Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63J—AUXILIARIES ON VESSELS
  • B63J2/00—Arrangements of ventilation, heating, cooling, or air-conditioning
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
  • E21B17/01—Risers
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
  • E21B19/002—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling
  • E21B19/004—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling supporting a riser from a drilling or production platform
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
  • F25J1/0022—Hydrocarbons, e.g. natural gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
  • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
  • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
  • F25J1/0277—Offshore use, e.g. during shipping
  • F25J1/0278—Unit being stationary, e.g. on floating barge or fixed platform
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
  • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
  • F25J1/0296—Removal of the heat of compression, e.g. within an inter- or afterstage-cooler against an ambient heat sink
  • F25J1/0297—Removal of the heat of compression, e.g. within an inter- or afterstage-cooler against an ambient heat sink using an externally chilled fluid, e.g. chilled water
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B13/00—Conduits for emptying or ballasting; Self-bailing equipment; Scuppers
  • B63B13/02—Ports for passing water through vessels' sides
• • 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 
  • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
  • B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
  • B63B21/507—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers with mooring turrets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63J—AUXILIARIES ON VESSELS
  • B63J2/00—Arrangements of ventilation, heating, cooling, or air-conditioning
  • B63J2002/005—Intakes for coolant medium other than sea chests, e.g. for ambient water
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T70/00—Maritime or waterways transport

Definitions

• the present invention regards bottom anchored riser systems for taking up large amounts of cold seawater from large depth to a stationary turret or similar in a vessel that lays in a fixed position and can rotate freely around said turret.
• the invention is in particular relevant where a huge demand for cooling is present, such as for LNG- production from natural gas on a vessel of the type FPSO (Floating Production Storage and Offloading).
• the invention regards bottom anchored riser systems for taking up large amounts of cold seawater from large depth to a turret or an equivalent arrangement on board a vessel which by spread anchoring from the turret or by dynamical positioning lays in a fixed position on the sea surface, such that the turret is fixed positioned and in principle without rotation with respect to the sea surface while the vessel can rotate freely around the turret according to the impact of the weather.
• patent publication JP 57008369 an arrangement is described to reduce movements and thereby strain while taking in a subsea line, by use of a special arrangement outside the hull of the vessel.
• a seawater intake is described having a fixed installation, with which seawater can be brought up from large depth. Since the arrangement is an installation fixed to the seabed, without a vessel, the described art is less preferable with respect to seawater intake from depths from several hundred meters and deeper.
• the pipe to take up the cold seawater is not a specific topic, however, it is described that the pipe is flexible and preferably fabricated from reinforced synthetic material, comprising cylindrical components whose actual length is substantially equal to the radius, stiffened by hoops which are preferably fabricated from glass fiber reinforced plastic material and connected to one another by woven lanyards of a nylon-type synthetic material. (Column 7, lines 40-47). Above the pipe for intake of cold seawater are arranged pumps and other equipment which are used in connection with the power production on the platform. It is not known that a platform according to the above publication has been fabricated.
• seawater intake pipes without limited length to avoid collisions with the anchor lines, at the same time as cold seawater can be taken up from large depths. This is achieved by having the cooling water pipes located within the anchoring system and geostationary positioned with respect to the seabed, whereby they will not be in conflict with the anchoring system and the production risers when the vessel is weathervaning.
• the system for supplying cooling water to the production processes on the vessel includes one or more seawater risers which are shown to extend between a turning unit and the seabed, and which are connected at a lower end to an anchoring means to the seabed, for instance a seawater lifting pump (page 4, lines 14-17).
• a seawater pump is also shown to be arranged on the buoyancy unit (page 4, lines 21-22). Further it is apparent that the seawater risers generally may consist of one large or several smaller risers extending down to the seabed or to a chosen depth at which the seawater temperature is sufficiently low (page 4, lines 24-26). Further it is described that the seawater pipes between the buoyancy unit and the seabed may have the same course as the production risers or they may in general extend vertically from the buoyancy unit to the seabed. In both cases they will be kept in position at the seabed by anchoring means (page 4, lines 26-29). There is no focus on the number of risers for seawater intake, and on the drawings only one embodiment with several risers for seawater intake is illustrated.
• the invention according to PCT/NO00/00447 in reality regards provisions with respect to the turning unit in the vessel, and there is no guidance with respect to particular choices regarding number and dimensions of the seawater risers in particular or the seawater risers in general. There is no guidance with respect to specific methods to arrange further risers, for example production risers, in particular ways with respect to the seawater risers.
• the above mentioned pumps appear to be obligatory in the system for seawater intake. It is mentioned that a process plant on a FPSO vessel can require intake of a cooling water amount up to 30000 m /h, which will require use of a seawater riser with a flow area corresponding to a pipe having a diameter up to about 2000 mm.
• a riser system for taking up large amounts of cold seawater from large depth to a turret or similar in a vessel that in principle lays in a fixed position on the sea surface by spread anchoring from the turret or by dynamical positioning, which vessel can rotate freely around the turret while the turret in principle is without rotation with respect to the sea surface.
• the riser system is distinguished in that it comprises: a single riser having a large flow cross-section, which riser in operation extends from a lower bottom anchored end at large depth from where large amounts of cold seawater are taken in through at least one opening and is passed through the riser to an upper end a little below or in the sea surface, a buoyant body arranged in the upper end of the riser, which buoyant body holds the riser in upright position, one or more flexible pipes arranged from the upper end of the riser to the turret, to pass the cold seawater from the riser to the vessel, with fluid communication through or by-passing the buoyant body.
• the vessel With in principle fixed position it is meant that the vessel has a drift of maximum 7 % of the ocean depth from the nominal position on the sea surface. The drift will typically be far less.
• a turret in principle without rotation it is meant a maximum rotation which is given of the stiffness of the anchoring system and the riser system, more specific ⁇ 270° to ⁇ 360°, dependent on the design of the riser system.
• large depth it is meant several hundred meters depth, preferably at least 600 m, typically 1000 m depth, in principle to a depth where the water temperature is stable and low in all conditions and seasons. In cold waters sufficient depth may accordingly be shallower than in warm waters.
• the riser system comprises further risers, pipes, cables and/or buoyancy material, which in principle extend parallel with the riser system and are fastened to the riser, so that the riser with connected equipment acts as one single unit.
• the riser system comprises one single round pipe having a length of about 1000 m and diameter of from 1.5 m to 5 m, whereby the riser can take up a flow rate from 11000 to over 50000 m /h cold seawater from about 1000 m depth. More preferable the riser system comprises a riser having diameter 2.5-3.2 m, whereby the riser can take up a flow rate of 30000 to 50000 m /h cold seawater from large depth.
• the riser is preferably built from joined pipe sections of reinforced polymer material having external frames for fixation of a number of external symmetrically arranged risers for natural gas, with a buoyancy body in the upper end of the riser and four flexible pipes of 42" from the buoyancy body to the vessel, with bottom anchoring of the riser from its lower end, upper end and optionally intermediate positions.
• the riser is constructed of one single or several joined sections of corrosion protected steel pipes with external buoyancy material, or polymer pipes reinforced with steel armor and/or synthetic fiber armor, for example kevlar, aramide fiber, boron fiber, carbon fiber or glass fiber, which sections of polymer pipes optionally are provided with buoyancy material, so that each section with connected further risers and equipment is having neutral or a slight negative buoyancy.
• polymer pipes reinforced with steel armor and/or synthetic fiber armor, for example kevlar, aramide fiber, boron fiber, carbon fiber or glass fiber, which sections of polymer pipes optionally are provided with buoyancy material, so that each section with connected further risers and equipment is having neutral or a slight negative buoyancy.
• the riser system has a slight negative buoyancy so that the weight of the bottom anchoring and the lower part ensures the negative buoyancy and positioning with respect to the seabed, while the remaining parts of the riser system have positive buoyancy so that by means of own buoyancy it takes an in substance upright position, which upright position is secured by anchoring from the upper end of the riser and optionally from positions along the riser.
• the riser is preferably manufactured from curved, long, joined plates, which riser around the cross-section comprises two wide convex plates joined in one (side) end, and one narrower concave plate, placed in between and joined to the wider plates in their other (side) end, with a number of additional risers, cables, buoyancy material and fixation elements in substance arranged within the concave part of the smaller plate, so that the form of the cross-section will become torpedo like or like a drop.
• the riser consists in principle of one load-bearing part and one part for cooling water transport, which parts are integrated or separated.
• the riser system is preferably connected to a FPSO-vessel having a LNG-plant, wherein the riser system supply cooling water to the LNG-plant, and wherein the riser system further comprises one or more risers for taking up natural gas to the LNG-plant, which risers for natural gas are arranged external to the riser for taking up cooling water.
• Another embodiment of the present invention comprises a riser system of the above-mentioned type, distinguished in that it comprises one single riser having a large flow cross-section, which riser in operation extends from a lower bottom anchored end at large depth wherefrom large amounts of cold seawater are taken up through at least one opening and is passed through the riser to an upper end that is located within the turret, in a suspension that is elastic around a nominal suspension position, and optionally one or more further risers, pipes, cables or buoyancy material arranged in substance parallel with and fastened to said riser, so that the riser together with connected equipment acts as one unit.
• the riser system having the upper end of the riser placed directly into the turret preferably comprises one or more of the above mentioned features regarding the riser.
• the riser system With the riser system according to the present invention it can, dependent on the embodiment, be brought up from 11000 to more than 50000 m /h cold seawater for cooling in connection with a LNG-plant on a FPSO-vessel.
• a typical LNG-plant with production of 5 mill tons LNG per year and with cooling water intake on typical 1000 m depth versus 50 m depth, it is achieved in typically chosen warm waters, about 30 % less cooling water demand.
• the power consumption is reduced with about 50 MW in a plant for LNG-production.
• two gas turbines will not be required, which each costs about 250-300 millions Norwegian kroner (for example LM 6000 Nouvo Preone).
• riser systems With the riser systems according to the present invention it is achieved significant advantages with respect to installation, reduced risk for collisions and easier manipulation of the components.
• the riser systems can in principle be handled as one single unit. Further, the flow loss through the riser system will be reduced, in particular for embodiments with round cross section of the riser. Thereby it is achieved a so called “draw down-effect" of only about 7-8 m pressure height, which has to be exceeded for cold seawater to flow by itself into the turret from large depth. Said pressure height corresponds to loss of pressure measured as water column because of effects of friction, temperature, pressure and salinity.
• the water surface in the turret accordingly has to be at least 7-8 m lower than the water surface of the sea to avoid use of pumps in the riser system, however, in practice the water surface of the turret will be kept lower, more specific at a level that ensures sufficient pressure height for lifting pumps that is to be placed in the turret to bring the cold seawater further. It is obligatory that the riser system does not contain any pump, which is possible because of the lowered water surface in the turret.
• the amount of armoring per unit flow rate will be reduced. Likewise the weight per unit flow rate will be reduced.
• FIG. 1 On Figure 1 is shown a riser system with flexible pipes hanging as catenary lines from the top of the riser to a turret or similar in a FPSO-vessel, for example 170 m horizontally from the upper end of the riser.
• turret or similar it is meant also turning sea-chests, rotating bodies and other rotating units that can take in seawater lines and other equipment in a similar way as a turret, and with lowered water surface for the cold seawater, and with space for equipment to transport the cold seawater further.
• the catenary lines are hanging in three layers, which from the top is consisting of cables and umbilicals; seawater intake pipes, for example 4 flexible pipes of 42"; and below a layer with production pipes, which means flexible pipes for transport of natural gas.
• the commercially available flexible pipes at present having largest diameter are 42". Flexible pipes having even larger diameter will be preferable, if they can be handled and can be provided.
• the flexible pipes are connected to the upper part of a riser, for example at 50 m depth, where a buoyant body is arranged that keeps the riser upright.
• the buoyant body has buoyancy adapted to keep the riser in a convenient pretensioning and vertical position under the prevailing conditions, such as by ocean current.
• the riser From its upper end the riser extends down to a lower end 1000 m down into the sea, where it is indicated a number of inlets for seawater on a specific detail on the figure.
• Below the lower end of the riser is bottom anchoring, parallel to which riser for natural gas is arranged.
• the anchoring On the figure the anchoring is in the form of tension legs or wires.
• On the seabed is provided a basis structure for the anchoring, illustrated as a basis structure for single point anchoring, and it is also indicated how the pipelines for natural gas can be arranged.
• FIGS 2a, 2b and 2c cross-sections of the riser system illustrated on Figure 1 are shown, at the buoyancy body, along the riser and below the lower end of the riser, respectively. It is shown a typical example of design.
• the buoyancy body has a diameter of for example 9 m and a length of for example 60 m.
• the buoyancy material of the buoyancy body and further in the riser system is chosen conveniently with density and design life adapted to the design life of the riser system.
• the risers for natural gas, more specific 3 risers, and cables and further 5 risers for future field connections, are arranged around the riser for seawater intake along its full length, and further down to the seabed anchoring.
• the outer diameter is for example 3.3 m and the lower riser for example 2.4 m.
• Fabrication of the riser preferably takes place at a plant with a harbor, such that the whole riser or sections thereof can be filled with air and towed to a FPSO that can be anchored or without anchor in desired position.
• the installation can take place by use of a crane vessel by deploying the lower end of the riser as a pendulum.
• External equipment such as fixation frames, risers for natural gas and buoyancy material, are preferably prepared and connected beforehand, as far as possible.
• handleable sections of the riser can be connected in position, completely fitted and deployed successively through the turret, with lifting and handling equipment on the vessel and optionally a crane vessel.
• the flexible pipes between the riser and the vessel are preferably installed at last.
• the lowest flow resistance for the cold seawater is achieved with a round cross section of the riser and one single flexible riser for seawater intake from the riser to the vessel, because of the lowest ratio pipe surface/flow cross section.
• the riser can be manufactured of curved plates that are joined, and the riser as fully equipped can be given a torpedo like or drop like cross- section.

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• Engineering & Computer Science (AREA)
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• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
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• Environmental & Geological Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Geochemistry & Mineralogy (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• General Chemical & Material Sciences (AREA)
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Cited By (4)

Citations (5)

• 2002
  • 2002-06-11 NO NO20022774A patent/NO315953B1/no not_active IP Right Cessation
• 2003
  • 2003-06-05 AU AU2003238736A patent/AU2003238736B2/en not_active Expired
  • 2003-06-05 WO PCT/NO2003/000182 patent/WO2003104605A1/en not_active Application Discontinuation

Patent Citations (5)

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