EP1257460A1 - Structure de levage en mer semi-submersible et son procede d'utilisation - Google Patents

Structure de levage en mer semi-submersible et son procede d'utilisation

Info

Publication number
EP1257460A1
EP1257460A1 EP01910248A EP01910248A EP1257460A1 EP 1257460 A1 EP1257460 A1 EP 1257460A1 EP 01910248 A EP01910248 A EP 01910248A EP 01910248 A EP01910248 A EP 01910248A EP 1257460 A1 EP1257460 A1 EP 1257460A1
Authority
EP
European Patent Office
Prior art keywords
lifting
vessel
platform
semi
deck
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.)
Withdrawn
Application number
EP01910248A
Other languages
German (de)
English (en)
Inventor
Jan Vatsvag
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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 NO20000833A external-priority patent/NO311336B1/no
Application filed by Individual filed Critical Individual
Publication of EP1257460A1 publication Critical patent/EP1257460A1/fr
Withdrawn legal-status Critical Current

Links

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
    • B63B35/003—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting very large loads, e.g. offshore structure modules
    • 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 
    • B63B77/00—Transporting or installing offshore structures on site using buoyancy forces, e.g. using semi-submersible barges, ballasting the structure or transporting of oil-and-gas platforms

Definitions

  • a semi-submersible offshore lifting structure and a method for using the same.
  • the invention relates to vessels for lifting heavy loads offshore, and particu- larly to vessels for decommissioning offshore platforms with a platform deck placed on jacket legs.
  • a method for using the vessel is also disclosed.
  • topsides consist of several modules installed separately. These could be removed individually in a reverse installation process. This would require several lifts using expensive SSCVs including preparations and engineering.
  • topside By lifting a topside in one single lift, preparations are only required for one operation. A lot of the work onboard the topside, e.g. separating the modules, could then be carried out much cheaper onshore.
  • Norwegian patent NO 306385 shows a method and a transportation device for use in connection with installation or removal of offshore platform decks on or from jackets.
  • the platform decks are removed from the jacket in one lift, and the transportation device comprises pontoons with controllable buoyancy.
  • Norwegian patent NO 831997 shows a floating device for the lifting and trans- portation of a load, and a method for the same.
  • a platform deck can be removed from a jacket in one lift, and the transportation device comprises pontoons with controllable buoyancy.
  • the cost of a lifting or decommissioning vessel can be substantially reduced. It is expected that a weight of 5000 - 10000 tonnes of new steel can be saved.
  • the existing vessel is relative cheap due to the current situation in the North Sea.
  • the integration between the existing and new structure should and can be kept to a minimum to control the cost.
  • the present invention relates to an lifting vessel with controllable buoyancy for lifting offshore platforms placed on a jackets with jacket legs, the vessel having two, in a longitudinal direction, first substantially parallel pontoons and a between the two first substantially parallel pontoons and an, at one end of said first pontoons, an extending transversal second pontoon for connecting said first pontoons to form a first U, two longitudinal, substantially parallel first deck beams and an, at one end of said first deck beams, extending transversal second deck beam for connecting said first deck beams to form a second U and columns extending between the first U and the second U to form a unitary construction where the first U and the second U are substantially parallel; said vessel is adapted to be rigidly attached to a second semi-submersible vessel.
  • the invention relates to using an existing vessel, (drilling, accommodation etc.) together with the steel unit or vessel of the invention. Both the existing vessel and the steel lifting unit of the invention are preferably semi submersible.
  • the steel unit or lifting vessel of the invention with sufficient strength and buoyancy to lift platform decks or topsides, is secured.
  • the steel unit comprises at least two longitudinal pontoons, at least one transversal pontoon, two or more, preferably four, columns, at least two longitudinal deck beams, and at least one transversal deck beam.
  • the steel unit is secured to the exiting vessel with its at least two longitudinal pontoons as extensions of the pontoons of the existing vessel.
  • the pontoons of the unit are interconnected to form a substantially U shaped pontoon, and the three deck beams are interconnected to form a substantially U shaped deck beam.
  • the two U shaped constructions are interconnected with the columns to form the unit.
  • the steel unit is preferably constructed to carry all the weight of the platform by is self, but the possibility of letting the existing vessel carry some of the load should also be contemplated.
  • the number of intersections between the existing vessel and the new steel unit should be kept to a minimum for simplicity.
  • ballasting systems, anchoring systems, cranes, quarters, power supplies, lighting systems, deck area are features of the existing system that can be utilised of the joint vessel. This will provide for considerable cost and resource savings, as compared to the production of an entirely new vessel. Due to the facilities of the existing vessel, the joint vessel is suitable for the initial preparations necessary before the lift is made A footpath or bridge can be placed between the vessel and the platform to be moved
  • the first and preferred method is connecting the vessel to jacket legs through flexible connections 5
  • the flexible connection is achieved with a fender system of the invention
  • the fender system is preferably hydrau cally controlled and is placed between the vessel and the jacket legs of the platform
  • the stiffness or resiliency of the fenders is controlled and optimised to dampen the movements without inf ct- 0 ing damage to the jacket
  • the vessel may move freely in a substantially vertical direction
  • the fender system can be adjusted to follow the inclination of the jacket legs before, during and after the platform has been lifted from the jacket
  • connection system also has to be made sufficiently flexible to cope with the varying draft of the lifting vessel from docking, through load transfer and to lifting off.
  • the second way of maintaining the position between the vessel and the platform is with the vessel fixed to the jacket legs or topside frames.
  • All jackets are stiff structures and the dynamic responses are controlled by the stiffness, in contrary to a moored vessel that has a low stiffness and the dynamic responses are controlled by the mass.
  • jacket structures are slender structures, and attract therefore low hydrodynamic forces.
  • the natural periods of these structures in operation ranges from 0.5 - 3.0 seconds depending on the topsides weight, water depth, piles and soil conditions and number and distance between the legs.
  • the increased mass (displaced mass + added mass of the lifting vessel) will also change the natural periods of the combined structures, which means a considerable increase in the dynamic response of the jacket.
  • the third way is not to connect to the jacket and vessel at all, and control the position of the vessel either by dynamic positioning, mooring lines or tugs.
  • the position of the vessel is, until load transfer starts, only controlled by a catenary mooring (or attached to tugs) or by dynamic positioning.
  • the vessel motions cannot be to large in order to position the respective load transfer points at the jacket/topsides with the vessel and to maintain the position enve ⁇
  • a vessel moored with catenary moorings have stiffness in the region of 30- 40t/m, which means that the second order motion responses are much greater than the first order motions and the resulting responses are too excessive to
  • a line failure would also have a high probability of resulting in a catastrophic consequence due to the likelihood of collision between the vessel and the jacket.
  • a vessel maintaining position by dynamic positioning would also have prob- i5 lems to operate within the small footprint as required for positioning and load transfer.
  • the risk of drive off and drift off of DP systems are very high (1.5 - 2.5x10-5 pr. DP hour) in addition during load transfer between the jacket and vessel the input signals to the computer analysing the external loads will be corrupted. This results in unstable responses, which again results in a high 2o probability of failure.
  • the vessel also comprises a load bearing system that incorporates lifting beams, controllable jacking systems, low friction pads and a horizontal load transmittal system.
  • the lifting beams are designed to be thread under the platform to be lifted, and to extend between the deck beams.
  • the jacks of the jacking system are attached to the lifting beams and are placed under the solid
  • the strong load bearing points are adjacent to the jacket legs. It is for 4-legged jackets sufficient therefore to lift the topsides supported from the outside. For larger jackets (12 leg ged jackets) most of the topsides do not have sufficient strong load bearing frame to transfer the entire load through the outer support points.
  • the load bearing system has therefore either to be extracted to transfer the loads through all jacket support points/ or alternatively to rein- force the topside to transfer the loads to the outer points. Studies have revealed that massive reinforcement of topsides is required.
  • the jacking system controls the force applied to the various parts of the platform.
  • the lifting beams may be adjusted back and forth on the deck beams by means of a wire system, hydraulic motors or hydraulic cylinders.
  • the anti friction pads are placed between the jacks and the platform to prevent horizontal loads on the jacks.
  • the platform is held in the horizontal direction by the horizontal load transmittal system.
  • the coupling means comprises an upper and a lower part releasably connected.
  • the upper and lower part of the coupling means can be released from each other by using any suitable method such as hydraulically controlled cutting of bolts, with frangible elements/shear pins or slips.
  • the coupling means are secured to the jacket legs with mechanical fasteners, welding or other suitable securing means. It is an essential feature to be able to cut the jacket leg between the upper and lower part of the coupling means. Disconnection of the coupling means can be initiated automatically at a predetermined load, or manually in response to a signal from an operator. The object is to hold the platform to the jacket until everything is ready for lift off.
  • figure 1 shows a perspective view of a lifting decommissioning vessel according to the present invention
  • figure 2 shows a perspective view of the steel unit in more detail
  • figure 3 shows a perspective view of the steel unit in more detail showing a 5 platform deck, jacket legs, parts of the hydraulic jacking system and the controlled fenders
  • figure 4 shows a perspective view of a platform jacket with coupling means attached to the jacket legs
  • Fig 1 shows the lifting vessel (1 ) for removal of platforms in one lift including a semi-submersible vessel (2) of a drilling, construction or accommodation type (for instance an Aker H3 type)
  • the steel unit of the invention (3) is attached to the existing semi-submersible vessel to form the complete lifting or decommissioning vessel (1 )
  • the vessel (1 ) can provide for offshore preparations, for is lifting, accommodation for working personnel, power and crane supply, ROV supporting operations and ballasting
  • Fig 2 shows the steel unit of the invention with two longitudinal pontoons (4), one transversal pontoon (5), four columns (6), two longitudinal deck beams 20 (7), one transversal deck beam (8) and six lifting beams (9)
  • This unit may have a 40 100-tonn displacement and a topside lifting capacity of 12 000 tonnes
  • the vessel of the invention is shown with its fender system (10) se- ⁇ cured to the four columns (6)
  • the deck of the platform (11) to be lifted is shown only as a steel frame for better clarity
  • Jacks of a jacking system (12) extend between the lifting beams (9) and strong points of the platform (11 ) Low friction pads are placed between the jacks and the platform (11)
  • Reference numeral (13) denotes load transferral systems that hold the platform (11 ) 3o in a horizontal direction
  • the jacket with jacket legs is shown on fig 4 with coupling means (14) connected to the jacket legs
  • the lifting vessel is manoeuvred below the platform to be lifted by means of winches and/or tugs and is, in a horizontal direction, held to the jacket legs of the platform with the fender system (10).
  • the vessel (1) is free to move vertically.
  • the lifting beams (9), supported on the deck beams (7) are thread under the platform (11) and directed towards strong points on the platform (11). Ballast in the lifting vessel (1) is then pumped out, and the weight of the platform (11) is supported of the lifting vessel (1).
  • the jacking system (12) controls the load on the contacting points between the vessel (1) and the platform (11).
  • the horizontal load transferral systems (13) are applied to hold the platform (11).
  • the coupling means (14) subsequently disconnects the platform from the jacket when a predetermined load is applied to the platform (11) or the coupling means (14), and the platform is lifted off the jacket.
  • the platform is now free to be hauled to a place where it can be transferred to a barge, and further be brought on shore with any suitable sys- tern known in the art.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Transportation (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Earth Drilling (AREA)

Abstract

La présente invention concerne une structure de levage semi-submersible (3), dont la flottabilité peut être commandée et qui permet de lever des plates-formes de forage en mer (11) placées sur des jackets pourvus de jambes de jacket. Cette structure de levage (3) présente, dans une direction longitudinale, deux premiers pontons sensiblement parallèles (4) et, entre ceux-ci, un second ponton (5) qui s'étend transversalement à une extrémité desdits premiers pontons (4) et permet de connecter lesdits premiers pontons, afin de former un premier U. Cette structure présente également deux premiers barrots de pont (7), longitudinaux et sensiblement parallèles, et un second barrot de pont (8) qui s'étend transversalement à une extrémité desdits premiers barrots de pont (7) et permet de connecter lesdits premiers barrots de pont, afin de former un second U. Les colonnes (6) s'étendent entre le premier U et le second U, afin de former une construction unitaire dans laquelle le premier U et le second U sont sensiblement parallèles. Cette structure est conçue pour être attachée de manière rigide à un second bâtiment semi-submersible (2), afin de former un bâtiment de levage complet (1). La présente invention concerne également un procédé d'utilisation dudit bâtiment de levage (1).
EP01910248A 2000-02-18 2001-02-16 Structure de levage en mer semi-submersible et son procede d'utilisation Withdrawn EP1257460A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
NO20000833A NO311336B1 (no) 2000-02-18 2000-02-18 Halvt nedsenkbar offshore löfteanordning samt en fremgangsmåte for bruk av denne
NO20000833 2000-02-18
US18374800P 2000-02-22 2000-02-22
US183748P 2000-02-22
PCT/NO2001/000055 WO2001060688A1 (fr) 2000-02-18 2001-02-16 Structure de levage en mer semi-submersible et son procede d'utilisation

Publications (1)

Publication Number Publication Date
EP1257460A1 true EP1257460A1 (fr) 2002-11-20

Family

ID=26649207

Family Applications (1)

Application Number Title Priority Date Filing Date
EP01910248A Withdrawn EP1257460A1 (fr) 2000-02-18 2001-02-16 Structure de levage en mer semi-submersible et son procede d'utilisation

Country Status (3)

Country Link
EP (1) EP1257460A1 (fr)
AU (1) AU2001237824A1 (fr)
WO (1) WO2001060688A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO315898B1 (no) * 2001-11-21 2003-11-10 Mpu Entpr As Ballasterbart löftefartöy og fremgangsmåte for bruk av et ballasterbart löftefartöy for löfting, transportering, posisjonering oginstallasjon av minst ±nmarin konstruksjon, fortrinnsvis ±n eller flere vindmöller
SE527745C2 (sv) 2004-04-02 2006-05-30 Gva Consultants Ab Ett semisubmersibelt offshore-fartyg och metoder för att positionera arbetsmoduler på sagda fartyg
DK177714B1 (da) * 2012-11-19 2014-03-31 Kartin Hentze Fartøj til at bære en platform
CN104192277B (zh) * 2014-07-24 2016-04-27 中山大学 一种浮式防波平台的可升降加强延拓控制方法
ES2635281B1 (es) * 2016-03-31 2018-07-30 Ocean Shift, S.L. Equipo para el transporte e instalación de aerogeneradores sobre el fondo marino
NL2021841B1 (en) 2018-10-19 2020-05-13 Heerema Marine Contractors Nl Combination of heavy lift vessel and floating appendage structure
CN109625174A (zh) * 2018-12-18 2019-04-16 海洋石油工程（青岛）有限公司 半潜式平台上部组块与下部浮体结构滑道顶升合拢的工艺
CN109625172A (zh) * 2018-12-18 2019-04-16 海洋石油工程（青岛）有限公司 半潜式平台上部组块与下部浮体结构滑道提升合拢的工艺

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3078680A (en) * 1958-12-15 1963-02-26 Jersey Prod Res Co Floating rig mover
FR2514317A1 (fr) * 1981-10-12 1983-04-15 Doris Dev Richesse Sous Marine Dispositif de levage et de transport de charge, a flottabilite reglable, pour travaux en mer et procede pour la mise en oeuvre dudit dispositif
NO306289B1 (no) * 1996-12-18 1999-10-18 Offshore Shuttle As FremgangsmÕte og transportör til bruk ved installasjon eller fjerning av et understell for en offshoreplattform

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0160688A1 *

Also Published As

Publication number Publication date
WO2001060688A1 (fr) 2001-08-23
AU2001237824A1 (en) 2001-08-27

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