WO2000018664A1 - Embarcation - Google Patents

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Publication number
WO2000018664A1
WO2000018664A1 PCT/GB1999/003130 GB9903130W WO0018664A1 WO 2000018664 A1 WO2000018664 A1 WO 2000018664A1 GB 9903130 W GB9903130 W GB 9903130W WO 0018664 A1 WO0018664 A1 WO 0018664A1
Authority
WO
WIPO (PCT)
Prior art keywords
density
vessel
water
ballast
sea
Prior art date
Application number
PCT/GB1999/003130
Other languages
English (en)
Inventor
Martin John Moody
Original Assignee
The Secretary Of State For Defence
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 The Secretary Of State For Defence filed Critical The Secretary Of State For Defence
Publication of WO2000018664A1 publication Critical patent/WO2000018664A1/fr

Links

Classifications

    • 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
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/14—Control of attitude or depth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/14—Control of attitude or depth
    • B63G8/22—Adjustment of buoyancy by water ballasting; Emptying equipment for ballast tanks

Definitions

  • This invention relates to a vessel for deployment underwater, in particular a vessel suitable for oil and gas exploration.
  • Conventional techniques for offshore sea bed exploration involving the use of rigs or floating platforms face a number of technical problems which increase for exploration in deeper water.
  • One solution to the problems involved in exploration at depths of up to 4500 metres is to place an exploration vessel directly on the sea bed.
  • the vessel needs to be anchored in position in use, but be able to be redeployed once exploration of that site has been completed.
  • deployment of such a vessel is achieved by towing the vessel to the site of interest using air filled tanks to give the vessel buoyancy. Once the vessel is in position, the air filled tanks are flooded with sea water, increasing the weight of the vessel and allowing it to sink to the sea bed.
  • GB 2284629 describes a method of installing an underwater storage tank on the sea bed, whereby a liquid which is less dense than water and not water based, e.g. a light petroleum product, is replaced with sea water ballast.
  • a liquid which is less dense than water and not water based e.g. a light petroleum product
  • GB 1407497 describes a method of ensuring that an underwater crude oil storage tank, tethered to the sea bed by mooring chains, does not alter in buoyancy either positively, which would place undue strain on the mooring chains, or negatively, causing the storage tank to sink to the sea bed.
  • This depth control is achieved by altering the amount of sea water or compressed air in the storage tank to compensate for the addition or removal of crude oil.
  • the use of air means that there will be a large hydrostatic pressure difference between the inside and outside of the tank, which will increase with depth. Such a structure would therefore either be limited to relatively shallow waters or necessarily be of robust and thus heavy construction.
  • a vessel for deployment underwater comprises a ballast container and water ballast, wherein in use, the density of the water ballast is altered between a first density and a second density, such that the weight of the vessel is increased to anchor it in place.
  • the present invention overcomes the problem of the heavy construction required when air filled ballast tanks are used because they are subject to compression by the hydrostatic pressure encountered at depth. Using liquids which are substantially incompressible allows a lighter construction to be used, reducing cost and weight. By altering the density of the water, rather than replacing the water with another liquid such as oil, the vessel can be made heavier to anchor it in place, or made lighter to allow it to be moved again, without the risk of pollution of the environment inherent in use of oil based ballast.
  • the water ballast at the second density is heavier than at the first density and so performs an anchoring function, but preferably, the density of the water ballast is altered from the first or second density to a third density.
  • the third density is greater than the first and second and so enables the vessel to be anchored more firmly.
  • the water ballast at the first density comprises fresh water; at the second density comprises sea water or saline; and at the third density comprises brine.
  • the density of the water ballast is altered by reverse osmosis.
  • a by-product of reverse osmosis is water having a salt content higher then both fresh water and sea water.
  • the process of reverse osmosis is well known in the art and is used, for example, to produce fresh water from sea water onboard sea-going vessels, such as warships.
  • Water ballast at one density need not entirely replace water ballast at another density, but partial replacement will effect a lesser change in the overall weight of the vessel.
  • the ballast container may comprise one or more tanks attached to the vessel but preferably, the ballast container is integral with the structure of the vessel. This has the advantage of providing a more compact vessel and simplifies construction.
  • the vessel may be an exploration vessel, a production platform for use in the oil or gas industry or any other vessel or structure which it is desired to anchor to the sea bed.
  • a method of reversibly installing a vessel on the sea bed comprises arranging for the vessel to have substantially neutral buoyancy by means of water ballast; manoeuvring the vessel onto the sea bed at the desired position; and altering the density of the water ballast from a first density to a second density; the second density being greater than the first density, such that the vessel is anchored on the sea bed.
  • the method further comprises altering the density of the water ballast to a third density, the third density being greater than the first or second densities, such that the vessel is more firmly anchored on the sea bed.
  • the water ballast at the first density comprises fresh water
  • at the second density comprises sea water or saline
  • at the third density comprises brine.
  • the alteration of the density of water ballast from the second density to the first density is by means of reverse osmosis.
  • the alteration of the density of the water ballast from the first or second density to the third density is by replacement with a by-product of reverse osmosis.
  • Figure 2 shows a schematic of an oil exploration platform according to the invention.
  • Fig. 1a shows a vessel 1 containing fresh water 2 in its integral ballast tanks moving in a body of sea water 3.
  • the fresh water 2 in this example has a density of 1000kg/m 3 and the vessel 1 is arranged to have substantially neutral buoyancy by means of optional permanent buoyancy and the water ballast.
  • the vessel uses a vectored thrust system (not shown) to manoeuvre through the sea to a predetermined position on the sea bed 4.
  • Fig. 1b shows the vessel in place on the sea bed 4 where the fresh water 2 is pumped out and replaced with sea water 5 having a density of 1030 kg/m 3 .
  • the density of sea water used is dependent on the location, temperature and depth of the water.
  • the effect of increasing the density of the water is to increase the weight of the vessel 1 , so that it is anchored to the sea bed 4.
  • the water may be replaced with brine which for sea water at this density has a density of 1038 kg/m 3 , so increasing the weight of the vessel still further, to anchor it to the sea bed more firmly.
  • the brine may be obtained as a byproduct of reverse osmosis.
  • the vessel may be moved by replacing the sea water 5 or brine (not shown) with fresh water 2, thereby restoring neutral buoyancy as shown in Fig. 1c.
  • the vessel 1 can then be manoeuvred to a new location or recovered.
  • the fresh water required may be obtained from sea water by reverse osmosis.
  • the reverse osmosis equipment may be an integral part of the vessel or supplied as a separate unit.
  • the vessel may have an on-board power supply and so be entirely autonomous, or else have a light weight electrical power connection to the surface, rather than the expensive and bulky cables requried in the prior art.
  • FIG. 2 shows an oil exploration platform 6 suitable for use at great depth.
  • Permanent buoyancy 7 is added to the platform to offset the weight of the platform's structure and ballast tanks 8 are filled with fresh water.
  • the platform has positive buoyancy and thus floats on the surface of the sea and can be moved to a location where exploration is to take place.
  • Auxiliary ballast tanks 9 are filled with sea water, thereby giving the structure slight negative buoyancy so that it can be moved, under the control of vectored thrusters into position on the sea bed 4.
  • the ballast tanks are integral to the structure of the platform, although they could also be provided as additional tanks.
  • the fresh water contained within the ballast tanks 8 is replaced with sea water, increasing the weight of the platform and anchoring it to the sea bed. If further stability on the sea bed is required, for example in regions of strong ocean currents, or when reaction forces to drilling operations are high, the weight of the platform is further increased by replacing the sea water in the ballast tanks with brine and, if necessary, replacing the sea water in the auxiliary ballast tanks 9 with brine.
  • the brine or sea water in the ballast tanks 8 is replaced with fresh water, obtained by reverse osmosis. If brine was used in the auxiliary ballast tanks 9, this is replaced with sea water.
  • the invention is designed for use at great depths where the extreme hydrostatic pressure would necessitate the use of robustly engineered and thus heavy and cumbersome ballast tanks, if traditional air filled tanks were employed.
  • ballast there is no requirement for the density of the ballast to be altered rapidly.
  • Existing reverse osmosis equipment such as that used for desalination plants on sea going vessels, could be used to generate the required fresh water and allow the platform to be moved over a period of several days.
  • the scaling up or linkage of several, existing technology, reverse osmosis plants could be employed if more rapid re-deployment was required.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne une embarcation (1) destinée à être déployée sous l'eau et contenant un récipient pour lest et du lest liquide. Pendant l'utilisation, on peut modifier la densité du lest liquide en rendant l'embarcation plus lourde, de manière à la déplacer dans une direction désirée au fond de la mer puis à l'ancrer. La densité de l'eau peut être davantage augmentée grâce à un sous-produit d'osmose inverse, et ce pour ancrer l'embarcation plus solidement. Pour déplacer l'embarcation après usage, on diminue de nouveau la densité du lest liquide en remplaçant l'eau salée par de l'eau fraîche; ainsi l'embarcation peut-elle être déplacée dans une nouvelle position ou ramenée à la surface pour récupération.
PCT/GB1999/003130 1998-09-25 1999-09-20 Embarcation WO2000018664A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9820865.5A GB9820865D0 (en) 1998-09-25 1998-09-25 Improvements relating to water-bourne vessels
GB9820865.5 1998-09-25

Publications (1)

Publication Number Publication Date
WO2000018664A1 true WO2000018664A1 (fr) 2000-04-06

Family

ID=10839442

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/003130 WO2000018664A1 (fr) 1998-09-25 1999-09-20 Embarcation

Country Status (2)

Country Link
GB (1) GB9820865D0 (fr)
WO (1) WO2000018664A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO337169B1 (no) * 2012-05-10 2016-02-01 Abyssus Marine Services As Anordning for undersjøisk transport av målesystemer

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1407497A (en) 1972-09-15 1975-09-24 Mitsui Shipbuilding Eng Underwater oil storage apparatus
GB1407979A (en) * 1971-10-05 1975-10-01 Plessey Co Ltd Watergoing craft
NO912371L (no) 1991-06-18 1992-12-21 Norwegian Contractors Fremgangsmaate og anordning for nedsenking og installasjonav fundamentkonstruksjoner paa havbunnen.
GB2284629A (en) 1993-12-10 1995-06-14 Norwegian Contractors Installing underwater storage tank
US5516235A (en) * 1991-01-25 1996-05-14 Controlled Lifting International Limited Method and apparatus of raising objects from the sea bed

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1407979A (en) * 1971-10-05 1975-10-01 Plessey Co Ltd Watergoing craft
GB1407497A (en) 1972-09-15 1975-09-24 Mitsui Shipbuilding Eng Underwater oil storage apparatus
US5516235A (en) * 1991-01-25 1996-05-14 Controlled Lifting International Limited Method and apparatus of raising objects from the sea bed
NO912371L (no) 1991-06-18 1992-12-21 Norwegian Contractors Fremgangsmaate og anordning for nedsenking og installasjonav fundamentkonstruksjoner paa havbunnen.
GB2284629A (en) 1993-12-10 1995-06-14 Norwegian Contractors Installing underwater storage tank

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO337169B1 (no) * 2012-05-10 2016-02-01 Abyssus Marine Services As Anordning for undersjøisk transport av målesystemer
US9381984B2 (en) 2012-05-10 2016-07-05 Abyssus Marine Services As Apparatus for subsea transport of sensor systems

Also Published As

Publication number Publication date
GB9820865D0 (en) 1998-11-18

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