WO2002030738A1 - Floating storage system - Google Patents

Floating storage system Download PDF

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Publication number
WO2002030738A1
WO2002030738A1 PCT/NO2001/000408 NO0100408W WO0230738A1 WO 2002030738 A1 WO2002030738 A1 WO 2002030738A1 NO 0100408 W NO0100408 W NO 0100408W WO 0230738 A1 WO0230738 A1 WO 0230738A1
Authority
WO
WIPO (PCT)
Prior art keywords
storage
floating
tank
storage system
oil
Prior art date
Application number
PCT/NO2001/000408
Other languages
French (fr)
Inventor
Arnstein Godejord
Trond LANDBÖ
Kåre O. HÆREID
Original Assignee
Dr. Techn. Olav Olsen As
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dr. Techn. Olav Olsen As filed Critical Dr. Techn. Olav Olsen As
Priority to AU2001294427A priority Critical patent/AU2001294427A1/en
Publication of WO2002030738A1 publication Critical patent/WO2002030738A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B25/00—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/78—Large containers for use in or under water
    • 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
    • B63B2035/448—Floating hydrocarbon production vessels, e.g. Floating Production Storage and Offloading vessels [FPSO]
    • 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

Definitions

  • the present invention relates to a floating storage system for hydrocar- bons, primarily for use in a floating production platform with requirements for constant draught.
  • the invention describes a storage system for oil or condensate for use in a floating production platform with surface wells and rigid risers. Independent of the amount of hydrocarbons in the storage the platform has a constant draught without any active ballasting.
  • the system has a potential for significant cost savings compared to traditional systems, both in fabrication cost and in operation cost.
  • wet storage For fixed platforms, in the North Sea and in other parts of the world, an alternative system has been used with hydrocarbons stored on top of seawater (wet storage) and the difference in density causes separation of hydrocarbons from the water, and the hydrocarbons will float to the top of the storage.
  • This sys- tern can also be used in floating platforms.
  • Such wet storage requires less ballasting to keep constant draught due to the fact that only the difference in density between water and hydrocarbons (typically 0,15-0,25 t/m 3 ) needs to be compensated for. It is also one alternative to allow for change in draught. Without ballasting the changes in draught for a wet storage will be significantly reduced com- pared to a dry storage.
  • GB 2.071.020 describes a structure designed for oil and gas recovery, and has no direct ventilation in the top, but a complex system of valves and pipes for delivering a mixture of oil and gas to a storage vessel. The draught of the latter will depend on the gas pressure inside the structure. The two structures are not designed for permanent storage of hydrocarbons due to the danger of pollution through the open base.
  • the present invention utilise some of the same principles as the two inventions described above since it communicates to sea in the bottom and is venti- lated in the top.
  • these structures are intended for completely different objects than the present invention, and this structures cannot be utilized in a floating production platform including oil storage and with the requirement to constant draft due to the use of rigid rises and well heads on the platform.
  • One object of the present invention is to provide a storage system that will not affect the draught of the storage platform when the amount of hydrocarbons in the storage changes. This will eliminate the need for an active ballast system even for platforms with surface wells and rigid risers, and will simplify operation of the platform.
  • Another object is to provide a safe storage system that eliminates the risk of leakage.
  • a floating storage system for oil and condensate primarily for use in a floating production platform with requirements for constant draught, characterised in that the storage system consisting of a floating structure having one or more buoyancy tanks and one or more storage tanks, with the buoyancy tank designed to carry the floating structure in a predefined constant draught, and the storage tank is equipped with a ventilation system in the top and communicates with outer sea through pipes in the bottom, pressing air out of the top and pressing seawater out of the bottom when filling oil or condensate into the storage tank.
  • Figure 1 presents the storage structure filled with oil
  • Figure 2 presents the storage structure half full of oil
  • Figure 3 presents an empty storage structure.
  • a storage system is presented floating at a predefined draught, filled with oil.
  • the structure 1 has buoyancy tank(s) 2 creating an outer barrier encircling the storage tank(s) 3.
  • the buoyancy tank(s) (2) carry the structure at a constant draught.
  • the storage tank(s) 3 has ventilation system 4 in the top and communicates to sea 5 in the bottom.
  • the communication to sea 5 goes through a buffer tank 6, from the bottom of the storage tank to the top of the buffer tank 6. It is possible to connect a number of buffer tanks in series to improve safety against pollution.
  • the buffer tank 6 is connected to outer sea through openings 7 in the bottom.
  • the communication of the storage tank(s) 3 to sea via the buffer tank 6 eliminates the risk of leakage from the storage 3 and pollution to the outer sea.
  • the ventilation system 4 in the top of the storage tank allows ventilation to atmosphere, and Nitrogen will be purged into the gas at the top of the storage to prevent explosions.
  • the storage 3 is full of oil stored on top of water, and with air in top. The surface level of oil will in this case be higher than the surface level of outer seawater.
  • the storage 3 is half full of oil stored on top of water.
  • the surface level of the oil is lower than in figure 1 , but still above outer seawater.
  • the storage 3 is "empty", i.e. has no oil inside.
  • the surface level of the water inside the storage 3 is equal to the surface level of the outer seawater.
  • Figures 1-3 illustrate how the storage platform maintains a constant draught independent of the amount of oil in the storage, and without any active ballasting.
  • the storage system is designed so that the seawater carries the weight of the oil, and the platform structure is carried by the buoyancy tank(s).
  • the storage acts as it is open in the bottom, but the base slab and the communication through the buffer tank(s) eliminates the risk of pollution.
  • the storage system can have different configurations, but the principle is the same for any configuration. Due to the fact that the weight of the oil is not carried by the floating structure the resulting vertical pressures on all parts of the storage structure must be zero.
  • the simplest shape of such a storage system has one or more storage tanks with constant area over the entire height, and with buoyancy tanks placed around the storage tanks. Some of the buoyancy tanks need to penetrate the sea surface to provide intact and damage stability and optimal hydrodynamic motion characteristics.
  • the storage system can also be used for alternative configurations with extensive submerged volume to improve motion characteristics. If storage tanks are located at different elevations the areas of the tanks need to calibrated to minimise the draught variations due to amount of oil in storage.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Earth Drilling (AREA)
  • Removal Of Floating Material (AREA)
  • Underground Structures, Protecting, Testing And Restoring Foundations (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

Floating storage system for oil and condensate, primarily for use in a floating production platform with requirements for constant draught. The storage system consists of a floating structure (1) with one or more buoyancy tanks (2) and one or more storage tanks (3), with the buoyancy tank (2) designed to carry the floating structure in a predefined constant draught without ballasting. The storage tank (3) is equipped with a ventilation system (4) in the top and communicates with outer sea through pipes (5) in the bottom, pressing air out of the top and pressing seawater out of the bottom when filling oil or condensate into the storage tank (3).

Description

Floating Storage System
The present invention relates to a floating storage system for hydrocar- bons, primarily for use in a floating production platform with requirements for constant draught.
More specific the invention describes a storage system for oil or condensate for use in a floating production platform with surface wells and rigid risers. Independent of the amount of hydrocarbons in the storage the platform has a constant draught without any active ballasting. The system has a potential for significant cost savings compared to traditional systems, both in fabrication cost and in operation cost.
In the Oil & Gas industry floating production platform systems have been used for many years. Some of these have capacity for storing oil, condensate or other liquefied hydrocarbon products.
Today the industry is dominated by a system with oil/air in the storage tanks (used in tankers). This is a simple system, but requires ballasting to compensate for oil export/production in order to keep a constant draught. Another option is to allow for varying draught. This storage system requires purging of Nitrogen to eliminate chances of explosions.
For fixed platforms, in the North Sea and in other parts of the world, an alternative system has been used with hydrocarbons stored on top of seawater (wet storage) and the difference in density causes separation of hydrocarbons from the water, and the hydrocarbons will float to the top of the storage. This sys- tern can also be used in floating platforms. Such wet storage requires less ballasting to keep constant draught due to the fact that only the difference in density between water and hydrocarbons (typically 0,15-0,25 t/m3) needs to be compensated for. It is also one alternative to allow for change in draught. Without ballasting the changes in draught for a wet storage will be significantly reduced com- pared to a dry storage.
With subsea wells and flexible risers the requirement for constant draught is less important than with rigid risers and surface wells. Rigid risers will require constant draught and very favourable motion characteristics for the platform. Surface trees are often cost efficient with regard to utilisation of the reservoir and well intervention and hence the demand for surface trees has increased over the last years.
In the prior art systems are described for capturing and storing oil and gas, such as oil and gas flowing uncontrollably from an offshore well (blow out situations), that have certain similarities with the present invention. Reference is made to the publications GB 2071.020 and US 3.653.215. The publications describe oil and gas recovery structures with roof and walls and with an open base, designed for installation above the source of leakage. US 3.653.215 describes a structure preferably designed for oil recovery, and this structure is floating on a buoyant ring, has ventilation in the top and has a thin flexible wall that can be lowered down to the seabed to encircle the source of leakage. GB 2.071.020 describes a structure designed for oil and gas recovery, and has no direct ventilation in the top, but a complex system of valves and pipes for delivering a mixture of oil and gas to a storage vessel. The draught of the latter will depend on the gas pressure inside the structure. The two structures are not designed for permanent storage of hydrocarbons due to the danger of pollution through the open base.
The present invention utilise some of the same principles as the two inventions described above since it communicates to sea in the bottom and is venti- lated in the top. However these structures are intended for completely different objects than the present invention, and this structures cannot be utilized in a floating production platform including oil storage and with the requirement to constant draft due to the use of rigid rises and well heads on the platform.
One object of the present invention is to provide a storage system that will not affect the draught of the storage platform when the amount of hydrocarbons in the storage changes. This will eliminate the need for an active ballast system even for platforms with surface wells and rigid risers, and will simplify operation of the platform.
Another object is to provide a safe storage system that eliminates the risk of leakage.
The objects are met with a floating storage system for oil and condensate, primarily for use in a floating production platform with requirements for constant draught, characterised in that the storage system consisting of a floating structure having one or more buoyancy tanks and one or more storage tanks, with the buoyancy tank designed to carry the floating structure in a predefined constant draught, and the storage tank is equipped with a ventilation system in the top and communicates with outer sea through pipes in the bottom, pressing air out of the top and pressing seawater out of the bottom when filling oil or condensate into the storage tank.
Preferred embodiments of the invention are described in claims 2-6.
In the following the invention is described by an example with references to the attached drawings 1-3 wherein
Figure 1 presents the storage structure filled with oil, Figure 2 presents the storage structure half full of oil, and
Figure 3 presents an empty storage structure.
With reference to fig. 1 a storage system is presented floating at a predefined draught, filled with oil. The structure 1 has buoyancy tank(s) 2 creating an outer barrier encircling the storage tank(s) 3. The buoyancy tank(s) (2) carry the structure at a constant draught. The storage tank(s) 3 has ventilation system 4 in the top and communicates to sea 5 in the bottom.
The communication to sea 5 goes through a buffer tank 6, from the bottom of the storage tank to the top of the buffer tank 6. It is possible to connect a number of buffer tanks in series to improve safety against pollution. The buffer tank 6 is connected to outer sea through openings 7 in the bottom. The communication of the storage tank(s) 3 to sea via the buffer tank 6 eliminates the risk of leakage from the storage 3 and pollution to the outer sea. The ventilation system 4 in the top of the storage tank allows ventilation to atmosphere, and Nitrogen will be purged into the gas at the top of the storage to prevent explosions. In figure 1 the storage 3 is full of oil stored on top of water, and with air in top. The surface level of oil will in this case be higher than the surface level of outer seawater.
In figure 2 the storage 3 is half full of oil stored on top of water. The surface level of the oil is lower than in figure 1 , but still above outer seawater.
In figure 3 the storage 3 is "empty", i.e. has no oil inside. The surface level of the water inside the storage 3 is equal to the surface level of the outer seawater.
Figures 1-3 illustrate how the storage platform maintains a constant draught independent of the amount of oil in the storage, and without any active ballasting. The storage system is designed so that the seawater carries the weight of the oil, and the platform structure is carried by the buoyancy tank(s). In principle the storage acts as it is open in the bottom, but the base slab and the communication through the buffer tank(s) eliminates the risk of pollution. There will be in- strumentation to measure the level of the segregation between oil and water inside the tank, and to detect any oil particles inside the buffer tank(s).
The storage system can have different configurations, but the principle is the same for any configuration. Due to the fact that the weight of the oil is not carried by the floating structure the resulting vertical pressures on all parts of the storage structure must be zero. The simplest shape of such a storage system has one or more storage tanks with constant area over the entire height, and with buoyancy tanks placed around the storage tanks. Some of the buoyancy tanks need to penetrate the sea surface to provide intact and damage stability and optimal hydrodynamic motion characteristics. The storage system can also be used for alternative configurations with extensive submerged volume to improve motion characteristics. If storage tanks are located at different elevations the areas of the tanks need to calibrated to minimise the draught variations due to amount of oil in storage.

Claims

PATENT CLAIMS
1. Floating storage system for oil and condensate, primarily for use in a floating production platform with requirements for constant draught, character- ised in that the storage system consisting of a floating structure (1) having one or more buoyancy tanks (2) and one or more storage tanks (3), with the buoyancy tank (2) designed to carry the floating structure (1) in a predefined constant draught, and the storage tank (3) is equipped with a ventilation system (4) in the top and communicates with outer sea through pipes (5) in the bottom, pressing air out of the top and pressing seawater out of the bottom when filling oil or condensate into the storage tank (3).
2. Floating storage system according to claim 1 , characterised in that the storage tank (3) is connected to a buffer tank (6), or alternatively a number of buffer tanks (6) connected in series, through a communication system
(5) to outer sea.
3. Floating storage system according to claim 2, characterised in that the buffer tank (6) is connected to the communication system (5) in it's upper area and further the buffer tank (6) in it's lower area is provided with one or several communication outlets (7) to outer sea.
4. Floating storage system according to claim 1 ,2 or 3, characterised in that the buoyancy tank (2) is located separate from the storage tank (3).
5. Floating storage system according to claim 1 ,2,3 or 4, characterised in that the buoyancy tank (2) penetrating the outer sea surface.
6. Floating storage system according to claim 1 ,2,3,4 or 5, characterised in that the air in top of storage tank (3) is purged with Nitrogen.
PCT/NO2001/000408 2000-10-10 2001-10-08 Floating storage system WO2002030738A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001294427A AU2001294427A1 (en) 2000-10-10 2001-10-08 Floating storage system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20005099 2000-10-10
NO20005099A NO314720B1 (en) 2000-10-10 2000-10-10 Liquid platform construction for storage of oil and / or condensate produced from an underwater well

Publications (1)

Publication Number Publication Date
WO2002030738A1 true WO2002030738A1 (en) 2002-04-18

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ID=19911671

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NO2001/000408 WO2002030738A1 (en) 2000-10-10 2001-10-08 Floating storage system

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AU (1) AU2001294427A1 (en)
NO (1) NO314720B1 (en)
WO (1) WO2002030738A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012153425A (en) * 2011-01-28 2012-08-16 Sekisui Chem Co Ltd Apparatus and method for submerged storage, and fresh water production and storage system
CN103449063A (en) * 2012-07-09 2013-12-18 中国海洋石油总公司 Zero-pollution underwater oil storage system with oil and water displacement function
WO2014165765A1 (en) * 2013-04-06 2014-10-09 Safe Marine Transfer, LLC Large subsea package deployment methods and devices
NO20171505A1 (en) * 2017-09-19 2019-03-20 Subsea 7 Norway As Subsea storage of crude oil
CN110816791A (en) * 2018-08-09 2020-02-21 中国船舶重工集团公司第七六○研究所 Water injection and drainage control method for slender underwater buoyancy tank

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3631832A (en) * 1969-08-25 1972-01-04 Mobil Oil Corp Tanker construction
US4653960A (en) * 1986-05-20 1987-03-31 Chun Joong H Submersible offshore drilling production and storage platform with anti-catenary stationing
US5074715A (en) * 1987-03-04 1991-12-24 Norwegian Contractors A/S Oil storage system
JPH11105784A (en) * 1997-10-06 1999-04-20 Sumitomo Heavy Ind Ltd Corrosion prevention method of cargo oil tank of double hull structure crude oil tanker

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3631832A (en) * 1969-08-25 1972-01-04 Mobil Oil Corp Tanker construction
US4653960A (en) * 1986-05-20 1987-03-31 Chun Joong H Submersible offshore drilling production and storage platform with anti-catenary stationing
US5074715A (en) * 1987-03-04 1991-12-24 Norwegian Contractors A/S Oil storage system
JPH11105784A (en) * 1997-10-06 1999-04-20 Sumitomo Heavy Ind Ltd Corrosion prevention method of cargo oil tank of double hull structure crude oil tanker

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 199926, Derwent World Patents Index; AN 1999-307548/26, XP002953202 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012153425A (en) * 2011-01-28 2012-08-16 Sekisui Chem Co Ltd Apparatus and method for submerged storage, and fresh water production and storage system
CN103449063A (en) * 2012-07-09 2013-12-18 中国海洋石油总公司 Zero-pollution underwater oil storage system with oil and water displacement function
CN103449063B (en) * 2012-07-09 2015-06-24 中国海洋石油总公司 Zero-pollution underwater oil storage system with oil and water displacement function
WO2014165765A1 (en) * 2013-04-06 2014-10-09 Safe Marine Transfer, LLC Large subsea package deployment methods and devices
NO20171505A1 (en) * 2017-09-19 2019-03-20 Subsea 7 Norway As Subsea storage of crude oil
NO345571B1 (en) * 2017-09-19 2021-04-19 Subsea 7 Norway As Method and storage tank for subsea storage of crude oil
CN110816791A (en) * 2018-08-09 2020-02-21 中国船舶重工集团公司第七六○研究所 Water injection and drainage control method for slender underwater buoyancy tank

Also Published As

Publication number Publication date
NO314720B1 (en) 2003-05-12
AU2001294427A1 (en) 2002-04-22
NO20005099D0 (en) 2000-10-10
NO20005099L (en) 2002-04-11

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