GB2080860A - A process for mounting in relatively shallow or moderately deep water and installing at the work site a drilling and oil-production platform with base-weight. - Google Patents

Abstract

In shallow water the deck 8 is mounted on the base I, then the columns 13 on the base, through openings 10 in the deck; then, with the base forming a floating transport body, the whole is towed to the site, the base is ballasted, it descends to the sea bed, the floating deck then retaining the base through the columns and finally the deck is hoisted to its final height. <IMAGE>

Description

SPECIFICATION A process for mounting in relatively shallow or moderately deep water and for installing on the working site a drilling and oil-production platform having a baseweight The present invention relates to a process for mounting in relatively shallow or moderately deep water and for installing at the working site a drilling and oil-production platform having a base-weight.

By the terms "platform with base-weight", there is here generally designated oil-working platforms which are formed essentially from a surface working deck, intended principally to receive the drilling and other equipment, and resting, at some distance above the surface of the water, on columns whose feet are fixed to a-base weight anchored to the sea bottom.

Deck, columns and base are essentially made from metal and formed into caissons or ballast tanks suitably framed and forming floating bodies able to be ballasted. The base-weight may be provided so as to form or support oilstorage reservoirs; the same may possibly hold good for at least the lower part of the columns.

The aim of the present invention is essentially to reduce the total cost of such a structure once installed at the working site.

An examination of the usual mounting and installing processes shows that a large part of this total cost is due to the use of derrickbarges operating at sea for installing the deck and the columns and for mounting, on said deck, integrated or modular equipment. Such use of derrick-barges for carrying out these delicate operations is very costly and dependent on meteorological conditions which, if they are bad at the time of working on the site, may be further cause of considerable increase in costs because of the delay which they cause.

The aim of the invention is then to provide a process which eliminates as much as possible the work to be carried out at the working site, at sea, not only insofar as the assembly of deck, columns and base is concerned but also insofar as the equipment of the deck is concerned.

To this end, process in accordance with the invention, in one of its embodiments, is essentially characterized in that it comprises the following essential phases: a) use of an existing naval dockyard and a relatively shallow water site for; aa) constructing the deck, the columns and the base; ab) putting the base into the water, putting the deck into the water, and installing the deck on the base; ac) installing columns on the base, through openings provided in the deck, and mounting, along the columns, on them or parallel to them, hoisting means adapted to create a relative movement, along the columns, of the deck and of the base; ad) positioning, on the deck, the major part of the production and other equipment, and using provisional locking means between the base and the deck;; b) towing the assembly thus formed to the work site, the base, unballasted, forming a floating transport body; c) at the work site, using ballasts and said hoisting means, after freeing said provisional locking means, for: ca) immersing the base by the downward movement of the columns, with floating of the deck and anchoring of the base to the sea bed; cb) hoisting the deck along the columns, as far as its normal service position; cc) finally fixing the deck to the columns; cd) mounting complementary accessories or equipment on the deck.

Thus it can be seen that the invention consists, in short, and contrary to the existing process, in completely installing on the platform, before the operation of towing out to sea, as much as possible of the production equipment, and in using a structure able to be installed by its own means at the site, without the help of costly external means such as derrick-barges.

Advantageously, the operation for putting the base into the water is followed by connecting to its edges sealed stability caissons extending upwards beyond the roof of the base and allowing the immersion thereof to be controlled during the following operation for installing the deck on the base.

As for this latter, it may be carried out, with the base immersed by ballasting and maintained afloat by said sealed stability caissons, by bringing said deck, in the floating condition, between the caissons, then in removing the ballast from the base, which progressively takes up the weight of the deck and carries it out of the water, after which said stability caissons may be disconnected.

In the case where the structure will need to have larger storage capacity and where, accordingly, the columns will have to have, at least in their lower part, a larger diameter than that required solely for their function of supporting the deck, it may be arranged to install the deck, during the preliminary operations which have just been described, not directly on the base but on lower parts of the columns, of a larger diameter, themselves fixed to the base, at the assembly site. Of course, that will be possible if a sufficient depth of water is available at the assembly site and in any case considerably greater than that which is sufficient (about ten metres or so) when the deck is placed directly on the base.

A process in accordance with the invention may then also be characterized, according to another embodiment, in that it comprises the following essential phases: a) use of an existing naval dockyard and of a moderately deep water site for: aa') constructing the deck, the columns, the base and lower column parts, of a greater diameter; ab') placing the base in the water, placing thereon lower column parts, placing the deck in the water and installing on the deck said lower column parts; ac') installing the columns on said lower column parts, through openings provided in the deck, and mounting, along the columns, on them parallel to them, hoisting means adapted to create a relative movement, along the columns, of the deck and the base;; ad') positioning, on the deck, the major part of the production and other equipment, and using provisional locking means between the deck and said lower column parts; b) towing the assembly thus formed to the work site, said lower column parts forming a floating transport body, the base being possibly at least partially ballasted; c) at the work site, using ballasts and said hoisting means, after freeing said provisional locking means, for: ca) completely immersing said lower column parts by downward movement of the columns, with floating of the deck and anchoring of the base to the sea bed; the following operations being such as described under items cb), cc) and cd) above.

Insofar as the operation for anchoring the base to the sea bed is concerned, the procedure may comprise, whatever the embodiment contemplated moreover, complete ballasting thereof and of the columns, so as to cause stabilizing skirts of the base to penetrate into the ground, with possibly, after partial hoisting of the deck to bring it out of the water, provisional ballasting thereof, in order to load the foundations beyond the subsequent operating load.

Then, of course, the ballast is removed from the deck before this latter is hoisted to its normal surface position.

Sometimes, it may be necessary to install a drilling platform at the side of a structure containing heads of wells drilled previously.

In this case, a process in accordance with the invention may be further characterized in that, for supporting the conduits between said heads and the deck, a trellis structure or similar is provided, extending vertically from a lateral extension of the base and adapted to be guided by elements of a corresponding lateral extension of the deck, during the different relative movements of the deck and the base.

Embodiments of the invention will now be described by way of non-limiting examples, with reference to the figures of the accompanying drawings in which: Figures I to 1 7 show schematically different phases of a process in accordance with the invention, for mounting a platform, Figs.

1 to 10 showing the operations carried out in the naval dockyard or similar and at a relatively shallow water site and Figs. 11 to 1 7 the operations carried out at the work site, after the premounted assembly has been towed; Figures 18 to 20 show a variation with use of lower column parts having a greater diameter than that of the columns of the preceding embodiment, these figures showing only the operations carried out in moderately deep water with towing of the assembly to the work site; and Figures 23 and 24 show respectively in a, top view and in a side view a platform modified so as to be set up close to a pre-existing wellhead.

Fig. 1 shows a base 1, intended to form the base-weight of the platform and formed from sealed caissons 2 made rom flat steel-sheet panels suitably stiffened by means of a framework of beams and able to be ballasted individually. Reference 3 designates anchoring skirts for fixing base 1 in the ground of the work site, for example the bottom of the sea.

and for conferring thereon good horizontal stability. The base is shown on a naval dockyard slipway 4, ready to be anchored in shallow water, at 5. Base 1 may however be constructed and placed in the water in one or more steps, as this may also be the case for the deck. In any case, base, columns and deck may be constructed on any launching quay or in any adequate dock, with use of simple existing constructional techniques.

It should be noted that in accordance with an additional feature of the present invention, it may be advantageously provided for base'l to be constructed in a position, on the ground, which is upside down with respect to its normal anchored position. That will allow the skirts or spades 3 to be fitted only at the last moment, before launching, at the upper part of the upturned base, and thus leaves the user considerable extra time, which may be of the order of a year after ordering, for choosing the type of skirt to be mounted on the base; in fact, these skirts may be chosen precisely depending on the nature of the ground, at the anchoring site, and the fact of mounting them on the base at the end of construction of this latter, instead of mounting them at the begin ning, allows the considerable above-mentioned gain in time to be achieved. In this case, all that will be needed, after anchoring of the base, is to turn it over by static ballasting so that skirts 3 are in their normal service position.

Base 1 may be rectangular or square, but the four corners may also be cut or formed as bevels, as shown at 2a in Fig. 1 a, so that the base, seen from the top, has a general shape of a regular or irregular octagon. This arrangement reduces the anisotropic character of the base, considered as a body capable of exerting stresses on the ground: in fact, there is thus avoided the occurrence of high localized stresses at the corners which, on a conventional rectangular or square base, could be excessive and cause break-up of the ground; in other words, the stresses exerted by the base on the ground tend to be distributed more evenly and those which might become excessive at the corners tend to be reduced, because of gravity forces alone or because of forces which are added thereto under the action of currents, of the swell or of the wind.

From a similar point of view, a base 1 may also advantageously be considered which, at its centre, is hollowed out as shown at 2b.

Thus a base is obtained appearing to be formed from beams which, because of the previous arrangement concerning removal of the corners, have a relatively uniform width.

A better distribution of the stresses on the ground may thus also be obtained, and the occurrence of excessive stresses is more especially avoided which might otherwise arise at the centre, due to unevenness of the ground.

Furthermore, the central opening 2b may serve for passing therethrough different pipes coming from the deck.

Fig. 2 shows the base 1 after immersion. It is at this time equipped with sealed stabilizing caissons 6 connected to its edges and extending upwardly beyond the roof 7 of the base; these caissons 6 enable the immersion of base 1 to be controlled when it is totally immersed.

Fig. 3 shows, similarly to Fig. 1, the deck 8 on a slipway 4 of the dockyard and ready to be immersed in a shallow site, at 5.

Fig. 4 is a top view of deck 8.

The deck also is constructed essentially in the form of a floating box, which is stiffened by main beams in the form of sealed and ballastable caissons. It can be seen that there are in particular four main beams 9a connecting together four nodes formed by main beams disposed in rings 9b. These nodes form openings 10 for passing the columns therethrough. Deck 8, of which only the resistant structure can be seen in Fig. 4, is of course provided with a flooring and a bottom.

Two opposite ends 11 of the deck may be cantilevered, which increases its effective surface.

For installing deck 8 on base 1, the following procedure is preferred: with deck 8 afloat and towed to the place where base 1 is anchored, this latter is partially ballast so that it is entirely immersed and only maintained floating by its sealed stabilizing caissons 6 (Fig. 5); deck 8 is introduced between the caissons 6, then the ballast is at least partially removed from base 1, which causes it it take up the weight of the deck, chocks 1 2 being placed between the deck and the base (Fig.

6). Deck 8 is then brought out of the water and caissons 6 may be disconnected from base 1 (Fig. 7). For all these operations, it should be noted that a depth of water of about 10 metres may be sufficient, the height of the base and of the deck being, to give an idea, for example 7 metres.

Columns 1 3 may then be mounted on base 1 (Fig. 8), by passing them through the above-mentioned openings 10 in the nodes of the deck. For this, a quayside crane 14 may be used and the columns mounted in one or more steps.

The columns may be cylindrical with a square base and may have a diameter of the order of 7 metres; they form at least partially sealed caissons which may be ballasted or used as storage reservoirs. The columns are suitably reinforced by internal annular structures, at the places where they are likely to be subjected to high stresses, particularly at the position of their future junction with the deck.

At the same time (Fig. 9), hoisting means are mounted along columns 1 3 for creating at the desired moment (i.e. subsequently, after the above-described mounting phase, and when the platform has arrived at the site), relative movement, along the columns, of deck 8 and base 1, for positioning the deck.

Any adequate known hoisting system may be used.

For example a double-acting jack system may be used arranged and controlled so as to climb step by step along a rack suspended from the head of the columns, in the three following iterative operational phases: 1. Locking of the upper ends of the jacks on the rack and retraction of the jacks, so that their lower ends, fastened to the deck, raise this latter by a step (or lower the base by a step).

2. Locking of the lower ends of the jacks on the rack and unlocking of their upper ends.

3. Extension of the jacks and further locking of their upper ends of the rack in a position higher by one movement step than the prg ceding position.

There may also be used a system with rack and toothed pin ions driven by electric motors and reduction gear or else a suspended cable system.

In Fig. 9, there is schematically shown at 1 5 racks fastened at the top of columns 3.

Said hoisting means comprise additional removable parts 1 3a of the columns, provided at the top with beams 1 6 for suspending racks 15.

With these operations finished, the major part of the production and other equipment, shown symbolically at 1 7 (Fig. 10), may be positioned with the help of cranes. Temporary locking means 1 8 are positioned between the deck and the base.

The platform assembly thus premounted and pre-assembled may be towed to the work site 19 (Fig. 11).

It should be noted that this towing may be effected under very good conditions of stability, for the centre of gravity of the assembly is very low and, in any case considerably lower than if the deck occupied its normal surface position at the top of the columns. Furthermore, in this case, it would be necessary to provide the structure with considerable draught by completely immersing the base and a part of the columns by ballasting, which is not the actual case where the draught is small. Thus an advantage is obtained, with the invention, which could already be obtained, it is true, with certain processes for positioning drilling platforms, but not with the processes for positioning production platforms.

At site 19, the temporary locking means 1 8 are removed or released and base 1 is partially ballasted so that it is immersed and deck 8 floats. The deck no longer rests on the base, and chocks 1 2 may also be removed.

The ballasting of base 1 may then be increased and caused to descend by use of the above-defined hoisting means (Fig. 12).

The hoisting system plays here a restraining role and the whole is suspended from the floating deck 8; the descent of base 1 is easily controlled because of the increased floatability of the system, coming from the progressive immersion of columns 1 3.

When base 1 has touched the sea bed 20 (Fig. 13), it is fully ballasted, as well as columns 13, so as to preload the foundations and to cause the horizontal stabilizing skirts 3 to penetrate into the ground.

The implantation of the base may moreover be completed by hoisting deck 8 out of the water by means of the hoisting system, and by provisionally ballasting some of its caissons (Fig. 14); thus, the foundations are loaded beyond the normal subsequent operating load.

Then the ballast is removed from deck 8 and the deck is hoisted along columns 13, by using said above-described hoisting means (or similar), intil the deck reaches it normal service height (Fig. 1 5).

Then the deck may be locked vertically in position, with said hoisting means (locking of the jacks, drive motors or similar).

Additional provisional locking means may be used, for example screw systems. More especially, deck 8 may be locked laterally with respect to columns 1 3 by using two sets of four screws, at different levels (eight screws in all per column) so as to provisonally lock, in the transverse direction, the deck on the columns, at the position of the nodes of the deck.

After which, the final securing of columns 1 3 and deck 8 is carried out, similarly at the position of the nodes of the deck.

For this, four pairs of vertical webs 21 are used per column, connecting two horizontal webs 22 situated respectively at the level of the flooring and of the bottom of the deck (Figs. 1 6 and 17), all these webs being welded, on the one hand, to the correspond7 ing column 1 3 and, on the other hand, to the main beams 9a or 9b or deck 8.

The possible provisional locking means may then be removed, as well as the whole hoisting system, including the additional column parts 13a and beams 16.

The equipment lacking may then be installed on the platform.

It can be seen in any case that the heaviest mounting and assembly work has been able, to be carried out in the dockyard, without the help of derrick-barges, whereas the final positioning of the deck was able to be completed with the very means of the platform itself, similarly without having recourse to derrickbarges of other costly mounting or maintenance equipment at sea.

Another appreciable advantage of the invention is obtained because of the special hoisting means which are used and which, more especially, use, as was mentioned above, a rack suspension for the hoisting system at the top of the columns. With this arrangement, in fact, columns of any diameter may be used, particularly of large diameter, and the problems of resistance to shearing of the walls of the columns, such as there might arise if the racks were fixed along the length of the columns, ar not met with. Moreover, after final positioning of the deck, any hoisting system may be removed and reused, whereas it would be otherwise lost.

The use of suspended racks also avoids problems of tolerances which would arise if, contrary to the arrangement of the invention, the racks were fixed along the length of the columns, which would moreover involve a large number of welds. In addition, the not inconsiderable deformations which the columns undergo during the hoisting operation are avoided at the same time: these deformations do not react on the racks.

In some cases, if a greater depth of water is available at the assembly site, and if the structure must have larger storage capacity, the lower column parts may have a larger diameter than that which has been mentioned above and the deck may be installed not directly on the base, but on these lower column parts, themselves fixed to the base, for transport to the site.

For this, with base 1 anchored at the assembly site 5', it is equipped with said largerdiameter lower column parts, which are refeienced at 13' in Fig. 1 8. The assembly is then suitably ballasted and the emerging ends of said column parts 13' are equipped with sealed stabilizing caissons 6 whose role is the same as that of caissons 6 in the previouslydescribed embodiment (Fig. 19). The column parts 13' are optionally provided with crossbraces 13" at their upper ends.

Deck 8 is then anchored and with the ballast of the columns slightly increased, the deck may be brought between the caissons 6, above the then immersed ends of the column parts 13' (Fig. 20).

By partial removal of ballast, deck 8 is then brought out of the water (Fig. 21), by causing base 1 to take up its weight, through chocks 12, and caissons 6, being of no further use, are disconnected.

Still being at the mounting and assembly site 5', columns 13, of smaller diameter, may be installed on the lower column parts 13' (Fig. 22) through openings 10 in deck 8.

Similarly, rack-hoisting means 1 5 or similar, additional column parts 13a, beams 1 6 and large equipment 1 7 may be fitted, the whole as described in connection with the preceding embodiment.

After which, the assembly may be towed to the work site and the deck hoisted and finally fixed on columns 13, in its service position, the whole also as already described in what has gone before (operations designated above ca) to cd)).

Finally, it should be noted that the invention, in one or other of the preceding variations, or in any other equivalent variation using the same general means, may also be used for installing a platform in the vicinity of a structure 23 assembling together different pre-existing wellheads (Figs. 23 and 24).

In this case, an additional structure 24 is provided, made from trellis-work or similar, connected to the platform and intended to support the conducting tubes 25 which will connect the wellheads of structure 23 to deck 8, and maintain them in position, more especially against the horizontal action of the swell.

Structure 24 is itself supported by a lateral extension 26 of base 1, which extension may for example be formed from two beams in the form of caissons. Deck 8 is similarly provided with a corresponding lateral extension 27, which may also be formed by two beams in the form of caissons, connected by two other beams 28, having an I-shaped section.

These two beams 28 may form or support means for guiding the trellis-work structure 24, during the descent of base 1 onto the site, which may in all respects take place in the way described above. Any guide means are of course used for the accurate positioning of structure 24 above the pre-installed wellheads.

When the positioning of base 1 and of structure 24 has been carried out, deck 8 is hoisted up to its normal service position, also in the way described above and, once this deck is finally fixed to columns 13, the trelliswork structure 24 may also be finally fixed between beams 27 and between beams 28 (welded fixing shown symbolically at 29).

Conduits 25 may then pass downwards to the wells, through structure 24, by using an additional structure 30 positioned on extension 27 of deck 8.

It can be seen that this embodiment of the invention may be carried out according to the same general procedures and according to the same principles as the previously-described embodiments, and present consequently the same advantages.

As is evident, and as it follows moreover already from what has gone before, the invention is in no wise limited to those of its embodiments and modes of application which have been more specially considered; it embraces, on the contrary, all variations thereof.

Claims (16)

1. A process for mounting in relatively shallow water and installing on the work site a drilling and oil-production platform with baseweight, deck, columns and base being essentially made from metal and formed as caissons or ballast tanks suitably framed and forming at least partially floating bodies able to be ballasted, characterized in that it comprises the following essential phases: a) use of an existing naval dockyard and a relatively shallow water site for:: aa) constructing the deck, the columns and the base; ab) putting the base into the water, putting the deck into the water and installing the deck on the base; ac) installing the columns on the base, through openings provided in the deck, and mounting, along the columns, on them or parallel to them, hoisting means adapted to create a relative movement, along the columns, of the deck and of the base; ad) positioning, on the deck, the major part of the production and other equipment and using provisional locking means between the base and the deck; b) towing the assembly thus formed to the work site, the base, with the ballast removed, forming a floating transport body; c) on the working site, using ballasts and said hoisting means, after freeing said provisional locking means, for:: ca) immersing the base by downward movement of the columns, with floating of the deck and anchoring of the base to the sea bed; cb) hoisting the deck along the columns up to its normal service position; cc) fixing the deck finally on the columns; cd) mounting on the deck complementary equipment or accessories.

2. The process as claimed in claim 1, characterized in that the operation of putting the base into the water is followed by connecting to the edges thereof sealed stabilizing caissons extending upwards beyond the roof of the base for controlling the immersion thereof.

3. The process as claimed in claims 1 and 2, characterized in that the deck is installed on the base, with the base immersed by ballasting and maintained floating by means of said sealed stabilizing caissons, by bringing said deck, in the floating condition, between the caissons, then removing the ballast from the base, which gradually takes up the weight of the deck and bears it out of the water, after which said stabilizing caissons may be disconnected.

4. A process for mounting in moderately deep water and installing on the work site a drilling and oil-production platform with baseweight, deck, columns and base being essentially made from metal and formed as caissons or ballast tanks suitably framed and forming at least partially floating bodies able to be ballasted, characterized in that it comprises the following essential phases: a) using an existing naval dockyard and a moderately deep water site for:: aa') constructing the deck, the columns, the base and lower column parts, of larger diameter; ab') putting the base into the water, placing thereon the lower column parts, putting the deck into the water and installing the deck on said lower column parts; ac') installing the columns on said lower column parts, through openings provided in the deck, and mounting, along the columns, thereon or parallel thereto, hoisting means adapted to create a relative movement, along the columns, of the deck and the base; ad') positioning on the deck the major part of the production and other equipment and using provisional locking means between the deck and said lower column parts; b) towing the assembly thus formed to the work site, said lower column parts forming a floating transport body, the base being able to be at least partially ballasted;; c) at thee work site, using ballasts and said hoisting means, after freeing said provisional locking means, for: ca) completely immersing said lower column parts by downward movement of the columns, with floating of the deck and anchoring of the base to the sea bed; cb) hoisting the deck along the columns up to its normal service position; cc) fixing the deck finally on the columns; cd) mounting on the deck complementary equipment or accessories.

5. The process as claimed in claim 4, characterized in that the operation of putting the base into the water and placing thereon the lower column parts is followed by connecting, to the upper ends of said lower column parts, sealed stabilizing caissons extending upwards beyond said ends for control ling the immersion thereof.

6. The process as claimed in claims 4 and 5, characterized in that the deck is installed on said lower column parts, with the base and the lower column parts immersed by ballast ing and maintained floating by said sealed stabilizing caissons, by bringing said deck, in the floating condition, between the caissons, then removing the ballast from said lower column parts, which gradually take up the load of the deck and bear it out of the water, after which said stabilizing caissons may be disconnected.

7. The process as claimed in any one of claims 4 to 6, characterized in that said lower column parts are connected together, option ally, at their upper ends, by means of cross pieces.

8. The process as claimed in any one of the preceding claims, characterized in that the operation of anchoring the base to the sea bed is effected by completely ballasting said base and said columns so as to cause the stabilizing skirts of the base to penetrate into the ground, with possibly, after partial hoist ing of the deck to place it out of the water, provisional ballasting thereof so as to load the foundations beyond the subsequent operating load.

9. The process as claimed in any one of the preceding claims, for installing a drilling platform at the side of a structure assembling together the heads of previously drilled wells, characterized in that, for supporting the con duits between said heads and the deck, a trellis-work structure or similar is provided extending vertically from a lateral extension of the base and adapted to be guided by ele ments of a corresponding lateral extension of the deck during the different relative mov4 ments of the deck and the base.

10. The process as claimed in claim 9, characterized in that, after the deck has been hoisted to its final height, the trellis-work structure, at its top part, is secured to the deck.

11. The process as claimed in any one of the preceding claims, characterized in that the operation designated aa) or aa') includes con structing the base upside down with respect to its normal anchored position, which allows the skirts to be fixed thereto, at its upper part, only at the last moment, before launching, after which the base once anchored is turned over by static ballasting so that said skirts are in their normal service position.

1 2. The process as claimed in any one of the preceding claims, characterized in that a hoisting system is used comprising racks or similar suspended from the top of the col umns, which allows columns to be used hav ing as large a diameter as desired, without any problem of resistance to shearing on their walls and which allows, once the deck has been finally positioned, the whole hoisting system to be used again for positioning another platform.

1 3. The process as claimed in any one of the preceding claims, characterized in that the deck is connected to the columns by means of welded plates when the deck has been brought to its final position.

1 4. The process as claimed in any one of the preceding claims, characterized in that the base is constructed so that, seen from the top, it has the general shape of a regular or irregular octagon, i.e. the general shape of a square or a rectangle whose corners or angles have been chamfered.

1 5. The process as claimed in any one of the preceding claims, characterized in that the base is constructed with a central recess so that, seen from the top, it is in the form of an assembly of beams of relatively uniform width.

16. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 7. A platform installed by a process as claimed in any of the precediing claims.