WO2003078243A1 - A device and a method of a mooring buoy - Google Patents

A device and a method of a mooring buoy Download PDF

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Publication number
WO2003078243A1
WO2003078243A1 PCT/NO2003/000086 NO0300086W WO03078243A1 WO 2003078243 A1 WO2003078243 A1 WO 2003078243A1 NO 0300086 W NO0300086 W NO 0300086W WO 03078243 A1 WO03078243 A1 WO 03078243A1
Authority
WO
WIPO (PCT)
Prior art keywords
buoy
drilling
drilling vessel
mooring
vessel
Prior art date
Application number
PCT/NO2003/000086
Other languages
French (fr)
Other versions
WO2003078243A9 (en
Inventor
Jon Grude Gjedebo
Original Assignee
Hitec Vision 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 Hitec Vision As filed Critical Hitec Vision As
Priority to AU2003212718A priority Critical patent/AU2003212718A1/en
Publication of WO2003078243A1 publication Critical patent/WO2003078243A1/en
Publication of WO2003078243A9 publication Critical patent/WO2003078243A9/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B22/00—Buoys
    • B63B22/02—Buoys specially adapted for mooring a vessel
    • 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

Definitions

  • This invention concerns a device for and a method of mooring a floating vessel, more specifically a mooring device in which a buoy is moored to the seabed, and where a vessel may be moored to the buoy by means of frictional forces caused by buoyancy without utilising additional mooring elements.
  • the device is particularly suited for use in connection with the positioning of a drilling vessel during petroleum production.
  • a floating drilling platform or other appropriate vessel equipped with the required drilling equipment is brought, according to prior art, to the drilling site, where it is moored or maintained in the desired position by means of so-called dynamic positioning.
  • dynamic positioning no moorings are used, as the vessel is equipped with a control system and the necessary propeller system to allow it to be maintained in the same position under different wind and weather conditions. Due to the high energy costs, dynamic positioning is relatively costly, and such positioning may involve a
  • the first casings and a foundation frame are set after anchoring and preparation of the vessel is completed.
  • a wellhead containing the necessary valves is lowered to the seabed and connected up to the foundation frame, whereupon a riser is lowered and coupled to the wellhead at its lower end portion.
  • the riser is connected to the platform via a heave-compensating device, preferably in the form of one or more hydraulic cylinders designed to maintain relatively constant tension in the riser, also during the heaving motion of the vessel.
  • the object of the invention is to remedy the disadvantages of prior art.
  • buoy Prior to commencing the drilling operation a buoy is placed over the drilling site.
  • the buoy is equipped with the required mooring device in order to allow it to be moored to the seabed by means of a so-called mooring vessel.
  • mooring vessel After mooring of the buoy, it is lowered sufficiently deep into the sea to enable a drilling vessel to move inwards and over the central portion of the buoy to a desired position over the buoy, so that the drilling centre of the drilling vessel coincides with a vertical through opening in the buoy.
  • the buoy is emptied, whereby the buoyancy of the buoy exerts sufficient force against the drilling vessel to maintain the vessel in the desired position relative to the buoy by means of the frictional forces that arise in a system of fenders provided between the buoy and the drilling vessel.
  • the buoy is in two parts.
  • An upper buoy may be constructed with for example an L-shaped cross section, where the upward-facing surface of a horizontal buoyancy element forms a deck designed to abut the underside of the drilling vessel, while an upward-projecting buoyancy element connected to the horizontal buoyancy element projects over the surface of the sea, also when the horizontal buoyancy element is submerged.
  • the upward-projecting buoyancy element may be provided with connections for power transmission and communication with the drilling vessel.
  • the buoy may be provided with fixed ballast disposed underneath the upward- projecting portion in order to stabilise the upper buoy when the horizontal buoyancy element of the upper buoy is
  • the geometry of the upper buoy may also assume other shapes, for example a U-shape where the horizontal buoyancy element is provided with two upward-projecting buoyancy elements.
  • a drop pipe is placed vertically downwards into the sea.
  • the centre line of the drop pipe coincides with the through opening of the buoy, preferably forming a continuation of the through opening down into the sea.
  • a lower buoy is placed so as to movably enclose the drop pipe at a lower level underneath the upper buoy, and when anchored, the lower buoy is connected to the seabed by means of an anchor system.
  • a buoy according to the invention By using a buoy according to the invention it is possible to achieve a considerable reduction in fuel consumption when compared with the use of a drilling vessel having dynamic positioning means. Disconnection of the drilling vessel from the well, for example in expectation of bad weather, is considerably simpler, with the riser and the buoy with the anchoring remaining on the drilling site even though the drilling vessel is moved.
  • Figure 1 shows a cross section II-II in figure 2 of the buoy during transport
  • Fenders 18 are also placed on the side area 20 of the vertical buoyancy element 6 facing the opening 10.
  • the upward-facing area 22 of the vertical buoyancy element 8 is equipped with a structure 24 designed to carry power supply and communication lines 26 between the buoy 1 and a drilling vessel 28, see figure 5.
  • the lower buoy 4 is placed so as to movably enclose the drop pipe 12 at a level below the upper buoy 2.
  • Both the upper 2 and lower 4 buoys are provided with ballast tanks (not shown) that include required piping of a type that is known per se.
  • the two-part buoy 1 is trimmed during the transport to the drilling site, see figure 1, so that the horizontal buoyancy element 6 of the upper buoy 1 maintains freeboard above the surface of the sea 30, whereby it may carry a load.
  • the lower buoy 4 encloses the drop pipe 12 immediately under the horizontal buoyancy element 6.
  • the lower buoy 4 When the buoy 1 is positioned at the drilling site, the lower buoy 4 is anchored to the seabed (not shown) by moorings 32, whereupon the lower buoy is trimmed so as to make it enclose the drop pipe 12 at a suitable depth below the upper buoy 2, see figure 3.
  • the buoy 1 is maintained in position by the drop pipe 12 being slidingly and movably connected to the lower buoy 4.
  • the upper buoy 2 may therefore experience heave without imparting a similar motion to the anchored lower buoy 4.
  • the upper buoy 2 is lowered into the sea in order to provide the required draught for the drilling vessel, see figure 5.
  • the moment constituted by the horizontal distance between the centre of buoyancy of the vertical buoyancy element 8 and the centre of gravity of the fixed ballast 14, multiplied by the weight of the ballast 14 contributes to maintain the horizontal buoyancy element 6 in a substantially horizontal position when being submerged and maintaining an approximately neutral buoyancy.
  • ballast is pumped out of the upper buoy 2, whereby the fenders 18 on the deck 16 contact the bottom section 34 of the drilling vessel 28 in a pressure-transferring manner.
  • the contact force between the upper buoy 2 and the drilling vessel 28 is increased until the frictional force between the fenders 18 of the deck 16 and the drilling vessel 28 is sufficient to maintain the drilling vessel 28 in position on the upper buoy 2.
  • the propeller system of the drilling vessel 28 may optionally be used to keep the drilling vessel 28 and the upper buoy 2 on the desired compass bearing.
  • the drilling vessel 28 may then commence drilling operations.
  • a riser 36 is to be set, it is hung off a heave compensator device 38 of a type that is known per se, located in the through opening 10 and/or the drop pipe 12.
  • the drilling vessel 28 is positioned over the buoy 1, whereupon the riser 36 is reconnected to the drilling vessel 28.
  • the drop pipe 12 may be fixed to the lower buoy 4 and movably connected to the upper buoy 2.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Earth Drilling (AREA)
  • Ropes Or Cables (AREA)

Abstract

A device and a method concerning a mooring buoy (1) for mooring a drilling vessel (28) during drilling operations, wherein the drilling vessel (28) is connected to the mooring buoy (1) by means of buoyancy-induced frictional forces between the mooring buoy (1) and the drilling vessel (28).

Description

A DEVICE AND A METHOD OF A MOORING BUOY
This invention concerns a device for and a method of mooring a floating vessel, more specifically a mooring device in which a buoy is moored to the seabed, and where a vessel may be moored to the buoy by means of frictional forces caused by buoyancy without utilising additional mooring elements. The device is particularly suited for use in connection with the positioning of a drilling vessel during petroleum production.
When establishing a new petroleum well, a floating drilling platform or other appropriate vessel equipped with the required drilling equipment is brought, according to prior art, to the drilling site, where it is moored or maintained in the desired position by means of so-called dynamic positioning. In dynamic positioning no moorings are used, as the vessel is equipped with a control system and the necessary propeller system to allow it to be maintained in the same position under different wind and weather conditions. Due to the high energy costs, dynamic positioning is relatively costly, and such positioning may involve a
certain risk of the vessel drifting during adverse weather conditions.
When drilling according to techniques that are known per se, the first casings and a foundation frame are set after anchoring and preparation of the vessel is completed.
Then a wellhead containing the necessary valves is lowered to the seabed and connected up to the foundation frame, whereupon a riser is lowered and coupled to the wellhead at its lower end portion. At its upper end portion, the riser is connected to the platform via a heave-compensating device, preferably in the form of one or more hydraulic cylinders designed to maintain relatively constant tension in the riser, also during the heaving motion of the vessel.
It is therefore necessary during drilling operations according to prior art to position a drilling vessel at the drilling site before the mooring operation can be carried out.
Furthermore, it is necessary in bad weather to drain the riser of drilling liquid in order to then disconnect the lower end portion of this from the wellhead. Depending on the depth of the drilling site and how far the drilling operation has advanced, the work involved in disconnecting the drilling vessel from and subsequently connecting it to the borehole, and also the pull-up of the drilling tool, may be an extensive and costly operation.
The object of the invention is to remedy the disadvantages of prior art.
The object is achieved in accordance with the invention and by means of features stated in the specification below and in the subsequent patent claims.
Prior to commencing the drilling operation a buoy is placed over the drilling site. The buoy is equipped with the required mooring device in order to allow it to be moored to the seabed by means of a so-called mooring vessel. After mooring of the buoy, it is lowered sufficiently deep into the sea to enable a drilling vessel to move inwards and over the central portion of the buoy to a desired position over the buoy, so that the drilling centre of the drilling vessel coincides with a vertical through opening in the buoy. Then the buoy is emptied, whereby the buoyancy of the buoy exerts sufficient force against the drilling vessel to maintain the vessel in the desired position relative to the buoy by means of the frictional forces that arise in a system of fenders provided between the buoy and the drilling vessel.
Advantageously, the buoy is in two parts. An upper buoy may be constructed with for example an L-shaped cross section, where the upward-facing surface of a horizontal buoyancy element forms a deck designed to abut the underside of the drilling vessel, while an upward-projecting buoyancy element connected to the horizontal buoyancy element projects over the surface of the sea, also when the horizontal buoyancy element is submerged. The upward-projecting buoyancy element may be provided with connections for power transmission and communication with the drilling vessel. The buoy may be provided with fixed ballast disposed underneath the upward- projecting portion in order to stabilise the upper buoy when the horizontal buoyancy element of the upper buoy is
submerged. The geometry of the upper buoy may also assume other shapes, for example a U-shape where the horizontal buoyancy element is provided with two upward-projecting buoyancy elements.
From the horizontal buoyancy element of the buoy a drop pipe is placed vertically downwards into the sea. The centre line of the drop pipe coincides with the through opening of the buoy, preferably forming a continuation of the through opening down into the sea. A lower buoy is placed so as to movably enclose the drop pipe at a lower level underneath the upper buoy, and when anchored, the lower buoy is connected to the seabed by means of an anchor system.
The functioning of the buoy is described in greater detail in the specific part of the specification.
By using a buoy according to the invention it is possible to achieve a considerable reduction in fuel consumption when compared with the use of a drilling vessel having dynamic positioning means. Disconnection of the drilling vessel from the well, for example in expectation of bad weather, is considerably simpler, with the riser and the buoy with the anchoring remaining on the drilling site even though the drilling vessel is moved.
The following describes a non-limiting example of a preferred embodiment illustrated schematically in the accompanying drawings, in which:
Figure 1 shows a cross section II-II in figure 2 of the buoy during transport;
Fig. 5 viser bøyen etter at et borefartøy er anbrakt pa bøy- en;
Fig. 6 viser delvis i snitt bøyen etter at et stigerør er satt; og
Fig. 7 viser delvis i snitt bøyen etter at borefartøyet har forlatt bøyen.
Pa tegningene betegner henvisningstallet 1 en bøye omfattende en øvre bøye 2 og en nedre bøye 4. Den øvre bøye 2 er forsynt med et i hovedsak horisontalt flytelegeme 6 og et i hovedsak vertikalt flytelegeme 8. Det horisontale flytelegemet 6 og det vertikale flytelegemet 8 danner et L-formet tverrsnitt.
Fra en sentral gjennomgaende vertikal apning 10 i den øvre bøyes 2 horisontale flytelegeme 6, rager et senkerør 12 ned i sjøen. En fast ballast 14 er anbrakt vertikalt under det vertikale flytelegeme 8 og er forbundet til den øvre bøye 2. Det horisontale flytelegemes 6 oppovervendende plan som utgjør bøyens 2 dekk 16, er forsynt med fendere 18 i form av elas- tisk, eksempelvis gummiholdig materiale.
Fendere 18 er ogsa anbrakt pa det vertikale flytelegemes 6 mot apningen 10 vendende sideareal 20. Det vertikale flytelegemes 8 oppovervendende areal 22 er forsynt med en konst- ruksjon 24 som er innrettet til a bare energiforsynings- og kommunikasjonsforbindelser 26, se fig. 5, mellom bøyen 1 og et borefartøy 28.
Den nedre bøye 4 er anbrakt forskyvbart omkransende senkerø- ret 12 pa et niva under den øvre bøye 2.
Fenders 18 are also placed on the side area 20 of the vertical buoyancy element 6 facing the opening 10. The upward-facing area 22 of the vertical buoyancy element 8 is equipped with a structure 24 designed to carry power supply and communication lines 26 between the buoy 1 and a drilling vessel 28, see figure 5.
The lower buoy 4 is placed so as to movably enclose the drop pipe 12 at a level below the upper buoy 2.
Both the upper 2 and lower 4 buoys are provided with ballast tanks (not shown) that include required piping of a type that is known per se.
The two-part buoy 1 is trimmed during the transport to the drilling site, see figure 1, so that the horizontal buoyancy element 6 of the upper buoy 1 maintains freeboard above the surface of the sea 30, whereby it may carry a load. During the transport, the lower buoy 4 encloses the drop pipe 12 immediately under the horizontal buoyancy element 6.
When the buoy 1 is positioned at the drilling site, the lower buoy 4 is anchored to the seabed (not shown) by moorings 32, whereupon the lower buoy is trimmed so as to make it enclose the drop pipe 12 at a suitable depth below the upper buoy 2, see figure 3. Thus the buoy 1 is maintained in position by the drop pipe 12 being slidingly and movably connected to the lower buoy 4. The upper buoy 2 may therefore experience heave without imparting a similar motion to the anchored lower buoy 4.
Before the ballast of the drilling vessel 28 is adjusted and the drilling vessel 28 is positioned over the horizontal buoyancy element 6 of the upper buoy 2 , the upper buoy 2 is lowered into the sea in order to provide the required draught for the drilling vessel, see figure 5. In this submerged position, the moment constituted by the horizontal distance between the centre of buoyancy of the vertical buoyancy element 8 and the centre of gravity of the fixed ballast 14, multiplied by the weight of the ballast 14, contributes to maintain the horizontal buoyancy element 6 in a substantially horizontal position when being submerged and maintaining an approximately neutral buoyancy.
After the drilling vessel 28 has been located and positioned over the horizontal buoyancy element 6, see figure 5, ballast is pumped out of the upper buoy 2, whereby the fenders 18 on the deck 16 contact the bottom section 34 of the drilling vessel 28 in a pressure-transferring manner.
The contact force between the upper buoy 2 and the drilling vessel 28 is increased until the frictional force between the fenders 18 of the deck 16 and the drilling vessel 28 is sufficient to maintain the drilling vessel 28 in position on the upper buoy 2. The propeller system of the drilling vessel 28 may optionally be used to keep the drilling vessel 28 and the upper buoy 2 on the desired compass bearing.
The drilling vessel 28 may then commence drilling operations. When a riser 36 is to be set, it is hung off a heave compensator device 38 of a type that is known per se, located in the through opening 10 and/or the drop pipe 12.
When poor weather conditions are expected, or when the drilling vessel 28 has to leave the drilling site for other reasons, see figure 7, the riser 36 is disconnected from the drilling vessel 28 immediately above the heave-compensating device 38, whereupon the upper buoy is lowered sufficiently to provide clearance for the drilling vessel 28 to leave the buoy 1.
Once the conditions allow resumed drilling, the drilling vessel 28 is positioned over the buoy 1, whereupon the riser 36 is reconnected to the drilling vessel 28.
In an alternative embodiment the drop pipe 12 may be fixed to the lower buoy 4 and movably connected to the upper buoy 2.
Forming the upper buoy 2 with fenders 18 on the deck 16 enables connection to many types of drilling vessels that then may be used without having undergone any significant and costly reconstruction and adaptation work.

Claims

C l a i m s
1. A device for a mooring buoy (1) for mooring a drilling vessel (28) during drilling operations, c h ar a c t e r i s e d i n that the drilling vessel (28) is connected to the mooring buoy (1) by means of mainly buoyancy-induced frictional forces between the buoy (1) and the drilling vessel (28).
2. A device according to Claim 1, c h a r a c t e r i s e d i n that the mooring buoy ( 1 ) is connected to the seabed.
3. A device according to one or more of the preceding claims, c h a r a c t e r i s e d i n that the mooring buoy (1) consists of a lower buoy (4) designed to be moored to the seabed and an upper buoy (2) that is vertically displaceable relative to the lower buoy (4).
4. A device according to one or more of the preceding claims, c h a r a c t e r i s e d i n that the buoy (1) is provided with a fixed ballast (14) disposed underneath a vertical buoyancy element (8) of the buoy (1).
5. A device according to one or more of the preceding claims, c h a r a c t e r i s e d i n that the buoy (1) is provided with a heave-compensating device (38).
6. A device according to one or more of the preceding claims, c h a r a c t e r i s e d i n that the heave- compensating device (38) is placed in a drop pipe (12),
the drop pipe (12) constituting the vertically displaceable connection between the upper buoy (2) and the lower buoy ( 4 ) .
7. A device according to one or more of the preceding claims, c h a r ac t e r i s e d i n that the drop pipe (12) is fixedly connected to the lower buoy (4) and movably connected to the upper buoy ( 2 ) .
8. A method of mooring a drilling vessel (28) during drilling operations, c h a r ac t e r i s e d i n that the method comprises:
- placing the drilling vessel (28) over a submerged, moored buoy ( 1 ) ; and
- then adjusting the ballast of the drilling vessel (28) and/or the buoy (1), thereby creating, by means of the buoyancy force of the buoy (1) against the drilling vessel (28), a required frictional force between the buoy ( 1 ) and the drilling vessel (28) to maintain the drilling vessel (28) in position.
PCT/NO2003/000086 2002-03-19 2003-03-13 A device and a method of a mooring buoy WO2003078243A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003212718A AU2003212718A1 (en) 2002-03-19 2003-03-13 A device and a method of a mooring buoy

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20021347 2002-03-19
NO20021347A NO316169B1 (en) 2002-03-19 2002-03-19 Mooring buoy device and method

Publications (2)

Publication Number Publication Date
WO2003078243A1 true WO2003078243A1 (en) 2003-09-25
WO2003078243A9 WO2003078243A9 (en) 2004-08-12

Family

ID=19913446

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NO2003/000086 WO2003078243A1 (en) 2002-03-19 2003-03-13 A device and a method of a mooring buoy

Country Status (3)

Country Link
AU (1) AU2003212718A1 (en)
NO (1) NO316169B1 (en)
WO (1) WO2003078243A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005118389A1 (en) * 2004-06-03 2005-12-15 Remora Technology As A method of dynamic positioning of a vessel
FR2968267A1 (en) * 2010-12-06 2012-06-08 Ciel Et Terre Anchorage device for use in photovoltaic installation to anchor floating device support of photovoltaic panels, has guiding face arranged such that upper part of sliding element is arranged to be raised with water above upper end of pile

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5770789A (en) * 1980-10-14 1982-05-01 Hitachi Zosen Corp Method and device for mooring ship
JPS5940986A (en) * 1982-08-30 1984-03-06 Kawasaki Heavy Ind Ltd Mooring system for vessel
SE458519B (en) * 1987-08-12 1989-04-10 Goetaverken Arendal Ab FORCE STRENGTH OF SHIPPING FOR OFF-SHORE WORK
WO2000027692A1 (en) * 1998-10-26 2000-05-18 Lund, Mohr & Giæver-Enger Marin As Device for positioning of vessels
WO2000075008A1 (en) * 1999-06-09 2000-12-14 Hitec Marine As System for loading and unloading fluid products
WO2002072415A1 (en) * 2001-03-09 2002-09-19 Hitec Marine As A method and a means for connecting two floating units
US6485343B1 (en) * 1999-06-29 2002-11-26 Pgs Offshore Technology As Dynamic positioning dock-loading buoy (DPDL-buoy) and method for use of such a DPDL-buoy

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5770789A (en) * 1980-10-14 1982-05-01 Hitachi Zosen Corp Method and device for mooring ship
JPS5940986A (en) * 1982-08-30 1984-03-06 Kawasaki Heavy Ind Ltd Mooring system for vessel
SE458519B (en) * 1987-08-12 1989-04-10 Goetaverken Arendal Ab FORCE STRENGTH OF SHIPPING FOR OFF-SHORE WORK
WO2000027692A1 (en) * 1998-10-26 2000-05-18 Lund, Mohr & Giæver-Enger Marin As Device for positioning of vessels
WO2000075008A1 (en) * 1999-06-09 2000-12-14 Hitec Marine As System for loading and unloading fluid products
US6485343B1 (en) * 1999-06-29 2002-11-26 Pgs Offshore Technology As Dynamic positioning dock-loading buoy (DPDL-buoy) and method for use of such a DPDL-buoy
WO2002072415A1 (en) * 2001-03-09 2002-09-19 Hitec Marine As A method and a means for connecting two floating units

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005118389A1 (en) * 2004-06-03 2005-12-15 Remora Technology As A method of dynamic positioning of a vessel
US8028638B2 (en) * 2004-06-03 2011-10-04 Remora Technology As Method of dynamic positioning of a vessel
FR2968267A1 (en) * 2010-12-06 2012-06-08 Ciel Et Terre Anchorage device for use in photovoltaic installation to anchor floating device support of photovoltaic panels, has guiding face arranged such that upper part of sliding element is arranged to be raised with water above upper end of pile

Also Published As

Publication number Publication date
AU2003212718A1 (en) 2003-09-29
NO20021347D0 (en) 2002-03-19
WO2003078243A9 (en) 2004-08-12
NO316169B1 (en) 2003-12-22
NO20021347L (en) 2003-09-22

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