EP2771235B1 - Installation for anchoring a floating platform to the ground - Google Patents

Description

The present invention relates to floating platform anchoring installations, in particular for ground anchoring oil well platforms or production, storage and unloading vessels (also referred to as Floating Production Storage and Offloading ( Unit) - FPSO).

Conventionally, the platforms for the offshore exploitation of oil wells consist of floating supports connected to the wellhead and anchored to the ground by means of anchor chains (see for example WO98 / 33700 ).

These platforms, generally horizontal in cross section, can have several tens of meters of side and their weight can reach several tens of thousands of tons, even several hundreds of thousands of tons.

They support all the necessary means for the extraction of oil, and possibly its transformation on site, as well as sometimes equipment intended to ensure a human presence on board.

For anchoring, one generally uses several groups of a plurality of parallel chains (three to eight chains per group, for example), also called mooring lines, each group being formed at one of the corners of the platform .

Each anchor chain consists of a chain with metal links each of which has a length of a few tens of centimeters (made from a wire having for example 9 to 20 cm in diameter).

The lower end of each of these anchor chains comprises means for its attachment to the ground, through a solid sunken in the seabed. Their upper end extends to a maneuvering station which is arranged on the side of the platform, above its waterline, for their maneuver each by their own tensioner winch associated with activatable / deactivatable stopper means.
And between their upper and lower extremities, an intermediate zone of these chains is associated with a return device, called fairlead, fixed on the platform, generally below the level of the waterline.

From the maneuver station, the chains extend vertically along the platform, up to each associated fairlead; then they extend in an inclined way up to their massive anchoring on the ground.

The tension of each chain is adjusted by the tensioner winch associated with it, and the upstream free end of the chain, which extends behind the tensioner winch falls by gravity into a container-tank adapted to its storage.
Once properly tensioned, the chains are locked in position by the stopper means. These stopper means can be provided just downstream of the tensioning winches and / or at the return fairleads.

But current anchoring facilities are relatively complex because of the necessary multiplication of chains, fairleads, stoppers and tensioners. They have a relatively high cost and their weight can be very important (sometimes up to several thousand tons), which limits the payload capacity of the platform.

The object of the present invention is to remedy these drawbacks by proposing an original anchoring installation structure which, while retaining optimum anchoring characteristics (in terms of fastening and resistance), is of simpler design and easy to install. 'a lower weight than those of current installations. In addition, this installation has improved ergonomics of maneuvering.

For this, the anchoring installation corresponds to that mentioned in claim 1.

Such an installation, with a single tensioner winch that can be moved at will to manage the tension of the various anchoring chains, one after the other, simplifies the overall design of the anchoring installation, by limiting its cost of realization and decreasing significantly its weight.

According to another particularity of the invention, the tensioner winch is mounted on a rolling frame guided by a rail structure formed on a raceway parallel to said line of stopper means; this rolling chassis is associated with drive means for allow its movement along said line of stopper means, to allow its positioning above each of these stopper means, and ensure the operation of the associated anchor chain, after connection of the downstream link of the master chain of said winch tensioner, with the connecting link of said associated anchor chain.
The drive means of the rolling frame of the tensioner winch advantageously consist of a motorized gear integral with the rolling frame, which cooperates with a rack extending along the raceway.

According to a preferred embodiment, the axis of rotation of the tensioning winch extends parallel to the raceway; the vertical downstream end of the master chain strand which cooperates with said tensioning winch extends in a vertical plane passing through the stopper means and the associated reservoir-tanks; and the upstream vertical end of this master chain strand which cooperates with the stretcher winch extends in a vertical plane passing through the associated storage reservoir container.

Again according to a preferred embodiment, the storage container-tank for the upstream end of the master chain-strand - is fixedly mounted at the operating station and - extends over the entire length of the raceway; this container-tank has an upper opening for the passage of the master chain strand, which upper opening extends over all or substantially the entire length of said raceway. According to an alternative embodiment, this container-tank for storing the upstream end of the master chain strand is carried by the rolling chassis of the tensioner winch.

According to yet another particularity, the storage tank-housing free upstream strands anchor chains are arranged in the plane of the line of stopper means.
In this context, each housing-reservoir advantageously comprises an upper opening associated with a lateral support table, arranged in the extension of said upper opening, which support table comprises a notch, open facing said upper opening, for the passage of a link of said free upstream strand chain, and the locking of the link directly upstream, resting on said table.

The connecting link of the upstream free strand of the anchor chains preferably consists of a removable mesh, for example of the kind known as the "kenter mesh".

According to yet another particularity, the chassis on which the tensioner winch is mounted carries an additional winch allowing in particular the opening maneuvers of the chain stopper located in the return fairlead immersed above said tensioning winch.

• la figure 1 est une vue schématique de l'installation d'ancrage conforme à l'invention, vue en légère perspective ;
• la figure 2 est une vue agrandie de la partie supérieure de l'installation d'ancrage de la figure 1, vue de face ;
• la figure 3 est une vue en perspective de la partie d'installation illustrée sur la figure 2 ;
• la figure 4 est une vue en coupe de l'installation d'ancrage, selon le plan de coupe 4-4 de la figure 2 ;
• la figure 5 est une vue en coupe de l'installation d'ancrage, selon le plan de coupe 5-5 de la figure 2 ;
• la figure 6 est une vue en perspective, encore agrandie, d'une partie de l'installation d'ancrage illustrée sur les figures 2 à 5, montrant le détail des moyens stoppeurs de chaîne ;
• la figure 7 montre le détail de la figure 6, vu selon une autre perspective.

The invention will be further illustrated, without being limited in any way, by the following description of a particular embodiment, given solely by way of example and shown in the accompanying drawings in which:

• the figure 1 is a schematic view of the anchoring installation according to the invention, seen in slight perspective;
• the figure 2 is an enlarged view of the upper part of the anchor installation of the figure 1 , front view ;
• the figure 3 is a perspective view of the installation part shown on the figure 2 ;
• the figure 4 is a sectional view of the anchoring installation, according to sectional plane 4-4 of the figure 2 ;
• the figure 5 is a sectional view of the anchoring installation, according to the sectional plane 5-5 of the figure 2 ;
• the figure 6 is a perspective view, still enlarged, of a portion of the anchor installation illustrated on the Figures 2 to 5 showing the details of chain stopper means;
• the figure 7 shows the detail of the figure 6 , seen from another perspective.

As illustrated on the figure 1 the floating platform P , for example an oil platform, is anchored to the ground by means of an anchoring installation marked 1 in a general manner.

The platform P is here represented only partially; its ground anchoring installation 1 consists of several groups of a plurality of anchor chains 2, each of these groups being for example arranged at one of the corners of the platform P (on the figure 1 only one of these groups G of anchor chains 2 is shown).

The platform P floats on the body of water M , above the seabed soil S , by defining a waterline F.

In the illustrated embodiment, the group G consists of seven anchoring chains 2 juxtaposed, arranged parallel or substantially parallel to each other, each formed by a juxtaposition of interleaved metal links.

The corresponding chain links are steel links, whose length can be of the order of 50 to 120 cm and whose width can be of the order of 30 to 80 cm, made from a wire whose diameter is for example between 9 and 20 cm.

The lower downstream end 2 has anchoring chains 2 is fixed by any suitable means to a solid T placed on the ground S of the seabed, or preferably sunk into this soil S (on the figure 1 , Only the lower end 2a of one of the chains 2 is shown).

The upper upstream end 2b of the various chains 2 extends to a maneuvering station 3 arranged on the platform P , above the waterline F , and in this case, here at the level of the upper part of said platform P.

At this maneuvering station 3, there are in particular means for the tensioning of the chains 2 and stopper means to block this tensioning, as detailed below.

On the other hand, an intermediate zone 2 c of each chain 2 between the lower end 2a and the upper end 2b cooperates with a return fairlead 4, attached to the side of the platform P, here in the level of the waterline F.

The different return fairlocks 4 make it possible to move, beneath the waterline F , the point from which the chains 2 deviate from the platform P , as shown in FIG. figure 1 .
The fairleads 4 may include a stopper means to block the tensioning of the associated chain 2, equipped with control means in the active or inactive position, operable from the operating station 3.

From this operating station 3, the anchor chains 2 extend vertically or substantially vertically to the return fairlead line 4; from this line of fairleads 4, the chains 2 extend to the solid T , for example at an angle of the order of 45 ° relative to the horizontal. On their vertical portion, the chains 2 can be associated with sections of guide ducts 2 d (visible on the Figures 1 to 4 and 6 , 7 ).

• de moyens stoppeurs 5 pour chacune des chaînes 2, en aval desquels lesdites chaînes 2 s'étendent selon un axe vertical A en direction de leurs chaumards de renvoi 4 respectifs, et en amont desquels s'étend un brin libre amont 2' de chaînes 2, comportant un maillon d'extrémité 6, et
• des moyens en forme de treuil tensionneur 7 unique, monté mobile au-dessus des moyens stoppeurs 5, pour la mise en tension des différentes chaînes 2 au moyen d'un brin de chaîne maître 8.

Maneuver Station 3, detailed on Figures 2 to 7 , is equipped according to the invention:

• stopper means 5 for each of the chains 2, downstream of which said chains 2 extend along a vertical axis A towards their respective return fairleads 4, and upstream of which extends an upstream free strand 2 'of chains 2 , having an end link 6, and
• means in the form of a single tensioner winch 7 mounted movably above the stopper means 5 for tensioning the different chains 2 by means of a master chain strand 8.

The stopper means 5 which equip each chain 2, and which are formed on each vertical axis A , consist of mechanisms of the type with two jaws 9 articulated in rotation about horizontal axes and operable in opposite directions from each other by means of an operating wheel 10.

• de rapprocher les deux extrémités libres des mâchoires 9 pour leur faire prendre une position active de blocage, contre la chaîne 2, en appui sous l'un de ses maillons, ou
• d'écarter ces deux extrémités de mâchoires 9, pour leur faire prendre une position inactive dans laquelle elles ne sont plus en contact avec la chaîne 2.

The steering wheel 10, operable by an operator, allows:

• bringing the two free ends of the jaws 9 to make them take an active locking position, against the chain 2, resting under one of its links, or
• to separate these two ends of jaws 9, to make them take an inactive position in which they are no longer in contact with the chain 2.

The different stopper means 5 are arranged on the same horizontal line E ( figure 3 ) which extends along one side of the platform P and which is bordered by a passageway 11 for the movement of the operators, equipped with protective barriers 12.

In addition, each stopper means 5 has its own reservoir-housing 13 for storing the upstream free strand 2 'of the associated chain 2. Each housing-tank 13 is disposed on the side of the associated stopper means 5; and the different tank-housings 13 are placed on the horizontal line E mentioned above with stopper means 5.

These tank-housings 13 each consist of a housing delimited by a bottom and side walls, and which has an upper opening 14 on the side of which is formed a horizontal support table 15.

The different support tables 15 are also arranged on the horizontal line E stopper means 5, here on the other side of the opening 14 relative to the associated stopper means 5.

The opening 14 and the support table 15 are formed in a horizontal plane accessible to an operator standing on the path 11 (for example at a height of about 1 m 50 above the plane of this path 11) .

As can be seen in particular on figures 6 and 7 , the support table 15 has a lateral notch 16, open facing the opening 14 of the housing-reservoir 13. This notch 16, slightly wider than the thickness of the chain links, is adapted to allow the insertion of one of the links of the upstream chain strand 2 ', so as to block the link directly upstream.
In this way, the terminal connecting link 6 can rest in stable support on the table 15 so as to allow easy and ergonomic manipulation by an operator, as described below.
As illustrated on figures 6 and 7 , the link inserted in the notch 16 corresponds preferably to the third link of the upstream chain strand 2 ', starting from the connecting link 6.

This connecting link 6 is of the dismountable type (called "kenter mesh"), allowing its removable connection with the downstream link of the downstream end of the master chain strand 8 of the tensioner winch 7, as described below.

For its part, the tensioning winch 7 consists for example of an electric winch, able to maneuver in both directions the associated master chain strand 8.

This tensioning winch 7 is mounted on a chassis 18 guided by a rail structure 19 which is formed along a raceway 20 parallel to the horizontal line E stopper means 5, to allow its movement along this line horizontal E.

This displacement of the tensioner winch 7, through its rolling chassis 18, is of the translational movement type.

The axis of rotation 21 of the tensioning winch 7 extends parallel to the raceway 20 and to the line E of stopper means 5.

Side anchor chains 2, the vertical downstream end 8 'of the master chain strand 8 which cooperates with the tensioner winch 7 (output or input of this winch according to its direction of rotation), extends in a vertical plane passing through the axes A of chains 2, as well as by the stopper means 5 and the tank-housings 13.

On the other side, the vertical upstream end 8 "of the master chain strand 8 which cooperates with the tensioning winch 7 (at the outlet or inlet depending on its direction of rotation) extends in a vertical plane passing through a container. reservoir 22, and in particular by the upper longitudinal opening 23 of the container-reservoir 22 arranged on the operating station 3 of the platform P.

The master chain strand 8 is made by means of an assembly of links identical or similar to those constituting the anchor chains 2.
Its downstream link (not visible in the figures), intended to cooperate with the connecting link 6, is a standard link.

To save weight, the master chain strand 8 can be made with links whose wire diameter (for example 10 cm) is smaller than the diameter of wire (for example 18 cm) of the links of the anchor chains 2.

The reservoir container 22, fixed, is delimited by a bottom and side walls; its upper opening 23 extends parallel to the raceway 20, over all or substantially the entire length of the latter.
This upper opening 23 may comprise a closure device provided with a movable light adapted to the passage of the upstream end of the master chain 8 ", this closure device being adapted to move this moving light with the tensioning winch 7; particular sealing may consist of a succession of interconnected metal blades, which wind and unwind on cylinders located at the ends of the opening 23.

The raceway 20 of the tensioning winch 7 is bordered by a passageway 24 on which can move an operator responsible for moving maneuvers of this winch 7.
This path 24 is advantageously located on the other side of the longitudinal opening 23 of the container-reservoir 22, with respect to the rail structure 19 of the race 20. For safety reasons, this path 24 is advantageously bordered by suitable guardrails (not shown).

As can be seen in particular on Figures 2 to 7 , the race 20 of the tensioner winch 7 is provided behind and above the line E of stopper means 5.

For its movement maneuvers along the raceway 20, the chassis 18 of the tensioner winch 7 comprises driving means which here consist of a pinion 26, associated with a motorization carried by said frame 18, which cooperates with a complementary rack 27 formed along the entire length of the rail structure 19.

The operator can then control at will the motorized gear 26, by means of a suitable control box, to ensure the displacement of the tensioner winch 7 parallel to itself on the raceway 20, and to position it correctly facing of one of the support tables 15 and / or one of the stopper means 5, in order to allow the maneuvering the chain 2 opposite, after securing the master chain strand 8 with the connecting link 6 of this chain 2.

For example, to ensure chain retensioning, the downstream link of the downstream end of the master chain strand 8 is secured to the connecting link 6 of the upstream free strand 2 'of the chain 2.
This operation, carried out by one or two operators in position on the path 11 is performed on the support table 15, or just above. The operator or operators can use for this additional electric winch 28, integral with the frame 18, and therefore located above the support table 15 on which they work, able to assist the lifting of the connecting link 6 and facilitate its connection with the downstream link of the master chain 8.

Then, once this chain bonding 2, 8 made, the operator maneuvers the tensile winch 7 to absorb the chain slack; if this has not already been done, it correctly positions the tensioner winch 7 so as to align its pulling strand on the axis A of the associated anchoring chain 2.

After deactivation of the stopper means 5 (by opening the jaws 9 by means of the operating wheel 10), the operator can adjust the tension of the chain 2 by the tensioner winch 7. Once the desired tension is obtained, the stopper means 5 are operated in closing (active position) to lock the anchor chain 2, and its terminal link link 6 can be detached from the master chain strand 8.

The same operation can be carried out successively on the various anchoring chains 2 to be retightened.

It is also understood that similar maneuvers can be implemented for the initial tensioning of the anchoring chains 2, at the time of mounting of the anchoring installation 1.

As a variant, it will be noted that the fixed container-tank 22, ensuring the storage of the upstream end 8 "of the master chain strand 8, can be replaced by a container-tank directly carried by the chassis 18 of the tensioner winch 7 (and therefore mobile with this winch 7).

In the anchoring installation according to the invention, the return fairleads 4 advantageously still have chain stopper means which are specific to them (not visible in the figures), actuated in activation or deactivation by a cable 30 of which end of maneuvering leads to the level of the associated support table 15, blocked by an upper stop provided with a hook 31 ( figures 6 and 7 ).
If necessary, for example during the retensioning maneuvers of the chains 2, these stopper means of the fairleads 4 can be actuated in deactivation, using the winch 28 (or another) mounted on the frame 18 of the tensioner winch 7. For that , the operator hooks the end of the winch cable 28 on the hook 31 and he maneuver this winch in traction, upwards.

It is understood that the presence of a single tensioner winch substantially simplifies the general structure of the anchoring installation according to the invention, with a reduced cost and a reduced weight, compared to existing conventional facilities.

Claims (10)

1. A ground anchor system for a floating platform (P), wherein said system (1) comprises at least one group (G) formed of a plurality of juxtaposed anchor chains (2), arranged parallel or substantially parallel to each other, and an operating station (3),and a bending device (4),
   the lower end (2a) of each of said chains (2) comprising means for fastening to the ground (S), the upper end (2b) thereof extending up to the operating station (3) able to be arranged on said platform (P), above the waterline (F) thereof, and an intermediate area (2c) of each of said chains (2), between the lower (2a) and upper (2b) ends thereof, cooperating with said bending device (4) able to be secured to said platform (P), advantageously under said waterline (F), wherein said operating station (3) comprise means (7) for tensioning said chains (2) and means (22) for storing the free end of said chains (2), upstream said tensioning means (7),
   characterized in that said operating station (3) comprises:

   - activatable/deactivatable stopper means (5) for each of said chains (2), for locking in position the associated chain (2) that ends by an upstream free strand (2') comprising an end connection chain link (6), wherein said stopper means (5) are arranged side by side, along a same line (E), and are each associated with one housing-reservoir (13) for the storage of said upstream free strand (2') of the associated chain (2), and

   - said tensioning means (7) common to the different chains (2), wherein said tensioning means comprise a single tensioning winch (7), movably mounted above said stopper means (5), parallel to said line (E) of stopper means (5), wherein said tensioning winch (7) comprises a master chain strand (8), whereof downstream end (8') comprises a downstream chain link adapted to be removably attached to the connection chain link (6) of the upstream free strand (2') of said anchor chains (2), and whereof upstream end (8") is stored in a container-reservoir (22).
2. The system according to claim 1, characterized in that the tensioning winch (7) is mounted on a rolling frame (18) guided by a rail structure (19) arranged on a rolling track (20) parallel to said line (E) of stopper means (5), wherein said rolling frame (18) is associated with driving means (26, 27) for moving it along said line (E) of stopper means (5), so as to position it above each of said stopper means (5), and to ensure the operation of the associated anchor chain (2), after connection of the downstream chain link of the master chain (8) of said tensioning winch (7) with the connection chain link (6) of said associated anchor chain (2).
3. The system according to claim 2, characterized in that the driving means of the rolling frame (18) of the tensioning winch (7) consist of a motorized pinion (26) integral with said rolling frame (18), cooperating with a rack (27) extending along said rolling track (20).
4. The system according to any one of claims 2 or 3, characterized in that the rotation axis (21) of said tensioning winch (7) extends parallel to said rolling track (20), wherein the vertical downstream end (8') of said master chain strand (8) that cooperates with said tensioning winch (7) extends in a vertical plane passing through said stopper means (5) and through said associated housings-reservoirs (13), and the vertical upstream end (8") of said master chain strand (8) that cooperates with said tensioning winch (7) extends in a vertical plane passing through said associated storage container-reservoir (22).
5. The system according to any one of claims 2 to 4, characterized in that the rolling frame (18) of the tensioning winch (7) carries said container-reservoir for the storage of the upstream end of said master chain strand (8).
6. The system according to any one of claims 2 to 4, characterized in that the container-reservoir (22) for the storage of the upstream end (8") of said master chain strand (8) is fixedly mounted at the operating station (3) and extends over the whole length of said rolling track (20), wherein said container-reservoir (22) comprises an upper opening (23), for the passage of said master chain strand (8), that extends over the whole length, or almost the whole length, of said rolling track (20).
7. The system according to any one of claims 1 to 6, characterized in that the housings-reservoirs (13) for the storage of the upstream free strands (2') of the anchor chains (2) are arranged in the plane of the line (E) of stopper means (5).
8. The system according to claim 7, characterized in that each housing-reservoir (13) for the storage of the upstream free strand (2') of the anchor chains (2) comprises an upper opening (14) associated with a lateral bearing table (15), arranged in the continuation of said upper opening (14), wherein said bearing table (15) comprises a notch (16), open opposite said opening (14), for the passage of a chain link of said upstream free chain strand (2'), and the locking of the directly upstream chain link, bearing on said table (15).
9. The system according to any one of claims 1 to 8, characterized in that the connection chain link (6) of the upstream free strand (2') of the anchor chains (2) consists in a removable chain link.
10. The system according to any one of claims 1 to 9, characterized in that the tensioning winch (7) in mounted on a rolling frame (18) that carries an additional winch (28), for example for the operation of said connection chain link (6) and/or of stopper means arranged on said bending devices (4).

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