention is not limited to the embodiments listed here, but extends to all variations thereof.

[Brief explanation of the drawing]

1 and 2 are constructed according to the present invention,
Elevation and horizontal section of an offshore platform with taut vertical cables, Figure 3 showing one pile of the platform and one cable passing through it, and for lifting this cable. FIG. 4 is an enlarged view of the main parts of the assembly of the cable exchange device for carrying out the cable exchange method according to the present invention when the lifting operation is started, and FIG. 4 is used in the cable exchange device shown in FIG. 3. Top view of the guiding device, Figure 5 is a view similar to Figure 3 at the start of lifting the assembly of Figure 3, Figure 6 is a similar view at the end of the lift, Figure 7 is a new cable installation. A similar view of the assembly at the time, FIG. 8 is a sectional view at - of FIG. 1...Deck, 2...Pile, 5...Sea floor, 6...Cable, 7...Mooring base, 10...Joining plate, 1
1...Adapter, 12...Well, 13...Drum, 14
...Guiding device, 15...Ratsupa, 20...Guiding wire,
70...tube.

Claims (1)

[Claims] 1. Removal of deteriorated or used cables from an offshore platform structure moored by cables stretched between the platform and a mooring base fixed to the seabed. In the method for replacement with a new one, these cables are routed through suitable individual wells provided in the platform, and (a) in the well 12 of the cable 6 to be replaced, the cable lowering at least two guide wires 20 on each side of the well until their lower ends emerge downwardly from the lower end of the well; (b) lowering the guide device 14 onto the lower ends of said guide wires 20 and the cable to be replaced; (c) lowering the guide wire 20 and guide device 14 assembly by the cable 6 toward the mooring point of the cable 6 to be replaced; (d) The lower end of the guide wire 20 is fixed to the coupling plate 10 and the mooring base 7 of the cable 6 to be replaced
(e) raising the cable 6 again through the individual wells 12 of said cable 6 and lifting the lower adapter 11 of said cable together with the guide device 14 guided close to the lower end of said guide well; (f) removing the old cable 6 and lowering the new cable 6; (g) ) guiding this assembly with the lower adapter 11 and the guiding device 14 by the guide wire 20 to the mooring point of the cable 6; (h) lowering the lower adapter 11 of the new cable 6 to said mooring. (i) raising again the assembly comprising the guide wire 20 and the guide device 14 guided by the new cable 6; and pulling up the assembly. 2. A method for replacing a cable according to claim 1, wherein the guide wire 20 is laid down from a suitable winch along the corresponding wall of the well, the cable preferably extending along the wall of the well. A method for replacing a cable that is laid along a well and through a pipe that also guides a rapper or the like within the well.