CA1064334A - Floating island for extracting or processing gas - Google Patents
Floating island for extracting or processing gasInfo
- Publication number
- CA1064334A CA1064334A CA270,129A CA270129A CA1064334A CA 1064334 A CA1064334 A CA 1064334A CA 270129 A CA270129 A CA 270129A CA 1064334 A CA1064334 A CA 1064334A
- Authority
- CA
- Canada
- Prior art keywords
- floating island
- base plate
- tension
- columns
- legged
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000007667 floating Methods 0.000 title claims abstract description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000000605 extraction Methods 0.000 claims abstract description 7
- 238000003860 storage Methods 0.000 claims description 9
- 239000013535 sea water Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- 230000005484 gravity Effects 0.000 claims 1
- 239000011810 insulating material Substances 0.000 claims 1
- 239000003381 stabilizer Substances 0.000 claims 1
- 239000007789 gas Substances 0.000 description 29
- 238000009434 installation Methods 0.000 description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 239000004567 concrete Substances 0.000 description 3
- 238000005553 drilling Methods 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000004873 anchoring Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 238000012432 intermediate storage Methods 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 241000271566 Aves Species 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000011513 prestressed concrete Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
- B63B35/4413—Floating drilling platforms, e.g. carrying water-oil separating devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/12—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly
- B63B2001/128—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly comprising underwater connectors between the hulls
Landscapes
- Engineering & Computer Science (AREA)
- Ocean & Marine Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
- Revetment (AREA)
- Extraction Or Liquid Replacement (AREA)
- Loading And Unloading Of Fuel Tanks Or Ships (AREA)
Abstract
Abstract The specification describes a floating island for the extraction or processing of gas. The island is characterized in that a plurality of submerged buoyancy units are provided which are arranged in a single plane on a base plate from which columns extend to above the water surface in accordance with expected wave heights. Supported on the upper end of the columns is a platform on which is situated an apparatus for the liquification of gas. The buoyancy of the buoyancy units is made such that when the island is floating freely, more than half of the columns project above the water surface.
Preferably the buoyancy units are also partially exposed.
Provided on the base plate are tension elements by means of which the island can be submerged such that half of the columns lie below the water surface. The tension elements include anchors arranged on the sea bed.
Preferably the buoyancy units are also partially exposed.
Provided on the base plate are tension elements by means of which the island can be submerged such that half of the columns lie below the water surface. The tension elements include anchors arranged on the sea bed.
Description
PRETJSSAG Aktiengesellschaft 420/41 Floating island for extracting or processing gae.
The invention relates to a floating island for extracting or processing gas.
From the publication "Floating Offshore LNG Lique~action Facility - A Cost Effective Alternative", author M.C. Terry, of - the Global Marine Development Inc. 9 published on the occasion . , .
of the Seventh Annual OffshQre Technology Conference in Hou~ton, Texas on 5th-8th May 1975, it is known for gas extracted in regions near the coast to be transported to the coast by way of a plpeline laid on the bottom of the sea, liquefied on ~hore in a stationary installation, and for the liqefied gas to be t~en shipped away in tankers. The outlay involved in transporting the as yet non-liquefied ~3 -~ gas is considerable. The pipeline and the liquefaction in6tallation are fixed in one place, so that such an insta~lation i6 worth while only when large deposits of natura~ gas are ava1lable, preferably ~ near the coast. This known installation is not suitable for using : 1 ;; natural gas deposits of low yield.
i The aforesaid publication describes a proposal according to which i a liquefaction installation is installed on a ship which, for safety reasons, is anchored not immediately over the gas field but always in the immediate vicinity thereof. The gas passes by way of a pipeline laid on the 6ea bed to the ship and is liquefied there. The ship l is of limited storage capacity, so that the intermediate storage tanks `! - 2 ~
,','' . . `~
, . .
in the ship have to be emptied correspondingly often by mean~
of relatively small tankers . An important disadvantage of this proposal is that the shi~ carries out movements because of the motion of the waves which are highly disadvantageous to the liquefaction plant. The standards required as regards steadiness in a liq~efaction plant are so high that use of this proposa] seems possible only if great disadvantages are accepted. In addition, owing to the movements o$ the ship there are also difficulties .
in the transfer of the l~efied gas to a tanker.
l The invention has as its object to provide a floating island :i for extrac~ing or processing gas which allows exploitation of relatively small gas deposits with little financial outlay, allows liquefaction and/or further processing of the gas, and permits ` adequate interim storage facilities.
:
The object of the invention is achieved in a floating island submerged in that a plurality of/buoyancy units are provided which are arranged in a single plane on a base plate, and from which columns extend to above the water surface in accordance with the wave height expected, said columns carrying on their upper ends a platform on which is situated an apparatus for the liquefac-tion of gas, that the buoyanc~ of the buoyancy unit 8 i8 BO
dimensioned that when the island is floating freely the columns project more than half way,and preferably the buoyancy units partly ~lso, above the water surface, and that there are situated on the base p~ate ties or tension elements by means of which the island can be submerged to about half way up the columns by means of j arranged ; anchors~on the sea bed.
The solution provided by the invention has the advantage ~ .
~ of extremely good floating stability, so that it i8 possible to j situate a gas liquefaction plant on the platform of the floating . island. The fl~oating steadine6s is so great that even in bad - weather and when a reDatively high sea is running it is not necessary to interrupt gas liqnefactiQn operations. The influence _ ~ _ of waves is greatly reduced by sub~lerr;ing the buoyancy unit.s completel~, an~,as ~aves pass, the colu~ns projecting through the surface of the water have the effect that there is only a slight buoyanc~ modification, which is taken up by the tensioned anchoring means.
From the periodical "Of~shore", l~ovember 1~7~, page 100, it is in fact already generally known to anchor floating bodies on the bottom of the sea under tension. ~ul: the floating bodies : project through the water surface with their entire cross-section, so that tihe passage of waves exerts a fairly considerable inf~uence, and there is little adaptation to different loads. The island, which is referred to as a~"Traction leg platform"~ i8 accordingly only intended and suited for drilling purposes.
From an article "Cable stayed submerged buoyant drilling/
production structures", pubI~ished in a "Paper 5" at the Technology Offshore ~North Sea) Conference on 30/31st July 1974, a traction leg platform is known which is intended for extracting and processing oil, and has several tanks which are intended.for buoyancy and storage purposes, and together form an integral unit ? which is held in the submerged state by obliquely tensioned cables, and from which columns extend above the water surface to a platform.
he use of tanks both for filling with ballast water and also . with oil presents no difficulties. Such principles of buoyancy 1 equalisation cannot be used in the case of rigs for extracting and processing gas since the storage chambers for liquefied gas ~ 1 .
I cannot be filled with sea water. In a constructional example :~
.
in the aforesaid article an additional buoyancy chamber is in :
fact provided, but this is indicated only schematically, 80 that information for practical construction cannot be deduced therefrom. It can be ascertained re~iably th~t the buoyancy ~ ' . ~ . . - . - ~ , . . . .
~o64334 chamber i5 situated above the tanks. If it were ~illed with watcr as indicated in the article to compensate for the buoyancy e.g. of empty of empty storage tan~s, the buoyancy stab;Dity would suffer amollgst other things, and in the event of using the tanks for storing liquefied gas such a chamber cou~d not be used.
~;; A further disadvantage of this known proposal i8 that the considerable forces of the excess buoyancy are taken up solely by obliquely tensioned cables. As result, the forces on the cables are greater than the buoyancy forces, 80 that the outlay for the traction legs is increased. In addition the increased 1 quantity of or the Iarger cross-section of the tension cables ~
results in the influence of water movements being increased e.g.
-~ oce~n currents or waves, so that as a resu~t the floating steadiness -~ of the complete island is reduced. Therefore, there would be considerabl~ difficulties as regards the procedsing of liquefied steady ~as, where extremely ~f~oating is necessary.
~Conveniently the buoyancy units and preferabIy the columns - -and the base p~ate also are made of concrete. Therefore they i~ are very resistant to the action of ~ea water. The concrete , ,~
-``! buoyancy units can also be used in an advantageous manner for j the storing of liquefied gas, for which purpose they are insulated at their internal wails by preferab~y PVC foam.
According to a further feature of the invention, the base pDate comprises ballast chambers for sea water. ~hese chambers can be givsn such a size that the buoyancy of the buoyancy units which are used for storage of Diquefied gas is reduced in the desired manner to make only the columns project through the water ~` surface in the region where there is wave motion. Therefore it is not necessary, as it i6 with known floating islands for the ~ .
.',1 `, i:
~ .-.~ ' ' . . , 106433~
extraction of petrolellm, to fill with sea water the tanks which have been used to store petroleum, when these are emptied, and this would not be possible ~ith I!iquefied ga8.
According to a further feature, the tension elements are taken from the base plate preferably through the buoyancy units and the columns above the water l~ne more particullarly to tensioning devices.
In this way the depth to which the isliand is submerged iB adjustable.
The tension ell~ments may all be of the same construction~ but it is convenient to construct at least one of them as a centrally arranged tube anchored securely in the sea bottom, giving access through this tube from the platform to the sea bottom. This tube can accept a substantial part of the tensiIe forces .
According to a further feature of the invention a transfer apparatus for transferring liquefied gas to a tanker is provided on the platform. This transfer apparatus enjoys the advantage that the ~ -is~and proposed by the present invention lies particurarly safel~
and steadily in the water.
Using the underlying principlle of the present invention, the i61and carries out substantially no re~ative movements with respect to the bottom of the sea, thus affordin~ advantages as regards the connection between the gas source and the isDand. But,in add;tion, there i8 less risk of col~ision between the islland and a moored tanker. This risk occurs more particularly when the tidal current changes round. In order to make it possible to follow the direction of the tide or the wind, it is advantageous to arrange the transfer apparatus and the mooring ~ne for a tanker on a carriage which is -capable of moving round about the circuDar pllatform. In this way ~7i transfer apparatus and moor~ng line can follow the direction of . , ~
the current al'ways. In addition the moored tanker can keep its distance also by running its engines in reverse.
-The invention will be discussed in detail with the use of a constructional example with the help of the drawings.
Fig. 1 shows in diagrammatic manner a side view of one constructional form of the island according to the invention, parts being shown in section, Fig. 2 shows a section on II-II through Fig. 1, Fig. 3 shows a plan view in the direction of an arrow III
in Fig. 1 The island shown in side view in Fig. 1 comprises substantially five buoyancy units 1 which are arranged on a base plate 2 and from which columns 3 extend upwards, these supporting on their upper ends 4 a platform 5. On the platform 5 there is situated an apparatus 6 for liquefaction of gas and also the necessary energy supply and operating installations.
Arranged on the outer edge-of the base plate 2 are vertical tension elements 7 and obliquely downwardly extending tension elements 8 and 9 which are secured to piles 10 arranged securely in -, the sea bed. The vertical tension elements 7 consist of steel chains or cables, whilst the oblique tension elements 8 and 9 consist of hawsers made of plastics material. The oblique tension elements 9 are secured to a base plate II held by anchoring tubes.
;. From the base plate 11 high pressure gas conduits 13 extend to the base plate 2, from which the gas passes by way of conduits not shown here to the installation 6 on the platform.
The platform comprises in the bottom region a plurality of ' closed chambers 14, ensuring that the platform is still capable of floating even if the bottom is damaged, more particularly by the i upper ends 4 of the columns 3, in emergency cases.
The buoyancy units 1 and the base plate 2 and the columns 3 are made of concrete. One of the buoyancy units 1 is shown in section.
:: .
" - 7 -. - . .: . - : : :
: , .
_ is hollow and has walls of prestressed concrete which are insulated internally by an insulating layer 15 of PVC foam.
The chambers 16 thus formed in the buoyancy units 1 can thus be used for the storage of liquefied gas, which has a temperature of -162C at atmospheric pressure. For emptying the chambers 16 there is provided a pump 17 and a conduit 18 leading upwards through the columns 3. The conduit 18 leads by way of a column 19 and a beam 20 to a transfer apparatus 21 by means of which the liquefied gas can be onloaded on to a tanker 22. 23 designates the surface of the water.
The mooring line 24 is situated on a carriage 25 which also -supports the transfer apparatus 21 and which can travel round about the round platform 5.
Fig. 2 shows the view in section on II-II throllgh Fig. 1, and illustrates clearly that the buoyancy units 1 are arranged in a regular pentagon on the platform 5. A through passage 26 is pro-vided centrally, eg to allow drilling.
Fig. 3 shows a view in the direction of an arrow III in Fig. 1.
It illustrates the round shape of the platform 5,-which makes it possible for the carriage 25 to travel round the platform 5, in order thus to align the location of the carriage and thus of the mooring line 24 and transfer apparatus 21 towards the tanker 22 which is lined up with the current.
. . .
The vertical tension elements 7 accept the greatest part of the tensile forces which hold the island such in the semi-submerged ' state that the columns 3 corresponds substantially to the greatest -r wave aplitude value expected. The buoyancy of the buoyancy units 1 is so great that under all operating conditions the tension elements 7,8 and 9 remain tensioned. In this way not only is the island held securely against lateral shifting, but the island is also secured ~ .
~ - ~ , . . ~ .......................... .. .. .. .
.. . . . - . , .. - .. . . -against tilting, leaning and rolling movements additionally to the inherent stability of the island itself. The steady floating ability of the island is so great that the apparatus 6 provided fo- gas liquefaction can operate continuously even in a relatively heavy sea and in storms.
Since liquid gas can be loaded direct from the island on to a tanker, there is no need to provide additional pipelines, more especially on the sea bed. No intermediate storage tanks are needed either. Therefore, the island according to the invention can be moved to another location after one natural gas field with relatively low yield is exhausted, without any difficulty, and anchored again on the new site.
Preferably the base plate 2 comprises ballast chambers for sea water. At least one of the tension elements may be a .: .
centrally arranged tube which is to be achored fast in the sea bed and through which access is possible from the platform 5 to the sea bed. It is advantageous to cement-in the piles 10 into the sea bed. If the island is used also for extraction :.
of gas through a bore hole one of the anchors is a bed plate 11.
'~ The platform 5 is preferably made of steel and may rest freely on the columns 3.
~ Although various embodiments of the invention have been - described herein in detail, it will be apparent to those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended ~:
;
~- claims.
~",~ . .
: ~ .
,;j, ~ .
-. ~
, ~', ~ _ g _ - , , ~
The invention relates to a floating island for extracting or processing gas.
From the publication "Floating Offshore LNG Lique~action Facility - A Cost Effective Alternative", author M.C. Terry, of - the Global Marine Development Inc. 9 published on the occasion . , .
of the Seventh Annual OffshQre Technology Conference in Hou~ton, Texas on 5th-8th May 1975, it is known for gas extracted in regions near the coast to be transported to the coast by way of a plpeline laid on the bottom of the sea, liquefied on ~hore in a stationary installation, and for the liqefied gas to be t~en shipped away in tankers. The outlay involved in transporting the as yet non-liquefied ~3 -~ gas is considerable. The pipeline and the liquefaction in6tallation are fixed in one place, so that such an insta~lation i6 worth while only when large deposits of natura~ gas are ava1lable, preferably ~ near the coast. This known installation is not suitable for using : 1 ;; natural gas deposits of low yield.
i The aforesaid publication describes a proposal according to which i a liquefaction installation is installed on a ship which, for safety reasons, is anchored not immediately over the gas field but always in the immediate vicinity thereof. The gas passes by way of a pipeline laid on the 6ea bed to the ship and is liquefied there. The ship l is of limited storage capacity, so that the intermediate storage tanks `! - 2 ~
,','' . . `~
, . .
in the ship have to be emptied correspondingly often by mean~
of relatively small tankers . An important disadvantage of this proposal is that the shi~ carries out movements because of the motion of the waves which are highly disadvantageous to the liquefaction plant. The standards required as regards steadiness in a liq~efaction plant are so high that use of this proposa] seems possible only if great disadvantages are accepted. In addition, owing to the movements o$ the ship there are also difficulties .
in the transfer of the l~efied gas to a tanker.
l The invention has as its object to provide a floating island :i for extrac~ing or processing gas which allows exploitation of relatively small gas deposits with little financial outlay, allows liquefaction and/or further processing of the gas, and permits ` adequate interim storage facilities.
:
The object of the invention is achieved in a floating island submerged in that a plurality of/buoyancy units are provided which are arranged in a single plane on a base plate, and from which columns extend to above the water surface in accordance with the wave height expected, said columns carrying on their upper ends a platform on which is situated an apparatus for the liquefac-tion of gas, that the buoyanc~ of the buoyancy unit 8 i8 BO
dimensioned that when the island is floating freely the columns project more than half way,and preferably the buoyancy units partly ~lso, above the water surface, and that there are situated on the base p~ate ties or tension elements by means of which the island can be submerged to about half way up the columns by means of j arranged ; anchors~on the sea bed.
The solution provided by the invention has the advantage ~ .
~ of extremely good floating stability, so that it i8 possible to j situate a gas liquefaction plant on the platform of the floating . island. The fl~oating steadine6s is so great that even in bad - weather and when a reDatively high sea is running it is not necessary to interrupt gas liqnefactiQn operations. The influence _ ~ _ of waves is greatly reduced by sub~lerr;ing the buoyancy unit.s completel~, an~,as ~aves pass, the colu~ns projecting through the surface of the water have the effect that there is only a slight buoyanc~ modification, which is taken up by the tensioned anchoring means.
From the periodical "Of~shore", l~ovember 1~7~, page 100, it is in fact already generally known to anchor floating bodies on the bottom of the sea under tension. ~ul: the floating bodies : project through the water surface with their entire cross-section, so that tihe passage of waves exerts a fairly considerable inf~uence, and there is little adaptation to different loads. The island, which is referred to as a~"Traction leg platform"~ i8 accordingly only intended and suited for drilling purposes.
From an article "Cable stayed submerged buoyant drilling/
production structures", pubI~ished in a "Paper 5" at the Technology Offshore ~North Sea) Conference on 30/31st July 1974, a traction leg platform is known which is intended for extracting and processing oil, and has several tanks which are intended.for buoyancy and storage purposes, and together form an integral unit ? which is held in the submerged state by obliquely tensioned cables, and from which columns extend above the water surface to a platform.
he use of tanks both for filling with ballast water and also . with oil presents no difficulties. Such principles of buoyancy 1 equalisation cannot be used in the case of rigs for extracting and processing gas since the storage chambers for liquefied gas ~ 1 .
I cannot be filled with sea water. In a constructional example :~
.
in the aforesaid article an additional buoyancy chamber is in :
fact provided, but this is indicated only schematically, 80 that information for practical construction cannot be deduced therefrom. It can be ascertained re~iably th~t the buoyancy ~ ' . ~ . . - . - ~ , . . . .
~o64334 chamber i5 situated above the tanks. If it were ~illed with watcr as indicated in the article to compensate for the buoyancy e.g. of empty of empty storage tan~s, the buoyancy stab;Dity would suffer amollgst other things, and in the event of using the tanks for storing liquefied gas such a chamber cou~d not be used.
~;; A further disadvantage of this known proposal i8 that the considerable forces of the excess buoyancy are taken up solely by obliquely tensioned cables. As result, the forces on the cables are greater than the buoyancy forces, 80 that the outlay for the traction legs is increased. In addition the increased 1 quantity of or the Iarger cross-section of the tension cables ~
results in the influence of water movements being increased e.g.
-~ oce~n currents or waves, so that as a resu~t the floating steadiness -~ of the complete island is reduced. Therefore, there would be considerabl~ difficulties as regards the procedsing of liquefied steady ~as, where extremely ~f~oating is necessary.
~Conveniently the buoyancy units and preferabIy the columns - -and the base p~ate also are made of concrete. Therefore they i~ are very resistant to the action of ~ea water. The concrete , ,~
-``! buoyancy units can also be used in an advantageous manner for j the storing of liquefied gas, for which purpose they are insulated at their internal wails by preferab~y PVC foam.
According to a further feature of the invention, the base pDate comprises ballast chambers for sea water. ~hese chambers can be givsn such a size that the buoyancy of the buoyancy units which are used for storage of Diquefied gas is reduced in the desired manner to make only the columns project through the water ~` surface in the region where there is wave motion. Therefore it is not necessary, as it i6 with known floating islands for the ~ .
.',1 `, i:
~ .-.~ ' ' . . , 106433~
extraction of petrolellm, to fill with sea water the tanks which have been used to store petroleum, when these are emptied, and this would not be possible ~ith I!iquefied ga8.
According to a further feature, the tension elements are taken from the base plate preferably through the buoyancy units and the columns above the water l~ne more particullarly to tensioning devices.
In this way the depth to which the isliand is submerged iB adjustable.
The tension ell~ments may all be of the same construction~ but it is convenient to construct at least one of them as a centrally arranged tube anchored securely in the sea bottom, giving access through this tube from the platform to the sea bottom. This tube can accept a substantial part of the tensiIe forces .
According to a further feature of the invention a transfer apparatus for transferring liquefied gas to a tanker is provided on the platform. This transfer apparatus enjoys the advantage that the ~ -is~and proposed by the present invention lies particurarly safel~
and steadily in the water.
Using the underlying principlle of the present invention, the i61and carries out substantially no re~ative movements with respect to the bottom of the sea, thus affordin~ advantages as regards the connection between the gas source and the isDand. But,in add;tion, there i8 less risk of col~ision between the islland and a moored tanker. This risk occurs more particularly when the tidal current changes round. In order to make it possible to follow the direction of the tide or the wind, it is advantageous to arrange the transfer apparatus and the mooring ~ne for a tanker on a carriage which is -capable of moving round about the circuDar pllatform. In this way ~7i transfer apparatus and moor~ng line can follow the direction of . , ~
the current al'ways. In addition the moored tanker can keep its distance also by running its engines in reverse.
-The invention will be discussed in detail with the use of a constructional example with the help of the drawings.
Fig. 1 shows in diagrammatic manner a side view of one constructional form of the island according to the invention, parts being shown in section, Fig. 2 shows a section on II-II through Fig. 1, Fig. 3 shows a plan view in the direction of an arrow III
in Fig. 1 The island shown in side view in Fig. 1 comprises substantially five buoyancy units 1 which are arranged on a base plate 2 and from which columns 3 extend upwards, these supporting on their upper ends 4 a platform 5. On the platform 5 there is situated an apparatus 6 for liquefaction of gas and also the necessary energy supply and operating installations.
Arranged on the outer edge-of the base plate 2 are vertical tension elements 7 and obliquely downwardly extending tension elements 8 and 9 which are secured to piles 10 arranged securely in -, the sea bed. The vertical tension elements 7 consist of steel chains or cables, whilst the oblique tension elements 8 and 9 consist of hawsers made of plastics material. The oblique tension elements 9 are secured to a base plate II held by anchoring tubes.
;. From the base plate 11 high pressure gas conduits 13 extend to the base plate 2, from which the gas passes by way of conduits not shown here to the installation 6 on the platform.
The platform comprises in the bottom region a plurality of ' closed chambers 14, ensuring that the platform is still capable of floating even if the bottom is damaged, more particularly by the i upper ends 4 of the columns 3, in emergency cases.
The buoyancy units 1 and the base plate 2 and the columns 3 are made of concrete. One of the buoyancy units 1 is shown in section.
:: .
" - 7 -. - . .: . - : : :
: , .
_ is hollow and has walls of prestressed concrete which are insulated internally by an insulating layer 15 of PVC foam.
The chambers 16 thus formed in the buoyancy units 1 can thus be used for the storage of liquefied gas, which has a temperature of -162C at atmospheric pressure. For emptying the chambers 16 there is provided a pump 17 and a conduit 18 leading upwards through the columns 3. The conduit 18 leads by way of a column 19 and a beam 20 to a transfer apparatus 21 by means of which the liquefied gas can be onloaded on to a tanker 22. 23 designates the surface of the water.
The mooring line 24 is situated on a carriage 25 which also -supports the transfer apparatus 21 and which can travel round about the round platform 5.
Fig. 2 shows the view in section on II-II throllgh Fig. 1, and illustrates clearly that the buoyancy units 1 are arranged in a regular pentagon on the platform 5. A through passage 26 is pro-vided centrally, eg to allow drilling.
Fig. 3 shows a view in the direction of an arrow III in Fig. 1.
It illustrates the round shape of the platform 5,-which makes it possible for the carriage 25 to travel round the platform 5, in order thus to align the location of the carriage and thus of the mooring line 24 and transfer apparatus 21 towards the tanker 22 which is lined up with the current.
. . .
The vertical tension elements 7 accept the greatest part of the tensile forces which hold the island such in the semi-submerged ' state that the columns 3 corresponds substantially to the greatest -r wave aplitude value expected. The buoyancy of the buoyancy units 1 is so great that under all operating conditions the tension elements 7,8 and 9 remain tensioned. In this way not only is the island held securely against lateral shifting, but the island is also secured ~ .
~ - ~ , . . ~ .......................... .. .. .. .
.. . . . - . , .. - .. . . -against tilting, leaning and rolling movements additionally to the inherent stability of the island itself. The steady floating ability of the island is so great that the apparatus 6 provided fo- gas liquefaction can operate continuously even in a relatively heavy sea and in storms.
Since liquid gas can be loaded direct from the island on to a tanker, there is no need to provide additional pipelines, more especially on the sea bed. No intermediate storage tanks are needed either. Therefore, the island according to the invention can be moved to another location after one natural gas field with relatively low yield is exhausted, without any difficulty, and anchored again on the new site.
Preferably the base plate 2 comprises ballast chambers for sea water. At least one of the tension elements may be a .: .
centrally arranged tube which is to be achored fast in the sea bed and through which access is possible from the platform 5 to the sea bed. It is advantageous to cement-in the piles 10 into the sea bed. If the island is used also for extraction :.
of gas through a bore hole one of the anchors is a bed plate 11.
'~ The platform 5 is preferably made of steel and may rest freely on the columns 3.
~ Although various embodiments of the invention have been - described herein in detail, it will be apparent to those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended ~:
;
~- claims.
~",~ . .
: ~ .
,;j, ~ .
-. ~
, ~', ~ _ g _ - , , ~
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A readily movable and securable floating island for a gas extraction and liquefaction system of the type providing a liquefied gas product comprising, in combination:
a submerged base plate having at least one ballast chamber wherein sea water is storable;
a tension-legged mooring system for releasable and adjustably securing said submerged base plate to the sea bed whereby said floating island is readily moved between production sites and readily secured for operation;
a plurality of substantially hollow buoyancy chambers secured to said submerged base plate and defining submerged storage means for storing said liquefied gas product, said submerged base plate and said substantially hollow buoyancy chambers providing a buoyant force to counteract the weight of said gas extraction and liquefaction system and to maintain said tension-legged mooring system in a substantially tensioned state;
said submerged base plate, said tension-legged mooring system and said substantially hollow buoyancy chambers coopera-tively defining stabilizer means for substantially avoiding movement of said floating island during operation of said gas extraction and liquefaction system;
a series of columns extending upwardly from said substantially hollow buoyancy chambers, respectively, said tension-legged mooring system being adjusted to maintain said floating island in a position wherein said columns project substantially half way above the water surface; and a platform for supporting said gas extraction and liquefaction system, said platform being secured to and supported by said columns.
a submerged base plate having at least one ballast chamber wherein sea water is storable;
a tension-legged mooring system for releasable and adjustably securing said submerged base plate to the sea bed whereby said floating island is readily moved between production sites and readily secured for operation;
a plurality of substantially hollow buoyancy chambers secured to said submerged base plate and defining submerged storage means for storing said liquefied gas product, said submerged base plate and said substantially hollow buoyancy chambers providing a buoyant force to counteract the weight of said gas extraction and liquefaction system and to maintain said tension-legged mooring system in a substantially tensioned state;
said submerged base plate, said tension-legged mooring system and said substantially hollow buoyancy chambers coopera-tively defining stabilizer means for substantially avoiding movement of said floating island during operation of said gas extraction and liquefaction system;
a series of columns extending upwardly from said substantially hollow buoyancy chambers, respectively, said tension-legged mooring system being adjusted to maintain said floating island in a position wherein said columns project substantially half way above the water surface; and a platform for supporting said gas extraction and liquefaction system, said platform being secured to and supported by said columns.
2. A floating island according to claim 1 wherein said base plate has an outer edge, said tension-legged mooring system further including a plurality of tension elements attached between said outer edges and the sea bed, whereby the stability of said readily movable and securable floating island is enhanced.
3. A floating island according to claim 2 wherein said tension elements are secured between said base plate and the sea bed in a substantially vertical orientation and in an oblique orientation, whereby said readily movable and securable floating island is held in a predetermined horizontal position.
4. A floating island according to claim 3 wherein said obliquely oriented tension elements are manufactured from a material having a specific gravity of about 1.
5. A floating island according to claim 1 wherein said tension-legged mooring system includes a centrally positioned tube defining access means for reaching the sea bed from said readily movable and securable floating island.
6. A floating island according to claim 1 which includes a transfer means on said platform for transferring said liquefied gas product from said buoyancy chamber to a vessel adjacent said readily movable and securable floating island.
7. A floating island according to claim 1 wherein said buoyancy chambers are lined with heat insulating material, whereby storage of said liquefied gas product is facilitated.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2602747A DE2602747C3 (en) | 1976-01-26 | 1976-01-26 | Floating production platform |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064334A true CA1064334A (en) | 1979-10-16 |
Family
ID=5968250
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA270,129A Expired CA1064334A (en) | 1976-01-26 | 1977-01-20 | Floating island for extracting or processing gas |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5291705A (en) |
| CA (1) | CA1064334A (en) |
| DE (1) | DE2602747C3 (en) |
| FR (1) | FR2338841A1 (en) |
| GB (1) | GB1546976A (en) |
| NO (1) | NO770236L (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2137679A (en) * | 1983-04-05 | 1984-10-10 | Worley Eng | Underwater buoyant tension leg |
| GR80311B (en) * | 1984-09-07 | 1984-12-17 | Ioakeim Paulos | Prefabricated elements for the manufacture of unmoving jetty |
| GB2296686A (en) * | 1994-11-12 | 1996-07-10 | Mp | Storage of production fluids from undersea oil deposits or reservoirs |
| DE10206495A1 (en) * | 2002-02-16 | 2003-09-04 | Aloys Wobben | wind farm |
| GB0911472D0 (en) * | 2009-07-02 | 2009-08-12 | Tamacrest Ltd | Buoyant fluid extraction and ESP support system |
| ES2876053B2 (en) * | 2020-05-08 | 2022-03-22 | Seaplace Sl | FLOATING PLATFORM OF REINFORCED CONCRETE FOR APPLICATION TO THE INDUSTRY OF THE OFFSHORE WIND POWER SECTOR |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO132753B (en) * | 1973-02-23 | 1975-09-22 | Olav Mo |
-
1976
- 1976-01-26 DE DE2602747A patent/DE2602747C3/en not_active Expired
-
1977
- 1977-01-18 GB GB1954/77A patent/GB1546976A/en not_active Expired
- 1977-01-20 CA CA270,129A patent/CA1064334A/en not_active Expired
- 1977-01-21 FR FR7701771A patent/FR2338841A1/en active Granted
- 1977-01-25 NO NO770236A patent/NO770236L/en unknown
- 1977-01-26 JP JP763277A patent/JPS5291705A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2602747C3 (en) | 1978-10-12 |
| DE2602747A1 (en) | 1977-07-28 |
| NO770236L (en) | 1977-07-27 |
| FR2338841A1 (en) | 1977-08-19 |
| GB1546976A (en) | 1979-06-06 |
| JPS5291705A (en) | 1977-08-02 |
| DE2602747B2 (en) | 1978-02-23 |
| FR2338841B1 (en) | 1980-03-14 |
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