WO2007045850A1 - Support flottant amarre et procede pour son installation - Google Patents

Support flottant amarre et procede pour son installation Download PDF

Info

Publication number
WO2007045850A1
WO2007045850A1 PCT/GB2006/003846 GB2006003846W WO2007045850A1 WO 2007045850 A1 WO2007045850 A1 WO 2007045850A1 GB 2006003846 W GB2006003846 W GB 2006003846W WO 2007045850 A1 WO2007045850 A1 WO 2007045850A1
Authority
WO
WIPO (PCT)
Prior art keywords
tethers
assembly
buoyancy means
tether
buoyancy
Prior art date
Application number
PCT/GB2006/003846
Other languages
English (en)
Inventor
Keith Shotbolt
Original Assignee
Foster Wheeler Energy Limited
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
Priority claimed from GB0521189A external-priority patent/GB0521189D0/en
Priority claimed from GB0524939A external-priority patent/GB0524939D0/en
Application filed by Foster Wheeler Energy Limited filed Critical Foster Wheeler Energy Limited
Publication of WO2007045850A1 publication Critical patent/WO2007045850A1/fr

Links

Classifications

    • 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
    • E21B17/015—Non-vertical risers, e.g. articulated or catenary-type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
    • B63B27/24—Arrangement of ship-based loading or unloading equipment for cargo or passengers of pipe-lines
    • 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

Definitions

  • This invention relates to a mid-water tethered buoyant support for use in a riser system to a floating production vessel (FPV), and to a method of installation thereof.
  • FV floating production vessel
  • Riser systems are used to bring fluids, such as oil, from seabed equipment to a floating production vessel. This is achieved by providing one or more lower J-shaped catenaries from the seabed to a buoyant support that is tethered to float below the surface, with one or more upper U-shaped catenaries extending from the support to the vessel floating at the surface.
  • a catenary is the curve formed by a rope or chain of uniform density and perfect flexibility, hanging freely between two points of suspension, not in the same vertical line.
  • the upper U and lower J riser catenaries can be fabricated from any pipe material that has substantial flexibility, so that it can form a geometry that is close to a catenary.
  • the upper U catenary is normally required to bend to a smaller bend radius than the lower J catenary, and it is subject to more cyclic, fatigue-type loading due to motion of the FPV in waves and hydrodynamic drag from wave particle motion.
  • a riser system with a single buoyant support can comprise multiple riser pipes, all of them with lower and upper catenaries.
  • the tethers need to be axially stiff to minimise changes in their length as loads on the beam vary, such as when adding or removing risers or when hydrotesting a gas riser.
  • Axially stiff steel tube tethers have been applied as mooring tendons to many Tension Leg Platforms. It is known to provide tendons with buoyancy at their top ends to keep them near vertical after attaching them to seabed anchors.
  • a method for installing a mid-water tethered buoyant support assembly for a riser system to bring fluids from seabed equipment to a production vessel at the surface including the step of:
  • the tethers including buoyancy means connected to the tethers for buoyantly supporting the tethers in a close to vertical position and to maintain tension in the tethers;
  • a riser support beam assembly including hangers for suspending lower riser portions of a riser system, the hangers being mounted at spaced positions along the beam assembly; lowering the riser support beam assembly to a mid-water position, and connecting each end of the riser support beam assembly to the buoyancy means or the tethers.
  • the tethers are first attached to seabed anchors with the upper end of the tethers being supported by buoyancy means. Then, the support beam is lowered into the water, and is connected to the buoyancy means in position. This procedure is more easily and accurately accomplished than the previous procedures in which the support beam with integral buoyancy means was positioned at the mid-water level and then tethered to the seabed.
  • the buoyancy means may be connected to the tethers after the tethers have been connected to suitable seabed anchors, or may be connected to the tethers before these are positioned.
  • the buoyancy of the buoyancy means is adjustable. This may be achieved by de-ballasting.
  • the tethers when connected to the seabed anchors, define a plane over at least a portion of their length.
  • the support beam is maintained in a generally horizontal orientation. It is therefore advantageous to ensure that the point of connection of the support beam to each of the buoyancy means or the tethers is at the same level. In one aspect of the invention, this can be achieved by adjustment of the length of the tethers to ensure that the point at which the support beam is to be connected to the buoyancy means or the tether is at the same height. This may be achieved by providing the tethers with a telescopic, screw or other assembly that can be used to adjust the length of at least one of the tethers, by an adjustable length connection between at least one of the tethers and the seabed anchor, by an adjustable length connection between at least one of the tethers and the buoyancy means or by other suitable means. It is preferred that the height of the tops of the tethers are within 0.3m, more preferably within 0.1m, of each other.
  • the position at which the support beam is connected to the buoyancy means or the tether may be varied when the support beam is connected to the buoyancy means or the tether.
  • each of the buoyancy means include a lower extension member.
  • the lower extension member may be used to connect the buoyancy means to the top of the associated tether, and can also provide a location for connection of the support beam. This will ensure that the centre of buoyancy of the combined beam assembly and buoyancy members is significantly above the level of the hangers and the attachments to the tethers.
  • the support beam can be connected to the buoyancy means or the tether by a suitable mechanical connection, such as a bolt, a chain stopper or a clamp or a strap, or by a physical connection, such as by welding, or by any other suitable method.
  • a suitable mechanical connection such as a bolt, a chain stopper or a clamp or a strap
  • a physical connection such as by welding, or by any other suitable method.
  • a plastic or elastomeric material pad or bearing surface may be provided between the support beam and the buoyancy means or tether to which the support beam is connected. This may help to absorb any slight misalignment between the beam and mating surfaces.
  • hangers on the beam assembly will be positioned closely adjacent to, or on, the plane defined by said tethers, as described in US Patent No. 6,595,725.
  • a mid- water tethered buoyant support assembly including at least two tethers, buoyancy means and a support beam suitable for installation in accordance with the method of the first aspect of the present invention.
  • the beam assembly is not formed with the buoyancy means or tethers, but is suitable for connection to the buoyancy means or the tethers at a mid-water location.
  • Figure 1 shows a view of the tethers to which buoyancy means are attached, and a beam attached to the buoyancy means;
  • Figure 2 shows the connection between the beam and the buoyancy means
  • Figure 3 shows a piping manifold mounted on the beam.
  • Figure 1 is an isometric view of the beam assembly structure with tethers and buoyancy tanks at each end, prior to the installation of any riser catenaries, but with centre lines of lower catenaries shown.
  • TLP tendons are made up of tubular sections of 50m to 100m length with connectors, so that for example, a complete tendon assembly could be made up to over 1700m length in a water depth of 2000m.
  • Tendon tubular section connectors are available from Oil States Industries Inc. under their Merlin TLE Trade Mark.
  • the tubular sections can be connected by welding, provided that can be done in a cost-effective manner.
  • a buoyancy means 2 having a lower extension member 3 is attached to the top of each tether 1.
  • the buoyancy means 2 can be de-ballasted at any time to provide the desired amount of tension in the tether 1.
  • the lower extension member 3 can be connected to tether 1 using a flexjoint 4, similar to the flexjoints used for TLP tendon attachment to the TLP hull. Suitable flexjoints are available from Oil States Industries, Inc.
  • the lower extension member 3 can be connected to tether 1 using a standard tubular tendon connector. This is possible provided lateral movement of the beam assembly during operation is not too large.
  • Guy lines 9 can be used to restrict lateral movement of the beam due to ocean current or to lateral component of riser hanging weight.
  • a beam assembly 5 with riser hangers 6 is lowered down until its ends are at the same level as the lower extension members 3 of the buoyancy members. The ends of the beam assembly are then connected to the lower extension members 3 of the buoyancy means 2.
  • the ends of the beam assembly 5 are moved into contact with mating surfaces on the lower extension members 3 and are clamped into position with a shaped plate 7 using bolted fasteners 8 as shown in Figure 1.
  • vertical plates could be welded to the ends of the beam assembly 5 for direct connection by bolted fasteners to matching flat plates on the lower extension members.
  • a preferred method for attaching the beam assembly 5 to the lower extension members 3 is to first ensure that the engagement surfaces for the beam assembly 5 on the extension members 3 are at close to similar elevation, so that the beam assembly 5 is close to parallel with the sea surface.
  • the elevation of engagement surfaces at the tether tops can be checked by mounting depth gauges, such as a Digiquartz Depth Sensors, on corresponding engagement surfaces of the two extension members 3 at the top end of tethers 1.
  • top of second-installed tether many hundreds of metres long, will not be at the same elevation as the top of the first-installed tether.
  • the tops of the tethers should preferably be within 0.3m of similar elevation, and more preferably within 0.1m of similar elevation.
  • a telescoping assembly is incorporated in the second tether so that it can be adjusted to match the top elevation of the prior-installed first tether.
  • Telescoping assemblies are known, and are available from Vetco and Oil States Industries, in which slips cause engagement of a series of teeth on the tendon when at correct level.
  • a single large diameter threaded screw may be incorporated in the top of the tether, or a tumbuckle-type mechanism with right-hand and left-hand threads, so that a diver or an ROV can turn it to adjust tether length .
  • Another method of adjusting the tether length would be to lower the second tether down into its seabed foundation with an adjustable spool at the top end, and then check the tether top elevations using the depth gauges.
  • a suitable spool would be a 3m spool. If adjustment is required, the tether can be raised to allow removal of the adjustable spool, and adjust the adjustable spool length to ensure the top of the second-installed tether is at a similar elevation to the top of the first-installed tether.
  • the beam assembly 5 can be lowered down for connection to the tethers 1 via extension members 3.
  • Figure 2 is an elevation view looking on one end of steel beam assembly 5 along its main axis.
  • One extension member 3 is part-shown at the level where the beam assembly 5 engages with it.
  • the two main tubes of beam assembly 5 are cut shorter than shown in Figure 1 at both ends with a plate 10 welded to them at both ends, and stub 11 welded to the outside of plate 10 at both ends of beam assembly 5.
  • the beam assembly 5 After lowering vertically down in an offset position to the correct elevation, the beam assembly 5 needs to be moved laterally (right to left) into engagement with the generally vertical surfaces of the extension members 3. Its axial position relative to the extension members 3 can be simultaneously ensured by incorporating 'tongue and groove' engagement means (not shown) between plate 10 and a horizontal 'V guide slot hidden at the rear (in Figure 2) of extension member 3.
  • the beam assembly 5 can then be lowered further so that stub 11 engages extension member 3 at surface 12, which is set at around 10 degrees to the horizontal, i.e. approximately perpendicular to the future main riser load W.
  • Surface 12 may incorporate a plastic or elastomeric layer or inserts to improve load distribution. In very deep water, the riser load can apply around 1000 tonnes to each extension member 3, so the engagement area of surface 12 should be sufficient to limit the contact stress to an acceptable value.
  • Slide assembly 13 is located under the surface 12 and contains a jaw 14, which is initially in an open position as shown in dotted lines. After both ends of the beam assembly 5 are 'hooked' in position on surfaces 12 (one on each extension member 3), the jaw 14 is pulled towards the stub 11 by applying torque to a screw 15. The jaw 14 clamps the stub 11 in the manner of a vice when a diver or an ROV applies torque to the screw 15. There could be two or more jaws 14 acting on each stub 11.
  • stubs 11 can be welded or otherwise connected to the plates 10 only after the difference in the elevations of two surfaces 12 has been determined, for example using depth gauges. If the difference is up to, for example 2 metres, the stubs 11 can be welded (or bolted) to plates 10 with one stub 11 up to 1 metre high, and the other up to 1 metre low, so that their elevations match the difference in elevations of the surfaces 12. When lowered into the water and down on to the surfaces 12, beam assembly 5 will then rest close to horizontal, ready for clamping in position by jaws 14.
  • Another method of clamping the stubs 11 in position on extension members 3 would be to apply a wrap-round strap mechanism instead of a vice-like mechanism.
  • risers can be installed to hang from riser hangers 6.
  • An alternative tether material may be synthetic fibre rope with short chain ends at the top and bottom for top attachment to the extension member 3 of buoyancy means 2 and lower attachment to the seabed anchor.
  • the risers consist of upper U-shaped catenaries and lower J-shaped catenaries.
  • upper riser portions 16 extend from the beam assembly to the vessel at the sea surface
  • lower riser portions 17 extend down from the riser hangers 6 (centrelines only of riser portions are shown).
  • US Patent No. 6,595,625 describes various methods of joining the upper and lower riser portions at the tethered buoyant support, including "inverted U-shaped piping spools" forming the over-bend.
  • the assembly may include at least one piping manifold for the purpose of distributing flushing water, or lift gas, or chemical injection, or control signals, and can include at least one distribution box for power or instrumentation cables, or alternative forms of flowline trace heating.
  • Isolation Valves and large diameter export line pig traps on the support, if required.
  • This description relates to the additional possibility of mounting manifolds; such as flushing water, lift gas, chemical injection, and control systems manifolds; on the support. It could also be used for supporting distribution of power and instrumentation cables, or alternative forms of flowline trace heating.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mining & Mineral Resources (AREA)
  • Ocean & Marine Engineering (AREA)
  • Civil Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Architecture (AREA)
  • Structural Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Earth Drilling (AREA)

Abstract

Ensemble support flottant amarré entre deux eaux pour système de colonne montante sous-marine, destiné à amener des fluides depuis un équipement sur le fond marin jusqu'à une plate-forme flottante de production (FPV). Le système de colonne montante muni d'un support flottant unique peut comporter des colonnes montantes multiples, toutes munies de caténaires supérieures et inférieures. L'ensemble support flottant amarré comporte au moins deux amarres (1) reliées à des ancres de fond, des moyens de flottabilité (2), des éléments prolongateurs inférieurs (3) étant fixés au sommet de chacune desdites amarres pour les soutenir par flottabilité dans une position proche de la verticale et pour maintenir une tension dans lesdites amarres ; au moins un ensemble poutre (5), comprenant des suspensions (6) destinées à suspendre les portions inférieures de colonnes montantes, lesdites suspensions étant montées en des positions espacées le long dudit ensemble poutre, ledit ensemble poutre pouvant être descendu dans une position proche de l'horizontale jusqu'au niveau des deux moyens de flottabilité préinstallés, et des moyens de liaison (7,8) pour permettre à chaque extrémité de la poutre (5) d'être relié aux éléments prolongateurs inférieurs (3) des moyens de flottabilité. L'ensemble est conçu en particulier pour une utilisation en eau profonde.
PCT/GB2006/003846 2005-10-18 2006-10-17 Support flottant amarre et procede pour son installation WO2007045850A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB0521189A GB0521189D0 (en) 2005-10-18 2005-10-18 Tethered buoyant support for risers to a floating production vessel
GB0521189.1 2005-10-18
GB0524143A GB0524143D0 (en) 2005-10-18 2005-11-28 Tethered buoyant support for risers to a floating production vessel
GB0524143.5 2005-11-28
GB0524939.6 2005-12-07
GB0524939A GB0524939D0 (en) 2005-10-18 2005-12-07 Tethered buoyant support for risers to a floating production vessel

Publications (1)

Publication Number Publication Date
WO2007045850A1 true WO2007045850A1 (fr) 2007-04-26

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PCT/GB2006/003846 WO2007045850A1 (fr) 2005-10-18 2006-10-17 Support flottant amarre et procede pour son installation

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011150945A1 (fr) 2010-06-04 2011-12-08 Nkt Flexibles I/S Système de canalisation flexible
WO2014062064A1 (fr) * 2012-10-16 2014-04-24 Riser Support Systems Système d'arche à mi-eau
FR3005484A1 (fr) * 2013-05-13 2014-11-14 Saipem Sa Dispositif d'ancrage d'un support de goulottes d'une installation fond-surface
CN113525639A (zh) * 2021-07-15 2021-10-22 哈尔滨工程大学 一种海底声呐机器人用浮潜装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793737A (en) 1986-06-05 1988-12-27 Bechtel Limited Flexible riser system
GB2295408A (en) * 1994-10-12 1996-05-29 Mobil Oil Corp Marine steel catenary riser system
US5957074A (en) * 1997-04-15 1999-09-28 Bluewater Terminals B.V. Mooring and riser system for use with turrent moored hydrocarbon production vessels
US6595725B1 (en) 1998-11-23 2003-07-22 Foster Wheeler Energy Limited Tethered buoyant support for risers to a floating production vessel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793737A (en) 1986-06-05 1988-12-27 Bechtel Limited Flexible riser system
GB2295408A (en) * 1994-10-12 1996-05-29 Mobil Oil Corp Marine steel catenary riser system
US5957074A (en) * 1997-04-15 1999-09-28 Bluewater Terminals B.V. Mooring and riser system for use with turrent moored hydrocarbon production vessels
US6595725B1 (en) 1998-11-23 2003-07-22 Foster Wheeler Energy Limited Tethered buoyant support for risers to a floating production vessel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
FOSTER WHEELER., "DEEPWATER RISERS - EVELUATION OF SIX OPTIONS, REVIEW OF TETHERED BUOYANT SUPPORTS", 1999

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011150945A1 (fr) 2010-06-04 2011-12-08 Nkt Flexibles I/S Système de canalisation flexible
CN103052562A (zh) * 2010-06-04 2013-04-17 国民油井华高丹麦公司 软管系统
CN103052562B (zh) * 2010-06-04 2016-03-09 国民油井华高丹麦公司 软管系统
WO2014062064A1 (fr) * 2012-10-16 2014-04-24 Riser Support Systems Système d'arche à mi-eau
GB2520906A (en) * 2012-10-16 2015-06-03 Riser Support Systems Midwater arch system
AU2013332507B2 (en) * 2012-10-16 2017-06-01 Riser Support Systems Midwater arch system
FR3005484A1 (fr) * 2013-05-13 2014-11-14 Saipem Sa Dispositif d'ancrage d'un support de goulottes d'une installation fond-surface
WO2014184480A1 (fr) * 2013-05-13 2014-11-20 Saipem S.A. Dispositif d'ancrage d'un support de goulottes d'une installation fond-surface
US9702109B2 (en) 2013-05-13 2017-07-11 Saipem S.A. Device for anchoring a raceway mounting of a seabed-to-surface facility
CN113525639A (zh) * 2021-07-15 2021-10-22 哈尔滨工程大学 一种海底声呐机器人用浮潜装置
CN113525639B (zh) * 2021-07-15 2022-03-08 哈尔滨工程大学 一种海底声呐机器人用浮潜装置

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