WO1995015428A1

WO1995015428A1 - Method for developing an offshore hydrocarbon reservoir and an underwater station for use in exploring an offshore hydrocarbon reservoir

Info

Publication number: WO1995015428A1
Application number: PCT/NO1993/000182
Authority: WO
Inventors: Kjell O. Stinessen
Original assignee: Kvaerner Energy A.S
Priority date: 1993-12-03
Filing date: 1993-12-03
Publication date: 1995-06-08
Also published as: AU5980294A

Abstract

In connection with the development of hydrocarbon field offshore it is proposed to position an upwardly open silo (1) into the seabed, the said silo being prepared for receipt/placing of a separator and/or mechanic rotating equipment requiring cooling. In step with the development of the hydrocarbon field, the necessary equipment can be positioned into the prepared silo. Particularly advantageously the equipment may be in modular form, for example in the form of a separator-cooler-scrubber-module (16), a pump module (33) and/or a compressor module (36).

Description

METHOD FOR DEVELOPING AN OFFSHORE HYDROCARBON RESERVOIR AND AN UNDERWATER STATION FOR USE IN EXPLORING AN OFFSHORE HYDROCARBON RESERVOIR

The invention relates to a procedure in the development of a hydrocarbon field offshore and an underwater station for use in exploiting a hydrocarbon field offshore, including a silo embedded into the seabed.

Offshore production of oil and gas today is generally carried out as follows:

Production wells are drilled from a platform down into the hydrocarbon reservoir. The platform is positioned above the height of the waves on a substructure resting on the seabed or floating at sea level. The well-head valves which shut off the reservoir pressure, are situated on the platform, usually straight above the production wells.

The oil which is present at high pressure in the hydro- carbon reservoir, contains large quantities of dissolved gas. The capacity of the oil to retain the dissolved gas will decrease with subsiding pressure and rising tempera¬ ture. When the oil flows upwards through the production well from the reservoir and past the well-head valve on board the platform, whereby the pressure drops, gas will thus be released from the oil. It will consequently be a mixture of oil and gas (in actual fact a mixture of liquid (oil/water) and gas) which emerges from the top of the well-head valve.

This mixture of liquid and gas is carried to a processing plant which usually stands on the platform. The function of the processing plant is chiefly to separate oil and gas and make the oil suited for transportation and the gas suited for transportation or for being returned to the reservoir. Seeing that the process requires energy, and hydrocarbons are flammable, a number of auxiliary functions and emergency systems will need to be constructed round the processing plant. Besides, operation of the processing, auxiliary and emergency systems requires a crew, who will in turn need to be accommodated, and a number of additional functions. As a result plants tend to be large and costly both as investments and in operation. At greater ocean depths the problem of costs is aggravated when the platform with the plant has to stand on an expensive substructure anchored to the seabed or afloat.

Large development projects are currently in progress with a view to reducing costs. .Among other things, technology has been developed allowing the well-head valves to be placed on the seabed - so-called underwater production plants. This is of great financial significance because the number of platforms required for draining a hydrocarbon reservoir may be reduced. An underwater production plant is installed above an area of the hydrocarbon reservoir which is inaccessible via production wells from the platform.

The production wells in an underwater production plant are drilled from floating or jack-up drilling vessels. Oil and gas from the hydrocarbon reservoir flow upwards and past the the well-head valves on the seabed and then pass as a two-phase flow (oil and gas admixed) in a pipeline which connects the underwater production plant to the platform. Such two-phase flows will entail the formation of slugs of liquid resulting in hard impacts of liquid, uncontrolled flow conditions, and a large pressure drop in the pipeline. The distance from the underwater production plant to the platform, therefore, must not be great. A practical limit today is considered to be about 5 km.

Technical solutions which may increase this distance will be of great economic potential. The extreme consequence may be that the platform becomes superfluous, since the well-head valves could stand on the seabed near the hydro¬ carbon reservoir while the processing, auxiliary and emergency systems are placed onshore.

Work is currently being done on major development projects in order to resolve the problem of transportation of the oil/gas admixture across large distances. Some of these projects aim at supplying pressure to the oil/gas admixture by placing two-phase pumps on the seabed in order to compensate the large pressure drop. Other projects aim at separating the oil and gas on the seabed and then pumping oil and gas in separate pipelines to a processing plant. Oil and gas will thus be supplied with the necessary transportation energy for onwards efficient transport to the receiving terminal. Liquid and gas will be conveyed in separate pipelines, but the liquid and gas pipelines may optionally converge in a multi-phase conduit if that is deemed optimal.

The production from several wells may be collected and conveyed onwards in a common flow. One problem in this connection is the dissimilar well flow pressures which may occur. This may be resolved by conducting the well flows via separate stations where the well flow pressure will be adapted to one common value, whereupon the well flow is gathered in a manifold station for onwards transportation.

Transporting unprocessed well flows across large distances to onshore processing plants represents major potential gains. By placing as much as possible of the heavy, bulky processing plant onshore, designers have greater freedom in respect of an optimal solution because the restrictions in terms of weight and space inherent in permanent, and especially floating platforms, no longer exist.

For the transportation of a well flow across large dist- ances to the shore or to existing processing platforms with spare capacity some distance away, underwater pumping stations may be used. Placing these on the seabed offers many advantages. Compressors and pumps will be surrounded by a cooling medium (the sea water) of approximately constant temperature. The danger of explosion has been eliminated, and the plant will not be affected by wind and waves, nor be covered with ice. Major savings can be obtained on the platform costs, accommodation costs and transport of personnel and equipment to and from the shore.

Underwater pumping stations are, however, at the outset encumbered by a number of disadvantages and problems. Thus, daily simple inspection and maintenance will be precluded. The system and components for controlling and monitoring remote underwater stations are still relatively untried technology. The necessary electrical energy needs to be transferred across large distances, and connecting it to the equipment at the underwater station must be done in a satisfactory manner.

All equipment and components must be of a high standard and be highly reliable. The maintenance must be planned according to certain systems, allowing for replacement of equipment.

For pumping a well flow, an underwater station is known which comprises a separator for separating the well flow into liquid (oil/water) and gas, a pump assembly comprising a pump and a motor, and a compressor unit comprising a compressor motor, as well as fluid carrying conduits between separator and pump and compressor, respectively. The components of the underwater station, i.e. separator, pump assembly, and compressor unit are built as a compact unit with the three components arranged in a columnar structure where the pump unit is at the bottom, followed by the separator, and with the compressor assembly at the top. The fluid carrying conduits are designed to be connected to the bottom of the columnar structure. Advantageously, they are gathered into a common connector unit.

With this type of underwater pumping station it will be possible to pump a well flow from the field to a receiving terminal onshore or on a neighbouring platform. Mounting and dismantling may be done using unmanned diving vessels and/or hoisting devices guided from the surface. Service / maintenance which may take place by replacing entire units, could be performed at desired intervals of at least l to 2 years. Operations inspection and adjustment could be kept at a minimum, and to a large degree it would be possible to manage without monitoring the station during operation.

The known underwater station constitutes a compact unit which contains a simple separator, a pump and a compressor which may be placed on the seabed. The unit splits the hydrocarbon flow from one or more underwater wells into gas and liquid phases. After that, the pressure in the gas and the liquid increases, enabling the production flow to be transported across large distances. Transport from the unit may be done either in a common pipeline or in separate pipelines for oil and gas. The compact unit may be installed by means of a drilling rig or as an example, by a modified diving vessel with a large moon-pool.

The compact design means that long fluid carrying conduits in the station are obviated, which in turn means that it is possible to avoid pressure drops in these conduits. The number of valves and couplings required is thus reduced. Because to a large extent fluid conduit connections in the station are avoided, undesirable effects resulting from so- called slugs, i.e. liquid trains and gas bubbles, will also be avoided. By having the compressor as the topmost unit, self-draining of the gas is achieved. Any liquid forming in the compressor section will run downwards from the compressor or the gas section. The gas will often be at dew point, and consequently, con¬ densation will readily form in the gas carrying sections. The pump unit lying below is self-draining in the same way as the compressor unit which lies above. In the same manner that condensate gas trickles down from the upper compressor unit, any gas in the pump unit below will bubble upwards into the separator.

The underwater station utilises fully its favourable ambient environment, namely the sea water, for cooling of the compressor and pump.

The underwater station is surrounded by a sturdy frame which serves to protect the station from damage in transit and during installation. The compact, vertical embodiment of the station, it may be a case of a station of a height of for example 12 m, could also suitably be placed in a seabed silo. A location in a silo will provide additional good protection, and will be particularly advantageous in arctic waters and on or in the vicinity of fishing grounds.

An offshore hydrocarbon field will very often change its condition over a period of time. In the initial exploita¬ tion the pressure in the underground formations will often be sufficiently high for the well flow to be forced upwards of its own. Gradually the pressure will subside, and it will then be necessary to provide energy to the well flow. This recognition, and recognition of the fact that the underwater station and the use of these will in time represent an ever more favourable and correct technology in the area of offshore hydrocarbon production, form the background to the development of the inventive concept to be defined in further detail below.

The invention takes hold of the said aspect of time, the cost aspect, and the safety and security aspect. The invention thus provides a system which may be extended / complemented according to relevant needs, in step with the field production, while at the same time the safety and security will be greatly increased. Costs will be reduced due to the underwater station being built as required, and the safety and security of the entire plant drastically increased in that the silo technique is utilised.

More precisely, proposed according to the invention is a procedure in the development of a hydrocarbon field off¬ shore, characterised in that embedded into the seabed is an upwardly open silo which is prepared to receive, or which already contains, a separator and/or mechanically rotating equipment requiring cooling, the equipment being placed in the silo in step with the relevant need, the silo being prepared for sequential placement of equipment as stated.

Usually, the initial equipment will be a separator, but the sequence will depend on the need in each case.

With regard to an expected normal progression it would be advantageous to let the separator be part of a separator- cooler-scrubber-module, because the cooler will be necessary in the subsequent positioning of and operation of mechanically rotating equipment (compressor) providing energy to the gases.

An advantageous procedure according to the invention is one where a separator-cooler-scrubber-module is first placed in the silo, and in step with the need in each case additional modules are placed in the silo, e.g. pump, compressor modules etc.

To begin with, in the initial field production phase, it will suffice to have the separator-cooler-scrubber-module, because the well flow pressure will be high enough to provide satisfactory well flow transport without supply of energy, in step with the need, i.e. at subsiding pressure in the hydrocarbon producing formations, the equipment in the silo may be complemented by a pump module and/or a compressor module. In a particularly advantageous manner arrangements are made for prepared interfaces between the separator and the pump, the separator and the compressor, and between the individual fluid conduits and pump as well as compressor. It is this, plus the fact that the silo is dimensioned to receive modules by degrees as they are needed, which is inherent in the expression that the silo is prepared.

In addition to the novel procedure there is proposed according to the invention an underwater station for use in exploiting a hydrocarbon field offshore, comprising a silo embedded into the seabed and characterised in that the silo is intended for successive receipt/placing of equipment in modular form in step with the need for such equipment in each case, and is prepared for placing/receipt as stated.

Such an underwater station may be built up step by step from modular components, so that it is made possible to build an underwater plant in step with the production of the field.

In a field where the well flow has sufficient own pressure, the underwater station in the silo may advantageously contain a separator-cooler-scrubber-module.

Particularly advantageously the said module may be designed so that the cooler (gas cooler) is arranged with continuous drop without substantial low points, towards the scrubber so that condensate released will flow into the scrubber which is arranged above the separator.

Such an embodiment of the separator-cooler-scrubber-module is considered to be of independent inventive significance. Also outside a silo embedded into the seabed constructing this module thus will entail major advantages. The design ensures that condensate released in the cooler will flow into the scrubber. In addition to avoiding gathering of liquid at unwanted points, a possibility will at the same time be obtained of maintaining a low flow rate in the cooler and hence slight pressure drop. This in turn entails that the scrubber may be mounted at comparatively slight extra elevation above the separator which helps provide as compact an installation as possible.

In a particularly advantageous manner the underwater station according to the invention may be provided with or complemented by a pump module. This pump module is arranged below the separator in the silo.

The underwater station according to the invention may also advantageously contain or be complemented in that the silo arranged in connection with the separator-cooler-scrubber- module contains a compressor module arranged above the separator. The underwater station may thus consist of the separator-cooler-scrubber-module with a compressor module attached, or the underwater station may fully developed contain the separator-cooler-scrubber-module arranged in connection with the said pump module below the separator, and a compressor module arranged above the separator.

The construction provides the advantages offered by the known columnar structure, and the silo constitutes an efficient protection of the installation. Also when placed in a silo submerged into the seabed, the sea water may be utilised in cooling the various components. ith suitable measures there may be a possibility of achieving regulation of the sea water temperature round the installation in the silo. Thus, the silo may advantageously have a cover device for closing the top of the silo wholly or partially. This will affect the convector flows which result from the heat exchange. In a way, the silo may be seen as a potential thermos flask, and the thermos effect can for instance advantageously be utilised in a possible inter- ruption of operations, because the silo can be closed off, and thus the amount of heat around the installation be conserved, something which could also be an advantage e.g. in connection with the unwanted formation of hydrates and precipitation of wax. Keeping the temperature as high as possible in the silo can delay/prevent the formation of hydrates and precipitation of wax.

In a practical embodiment the wall of the silo may advantageously be designed with an upper wall band, with openings for water to flow through. This is a case of an upper wall area protruding above the seabed, thus enabling surrounding sea water to flow into the silo. In the said openings suitable particle deflectors may advantageously be arranged in order thereby to prevent mud and such like from entering to an undesired extent. Such particle deflectors may for instance be in the shape of simple elements re¬ sembling Venetian blind slats in the openings.

The cold water may also be let in through the actual top of the silo or opening. The cover arrangement may be utilised/designed to facilitate this, so that the water inlet may be throttled. The cover arrangement can also be designed to throttle the water outlet (the upwards rising heated cooling water) , instead of or in combination with the throttling of the inlet. The upper side openings, if any, can of course also comprise throttling means.

It is naturally important, in addition to preventing mud from being carried into the silo, to ensure that inflowing cold sea water passes efficiently through the silo, i.e. that there is no short-circuiting of the water flow. According to the invention it is therefore proposed that the silo should have an inner cylinder to surround the equipment placed in the silo. The said inner cylinder will be open at the bottom to allow water to flow from the ring shaped space between the inner cylinder and the surrounding silo wall into and upwards in the inner cylinder.

For the purpose of affecting the water flow, the inner cylinder may advantageously have a perforated shell. The openings thus formed are positioned exactly so as to lead the water to the greatest extent possible past those components requiring the most cooling. The water flow may also be affected by an appropriate design of the silo top where according to the invention a perforated protective cover or a grate may advantageously rest.

As a further protective measure against mud entering, a mud trap may advantageously be arranged round the top of the silo. A mud trap as stated may for instance be realised in the form of a surrounding ditch in the seabed.

The cooler of the separator-cooler-scrubber-module may advantageously be of a spiral tube shape and pass round (make room for) compressor modules above the separator.

Any mud penetrating into the silo can be removed by suction points being arranged in the silo and connected to a suction device (pump) , and likewise flushing equipment may advantageously be arranged in the silo with which mud can be stirred up and more readily be able to follow the rising water flow and/or pass out at the suction points.

The invention will now be explained further with reference to the drawings where:

Fig. l shows a schematic section through a silo embedded into the seabed, fig. 2 shows the silo with a separator-cooler-scrubber- module arranged therein, fig. 3 shows the underwater station of fig. 2 supplemented by a pump-module attached to the separator, and fig. 4 shows a complete underwater station where, in addition to the pum -module, a compressor module is attached to provide energy to the gas separated off in the separator.

The silo 1 shown in schematic section in fig. 1 is designed as a cylindrical beaker, with a silo wall 2 and a silo bottom 3. The silo 1 is shown embedded into a seabed 4.

The silo may be embedded into the seabed by means of known technology. Indicated in a broken line in fig. 1 is thus at the bottom a skirt 5. In the silo bottom 3, flow valves 6 are indicated. The positioning of the silo is done in the manner that the silo body, shaped as a cylindrical beaker, is lowered towards the seabed, and the skirt 5 caused to penetrate the seabed. During the lowering, the valves 6 are open, to avoid unwanted air pockets underneath the silo bottom 3. The silo is made to enter the seabed 4 until the position shown in fig. 1. The positioning of the silo may be facilitated by using known technology and known means for instance providing an underpressure underneath the silo bottom 3. Equipment used in this connection may for instance comprise flushing and suction devices etc. well known to someone skilled in the art.

The silo may also be realised in that at the outset it only has the shape of a shell, i.e. with an open bottom. When the shell has been positioned, its contents can be dug out or flushed out, thereby realising a silo of the type shown schematically in fig. l.

Round the silo 1 a mud trap has been realised as shown, in the form of a ditch 7 in the seabed 4, round the upper part of the silo. The silo wall 2 is in this upper wall band provided with openings 8 which make it possible for the sea water to pass through the silo wall there. 9 indicates particle deflectors in the openings. The purpose of these is to prevent that for instance mud particles enter unimpeded into the silo through the openings 8. The particle deflectors 9 are in fig. I indicated in the form of horizontal elements resembling Venetian blind slats.

The silo is at its top fitted with a protective cover 10. This protective cover is perforated or made as a grate 11 across an area corresponding to the cross section of an inner cylinder 12 in the silo 1. The said inner cylinder 12 has perforations in the cylinder shell, indicated by 13. The dimensioning and location of these perforations 13 are determined by the influence it is desired to lend to the flowing water, to obtain the desired cooling of the equip¬ ment in the underwater station which is inside the silo, surrounded by the inner cylinder 13. The inner cylinder 13 extends as is shown only to some distance above the silo bottom 3, allowing for a large opening at the bottom where water may flow from the ring-shaped compartment 14 between the inner cylinder 12 and the surrounding silo wall 2.

The top of the silo has, optionally as an integrated part of the protective cover 10, a schematically shown cover or shut-off device 15 with which complete or partial closure of the silo top may be provided (the grate 11) .

Shown in fig. 2 is purely schematically an underwater station ready to receive a well flow. The underwater station comprises a module 16 placed in the silo 1 and comprising a separator 17, a cooler 18 and a scrubber 19.

The separator 17 is as shown in the form of a container of which the lower part forms a liquid compartment and the upper part forms a gas compartment. From the separator's gas compartment a pipe 20 passes which is at its top, at 21 flanged to the scrubber 19. The pipe 20 is closed at its upper end, but from the scrubber 19, as indicated by the broken line 22, a condensate conduit passes from the scrubber 19 back to the separator 17. From the upper sec¬ tion of the pipe 22, an insulated pipe 23 passes to the top of a cooler 18, in this instance helically winded, of which the lowest point at 24 is connected to the scrubber 19.

From the scrubber 19 a conduit 25 leads to a connector 26.

The said connector 26 advantageously constitutes an inter¬ face between the underwater station and the production flow not shown, respectively the receiving terminals not shown for oil and gas. Thus the connector 26 also comprises a connection to a conduit 27 which passes to the separator

17 , and a conduit 28 coining from the lower part of the separator 17 i.e. its liquid compartment, indicated at 29.

From the well not shown a well flow conduit 30 extends which is carried into the lower part of the silo and linked to the connector 26. Furthermore the connector 26 is attached to a gas export conduit 31 and an oil export conduit 32.

When the underwater station of fig. 2 is in operation, a well flow passes through the well flow conduit 30 to the connector 26 and onwards from there into the separator 17 through the conduit 27. In the separator 17, oil and gas are separated. The oil, or rather the liquid (a mixture of oil and water) passes through the conduit 29, 28 to the connector 26 and onwards through the conduit 32. The gas released in the separator 17 passes through the pipe 20 and onwards through the insulated pipe run 23 and to the cooler

18, through it and to the scrubber 19 from where the gas continues through the conduit 25 to the connector 26 and onwards through the conduit 31. Condensate from the cooler will pass to the scrubber 19 and through the condensate pipe 22 indicated back to the separator.

The separator-cooler-scrubber assembly shown and described is presumed as stated above to have independent inventive significance, i.e. irrespective of its position in the silo. The main idea behind the special unit is the vertical arrangement of the scrubber above the separator and the gas cooler between separator and scrubber, the gas cooler being arranged as a cooler where the inlet is the highest point and the outlet is connected to the scrubber as the cooler's lowest point. This means that all the way the gas cooler slopes downwards, i.e. it has no low point of any significance, as shown by the pipe spiral indicated. This will ensure that condensate flows continuously out of the cooler into the scrubber, and from there to the separator. In this way, build-up of liquid plugs is avoided, with pulsating build-up of pressure and sudden influx to the scrubber, and smooth operation of the cooler is achieved at slight pressure drop.

As will be understood, the cooler 18 has heat exchange with the surrounding sea water. The inner cylinder 12 which surrounds the separator module 16, causes a favourable water flow as the sea water will enter through the openings 8 in the upper silo wall band, and down into the ring shaped compartment 14, and then upwards through the inner cylinder 12 and out through the grate 11 at the top of the silo 1. Through the perforations or openings 13 it is possible in an advantageous manner to affect the water flow so that it may be caused to flow advantageously past precisely that component which needs cooling, i.e. the cooler 18. The perforations or openings 13 may be adjusted by using means not shown, or may optionally be omitted, always depending on conditions.

The water flow/temperature may also be influenced by means of the cover arrangement 15 with which the grate area of the grate 11 may be adjusted.

Fig. 3 shows the underwater station complemented by a pumping module 33 of which the pum part is connected to the liquid compartment of the separator 17, the pump outlet being connected to the conduit 28. The pumping module is shown in a horizontal position, but it is naturally also possible to use a pumping module with vertical orientation i.e. with the motor section 34 of the pumping module arranged vertically below the pump part 35 of the module, the essential point being that the pumping part is arranged as shown below the separator.

The installation shown in fig. 3 works in the same manner as described in connection with fig. l. In addition there is only the fact that the pump part 33 provides energy to the oil flow through the conduit 32. The pump module 33 obtains its requisite cooling from the sea water in the silo.

In fig. 4 the underwater station according to the invention is shown complemented by a compressor module 36. The compressor part is defined as 37 and the motor part is defined as 38. The inlet of the compressor part 37 is, in a manner not shown in greater detail, connected to the outlet 25' of the scrubber 19, and the outlet from the compressor part 37 is connected to the conduit 25" which passes to the connector 26 and is thereby attached to the gas conduit 31.

The installation of fig. 4 works in the same manner as described above in connection with fig.s 2 and 3, the compressor now in addition providing energy to the gas. The compressor module is cooled in the same manner as the pumping module by the sea water in the silo. The underwater station may also be envisaged complemented by just a compressor module, the pumping module thus then being omitted, there being no need for it.

It is mentioned above that the silo 1 is embedded into the seabed 4. This is, however, only the preferred version. It ought to be clear that the silo may also rest on the seabed, since it will then naturally also offer the requisite protection for the equipment, and the desired cooling of the components in the silo will then also be achieved. Placing the silo on the seabed does, however, require that a frame or such like be built round the silo so that ice, fishing tackle and other objects in the sea will be guided/lead away from the silo. Such frames are known from the common bottom frames.

The requisite electrical cables etc. for operating the pump and compressor as well as monitoring equipment, are not shown. In the same way as the connector 26 forms the interface to fluid carrying conduits, the underwater station may have one or several suitable connectors for simple and efficient attachment of signal and power lines.

Throttling of the water into and out of the silo may be arranged for by simple means, not just in connection with the upper side openings shown, but also in connection with water outlet in the actual silo top and down into the ring shaped compartment. As stated, the silo may have suction and flushing devices for controlling mud conditions. These devices are not shown. They may for instance be realised as suction openings in the silo wall, connected to a separate pump, respectively as flushing nozzles through which water jets may be directed which may cause any mud to be stirred up.

Claims

P e n C l a i m s

1.

A procedure in developing a hydrocarbon field offshore where in step with the need in each case in connection with transporting a well flow a supply is made to the well flow of separation and/or energy, c h a r a c t e r i s e d i n that into the seabed as is known per se, is embedded an upwardly open silo, that the silo is prepared to receive a separator module and/or energy providing modules for supplying energy to the well flow, and that the separator module and/or the energy providing modules are placed in the positioned silo in step with the needs i each case for separation of and/or supply of energy to the well flow.

2.

A procedure according to claim l, c h a r a c t e r i s e d i n that placed initially into the silo is a separator module comprising a separator, a gas cooler and a scrubber, and that subsequently, in step with the need in each case, a pump and/or a compressor module is placed in the silo.

3.

An underwater station for use in exploiting a hydrocarbon field offshore, comprising a silo (l) embedded into the seabed and containing wellflow-flow equipment, c h a r a c¬ t e r i s e d i n that the silo (1) is prepared for successive receipt/placing of a separator module (16) and/or energy providing modules (33;36) for supplying energy to the well flow in step with the need in each case for separation and/or supply of energy to the well flow.

4.

An underwater station according to claim 3, c h a r a c¬ t e r i s e d i n that the silo (1) as separator module (16) contains a module including a separator (17), a gas cooler (18) and a scrubber (19) .

5. An underwater station according to .claim 4, c h a r a c¬ t e r i s e d i n that the said modular cooler (gas cooler) (18) is arranged with a natural drop all the way towards the scrubber (19) so that precipitated condensate will flow into the scrubber, and that the scrubber (19) is arranged above the separator (17).

6.

An underwater station according to claim 4 or 5, c h a r¬ a c t e r i s e d i n that the silo (l) as an attachment to the separator-cooler-scrubber-module (16) contains a pump-module (33) arranged below the separator (17).

7.

.An underwater station according to claim 4,5 or 6, c h a r a c t e r i s e d i n that the silo (1) as an attachment to the separator-cooler-scrubber-module (16) contains a compressor-module (36) .

8. An underwater station according to one of the preceding claims 3-7, c h a r a c t e r i s e d i n that the silo (1) has a cover device (15) for complete or partial shut- off of the silo top (11) .

9.

An underwater station according to one of the preceding claims 3-8, c h a r a c t e r i s e d i n that at the silo wall (2) an upper wall band is arranged with openings (8) for water to flow through.

10.

An underwater station according to claim 9, c h a r a c- t e r i s e d i n that in the openings (8) particle deflectors (9) are arranged

11. An underwater station according to one of the claims 3-10, c h a r a c t e r i s e d i n that the silo (1) has an inner cylinder (12) which surrounds the equipment placed in the silo and is open at the bottom allowing water to flow from the ring shaped compartment (14) between the inner cylinder (12) and the silo wall (2) and into and up into the inner cylinder (12) .

12.

An underwater station according to claim 11, c h a r a c- t e r i s e d i n that the inner cylinder (12) has per^¬ forations (13) in its shell.

13.

An underwater station according to one of the claims 3-12, c h a r a c t e r i s e d i n a perforated protective cover (grate) (11) across the silo top.

14.

An underwater station according to one of the claims 3-13, c h a r a c t e r i s e d i n a mud trap (7) round the top of the silo.

15.

An underwater station according to claims 4,5,6 and 7, c h a r a c t e r i s e d i n that the cooler (18) in the separator-cooler-scrubber-module (16) is of spiral tube shape and passes round (makes room for) the compressor module (36) above the separator (17) in the separator- cooler-scrubber-module (16) .

16.

An underwater station according to one of the claims 3-15, c h a r a c t e r i s e d i n that arranged in the silo are preferably evenly distributed suction points connected to a pump.

17.

An underwater station according to one of the claims 3-16, c h a r a c t e r i s e d i n that arranged in the silo is flushing equipment for stirring up mud.

True translation certified:

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